Glossary Of

Petroleum Engineering Terms

Here’s a nifty resource to lookup those pesky petroleum engineering terms and acronyms that you can never remember. Note: U.S. spelling is used.

TermDescription
A AnnulusThe inside annulus; tubing-by-production casing annulus. (Note, there may be regional differences in the A, B, C annulus designations and some are reversed. Inside annuli (IA) and outside annuli (OA) are more universally descriptive.)
AAIORAnnualized average incremental oil rate.
AAODCAmerican Association of Oilwell Drilling Contractors.
AAPEAAustralian Petroleum Production and Exploration Association.
AAPGAmerican Association of Petroleum Geologists.
AAPLAmerican Association of Petroleum Landmen.
AARAfter action review.
AASPAllowable annular surface pressure.
AAV (subsea)Annular access valve.
Abalation Debris (perforating)Small pieces of rock broken up by the perforating process.
AbandonTypically means to cease efforts, either temporarily or permanently, to produce a well. Abandon may have a legal meaning in some locations.
Abandonment CostCosts associated with the abandonment of facilities or services, including costs for the removal of facilities and restoration of the land.
Abiogenic TheoryA theory of petroleum generation in which petroleum is thought to have formed from hydrocarbons trapped inside the earth’s crust when the earth was forming. See also Biogenic and Organic theories.
Abject Failure (Risk)A failure mode that can cause the cancellation-of or immediate-halt-to a project or event. Generally expressed as a percent probability.
AbandonTo cease efforts to produce or inject fluids in a wells and to plug the well sufficiently to protect the environment and the ability to redrill and develop other reserves at a later date.
Abandonment PressureThe minimum pressure of the reservoir when the wells are abandoned.
Abnormally PressuredA pore pressure higher than a column of sea water for that true vertical depth.
Abrasion (geologic)A form of mechanical weathering where loose fragments are transported with water or wind.
Abrasion (mechanical)Wearing away by friction.
AbrasiveParticles propelled at a velocity sufficient to cause cleaning or wearing away of a surface.
Abrasive JettingA perforating process involving pumping a slurry of liquid and size particles through a nozzle to cut through steel and rock.
ABSAmerican Bureau of Shipping.
ABS (plastic)Acrylonitrile-Butadiene-Styrene.
Absolute AgesEstimation/measurement of age of a formation, fossil, etc., in years before the present.
Absolute Filter LevelA filter rating that purports to set the maximum size of an opening in a filter or the maximum size of the particle that can pass through the filter. The definition varies with use and company.
Absolute Open Flow (AOF)The maximum rate that a well can produce at the lowest possible bottom hole pressure.
Absolute Open Flow PotentialThe theoretical maximum flow that a well could deliver with a zero backpressure at the middle of the perforations.
Absolute PermeabilityPermeability to a single phase fluid in a cleaned core.
Absolute PorosityThe percentage of the total bulk volume that is pore spaces, voids or fractures.
Absolute PressureThe reading of gauge pressure plus the atmospheric pressure.
Absolute TemperatureTemperature measurement starting at absolute zero (total absence of heat).
Absolute ViscosityThe measure of a fluid’s ability to resist flow without regards to its density. It is defined as a fluid’s kinematic viscosity multiplied by its density.
Absolute VolumeThe volume a solid occupies when added to a fluid divided by its weight. m3/kg or gal/lb.
Absolute ZeroZero point on the absolute temperature scale; equal to -273.16 degrees C, or 0 degrees K (Kelvin), or -459.69 degrees F, or 0 degrees R (Rankine).
AbsorbTo fill part or all of the pore spaces.
AbsorberA vertical, cylindrical vessel that recovers heavier (longer carbon chain) hydrocarbons from a mixture of lighter hydrocarbons.
Absorptance (seismic)The ratio of the energy absorbed by a formation in relationship to the total energy passing through it.
Absorption (processing)The ability of one material to absorb another.
Absorption GasolineGasoline extracted from wet natural gas by putting the gas in contact with oil.
Absorption Oil (facilities)The wash oil used to remove heavier hydrocarbons from the gas stream.
AbyssalDepositional environment of the deepest areas of the oceans.
Abyssal PlainLarge, flat ocean floor, usually near a continent and usually over 4km (13100 ft) ss.
ACAAfter closure analysis; a fracture performance test method.
AC Test DustA precision sized micron particle material used for testing the solids stopping capability of filters.
Accelerator (chemical)A chemical that speeds up the rate of a chemical reaction. Most common are the accelerators used in cementing.
Accelerator (drilling)An energy increasing device, with sudden energy release, used in a jarring string while fishing.
AccommodationPlace where personnel spend their off-duty time on a rig.
AccretionThe action of particles forming adhering clumps on pipe.
Accumulation (reservoir)An economic quantity of hydrocarbon trapped in a permeable rock strata.
Accumulator (pressure control device)Canisters of hydraulic fluid, pressurized with a nitrogen gas cap of sufficient pressure and volume to operate all the rams on a BOP in case of power failure to the BOP.
Accumulator (processing plant)A vessel that receives and temporarily stores a liquid used in the feed stock or the processing of a feed stream in a gas plant or other processing facility.
Accumulator PrechargeThe initial nitrogen charge on a BOP accumulator that is placed before the fluid is pumped in to charge the accumulator.
AccuracyThe closeness of agreement between the measure value and the exact value.
Acetic AcidA very weak organic acid used for minor and shallow damage removal. Also used as a moderately effective iron precipitation preventer. 4% acetic acid is vinegar.
ACFMActual cubic feet per minute.
AcidA reactive material with a low pH. Common oilfield mineral acids are HCl and HCl/HF.
Acid BrittlenessLow ductility of a metal due to its adsorption of hydrogen. More commonly called hydrogen embrittlement.
Acid EffectThe change in pulsed neutron capture created by acidizing a carbonate. Acidizing increases interconnected porosity and strands chlorides and other ions in the rock.
Acid Flowback AnalysisChemical analysis of the acid concentration and other chemical and physical measurements in the returning acid.
Acid FractureTo fracture stimulate a formation by injecting the acid over the parting pressure of the rock and using the acid to etch channels in the fracture face.
Acid GasAny produced gas, primarily H2S and CO2 that form an acid when produced in water.
Acid InhibitorAcid corrosion inhibitor. Slows the acid attack on metal.
Acid SolubilityThe percent by weight loss of exposing a sample of material to an excess of acid.
Acid StickA solid stick of chloro-acetic or sulfamic acid for small scale removal of acid soluble deposits.
AcidizingUse of a mineral acid (typically HCl or HCl/HF) or an organic acid (typically acetic or formic) to remove damage or stimulate the permeability of a formation.
Acoustic BasementFormations below the deepest zones that can be imaged by an acoustic process.
Acoustic ImpedanceThe velocity of an imposed sound wave (acoustic velocity) through a rock times the density of the rock.
Acoustic LoggingA sonic travel time record of a formation using a tool with an emitter and a detector. Measures porosity and is useful to compare to other porosity longs to estimate pore filling. Also used to generate rock strength evaluations.
Acoustic Travel TimeThe total time required for an acoustic wave to travel through a substance.
Acoustic VelocityVelocity of an imposed sound wave through a rock.
Acquisition LogThe raw, real time recording of the data, later formed into a digital or playback log.
AcreageLand leased for drilling exploration.
Acre-FtOne acre (43560 ft2) to a depth of one ft.
Acrylamide PolymerA nonionic polymer (polyacrylamide) used in flocculation, clarifying and even gelling acids and other brines. Very stable, but difficult to effectively break.
AcrylicA resin polymerized from one of several sources acrylonitrile, acrylic acid, methacrylic acid, etc.
ACSAmerican Chemical Society.
Activated CarbonA highly porous solid, usually a charcoal. Used for adsorption of unwanted materials.
Activation LoggingNear formation area is irradiated with neutrons that transform some nuclei into isotopes. The isotopes produced can be detected by radioactive energy levels and decay time. The original elements can be described from this behavior.
ActivatorA chemical, heat, radiation, or mechanical action that starts or accelerates a chemical reaction.
ActiveA corrosion state where a metal is corroding without control by a reaction product (or corrosion product layer).
ActuatorA device that, by remote influence, can operate valves or other equipment.
ACVAnnular safety valve.
ADAssistant driller.
AdaptorA piece of equipment that connects pipe, flanges or other equipment with different root threads or connection mechanisms.
Adaptor SpoolAn adaptor that allows BOP’s to be connected to wellhead flanges of various sizes.
AdditiveA compound incorporated into a gas, liquid, or solid system to alter the properties for a particular purpose.
AdhesionAttractive forces between unlike molecules or compounds. Example – the attractive forces between water molecules and the walls of a clean glass tube are stronger than the cohesive forces; this leads to an upward turned contact or meniscus at the wall.
AdiabaticNo exchange of heat with the surroundings.
Adjustable ChokeA pressure step-reduction choke that can be changed while actively flowing the well.
ADP (training)Accelerated development program.
AdsorptionThe attraction and holding of a layer of a chemical on the wall of a formation. Usually held by ionic charge or wetting preference.
Adsorption Band (seismic)The range of wavelength energy that can be adsorbed by a given formation.
AerationIntoduction of air.
Aerobic (bacteria)Bacteria that require oxygen to survive and multiply.
AerosolA suspension of fine liquid droplets or solid particles in a gas.
AFDAuthorization for definition.
AFE (expense)Authority for Expenditure on a well (authorized funds for drilling or workover).
AFE (well operation)Annular fluid expansion.
AFLASA high temperature seal elastomer.
After CoolerHeat exchangers for cooling gas after compression.
AFPAnnular friction pressure.
AFUDCAllowance for funds used during construction.
AFVAnnular flow valve.
AGArabian Gulf.
AGAAmerican Gas Association.
AgateSiliceous rock with alternating bands of chalcedony and colored chert.
AgglomeratesLarger particles of material made up of small, independent pieces.
AgglomerationForming larger droplets, bubbles, or particles from smaller droplets, bubbles, or particles.
Aggregate (cementing)An essentially inert mixture of particles of a particular size range.
AggregationAttraction and adherence of clumps of small particles.
AHD (depth)Along hole depth or measured depth.
AHV (subsea)Anchor handling vessel.
AIMEAmerican Institute of Mining, Metallurgical and Petroleum Engineers.
AIPAustralian Institute of Petroleum.
AIPGAmerican Institute of Professional Geologists.
AirStandard density of dry air, free of CO2 at 0℃ is 1.292 g/L.
Air CanBuoyancy device on a Spar.
Air Density0.763 lb/ft3 at standard temperature and pressure.
Air DrillingDrilling with air instead of drilling mud (requires diverters at the surface to handle cuttings and formation fluids).
Air GapThe clearance between the highest water surface that occurs during the extreme environmental conditions and the underside of the deck.
Air GunSeismic source for ocean seismic work.
Air LiftA surface piston driven pumping unit, similar to a beam lift unit.
Air StrippingRemediation technique to strip volitile contaminants from contaminated ground water after a spill. Works to oxidize components and to activate bacteria that can digest hydrocarbons.
Air WeightThe weight of a string in air without the effect of buoyancy provided by wellbore fluids.
AISAnnular isolation sleeve.
ALArtificial lift.
ALARAAs low as reasonably achievable.
Alarm PointPreset value of a monitored parameter at which an alarm is actuated to warn of a condition that requires corrective action.
AlbianThe oldest terrain from the Cretaceous period.
ALGAlgerian.
AliphaticCarbon and hydrogen compounds that may be branched of straight chained. Aliphatics may be paraffin (saturated) or olefinic (unsaturated).
AlkaliA strongly basic solution.
Alkali MetalA strongly basic metal such as sodium or potassium.
AlkalineBasic or pH over 7.
Alkaline FloodingLarge scale injection of pH>7 fluids. The basic materials may react with oils to form reactants that can reduce viscosity or affect wetting.
AlkanesStraight or branched chain hydrocarbons with single bonded carbon atoms. Describes most oils.
AlkenesStraight or branched chain chemicals with some double bonds between carbons.
AlkydA resin formed by reaction of polyhydric alcohols and polybasic salts. Saturated or unsaturated oils or fats are involved.
AlkylationA reverse cracking process that convents hydrocarbon light ends (olefins) into longer chain, liquid fuels.
Allocated PoolA pool in which the total oil or gas production is restricted and allocated to specific wells as defined in a proration agreement.
AllocationThe process of determining ownership of hydrocarbons delivered to the meter or LACT unit on a lease.
Allocation MethodA method of allocating volumes to affected parties when an imbalance occurs.
AllochthonousFormations transported by fault or similar earth shift movements.
AllogenicRock constituents and minerals derived elsewhere from older formations and redeposited.
AllowableThe production limit set on a specific well by a government regulatory body. Rarely seen.
Allowable Working Pressure or StressThe maximum stress allowed by code or other agreement or study as a fraction of test pressure. Design pressure of the system is related to hoop stress.
Alluvial FanLand counterpart of a river delta. Characteristic of sediments that have been transported by a fast moving stream then dropped out of the flow as the stream velocity drops as it spreads out. Typical of zones of heavy water runoff such as found at the base of mountains in arid and semi arid climates where flash floods may be seen. Often poorly sorted with pebble to boulder sized sediments. Weak cementing typical.
AlluviumUnconsolidated to well sorted to poorly sorted (gravel to sand sized) particles transported by water.
Alpha DecayRadioactive decay process where the loss of an alpha particle from the nucleus lowers the atomic number by two and the atomic mass by four.
Alpha WaveThe initial wave of gravel transport when packing a well with a deviation over 55o.
Alternate Path TechnologyA patented screen design that allows gravel packing slurry to flow past an annular bridge point that would normally stop the placement of gravel.
AlumAluminum and potassium sulfate compound. Used was water clairfying.
Aluminum Activation LogAn investigation that focuses on aluminum content, an indirect measurement of clay content.
Aluminum StearateA mud degasser chemical.
Ambient TemperatureThe temperature of the surroundings, usually an average surface temperature or test surface temperature.
AmidesLinear or ring compounds with a CO-NH2 attachment. Common in surfactants.
AminesAmmonia based materials (NH3), in which one of more of the hydrogen atoms are replaced by hydrocarbons.
AmorphousWithout crystal form.
Amorphous KerogenKerogen that lacks distinct form or shape under microscopic exam. May describe oil prone Kerogen.
Amphoteric MetalMetal that may corroded in either acids or alkalines.
Amphoteric SurfactantA surfactant whose charge is dependent on another variable, normally pH.
AMPSA copolymer. Acrylamido-methyl-propane sulfonate polymer.
Anaerobic (bacteria)Bacteria that can survive and multiply without oxygen.
Analogous ReservoirA comparable reservoir with many similar characteristics (e.g., lithology, depositional environment, porosity, perm, drive mechanism, produced fluids, etc.) that can be used for behavior projections comparison studies.
AnchorA device with slips that holds equipment in the wellbore.
Ancillary ComponentA component (e.g., bend stiffeners and buoyancy modules) used to control flexible pipe behavior.
ANGAAmerican Natural Gas Association
Angle of Repose (sand in pipe)The deviation angle (from vertical) at which a solid material will no longer fall down the pipe, but will begin to accumulate on the pipe wall. The angle of repose for dry, round sand is about 62o and for wet sand about 50o to 60o depending on size, shape and moisture.
Angstrom10-10 meter.
Angular UnconformityAn unconformity in which the beds below the unconformity dip at different angles than the beds above it.
ANGTSAlaska Natural Gas Transportation System.
AnhydriteCaSO4 formation. Usually formed as an evaporite from a drying lake of trapped sea water.
AnhydrousDry – without water.
Aniline PointThe aromatics content of a mixture.
AnionAn ion with a negative charge.
Anion ExchangeProcess where a special resin exchanges chloride or hydroxide for contaminant anions such as fluoride, nitrate, sulfate and bicarbonate. Water purification is the primary use.
Anionic SurfactantA negatively charged surfactant. Normally water wets sands.
AnisotropyDifferences in rock – segments showing different responses when measured.
Anithic FaultA secondary fault, often in a set, with opposite direction to the primary fault.
AnnubarA gas flow rate measurement device using Pitot tubes. Common in pipelines.
Annular Blowout PreventerA device installed above or below the BOP that is capable of sealing around any device, and even on itself if the wellbore is empty.
Annular FlowUsing the annulus as the flow path.
Annular InjectionInjection of fluids down the annulus or “backside”. Common as a gas supply path for gas lift. Also used in some fracturing operations, to spot fluids downhole when no packer is used or a type of injection valve is in the tubing to allow entry of chemicals, gas or water.
Annular PackoffA device that seals the annulus to pressure or flow.
Annular PressurePressure in an annular area. May be a vented or trapped annuli.
Annular PreventerA elastomer bag or donut type seal, pushed into contact with the pipe or tools in the blow out preventer (BOP). It is designed to seal around pipe or any other irregular surface tool (packers, guns, pumps, etc.) that may be in the BOP. May also be called a Hydril preventer.
Annular Safety ValveA downhole safety valve that shuts off the annulus.
Annular ValveThe valve on the side of the tree that controls access to the annulus.
Annular VelocityThe velocity of fluids flowing in the annulus. Important in clean-up and displacement processes.
AnnulusThe area between the O.D. of an inside string and the ID of an outside string.
Annulus Sea AssemblyThe mechanism that provides pressure isolation between each casing hanger and the wellhead housing.
AnodeThe positively charged site in a cell. Oxidation site. The site of metal loss in corrosion.
Anode, sacrificialA formed metal bar (zinc, aluminum, etc.) attached by electrical wire to a structure to be protected and buried in conductive soil near that structure.
Anode Corrosion EfficiencyThe ratio of the mass loss of actual corrosion of an anode to the theoretical corrosion mass loss calculated from the quantity of electricity that has passed between the anode and the cathode using Faraday’s law (from NACE).
Anodic InhibitorA substance that slows the reaction at the anode.
Anodic ProtectionPolarization to a higher oxidizing potential to achieve a reduced corrosion rate (promotes passivity).
AnodizingOxide coating of a metal surface to reduce corrosion.
AnomalousUnusual data or measurement that is away from or out of the range of other data.
AnoxicConditions where concentration is very low, usually less than 0.1 mg/liter of water.
ANSIAmerican National Standards Institute.
Athie WagonA trailer or other vehicle, designed for soft ground, often used as the staging platform for fighting well fires.
AnthraciteThe most highly metamorphosed form of coal.
Anti-agglomerants (hydrate control)Chemicals which prevent hydrate crystals from sticking together and forming a larger mass.
AnticlineA convex-upward formation of rock layers (a fold with the strata sloping down on the sides from a common crest. In association with a sealing rock, an anticline may form a trap for hydrocarbons. Anticlines may be faulted or unfaulted. The majority of the hydrocarbons produced so far have been from anticlines.
AntifoamerA material that can quickly destabilize foam in a production fluid treating facility. Commonly needed after treatment with foamers, diesel, some polymers, some acids and gasified fluids.
AntifoulingAny action designed to reduce or prevent fouling (deposits) on a surface.
Antitheic FaultA secondary fault, often in a set, with an opposite direction to the primary fault.
Antiwhirl BitA drill bit that, by its cutter placement, causes the bit to be forced against the side of the hole.
Anvil (perforating)The strike plate over a TCP, drop-bar firing system.
AOFSee Absolute Open Flow. The maximum rate that a well can produce at the lowest possible bottom hole pressure (usually figured with a gas gradient).
AOFPAbsolute open flow potential.
AORAuthorized over-run.
APBAnnular pressure build up.
APDApproved permit to drill.
APD (DOI)Application for Permit to Drill.
APEArea petroleum engineer.
APEAuthorization for expenditure.
ApertureThe unobstructed opening size (diameter, length and width, or other shape factor).
APIAmerican Petroleum Institute.
API Fluid LossA standard fluid leakoff test published by API.
API GravityThe relative density of a hydrocarbon based on a scale of degrees API. Density in g/cc = (141 / (131 +API)).
API MonogramA stamp indicating that the item is manufactured to API specifications.
API RPA recommended practice published by the API.
API UnitThe unit of radioactivity used for natural gamma-ray logs.
Apparent ResistivityResistivity recording where the measured value differs from the true or defined state by the influence of the mud column, invasion of a zone by fluids, or wellbore anomalies.
Apparent ViscosityThe viscosity at a given shear rate and a given temperature.
Appraisal WellAdditional wells drilled after a discovery, to confirm the size of a hydrocarbon deposit. Normally used to run buildup tests, drill stem tests, top and bottom of formation, gather core or fluid samples or other evaluations.
APRAnnular pressure relief valve. Used in reverse circulating to prevent pipe collapse.
APRTrademarked name for an annular pressure response valve – for a DST string.
APRVAnnular pressure relief valve.
AQLAcceptance quality level.
AquicideA relatively impermeable stratum that does not transmit water fast enough to supply a well.
AquiferA water containing formation that may or may not be directly connected to the hydrocarbon bearing zone. A connected aquifer may or may not offer pressure support to the pay.
AquitardA geologic formation through which no water flows. It may be an effective seal to the movement of water.
ArchA large, load supporting formation that may serve to reduce the total overburden load on a pay zone. These formations may cover hundreds of square miles over a basin. A second use is as a semi-stable structure of sand grains around a perforation or other opening that keeps sand from flowing so long as the flowing pressure holds the arch in place.
ArcheanAn eon of geologic time extending from about 3.9 billion to 2.5 billion years ago.
Archie CorrelationEmpirical relationships between the formatu=ion resistivity factor, the porosity, water saturation and the restivity of the fluid in the pore in clean, granular rock.
Archie EquationAn empirical relationship between the formation resistivity, F, and porosity, ?, in which F=1/?m, where the porosity exponent or cementing factor, m, is a constant for a particular formation. Typical m’s are 1.8 to 2.0 for consolidated sandstones and 1.3 for poorly consolidated sandstones.
Area of influence (of a well)The area surrounding a well within which drawdown and production has changed the saturation and energy of the system.
Area Open To FlowThe flow area generated by perforations across a zone of interest. Typical calculated perforation entrance hole areas are 1% to 6% of the pipe body. Used in pressure drop calculations.
Area-to-Volume Ratio (mineral)The area of the surface of a grain to its physical volume.
Area-to-Volume Ratio (pore/frac volume)Exposed area of a pore or fracture to the volume of fluid in the pore or fracture.
ArenaceousSand particles, 0.625 to 2 mm on the Udden-Wentworth scale.
ArgillaceousRocks or substances composed of clay minerals, less than 0.625mm, or having a high proportion of clay in their composition such as shale
ArkoseA sandstone containing 25% or more of feldspar, usually derived from igneous rock.
ArmorShielding over a cable or other device that needs to be protected from crushing.
Aromatic (chemical)Describing members of a family of chemicals with a ring structure of carbon chains. Normally xylene, toluene, etc. Benzene is a aromatic but is not used.
Arrest Marks(failure/crack development)
ArryoA steep sided gulley in arid areas that carries runoff, usually at high velocities, for very short times after a rain.
Artesian WaterWater that is overpressured and may rise above the formation.
Artificial LiftOne of several methods that provide pressure assistance to increase flow from a well. The most common systems lighten (decrease density) of the flowing fluid (gas lift), or remove all or part of the liquid head from the reservoir (beam and electric submersible pumps).
ASMEAmerican Society of Mechanical Engineers.
AsphAsphaltene.
Asphalt or AsphalteneRing compound materials in the oil composed of carbon, hydrogen, sulfur, nickel and other trace materials. Asphaltenes are mostly very small platelets (35 A) suspended by micelles of maltenes and resins and carried through the oil. They precipitate by agglomeration as the micelles break apart on shear, mixing with acids, or other interruption of the micelle stability.
AssayAnalyze.
AssemblageThe collection of minerals that characterize a rock or facies.
Associated GasThe natural gas which occurs with crude oil. It may be free or dissolved. When it occurs as free gas, it may be called unassociated gas.
Associated LiquidsHydrocarbon condensates produced in conjunction with natural gas.
Associated ReservoirOil and gas reservoir with a gas cap. Gas production from these reservoirs may be restricted in order to preserve the gas cap energy and ultimate recovery.
AstenosphereThe weak section of soft rock in the upper mantle just below the lithosphere. It is involved in plate movement. Depth is 70 to 100 km below the surface.
ASTMAmerican Society of Testing Materials
ASVAnnular safety valve.
ATPAdvanced technology parts.
Attapulgite ClayA colloidal, viscosity building clay used in water based muds. They generate viscosity due to the mechanical interference of their straw shaped bodies.
AttenuationWhen a form of energy is propagated through a medium, its amplitude (energy level) is decreased. This decrease is termed attenuation.
ATVAll terrain vehicle.
Austenitic SteelA steel with a microstructure consisting of austentite at room temperature.
AuthigenicA clay or other mineral that was formed within the pore spaces of the rock. The material is most often formed by reaction or precipitation from connate fluids.
AuthochthonousFormations that formed in the present locations and have not been transported.
Automatic “J”A set or release mechanism where pickup or set down will release or set the tool.
AUV (subsea)Autonomous underwater vehicle.
AV (fluids)Apparent viscosity.
AV (flow)Annular velocity.
Available OverpullThe amount of unused pull capacity of a rig after picking up the entire string weight.
AW Rod ThreadA thread for tools and equipment that has three parallel threads per inch (similar to a BW thread). Used in applications of 1.75” OD thread or less.
AWGRSAlaska well’s group reporting system.
AWVAnnulus wing valve.
Axial LoadA tension or compression force, usually along the length of an object.
Azimuth (logging)In a horizontal plane, it is the angle (measured clockwise) of well path departure usually from true or magnetic north. It may also be expressed as the compass direction of the path of the well bore as measured by a borehole survey. (Note
B/DBarrels per day.
B AnnulusAn outside annulus, one out from the A annulus, usually production casing x production casing or surface casing. (Note, there may be regional differences in the A, B, C annulus designations)
B ProfileSeldom used name for a SSSV profile.
BabbittA soft metal alloy used in some seals and bearings.
BackbiteA backlash of tongs that results in a grip in the wrong direction.
Back FlowReturn flow from injection of a fluid into a formation.
Back FlushingReverse flow of a fluid, usually in a well treatment or injection well, where flow from the reservoir to the wellbore, often at high drawdown, is used to clean fluids and shallow particulate damage from the near-wellbore area.
Background RadiationThe radiation intensity existing in the environment before a specific radiation source is considered.
Back-HaulAn operation or transaction that results in movement of gas in a direction opposite of the normal flow direction in a pipeline.
Back-in (contract)A type of interest in a well or least that becomes active at a specified time or a specified event.
Back OffUnscrewing a tool or equipment. In pipe recovery, back-off of a joint precedes recovery of the upper section in a well. Common in plug and abandonment or sidetrack operations.
Back PressureA pressure caused by a restriction or fluid head that exerts an opposing pressure to flow.
Back Pressure ValveA flow control valve that provides some control when running or pulling a string.
Back ReamerA tool to enlarge a drilled hole.
Back ScuddlingReverse circulating.
Back-SideThe annulus above the packer.
Back SurgeSudden backflow of a well, usually to clean the perforations.
Back-Up Ring (seals)A ridged ring-like support next to a seal to provide higher pressure or temperature support.
Back-Up Wrench or TongThe tool that keeps the pipe string from rotating while a joint is made up.
Back WashUsually reverse circulation
BactericideA product that kills bacteria in the water or on the surface of the pipe.
Bacterial DegradationBreaking down alkanes by bacterial action. Common by psedomonis and ultramonis bacteria and other bacterial strains that digest parts of the crude oil structures. Useful for remediating oil spills or tank bottom residuals.
Bacterial Oxidation and ReductionReactions involving aerobic decay, organic matter oxidation, fermentation, anaerobic decay, etc.
Bacterial RemediationLiquefaction or break down of oily waste or clean-up of oil spills by the use of the naturally occurring oil consuming bacteria, chiefly ultramonis and pseudomonis.
Bag-OffInflatable devices in a pipeline meant to stop flow.
BafflesPlates in a separator on which the flow impinges and breaks out gas.
BailRemove solids or fluids from a well.
BailerA hollow tube with a trap door or ball seat, run on wireline, which can be used to spot or remove solid material from a well bore.
Balance PointThat point at which forces acting on pipe in a well (usually while running) are equal.
Balance Point (coiled tubing or snubbing)Static condition of the length of tubing in the well, where buoyed tube weight (well fluid sensitive) equals the well pressure acting against the cross-sectional area of the tube. The balance point does not include any frictional forces exerted by friction with the well or the stripper assembly.
Balanced PlugA cement plug, set with no downhole flow conditions, which allows temporary or permanent shut-off in a well. It takes into account the densities of all fluid columns, both in the string and in the annulus.
Balancing AgreementContractual agreement between legal parties to account for differences between chart measured quantities and the total confirmed quantities at a measuring point such as a plant. They are used to track over/under production relative to entitlements between producers; over/under deliveries relative to measured volumes between operators of wells, pipelines and LDCs.
Ball (tool operation)A steel, aluminum, brass or plastic ball pumped or dropped downhole to shift or operate a tool.
Ball CatcherA cylinder at surface to catch ball sealers before the fluid is routed through the choke.
Ball DiverterBall sealer.
Ball DropperA device that injected balls into the flowing treating fluid downstream of the high pressure pump.
Ball OperatedMechanical device activated by pumping a ball of a certain size down the tubing in the injected or circulated fluid.
Ball-OutWhen using ball sealers, to effectively shut-off the entire zone and cause pressure to rise sharply.
Ball SealersSmall, rubber-covered, hard centered balls that can seal individual perforations during a chemical treatment.
Ball ValveAny of several valves that rotate a ball with a flow passage to allow or deny flow.
Ballooning (drilling)A phenomenon in which fluids are lost to the rock during over-pressured operations, such as found in increased pressures from equivalent circulating density operations, and then flow back when pressure is reduced. This may be confused with a kick.
Ballooning (pipe)An increase in pipe O.D. as internal pressure is applied (shortens pipe) or a decrease in diameter (Reverse Ballooning lengthens pipe) as external pressure is applied.
Banana BladeA shape of a reamer blade that allow milling either up or down.
Band or BandedAn attachment strap to affix cable or capillary tube to the outside of the tubing.
Banded Iron OreA sediment with alternating layers of chert and iron rich minerals.
Bar (pressure)Pressure in atmospheres, approx 14.7 psia.
Bar (geologic)A mass of sand or other materials deposited in the bed of a stream channel.
Bar-Finger sandAn elongated lens of sand formed during distribution of sediment in a delta.
Bar HoleSmall diameter hole made in the ground to obtain a sample for the purpose of searching for a gas leak in a pipeline.
Bar-Vent (perforating)A vent in the tubing or treating string open by a drop bar used to fire a perforating gun.
BarchanA crescent-shaped sand dune with a convex face upwind and a concave face downwind.
Barefoot CompletionA very simple, open hole pay zone completion with a minimum of downhole equipment. Also called an open hole completion. The casing is usually run to the top of the pay and is cemented above the pay only.
BargeMarine vessel without its own propulsion.
BariteOne of the many forms of the barium sulfate mineral. The BaSO4 material is used in drilling mud as a weighting agent and can produce a slurry of over 20 lb/gal in water.
Barite PlugA settled plug made of particles or barite or even barite and sand that are placed to seal off a zone or the wellbore.
Barium Sulfate (scale)BASO4 scale is produced in the well and in facilities as the result of precipitation when incompatible waters (one having Ba ion and the other SO4 ion) are mixed or when the equilibrium of the flowing fluid reduced and a precipitate is triggered by over saturation or a physical upset. May also be associated with radioactivity or NORM scale when a radium or uranium isotope is part of the crystalline lattice structure.
BarrelAn oilfield measurement barrel is 42 US gallons or 5.615 ft3 or 6.28 barrels = 1 meters3. Note that reservoir barrels undergo shrinkage by the reservoir volume factor as gas escapes. Stock tank barrels are measured after gas escapes.
Barrel EquivalentA laboratory measuring scale for expressing mixtures of products used to formulate muds. One gram of material added to 350 cc of liquid is equivalent to 1 lb of material added to a 42 gallon barrel.
Barrel PumpA small, usually hand driven pump with a long dip tube used to move chemicals from drums and barrels.
Barrels of Oil Equivalent, BOEA method of equating the energy produced by a hydrocarbon gas to a standard oil measurement. One barrel of oil has about the same heat producing capacity as 6,000 ft3 of gas at standard conditions.
Barrier (NORSOK definition)One of several dependent barrier elements, which are designed to prevent unintentional flow of a formation fluid. A barrier is an envelope preventing hydrocarbons from flowing unintentionally from the formation, into another formation or, to surface. Barrier elements that make up the Primary barrier are those elements, which are or might be in direct contact with well pressure during normal operation. These elements provide the initial and inner envelope preventing unintentional flow of reservoir fluid to surface, or another zone. Barrier elements that make up the secondary barrier are those, which are or might be exposed to contact with well pressure should any of the elements described as a Primary barrier fail. These elements provide an envelope outside the Primary barrier envelope providing a second barrier preventing unintentional flow of reservoir fluid to surface, or another zone.
Barrier Coating (corrosion)A coating with a high resistance to permeation of liquids/gasses.
Barrier Coating (protective)A coating applied over a surface to prevent handling damage.
Barrier IslandA long thin sandbar parallel to shore formed by wave action.
BasaltThe most common volcanic rock. Usually fine grained.
Base FluidThe starting fluid for a pill or a treatment. Before additives.
Base GasThe gas required in a storage reservoir to cycle the working gas volume.
Base ManagementThe efficient delivery of proved developed reserves through excellence in Reservoir, Well and System management.
Base MapA map containing boundaries, locations and survey points.
Base PipeThe inside pipe of a sand screen or other equipment on which other equipment or parts are added.
Basement RocksUnproductive rocks, usually igneous or metamorphic, at the bottom of a sedimentary rock sequence.
Basic Sediment and Water or BS&WThe solids and water entrained in crude oil.
BasinA large area with a general containment and an often thick accumulation of rock.
Basket or Basket SubA device used to catch debris in the wellbore. Often a part of the string.
BaSO4Barium sulfate.
BAST (DOI)Best And Safest Technology.
Batch MixingMixing a specific volume of a treating fluid in a properly sized tank – as opposed to mixing-on-the-fly.
Batch Treating (chemical treating)Slugging a chemical such as a biocide or a corrosion inhibitor in high concentration to accomplish either placement or super concentrated treating.
BatholithAn irregular intrusion of an igneous rock into another rock.
BathymetryThe study and mapping of ocean floor topography.
Battery (fluid treating)The separation facilities.
Baume (density)A density scale used in mineral acid strength measurement.
BauxiteA sintered aluminum based proppant with very high strength, 3.2 g/cc density and high abrasion characteristics.
BayriteA clay-based drilling mud gelling agent.
BblA Standard Oil measure of 42 gallons, originally known as a blue barrel and abbreviated bbl. 0.16 m3.
Bc (drilling)Bearden units of consistency.
BcfBillions of cubic feet.
Bead TracerAn isotope tracer in a bead with the same density of the flowing fluid that is used to track fluid flow rates and therefore fluid entry and exit points along the wellbore.
Beam PumpAn artificial lift system, common to low pressure, lower rate oil wells, with a plunger type bottom hole pump operated from the surface by a rod string.
BeanA flow restriction common in downhole chokes, surface chokes and some SSSVs.
Bean-Up StrategyAn engineered sequence of choke settings in the start-up of a well to apply stresses in the formation in a manner that will strengthen the formation and avoid failure.
Bearden Unit of ConsistencyAn estimation of the pumpability of a slurry. Has no direct correlation to viscosity.
Beach Marks (failure/crack development)Characteristic markings (ridges, tears, risers, etc.) on fracture surfaces after fatigue crack of fracture propagation (also known as clamshell marks, conchoidal marks and arrest marks).
BedA subdivision of the classification of a sequence of rocks. A bed usually has similar lithographic features and is separated from other groupings by recognizable boundaries.
Bed FiltrationA build-up of particles on the upstream side of a filter that improves the filter’s ability to remove particles from fluid (will also raise the differential pressure across the filter).
Bed LoadThe sediment that moves slowly along the bottom of a river channel.
Bed RockThe first solid rock under loose sediments.
Bed WrapThe innermost wrap of coil or cable on a spool or reel.
Bedding PlaneSurface separating layers in a sandstone. Usually bedding planes mark the transition of the particle transport event. An accumulation of minerals or other materials laid down at the time of rock deposition or generated by reworking, that may create significant vertical permeability barriers in a sedimentary rock.
Behind Pipe ReservesBehind-pipe reserves are expected to be recovered from zones in existing wells, which will require additional completion work or future recompletion prior to the start of production.
BelchingFlowing slugs of material.
Bell NippleA funnel shaped pipe at the top of the casing that guides tool string entry and may have a side port for fluid pumping.
Below Rotary Time (drilling)A time that reflects the slide time in which the pipe is not rotating and drilling.
Belt EffectAdded friction in a deviated well as wireline or coil rubs against the top of the deviated section as the tube or cable is pulled out of a well.
BenchmarkA selected reference point for comparing performance.
Bend RadiusRadius of curvature of flexible pie measured to the pipe centerline.
Bending Cycle (coiled tubing)Cycling coiled tubing from a yielded position, through a transition region, and back again. Running coiled tubing from the reel into a well and back to the reel involves six bends or three cycles.
BeneficiationA chemical process that changes the state of a clay or other mineral to make it meet specific performance levels.
Bent SubA short section of a tool or pipe that is formed at an angle or is modified downhole by a motor to assist in entering deviated wellbores or drilling off the path of the wellbore.
BentoniteA reference to colloidal clay (generally montmorillinite or smectite), generates plastic viscosity due to clay behavior, size and electrostatic layer. A slurry of which used for P&A Purposes will weigh no less than 9 ppg.
BenzeneAn aromatic (cyclic or ring structure) compound, present in very minor quantities in many crude oils.
Benzoic Acid FlakesA common diverter. It can sublime, or go directly from a solid to a gas.
Berea SandstoneA quarried sandstone with from 4500 to 9000 psi UCS, used commonly in laboratory flow testing.
Bernoulli’s EquationThe equation is used in the design of chokes and explains the manner in which pressure in the body in the body of the choke, downstream of the first pressure drop, is lower than the eventual recovery pressure at the end of the choke.
Beta ParticleAn electron emitted with high energy and velocity from a decaying nucleus.
Beta Factor (flow)A correction factor for the Darcy Equation to account for changes in pressure and fluid saturation along a fracture.
Beta Rating (filtration)A conditional ratio requirement on a filtering system that compares the number of particles of a certain size in the unfiltered and filtered fluid. A beta rating of 1000 at 5 microns means that there is one particle of 5 micron or greater size in the filtered fluid for every 1000 particles of 5 micron or greater size in the unfiltered fluid.
Beta Wave (gravel packing)The returning wave of gravel after the alpha wave when packing a well over about 55o deviation.
BFBase flange.
BFEBase flange elevation.
BGBell guide.
BH (perforating)Big hole charge.
BH (well position)Bottom hole.
BHABottom hole assembly.
BHCIPBottom hole closed in pressure.
BHCPBottom hole circulating pressure.
BHCSBottom hole compensated sonic.
BHCTBottom hole circulating temperature.
BHFPBottom hole flowing pressure.
BHFTBottom hole flowing temperature.
BHGBottom hole gauge.
BHIBaker Hughes INTEQ.
BHIPBottom hole injection pressure.
BHLBottom hole location.
BHPBottom hole pressure.
BHpBrake horsepower.
BHPIBorehole pressure integrity.
BHSBottom hole seismic.
BHSIPBottom hole shut-in pressure.
BHSTBottom hole static temperature.
BHTBottom hole temperature.
BHTPBottom hole treating pressure.
BHTVBottom hole televiewer – a sonic caliper tool, not a television.
BholinA specialized viscosimeter.
BHSBottom hole sample.
Bias WeldA weld technique on diagonal cut strips of steel, superior to the butt weld process for joining flat strips of metal together before rolling into coiled tubing.
BiCBest in Class.
BicarbBicarbonate of soda, used in acid neutralization operations.
BicarbonateA compound containing the HCOO- ion.
Bi-Center BitA bit that, when rotated, drills a hole larger than its diameter.
Bi-Directional ValveValve designed for blocking the fluid in upstream and downstream directions.
Big Hole Charge (perforating)A perforating charge with the liner shaped to create a large entrance hole but a shallow penetration. See Deep Penetrating Charge.
Bi-Metal CorrosionA type of corrosion found when dissimilar metals are joined. One part becomes the cathode and the other the anode where accelerated corrosion may be seen.
Binder (coating)The nonvolatile portion of a coating.
Bingham PlasticA rheological model used to describe flow in some fluids. Bingham fluids have a linear shear stress, shear-rate behavior after an initial shear-stress boundary has been crossed. Plastic viscosity or PV is the slope of the line. Yield Point is the threshold.
BioaccumulationA test measuring the concentration or build-up of potential harmful chemicals in a living organism.
BioaugmentationRemediation technique that introduces natural hydrocarbon digesting bacteria and materials such as enzymes to remove hydrocarbons from soil, water or even air.
BiocideA chemical or treatment that bills bacteria.
BiodegrationBreakdown of a heavier oil to a lighter hydrocarbon by bacterial action.
Biogenic GasBacteria generated natural gas, found at shallow depths and in many water wells. Usually contains C14 isotope. See also thermogenic gas as a gas that has a biological origin but has been modified from the original organic state by time at temperature and other effects to produce a gas with no C14.
Biogenic Source (sedimentary rocks)Rocks such as coal resulting from decomposition of animal or plant deposition.
Biogenic TheoryA theory of petroleum formation in which the petroleum is thought to have originated from plant and animal material that has undergone transformation from deep burial.
Biological MarkerCompounds found in petroleum or rock extracts that possess a carbon chain or skeleton that contains a link with a natural product. Common biomarkers in petroleum include isoprenoids, triterpanes and steranes.
BiomassAny organic material.
BiophasicThe simultaneous flow of two immiscible fluids.
BiopolymerWater soluble polymers produced by bacterial action on carbohydrates.
BiostratigraphyA segment of geoscience where fossils are used to date or identify a reservoir.
BiotA theory of acoustic propagation in porous and elastic media that taken into account fluid behaviors.
Biot’s ConstantDescribes the relationship between pore pressure and stress
BioturbationReworking of the sediment by burrowing animals.
BioventingRemediation technique that provides air to increase bacterial growth.
BirdA device with moveable vanes attached to an under water seismic streamer.
BitA drill bit, commonly either a roller cone, button bit, PDC, diamond or drag bit, used with a rotary string or a mud motor to drill through rock.
Bit BreakerA heavy plate that can hold the bit in the rotary table to make or break it from the drill string.
Bit RecordA record of bit run, depth, rate of penetration, etc., in a wellbore.
Bit SubA short section inserted between the drill bit and the drill collar.
Bit Weight (drilling)The applied downhole axial force component from the string weight.
Bit Whirl (drilling)The motion that a bit makes when it does not rotate about its center. This may manifest itself in out of round holes and severe bit damage. Generally a poor drilling performance.
BitumenPyrogeneous, essentially non reactive, hydrocarbon. Most bitumen is not considered as movable through the reservoir under normal conditions of flow unless heated.
Bituminous CoalA soft coal, intermediate in coal development, containing 15 to 20% volatiles.
Bituminous CoatingAn asphatic or tar based protective surface coating.
BJByron Jackson Service Company.
BKBBase Kelly bushing.
BLBalance line.
Black OilA traditional crude oil, containing alkanes (straight carbon chains) of C5 to C30+ liquids.
Black ShaleAn in determinant term generally meaning a shale with a higher organic content than a brown or gray shale.
Blaine FinenessA measure of the particle size of a cement.
BlankAn unperforated piece of casing or tubing in an otherwise perforated section. Used for isolation.
Blank OffTo close in the end.
Blanking PlugA plug run to seal off tubing.
Blast JointAn abrasion and erosion resistant tube that is run where ever direct sand impingement is a problem.
Blasting CapAn initiating or detonating device in an explosive.
Bleed OffTo vent or drain of fluids from a pressured well.
Bleeding CoreA permeable core from which hydrocarbon escapes without differential pressure application.
BlenderThe device that takes in fluid feed, mixes in sand and then outputs to the pump truck.
Blind BoxA flat bottom, short steel tool run on wireline to tag the surface of water or solids in the well. It is nearly the drift diameter of the tubular.
Blind FlangeA flange plate without an opening, normally used as seal-off assurance over an unused line.
Blind NippleNipple that can be blocked off from formation pressure and give a false pressure measurement.
Blind PoolAn oil and gas partnership that has not committed to a specified project at the time of amassing capital.
Blind RamsThe ram sections in a BOP that are used to close against each other and isolate the well when no pipe is in the well.
Blind ZoneA layer of rock that cannot be detected by seismic or in logging where the recorded resistivity is too low..
Blinding (screen)Obstructing an aperture or opening by particles or debris.
Blistering (elastomer)A surface deterioration caused by gas trying to escape too rapidly from a elastomer and tearing the surface of the material.
Blistering (steel)Surface corrosion associated with gas adsorption.
BLMUS Bureau of Land Management.
BLM (wireline)Braided line measurement
Block (flow)An obstruction to flow, either partial or full.
Block (lease)A large geographical lease area that may contain separate structures, proven fields or other interests.
Block (rigging)A pulley (sheave) or set of pulleys, mounted in a housing. The blocks on a rig are the crown (stationary) block at the top of the derrick and the traveling block.
Block FaultA set of formation blocks, separated by normal faults into different elevations.
Block SqueezeA cement squeeze into a area of perforations. Often done initially over the frac pressure.
Block ValveValve that blocks flow into the downstream conduit when in the closed position.
Blooie LineA straight through flow line from the wellhead to a flare pit. Often used in diverting flow during a well control incident.
Blow DownTo release gas pressure. In a reservoir, blow down is often after the oil recovery phase has been complete and the majority of the gas from the gas cap needs to be recovered.
BlowdyFree gas separating from the liquid at the bottom of the separator. Generally indicates poor separator performance.
BlowoutAn uncontrolled release of fluids from a well.
Blowout Preventer or BOPA conditional surface pressure barrier often consisting of a set of hydraulically operated rams containing equipment designed to grip pipe, seal around pipe, shear off pipe or seal an open hole during drilling or a workover. It may also contain an annular preventer.
BLPDBarrels of liquid per day.
Blue GasGas volume that separates from produced water.
BMBenchmark.
BML (subsea)Below mud line.
BMPBest management practice.
BMTBase management team
BMXBase management excellence.
BoFormation oil volume factor.
BOCBase operations camp.
BOD (design)Basis of design.
BOD (reaction)Biochemical oxygen demand.
BodyAny portion of the wellhead or tree that contains wellbore pressure.
Body Lock RigLocks slips, mandrels or cones in place in a downhole tool.
BOEBarrels of oil equivalent. A method of equating the energy produced by a hydrocarbon gas to a standard oil measurement. One barrel of oil has about the same heat producing capacity as 6,000 ft3 of gas at standard conditions.
Boiling PointThe temperature at which the vapor pressure of the liquid is equal to the pressure exerted on it by the surrounding atmosphere.
Boll Weevil (various)A solid hanger or test cup in a BOP. A retrieval plug attached to drill pipe. An inexperienced worker.
BOMABall out mud acid.
BombA thick walled pressure container of pressure measuring instruments or a sample container.
Bomb HangerHanger for bottom-hole pressure recorder (bombs).
BondThe level of adherence of one substance to another.
BonnetThe section of the valve housing that covers the stem and protects the seals.
Bonus Money (contract)Any funds paid to a mineral owner in addition to least of royalties.
Booster CapA detonating cap between two detonating cords in a series of perforating guns.
Booster Pump (pipeline)A pump located along the length of a pipeline to raise the pressure and overcome friction or elevation losses.
Boot SubA device run in the drill string just above the mill to catch cuttings.
BOPBlow out preventer.
BorateA crosslinker for guar based gels.
Borax LoggingA test technique using an injected solution of borax and a detection tool to spot channels.
BoreThe inside diameter of a tool or pipe.
BoreholeThe drilled hole.
Borehole Compensated SonicA log that measures the interval transit time for a compression wave to move a unit of distance, usually one foot.
Borehole TeleviewerA sonic caliper, developed in the late 1960’s, which generated a sonar picture of the wellbore.
BOSSBall operated shear sub.
BOTBaker Oil Tools.
Bottle NeckA restriction in a flow path.
Bottom Casing PackoffThe seal in the annulus between a hanging pipe and the next pipe outward.
Bottom Hole Assembly or BHAThe equipment or tools at the bottom of the tubing or drill string. The BHA is changed to achieve a certain result.
Bottom Hole ChokeA restriction in a profile near the bottom of the well that allows some gas expansion and holds a backpressure on the formation. Rarely used, but considered for hydrate control.
Bottom Hole Gas SeparatorGas anchor or a separator used in front of a pump to deflect most of the free gas to improve pump efficiency.
Bottom Hole Pressure or BHPThe pressure at the bottom of the well. In a producing well the BHP may be the bottom hole flowing pressure or the bottom hole shut-in pressure. In a drilling or workover environment, the BHP is exerted by the column of fluid in the hole.
Bottom Hole SamplerA tool that takes bottom hole samples of fluids or solids.
Bottom Hole TemperatureEither static (non circulating, non flowing and stable), flowing, or circulating) – temperature at the bottom of the well.
Bottom OutReach final drilling depth.
Bottom PlugIn cementing, the first plug pumped in cementing with the two plug system. It isolates the mud and cement slurry and allows passage of the cement slurry when the plug “bumps” or reaches the float shoe or float collar. It is hollow with a diaphragm that is ruptured by pressure.
Bottom Shot DetectorA device in a perforating gun that signals through a delayed shot or sound that the detonating cord has fired to the bottom of a gun.
Bottoms UpCirculating the bottom hole fluid to the top of the well.
Bound Fluid LogAn NMR log that measures bound fluid volume.
Bound WaterWater that is trapped in or on the matrix minerals and cannot move.
Bow Spring CentralizerA low to moderate strength centralizer formed by arched spring-like straps of metal.
BowlA section of the wellhead or of a tool what allows slips to be inserted to hold pipe or equipment.
BoxThe female part of the connection.
Box TapAnother name for a tapered tap. Used to screw into boxed of connections.
Box ThreadsThe treats in the box or female connection.
Boycott Settling RangeThe deviation between 30o and 60o where refluxing (dropout and reverse flow) of particles and heavier liquid occurs in a lower rate well. The area in which gas bubbles may rise through fluid at 4 to 7 times that in a vertical well.
BPFormerly British Petroleum.
BP (well plugging)Bridge Plug.
BPDBarrels per day.
BPFluxA flux damage estimating system.
BPMBarrel per minute.
BPVBack pressure valve.
BRPetrobras.
Brackish WaterIndefinite term meaning water with small amounts of salt. Saltier than fresh water.
Bracelet AnodesClamshell-type rings of anodes that clamp around a pipeline.
Braden HeadAn older (actually trademarked name) for the wellhead.
BradenheadA packer or packoff installed at surface on a well that enables the use of one size pipe inside another and allows flow into or out of each pipe separately.
Braided StreamA depositional environment with several channels that may or may not be connected.
Braided WirelineA strong, braided wireline of various sizes used in retrieving tools heavier than slickline can handle. Electrical line is a braided line with a center conductor.
Brake (drilling)The main device for stopping the travel of the drawworks of a rig when running or pulling a drill string.
Branch ConnectionA pipe connection.
Break an EmulsionSeparate the emulsion into its components.
Break CirculationStart circulating fluid from a static condition.
Break-outUnscrewing a joint of pipe of part of a BHA.
Break TourTo start a work shift.
Breakout (drilling)An enlargement of the borehole.
BreakdownFracture.
BreakerA chemical added to a gel that breaks down the gellant structure.
Breaking Down (drill string)To separate the stands into single joints.
BreakthroughA flood front breaking through into a producing well.
BrecciaFragmented (not wear rounded) grains. Rock along moving faults may have this texture.
BrentA North Sea field with a light crude oil used for cost comparisons.
BridgeA blockage in the wellbore caused by a mass of particles that lock together and prevent pipe movement or flow.
Bridge PlugA permanent or retrievable plug set typically on wireline to isolate a section of the well.
BridgingCollection of materials, usually from the formation that interlocks at some point in the well, often in the annulus and may stop flow or stick the pipe in place.
Bridging MaterialFluid loss control material that bridges against the leakoff site.
Bridle (beam lift)The wire rope attachment of the horses head to the polish rod on a beam lift pump jack.
Bridle (logging)The insulated, downhole end of a logging cable.
Bright SpotA specific seismic reflection that may indicate gas.
Bright WaterA water control product.
BrineA mixture of water and a soluble salt. Most common brines are sodium chloride NaCl, potassium chloride KCl and calcium chloride CaCl2. Brine densities may range from 8.33 to > 19 lb/gal (1 to >2.28 g/cc). The USGS definition of a brine is a salinity of more than 35,000 mg/L (after USGS, 1984).
Brinell HardnessA measure of the hardness of the material, generally measured by pushing a small ball into the surface and measuring the force used to displace the ball to a set depth.
British Thermal Unit or BTUThe amount of heat input required to raise the temperature of one pound of water by 1oF at water’s maximum density at 39oF. It is approximately equal to 1 kilojoule.
Brittle FractureA fracture created with little or no plastic deformation.
BroachA device used to reround slightly collapsed tubulars.
Broaching (flow)Venting of fluids to surface through channels in cement or behind pipe (well control barrier failure) or unintended fracturing into a adjacent formation.
Brookfield RheometerA viscosimenter use for some fluid measurements, particularly when solid suspension properties are needed.
BrownfieldA mature field on decline or in the final stages of productive life.
Brownian MotionIrregular motion of colloidal sized particles when suspended in a fluid. The effect in simplest terms is caused by thermal driven motions.
BRT (drilling)Below rotary table.
BSBasic Sediment and Water or BS&W
BS&WBasic Sediment and Water. The solids and water entrained in crude oil.
BSIBritish Standards Institute.
BSRBending strength ratio.
BtBBeyond the best.
BtBcpBeyond the best common process.
BTMSBottoms.
BTUBritish Thermal Unit.
BTXBenzene, toluene, xylene.
BUBusiness unit.
Bubble FlowFlow of liquids enabled by the rise of gas bubbles in a well.
Bubble PointThe pressure at which gas begins to break out of an under saturated oil and form a free gas phase in the matrix or a gas cap.
Buck UpTo tighten a connection.
BucklingThe deformation of pipe in compression as it moves from straight to sinusoidal to helical shapes in the hole. Usually in the elastic range.
Buckling PointThe point in the well or the weight applied where the pipe buckles (sinusoidal bending) and stops or significantly slows during pipe running in a horizontal well.
BufferA chemical used to keep the pH in a certain range without extremes of high or low pH.
Build AngleThe angle of the inclination in the kickoff section when describing a deviated well.
Build RampThe rate of increase of the deviation of a well.
Buid SectionThe part of the wellbore that is changing deviation, usually building toward a maximum deviation angle.
Bulk DensityThe density of a rock as it naturally occurs (as compared to specific density of the grains). Includes the pore structure.
Bulk Modulus (K)Applied stress over change in volume.
Bull PlugA screw-in plug, normally used at the bottom of a string if no fluid entry is desired.
Bull WheelOld term for a large, often wooden wheel, in a cable tool rig.
Bullet GunAn older perforating method where hardened steel bullets were fired from short barrels and designed to penetrate the casing, cement and formation.
BullheadingForcing fluids in the pipe into the formation at a pressure higher than the pore pressure and sometimes higher than the fracturing breakdown pressure. Used to displace a kick out of the pipe when wellbore and wellhead pressure limits permits.
Bump DownRod string stoke too long and hitting the bottom of the pump.
Bump The PlugReaching bottom with the plug during a cementing operation or fluid displacement operation.
Bunker C OilA fuel oil, normally with high sulfur and high viscosity. API gravity of about 10.5o. Also called Navey Heavy and Number 6 fuel oil.
BuoyancyThe amount of weight that is offset by lift from the fluid when the piece of equipment is immersed in the fluid.
Buoyed WeightThe weight of a string or piece of equipment immersed in the wellbore fluid. It is strongly dependent of the density of the wellbore fluid.
BUR (drilling)Build up rates, increase in well inclination during drilling.
Burn OverTo mill a piece of equipment (and often to catch it with an overshot).
Burner Capacity or Rating (flare)The maximum BTU’s that can be released from a burner while burning with a stable flame and satisfactory combustion.
Burning ShoeUsually a flat bottom mill.
BurrA raised metal lip, e.g.; around a perforation.
BurstThe internal fluid pressure that will cause the onset of pipe yield.
Burst DiskA frangible disk designed to release pressure at a specific level.
Burst RatingThe actual minimum burst pressure derated by a safety factor. The derated burst is used as a maximum when pumping.
ButadieneA butane derivative used in manufacture of synthetic rubber (elastomers).
ButaneA four carbon chain alkane, may be a liquid in the reservoir, but vaporizes as pressure is released. Part of the natural gas liquid components.
Butt Cleat (coal)A transverse fracture.
Butt Fracture (in coal)A secondary, discontinuous fracture.
Butt WeldA welded connection using two pipe ends, cut straight across and welded together with minimum circumferential contact.
Butterfly ValveA quick opening, low pressure valve, common on large openings through which solids will move, that allows high flow rate when open.
ButtonA small disc-shaped electrode used in micro-resistivity pads.
Button SlipA slip for high alloy (hard) casing.
Button-UpSecure the well or close in.
Buy Back AgreementAgreement between a host and a contract lease holder under which the host pays the contractor an agreed price for all or part of the produced hydrocarbons.
BVBall valve.
BVI (logging)Proportion of capillary bound fluids occupying effective porosity.
BW Rod ThreadA thread for tools and equipment that has three parallel threads per inch (similar to a AW thread). Used in applications greater than 1.75” OD.
BWOBBy weight of the blend.
BWOCBy weight of cement.
BWOWBy weight of water.
BWPDBarrels water per day.
BX RingA metal-to-metal seal for a flange.
Bypass (piping)A secondary flow path that goes around a repair point or other feature.
Byproduct (reaction)A product, sometimes undesirable, of a reaction designed to create something else.
C&PCased and perforated.
C/K (drilling)Choke and kill line.
C AnnulusAn outside annulus, next out from the B annulus, usually production casing x production casing or surface casing. (Note, there may be regional differences in the A, B, C annulus designations)
C FactorA selected constant in the API 14-E equation on fluid erosion.
CAAClean Air Act.
CableOne of various braided cables, with or without isolated conductance wires, used for well operations.
Cable HeadThe connection of the braided cable to the rope socket or attachment to the tool string in a wireline conveyed BHA.
Cable Tool RigAn early drilling rig that uses a heavy chisel bit on a cable, dropped vertically, to pound through rocks.
CaBr2Calcium bromide.
CaCl2Calcium chloride salt.
CaCO3Calcium carbonate.
Cage WrenchA wrench for connecting the cage of a sucker rod pump to the rod string.
Caisson (pipe)Large outer pipe, often a form or a barrier.
CakeFilter or mud cake, stranded by dehydration on the face of a permeable formation by fluid loss.
Calcareous CoatingA calcium carbonate coating.
CalciteCalcium carbonate, CaCO3. May be rock (limestone) or a scale formed from super saturated solution at the site of a chemical or physical upset.
Calcium BromideCaBr2, water soluble brine weighting agent.
Calcium CarbonateCaCO3, limestone, a common formation or when in particles, a weighting or fluid loss agent.
Calcium ChlorideCaCl2, a water soluble brine weighting agent.
Calcium HydroxideCa(OH)2, slaked lime.
Calcium OxideCaO, quick lime.
Calcium ReducersSoda ash, bicarbonate of soda, caustic soda and some phosphates. Act to reduce the effects of calcium in a fluid.
Calcium SulfateGyp or anhydrite, CaSO4.
Calcium TreatedCalcium or other divalent ion added to a fluid to inhibit shale or clay dispersement.
CalibrationComparison to a standard and adjustment to fit.
CalicheA calcium rich surface soil.
Caliper LogA recording of the diameter changes in a well made by a tool with mechanical arms that touch the wellbore or a sonic signal bouncing off the borehole wall.
CambrianA geological time from 500 million to 570 million years ago. Often signals the earliest hydrocarbon productive rocks.
CAOFCalculated absolute open flow. A theoretical figure of a wells maximum production.
CAPCapacity.
Cap A WellControl a blow out or seal at the surface after a P&A.
Cap RockA sealing formation of very low permeability that forms the top or the seal in a reservoir.
Capacitance ToolMeasures the fluids capacitance – uses the wellbore fluid as the fluid between plates of a capacitor.
CAPEXCapital expenditure.
CapillaryA small passage, usually between rock grains. These passages may have ability to absorb fluids and the pressures necessary to expel the fluids may vary inversely with capillary diameter.
Capillary ActionA complex force governing some fluid movements, especially in smaller pores. Capillary action is the result of adhesion and surface tension forces. Adhesion (or attraction) by a fluid to the walls of a pore creates an attracting (or repelling) force, which along with surface tension and cohesion, keep the fluid together. Thus in a capillary or small pore, the level of the fluid may be above or below the surrounding level in larger pores. This helps explain water blocks.
Capillary pressurePressure differential between two immiscible fluid phases occupying the same pores caused by interfacial tension between the two phases that must be overcome to initiate flow.
Capillary Pressure CurveThe pressure necessary to achieve a given non-wetting fluid saturation of a rock.
Capillary StringA very small string, usually run along the outside of the tubing and banded to the tubing. Commonly used for hydraulic control of safety valves and sliding sleeves. May also transmit bottom hole gauge data.
Capital AssetAn investment or asset that can create a produce or service that will produce income.
Capital cost or expenditureCosts that apply to building or acquiring a capital asset.
Carbide Blast JointA erosion resistant covering or main pipe that is used when tubing is set deeper than the perforations or on the long string across from the upper perforations in a side-by-side completion.
Carbon 14 isotopeOne of three naturally occurring isotopes of carbon. The half life of the C14 isotope makes it idea for determining the difference between thermogenic methane (C14 absent) and biogenic gas.
Carbon DioxideA colorless gas. Corrosive when occurring with water. An acid gas. The most common cause of corrosion in the oil industry.
Carbon/Hydrogen RatioThe ratio, either on a weight or on a molecular basis, of carbon-to-hydrogen in a hydrocarbon material. Materials with a high carbon/hydrogen ratio (e.g., coal) are solid. The ratio is useful as a preliminary indication of the hydrogen quantity needed to convert the hydrocarbon to a gas and/or liquid (AGA).
Carbon-Oxygen LogA log that measures the ratio of carbon-to-oxygen within the formation. Useful for spotting oil.
Carbon SequestrationLong term storage of carbon dioxide under ground.
Carbon SteelA low alloy steel, containing a mass fraction maximum of 2% carbon, 1.65% manganese and residual quantities of other materials. Common in pipe manufacture.
CarbonateAny of the many rocks composed of calcium carbonate (limestone) or magnesium carbonate (dolomite) or other acid soluble rocks with a common CO3-2 ionic charge. The pores may be poorly connected and matrix permeability (non fractures) are often much lower than sandstones.
Carbonic AcidCO2 and water. A common corrosion source in wells.
CarboniferousA geologic time of 290 million to 365 million years ago.
CarboPropA trademarked name for ceramic (man made) proppant.
Carboxymethyl StarchA natural starch used in drilling fluids.
Carboxyl Methyl, Hydroxy Methyl CelluloseHEC, an anionic water soluble polymer used in various fluids. Can be relatively clean breaking under the right conditions.
Carboxy Methyl CelluloseCMC, a modified cellulose polymer used in drilling fluids.
CarburizingHeat-treating process where carbon is introduced into a solid iron alloy by heating above transformation temperature range while in contact with a carbonaceous material (solid, liquid, or gas form of carbon). Usually quenched to produce a hardened outer shell.
Carried InterestA fractional working interest in an oil and gas lease that arises from a deal between co-owners.
Carrier FluidThe fluid that carries proppant or other material into the well.
Carrier rigA self propelled drilling or workover rig.
Carrying CapacityThe capacity of an injected or circulated fluid to transport a given sized and density solid into a zone or from a well.
Cartridge FilterA filtering device that uses replaceable cartridge elements to filter liquids to a required level.
Case HardenedA hardening process that hardens only the outer surface of a metal. Processes include carburizing, nitriding, flame hardening, etc.
Cased and PerforatedA completion technique where casing is cemented in the drilled hole and perforations are placed at the most promising flow points based on log interpretations.
Cased Hole Gravel PackA sand control completion that uses a screen and a gravel pack to stop formation sand production.
Cased Hole LogAny of several radioactive, chemical or physical properties logs that are run in a cased hole environment. May be conveyed by electric line, coiled tubing, slick line (memory logs) or drill pipe (LWD).
CasingOne of several strings of steel pipe in a well design that, together with cement, forms a barrier to fluid movement along the drilled hole. It is commonly at least partly cemented in the wellbore.
Casing-Annular PressurePressure in the annulus between the tubing O.D. and the casing I.D.
Casing CentralizerOne of several centralizer designs intended to keep the casing better centered in the borehole to get better cement jobs.
Casing CladdingExpanding pipe installed in production casing or tubing to seal perforation holes or leaks caused by corrosion or erosion. Can be metal or plastic.
Casing Collar LogCCL, a downhole log recording, given by magnetic deflection, of the location of couplings or other equipment.
Casing CouplingThe threaded connection, almost always upset to the outside.
Casing CrewThe personnel that specialize in handling and running casing.
Casing CutterA mechanical, chemical or explosive device that cuts the casing at a specific point.
Casing GradeA generic grade classifying the strength of the pipe
Casing GunA large perforating gun, run into a well without tubing.
Casing HangerA support that is screwed onto the casing and fits into the casing head.
Casing HeadA term that applies to the wellhead flange that forms the transition between pipe and the flange-build tree. It may be attached by threads, welding, pressure forming or lock-ring/screw devices.
Casing Head Gas and GasolineNatural gas condensate, usually C2 to C8+. The C5-C8 components condense to a very volatile liquid when the temperature decreases near the wellhead.
Casing Inspection LogUses eddy currents in a magnetic field to estimate casing thickness and anomalies.
Casing JacksA set of hydraulic lift cylinders that can be used to lift casing strings.
Casing JointTypically a length of casing with a connection on each end. Length may vary from less than 30 ft (9 m) to about 40 ft (12 m).
Casing LinerA length of casing that runs from a set point to a point part way up in the previously set casing string, but usually not to surface. A liner may be used instead of a full casing string to save money, to maintain a larger ID for well equipment or to prevent creating a trapped annular space.
Casing PatchAny of several repair systems designed to set a patch over a leak in a well.
Casing PlungerA larger plunger designed to lift fluids when flowing gas up casing without presence of tubing
Casing PointThe depth at which a casing string is set, either by design or because the mud can no longer control the pressure of the next deeper zone without adding weighting agents that would break down upper intervals.
Casing PressurePressure (intended or not) that occurs on the various outside annuli.
Casing ReciprocationMovement of casing up and down to help remove mud and replace it with cement slurry.
Casing RollerA downhole tool, commonly run on pipe to try to reform the casing after a partial collapse.
Casing RotationRotating the casing string during primary cementing to remove mud and improve primary cement bonding and isolation.
Casing ScraperA downhole tool with scraping teeth and brushes that is used to remove perforating burrs, “lipped down” areas in connection pins and remove mill scale, dried mud or cement, pipe dope and other well completion debris.
Casing SeatThe set point of the end of casing. Should be in an impermeable, stable formation.
Casing Seat TestA LOT or an FIT test (check specifics for details), a pressurized test after primary cementing to make sure the bottom most seal with the formation will handle pressures needed for drilling the rest of the well.
Casing ShoeA tapered guid shoe on the bottom of a casing string to assist in passing ledges and dog-legs in the wellbore.
Casing Shoe TestA pressure test of the casing seal, after the cement job, to the pressures necessary to safely control the pressure of the deeper zones.
Casing StringA continuous string of casing, usually cemented over at least part of its length and usually extending back to surface from the set point.
Casing Swage or BroachA hardened steel tool, commonly run on wireline, which is used to reshape the casing.
Casing TongsWrenches specifically made for making up casing joints.
Casing ValveA gas lift valve that is controlled by the casing or annulus gas supply pressure.
Casing TongsPipe tongs used to make connections.
Casing WearReduction in thickness x 100 / original thickness. Most common wear is from rotating strings during drilling.
Casing WeightThe nominal weight per foot of the casing. Heavier weight casings of the same size are necessarily smaller I.D.
CaSO4Calcium sulfate
Cast Iron Bridge PlugA drillable plug that can be quickly and reliable set to isolate a section of the well.
Cat HeadA small drum on a winch on which a hoisting cable or rope can be wrapped.
Cat LineA small hoisting rope or cable.
Cat WalkA tool assembly/staging area before the Vee Door on a rig.
Cataclastic RockPowdered rock created by crushing and shearing of tectonic movements.
Catenary RiserA subsea riser with a large “S” that allows flexing and movement of the line.
CatalystA chemical that enables or speeds up a chemical reaction without being consumed by the reaction.
CathodeThe negative site of a corrosion cell. Reduction reactions are typical.
Cathodic CorrosionCorrosion, usually of an amphoteric metal, with a basic fluid.
Cathodic ProtectionImpressed current that offsets the current produced in a corrosion cell and reduces corrosion.
CationAn ion with a positive charge.
Cation Exchange CapacityRelated to concentration of cations on negatively charged clay surfaces that, when brine is present, can be exchanged/satisfied for/by cations in the brine. The total of exchangeable cations that a porous medium can absorb, expressed in moles of ion charge per kilogram of clay or mineral.
Cationic SurfactantA positively charged surfactant, normally oil wets sands.
CATs (subsea)Connection actuation tool.
CausticA strong base chemical. Caustic soda is sodium hydroxide.
CavingsLoose formation materials that falls into the wellbore.
CavitationThe creating of a high speed, very low pressure vapor bubble that quickly and violently collapses. Very detrimental to surfaces in the near proximity. Often seen in severe turbulent flow.
Cavity CompletionA completion that uses flow to purposely increase the size of the open hole wellbore.
Cavings RockRock fragments that spall or break off the wellbore walls. Usually found as fill in the hole.
CBHFP (rock mechanics)Critical bottom hole flowing pressure; a measurement of sanding potential of the formation.
CBHTCirculating bottom hole temperature.
CBJCarbide blast joint.
CBLCement bond log.
CBMCoal bed methane.
CBNGCoal bed natural gas.
CBTCement bond tool.
CCDSTClosed chamber DST.
CCLCasing collar locator log.
CCP (completion)Cased, cemented and perforated.
CCP (compression)Gas compression plant.
CCTConcentric coiled tubing.
CD (contract)Contract demand.
CDLCompensated formation density log.
CDPCommon depth point.
CDP (rock mechanics)Critical drawdown pressure; maximum drawdown pressure for sand free rate.
CDR (flow)Chemical drag reducer.
CDR (logging)Compensated dual resistivity.
CECompletions engineer.
CECCation exchange capacity.
CELCement evaluation log.
Cell SparA Spar platform with multiple floatation sections.
CellarA concrete or culvert pipe walled section below ground that often protects and shelters the annular access valves. Also used to house the BOP’s on a drilling well.
CelloflakeA fluid loss additive for cement.
Cement (completions)Typically the Portland, silicate, and/or pozzilin, etc., mixtures used to form a stone-like permanent seal between the pipe and the formation.
Cement and Cementation (formation)Formation binding agents (calcite, clay, silica overgrowth, heavy oil, etc.) that hold the formation grains together.
Cement AcceleratorAn additive such as calcium chloride, and salt in high concentrations that speeds the set of cement.
Cement BondThe strength and adherence of the cement to the pipe and the formation.
Cement Bond LogA sonic log that determines the top of the cement column and estimates the quality of the cement bond between the casing and the formation. Works on transmission of a sound wave and identifies areas that conduct the wave and those that do not (free pipe ringing). Communication is likely if CBL>10% of unbonded mv reading. Communication is unlikely is CBL < 5% of unbonded mv reading and bond length > 10 ft (3 m).
Cement ChannelA channel in the cement, usually caused by poor displacement of drilling mud.
Cement DensityThe specific gravity of the set well cement, generally about 3.15 for Portland cement. Do not confuse with slurry density.
Cement PackerA recompletion technique in which cement is injected down the tubing and through a punched hole in the tubing to form a 300 to 500 ft thick seal between the tubing and the casing, often far about the bottom of the well. Useful for isolation of upper zones to shut-off unwanted fluids or separate producing horizons.
Cement PlugA plug of cement set by various methods that plugs the tubulars or the open hole.
Cement PoisonA material that stops cement from setting.
Cement Pump TimeThe time after mixing of the cement slurry before the cement becomes so viscous that it cannot be pumped.
Cement RetainerA temporary set plug to allow cement work above the tool. It is drilled out after the cement job.
Cement RetarderA chemical additive such as lignosulfonate, salt in low concentration or most muds that slow down the cement.
Cement Slurry DensityThe specific gravity of the unset cement slurry as mixed at the surface. Does not account for water loss to leakoff or segregation before the cement sets.
Cementing HeadA device attached to the top of the casing that allows connection of the flush and cement lines and allows plugs to be dropped. Special models may allow the cement to be rotated during cementing.
CementationThe material in the rock between the grains that binds the grains together.
Cementation ExponentThe porosity exponent, m, in the Archie Factor.
Cementing HeadThe connection between the wellhead the lines from the cement trucks. A rotating head (uncommon except on top-drive rigs) allows the pipe to be rotated during the cement placement to assist in displacing mud and preventing channels.
CenozoicA geologic epoch from today to 65 million years ago. Few major hydrocarbon bearing strata unless fluids have migrated to a trap from older source rocks.
CentipoiseViscosity measurement, 1/100th of a poise.
CentralizerA bladed or bow spring tool that helps center tools or pipe in the wellbore.
Centrifugal PumpPump with an impeller or rotor that spins in a housing and the drag forces on the fluids cause them to flow.
CentrifugeA device that separates materials by density through a centrifugal motion.
CEQCouncil on environmental quality.
Ceramic (frac)Usually ceramic (man- made) proppant.
CERCLAA US Law – Comprehensive Environmental Response, Compensation and Liability Act of 1980.
CertsCertificates, usually on physical or chemical properties (e.g., MSDS Sheets).
Cessium AcetateA lower toxicity weighting agent for brine.
Cessium FormateA lower toxicity (than Zinc) weighting agent for higher density brines.
CETCement evaluation tool.
CFCompletion fluid.
CfdCubic foot per day.
CFD (fluids)Computational fluid dynamics.
CFECore flow efficiency.
CFPPCold filter plugging point.
CFHCubic feet per hour.
CFRCritical flow rate.
CGConnection gas, mud logging term.
CGACanadian Gas Association.
CGFCentral gas facility.
CGRCondensate gas ratio.
Chain TongsA type of hand or power operated wrench used to make up connections in pipe.
ChalcedonyA cryptocrystalline form of quartz with waxy luster.
ChalkAn often highly porous but lower permeability carbonate composed of fine grained marine sediments such a coccoliths.
Chamber LiftA type of gas lift that uses the tubing-casing annulus for accumulation of produced liquids between lift cycles.
Channel (cement)A flow area in the cement from inefficient cementing displacement of the drilling mud.
Channel (formation)An interconnected pathway through the matrix of the rock or an open fracture or other feature that connects a reservoir and the wellbore.
ChaseTo run a pipe through a wellbore to determine if it is open.
ChatAny of many types of conglomerates.
CheaterA length of pipe used on a wrench to extend the leverage. (HSE risk).
Check Shot Survey (seismic)Determines formation seismic wave velocities over specific intervals. Measurement is made of travel time from surface to downhole geophones.
Check TripA trip back to bottom after a cleanout or other operation, to check for clearance.
Check ValveA valve that only allow flow in one direction.
Checking (corrosion)Slight breaks in a surface coating that do not penetrate to the underlying surface.
ChelantA chemical that can tie up the molecules of an element, such as iron, and keep it in solution past the point where it should naturally precipitate.
Chemical cutterA pipe cutting tool that uses boron trifluoride sprayed through a nozzle at very high velocities.
Chemical DissolutionReactions involving the rock and connate fluids in which parts of the matrix are filled by scale or mineral growths or removed and become high permeability flow channels.
Chemical FloodingOne of several methods involving injecting a chemical into a formation to improve the production of hydrocarbon. May be from an injection well to a production well or injection into a producer with a soak period before recovery.
Chemical ResistanceThe ability to resist chemical attack.
Chemical SedimentSediment formed by precipitation from water, e.g., salt from dehydration and scales.
Chemical TracingUsing water soluble chemicals to track the flow channels in the reservoir.
Chemical TreatingVarious chemical treatments including acidizing.
Chemical WeatheringAll the chemical reactions that act on rocks to produce stable minerals.
CHEMRAZAn elastomer used in seals.
CHFRCased hole formation resistivity tool.
Cherry Picker (fishing)An overshot fishing tool with a bottom cutter surface to allow milling the top slips or all the slips prior to retrieving a packer.
ChertA hard, silicate sedimentary rock. Similar to flint, but with less ordered structure. A cryptocrystalline form of quartz.
CHESSChemical hazard employee safety system.
Chevron packing (seal)A V-shaped seal very common on moving and static seals.
Chevron Pattern (corrosion)A V-shaped pattern on a fatigue or brittle-fracture surface. The pattern may also be one of straight radial lines on round specimens.
CHFPCased hole frac pack.
CHGPCased Hole Gravel Pack.
ChicksanA surface treating line connector that allows quick, pressure tight bends in high pressure pipe.
Chisel BitA device with a single bit running the width of the hole. Also called a dove-tail bit.
CHKChoke.
CHKS (rig up)Chicksans
CHKSBack flow checks.
CHLCased hole log.
Chloride Stress CrackingCracking of a metal under combined action of tensile stress and corrosion in the presence of chlorides and an electrolyte (NACE). Starts at a pit, scratch or notch. Crack proceeds primarily along grain boundaries. The cracking process is accelerated by chloride ions and lower pH.
Chlorinated HydrocarbonsA chlorine atom substituted onto an alkane (hydrocarbon chain). These materials have been identified as refinery catalyst poisons.
Chlorine DioxideClO2, a free radical compound especially useful in killing bacteria in waters. It is a powerful biocide that dissolves biomass cell walls. It is nearly impossible for bacteria to develop immunity against ClO2.
Chlorine LogA cased hole log, using gamma ray capture by chlorine atoms, that helps estimate the salinity or water behind pipe.
ChloriteA clay type marked by high iron content. Usually not water sensitive and only slowly acid soluble. Very occasionally existing as fragile, free standing rims following sand grain dissolution over geologic time.
ChokeA device used to create a controlled pressure drop and allow some expansion of the gas. A choke holds a back pressure on the well fluids, controlling the expansion rate of the gas. It is useful for optimizing natural gas lift in oil wells with sufficient gas to flow naturally or in some gas lifted wells.
Choke BeanA flow tube for a fixed bean-type choke.
Choke LineA drilling and workover pressure control device. A line that attached to the BOP stack and through which kick fluids can be circulated when the BOP is closed.
Choke ManifoldA set of valves and/or chokes used to control drilling fluid returns on a drilling well or, in a few cases, used to control flow from a high rate well where the chokes may be in parallel or series.
Choke TrimPressure-controlling choke components, usually replaceable, expendable pieces.
CHOPSCold heavy oil production with sand.
Christmas TreeThe control sections that sits above the basic wellhead. It may contain hangers, master valves, annular valves, wing valves, and gauges or pressure, flow rate or monitoring measurement equipment.
ChromatogramAn analysis of hydrocarbons from a gas stream in order of molecular size.
Chrome TubingOne of several steel compositions for tubing that uses chromium for increased resistance to CO2.
Churn FlowA flow regime in which the rising gas bubbles have enlarged.
CIBHPClosed in bottom hole pressure.
CIBPCast iron bridge plug.
CID (subsea)Chemical injection for downhole.
CIMCanadian Institute of Mining
CIRCCirculate.
CirculateEstablishing flow down the tubing or drill pipe and up the annulus. Reverse circulating involves injecting down the annulus and up the drill pipe.
Circulate and Weight MethodA kick control method that circulates the well immediately and mud weight is brought up gradually. (Concurrent method).
Circulating PressureThe pressure generated by the mud pumps and, in normal circulation, exerted on the drill string.
Circulation ChargeSee Puncher Charge.
Circulation Control ValveValve normally placed across the circulation point to allow isolation of the tubing strings or tubing/casing during production.
Circulation LossesLosses for any reason while circulating the well.
Circulation SqueezeA secondary or repair cement method using upper and lower perforations and a packer set between. Circulation is established with water and mud remover chemicals to clean the channel. Cement is circulated with a set volume pumped, then the packer is released and pulled above the zone. The cement is displaced from the tubing. A secondary squeeze may be done.
Circulation SubA sub in the circulating string with a side port that can be opened remotely to allow circulation from that point.
Circulation ValveA downhole valve in the treating string, operated by pressure pulsing or wireline that will allow the annulus to be circulated.
CIT (corrosion)Corrosion inhibitor treatment.
CIT (pressure test)Casing integrity test.
CIT (subsea)Chemical injection for tree.
CIT-OACasing integrity test – outside annulus.
Citric AcidA weak organic acid that serves as a chelating agent for iron (slows iron hydroxide formation).
CIV (completion)Completion isolation valve.
CIVChemical injection valve.
CIWHPClosed in well head pressure.
CLControl line.
ClampOn Sand DetectorA brand name of a sand particle movement detector.
Clamshell Marks (failure/crack development)Characteristic markings (ridges, tears, risers, etc.) on fracture surfaces after fatigue crack of fracture propagation (also known as beach marks, conchoidal marks and arrest marks).
Class A CementConstruction grade Portland cement.
Class C CementFiner grind cement, higher early strength.
Class E and F CementsHigh temperature cements.
Class G and H CementsOilfield related cements.
ClasticA rock grain, formed somewhere else and transported into place to be part of another rock.
ClayA fine grain (<0.00015” or about 4 microns) – finely crystalline silica sheet minerals. Usually of silicate composition. In oil field terms, the most common clays are Smectite (montmorillinite), illite, kaolinite and chlorite. The characteristic for authogenic clay is to have extremely high surface area-to-volume ratio.
Clay-Bound WaterWater held in or on the surface of a clay and not free to move with other connate fluids.
Clay ExtenderA drilling additive to increase the viscosity of water based muds gelled with bentonite.
Clay FlocculationDropping suspended particles out of a fluid by agglomerating them into larger, easier separated particles.
Clay MigrationMovement of clay particles, usually after partial disintegration of the clay matrix due to absorption of water or reaction to other effects such as ions, velocity, crushing due to overburden, etc.
Clay SwellingThe absorption and modification of the clay matrix by a reactive water.
Clean Circulation (drilling)Fluids returning to the surface without cuttings or other solids removed from the well.
Clean OilOil with less than 1% water. Usually within pipeline spec.
CleanoutRemoval of fluids or solids from a well, usually by circulating.
Clear BrineA brine without suspended solids.
Cleat Fracture (in coal)A natural fracture along the cleat plane, usually parallel to max stress. Often extensive, especially in thin beds.
CLFPChoke line friction pressureClinker
ClintoptoliteA common zeolite mineral with sensitivity to some surfactants.
ClO2Chlorine dioxide, a powerful biocide that dissolves biomass cell walls. It is nearly impossible for bacteria to develop immunity against ClO2.
Close InTo shut-in a well.
Closed Chamber TestingTesting the well into a chamber open at the bottom, but closed at the surface. Fluid entering the wellbore is equal to the fluid production minus the gas volume charge. A material balance approach.
Closing RatioThe ratio between the pressure in the hole and the operating-piston pressure needed to close the rams on a given BOP design against a particular well head pressure.
Closure (fracture)The pressure at which a fracture closes. Related to the closure forces in a formation.
Cloud Point (Paraffin)The first appearance of microsized paraffin crystals in suspension in the oil.
Cluster PerforatingGrouping the perforations in small groups usually to generate multiple, regularly spaced fractures using hydraulic diversion or ball sealers (etc.).
CLW (SSSV)Control line to well communication.
CMCCarboxy methyl cellulose.
CMHPGCarboxy methyl, hydroxyl propyl cellulose.
CMIT – TxIACombination mechanical integrity test – tubing x inner annulus.
CMIT – IAxOACombination mechanical integrity test - inner annulus by outer annulus.
CMIT – TxIAxOACombination mechanical integrity test – tubing x inner annulus by outer annulus.
CMP (depth)Common mid point.
CMSCarboxy methyl starch.
CmtCement.
CMTDCable mounted tension device.
CNGCompressed natural gas.
CNLCompensated neutron log. Radioactive neutron source bombards the formation with high energy neutrons, which are slowed and captured by atoms of the formation. The low energy neutrons are reflected back to the tool and counted. The amount of neutrons returning is inversely proportional to the porosity of the formation.
COCirculate out, mud logging term.
COCarbon monoxide.
CO2Carbon dioxide.
CO2 InjectionSecondary recovery technique for oil. The carbon dioxide gas is injected and alternated with water. CO2 lowers the viscosity of most oils, but may trigger severe asphaltene and scale precipitates.
CoagulationForming a larger mass from smaller ones by collision and sticking together.
CoalSedimentary rock, often highly naturally fractured, composed of thermally modified plant remains.
Coal Bed MethaneNatural gas formed during the coalification process and trapped within and adsorbed to the coal.
Coal GasUsually methane which is adsorbed and absorbed to the high surface area of the coal.
Coal gasificationThe chemical conversion of coal to a gas.
Coal liquefactionChemical conversion of coal to a liquid hydrocarbon.
CoalescenceThe combination of bubbles or droplets in an emulsion to form larger bubbles or drops that will separate easier.
CoarseAPI designation of sand-type particles larger than 2000 microns.
CoatingA liquid, liquefiable, or mastic composition that, after application to a surface, is converted into a solid protective, decorative or functional adherent film (NACE).
Coating HolidayA break in an otherwise continuous coating.
CoccolithA marine, single celled (1 to 5+ micron) animal that is a component of chalks.
CODChemical oxygen demand.
COEControllable operating expense.
COFCAWA tertiary recovery mechanist consisting of combustion and water flooding.
CogenerationProduction of electrical or mechanical energy and heat or other power.
Coherence (seismic)A seismic comparison method. Reverse method is incoherence.
CohesionA force that holds fluids and sand grains together. The force is generated by attraction at the molecular level. Cohesion is often used to describe sand grains stuck together by a low viscosity fluid such as oil or water, although this is better explained as adhesion.
Coiled TubingA continuous reeled tube from 1” diameter to >3.5” diameter. The tubing is injected into a well via a coiled tubing unit (CTU) and can be used to unload wells with liquid, foams or gasses, logging, fracturing, etc.
Coiled Tubing CompletionA completion where CT and associated CT-mounted hardware is used as the primary completion flow path.
Coiled Tubing ConnectorA mechanical device used to join strings of CT or attach a BHA to the CT.
Coiled Tubing DrillingWhere CT is used as the primary drill string with a mud (less commonly an electric) motor to rotate the bit. Often used in underbalanced drilling.
Coiled Tubing Injector HeadThe hydraulic powered chain driven unit that snubs or strips coiled tubing into or out of a well.
Coiled Tubing UnitThe CT, reel, injector head, power pack, control unit and pressure control equipment used in a coiled tubing job.
CokeA generally insoluble hydrocarbon that has been oxidized to the point of a solid, often hard mass.
Cold Finger TestA device with a chilled probe that measures the temperature at which paraffin will precipitate of an oil solution.
Cold TreatingThe treating of an emulsion with chemicals to break an emulsion without resorting to the application of heat.
Coleman EquationEquations for deliquification of a well at operating pressures less than 1000 psi.
Collapse ChimneysA type of Karst (geologic time sink hole).
Collapse PressureExternal hydrostatic pressure that will cause the onset of pipe yielding. Heavily influenced by tension loads on the pipe.
Collapse RatingThe collapse pressure derated by a safety factor. Takes into account the effects of axial load. The formulas are only good for round pipe.
CollarThe connection or coupling on jointed pipe. It the strict sense, it is the section with female x female connections.
Collar LockA profile that can be set by wireline in the space in an API type coupling.
Collar LogA magnetic inflection log, run on wireline that is principally used to locate the depth of threaded pipe connections and other masses of metal.
Collar StopA wireline set plug without a profile. It is set in a coupling and grips with packer-like slips.
CollettA mechanical device used for holding or locking where segmented keys or fingers are pushed into a recess to hold, anchor or grasp the tool.
Collett Connector (coiled tubing)A type of connector that utilizes a collett-type device for attaching a BHA to coiled tubing.
Collett LockA type of lock used in a profile.
ColliderAn explosive charge in a tool designed to sever very heavy BHA tools such as drill string collars and stabilizers. It latterly uses a focused explosive to blown the string apart. A tool of last resort.
CollisionWhen the drill bit in a new-drill well contacts an existing wellbore.
ColloidA substance with particle size so fine that it exists as a stable dispersion rather than settling out.
Colloidal SuspensionA dispersion of fine particles, held by charge or other force in a stable suspension.
Combination LogA single assembly of various logging tools.
Combination TrapA trap that has both structural and stratigraphic character.
Combustible Limits (fuel gas)The range of gas concentration in air where the fuel gas or combustible gas will ignite.
Commercial Production LevelVaries with the well – an indicator of the minimum flow rate and type of fluids that can justify completing or continuing to operate the well.
CommingleMixing production. In a well, when two or more zones are mixed to assist in economic production. In a flow line, when multiple crude source streams are mixed.
Common Carrier (petroleum)Those engaged in the transport of petroleum products.
Common ProcessA common way of working that generates and/or protects value, sets out baseline expectations, to materially impact performance, is enduring and globally consistent, and helps advance the capacity of the global organization.
CommunicationAbility to circulate or pass fluids from one chamber in a well to another.
CompactionA crushing of the matrix structure as overburden loads press down on the rock, reducing the pore space. During production of the well, the load on the matrix increases as the pore-filling fluids are removed. These loads may reduce the porosity of the rock expelling fluids from the rocks (compaction recovery of fluids). Permeability may be decreased in compaction, first by closing natural (unpropped fractures) and then by reduction of matrix perm in severe cases.
Compaction DriveA drive mechanism in a weak zone that displaces fluid by reducing the overall volume of the formation.
Company Man (drilling)The operating company representative on location.
CompartmentalizationSeparate compartments or smaller reservoirs in a larger, common reservoir that may not be in communication.
CompartmentsSegregated flow units of a main reservoir that have a poor flow connection or no flow connection to the main reservoir.
Compensated Formation Density LogA dual spacing formation density log, using two detectors at different distances from the source.
Compensated LogA well log that is designed to correct for an effect associated with the borehole.
Completion Bore Protector (subsea)A removable sleeve that covers the internals of the subsea tree during drilling operations.
Compatible BrineA brine that does not create formation damage or permeability reduction when introduced into a formation.
Completed WellA well that has been drilled, cased and cemented and is ready to produce hydrocarbons.
Completion FluidA brine, oil or gas based fluid that is used as isolation (kill, separation, inhibition functions, etc.) fluid during the completion of a well. Commonly sea water, NaCl brine, formation water, KCl brine, CaCl2 brine, etc. Oil based fluids are common where formation sensitivities with shales, clays, minerals, etc., prevent use of aqueous fluids.
Completion IntervalThe pay zone exposed to the wellbore. This may or may not be the entire pay.
Completion Technical LimitsThe maximum production or flow capacity possible by the best completion attainable.
Complex FracturingOpening up secondary natural fractures that may be orthogonal to the planar fracture. Also – networked fractures and shear fracturing.
Complex WellA well design with engineering or application challenges that are out of the ordinary.
Compliant ExpansionA term used in expandable nomenclature signifying expansion that fits itself to non-gauge boreholes.
Composite Bridge PlugA bridge plug made mainly of plastic and composite materials.
Composite LogSeveral logs spliced or overlayed to form a single group log record.
CompressibilityThe volume change of a material when pressure is applied.
Compressional WaveA P wave.
Compression-Ignition EngineA diesel engine; an engine in which the air and fuel are ignited by the heat produced on the compression stroke.
Compression RatioThe ratio of the absolute outlet pressure of a compressor to the absolute inlet pressure.
Compression-Set PackerA retrievable packer where the slips are set and the seal energized by setting tubing string weight down on the packer. Releases by picking up the string. Useful where annular pressure could unseat a tension-set packer.
CompressorA type of pump that increases the pressure of gas. Commonly used as a production rate increaser by increasing the gas pressure delivered from low pressure gas wells to enter the pipe line. The intake into the compressor lowers the wellhead pressure creating a larger drawdown.
Compton ScatteringA gamma-ray reaction in which the gamma-ray, after colliding with an electron, shifts some energy to the electron. The higher the energy loss by Compton scattering in a zone, the higher the electron concentration or density. The basis for the density log.
CONCAWEConservation of Clean Air and Water in Europe.
Concentric CompletionA multiple completion in which the upper zone flows to the surface through the annulus formed by the casing and the deeper zone tubing. Usually used only in sweet, dry gas upper completions.
Concentric OperationsAny operation where a smaller tubing is inserted through a larger tubing string. Normally done with the wellhead in place. Often done with the well under pressure.
Concentric TubingOne string inside another.
Concentric Tubing WorkoverA workover using a small diameter tubing inside the existing tubing. Usually done with a hydraulic workover rig or coiled tubing. Commonly used with a positive surface well pressure and seals on the smaller tubing in a live-well workover.
Concession (lease)A grant of access for a defined area and time period that transfers certain rights to hydrocarbons that may be discovered from the host country to an enterprise. The enterprise is generally responsible for exploration, development, production and sale of hydrocarbons that may be discovered. Typically granted under a legislated fiscal system where the host country collects taxes, fees and sometimes royalty on profits earned (SPE).
Conchoidal Marks (failure/crack development)Characteristic markings (ridges, tears, risers, etc.) on fracture surfaces after fatigue crack of fracture propagation (also known as beach marks, clamshell marks and arrest marks).
Concurrent MethodA well pressure control operation in which circulation is started immediately and mud density is brought up in steps until the well has been completely circulated to the kill weight fluid.
CondensateThe part of the hydrocarbon stream that is a vapor in the formation and condenses to a liquid after being cooled. Normally the volatile condensate has a composition of C5 to C8 and an API gravity of >40.
Condensate BankingA relative permeability effect where condensate, usually hydrocarbon, drops out of the vapor phase around the wellbore when the pressure drops below the dew point in response to drawdown or depletion. Gas rates can be severely reduced by the permeability reduction.
Condensed WaterWater condensed from gas as it is produced. Usually fresh water.
Condition the MudCirculate the well to remove cuttings and gelled mud prior to running the casing.
ConductanceThe reciprocal of resistance in direct current logging measurements. Measured in siemens (formerly mhos).
Conduction Heat TransferHeat transfer when two solids are in contact and heat passes between them – heat transport by direct transfer of energy from one particle to another.
Conductive ConcreteA highly conductive cement and coke based material used an impressed current anode.
Conductivity (fracture flow)The permeability of the pack times its width. Expressed in md-ft.
Conductor PipeThe first string of casing run, usually to keep rocks or dirt out of the wellbore. It is usually not cemented in place. It may be jetted in, driven in, drilled in or installed in an excavated hole.
Confining BedA rock layer that through either low permeability or different modulus serves as a boundary for an event such as fluid flow or fracturing.
Confining PressureVarious earth forces acting on the formation. Includes overburden.
Confirmation WellOr delineation well; a secondary well, after a field discovery well, drilled to help determine field extent, volume or potential rate.
Conformation WellWell or wells drilled to prove the formation or resources discovered in the initial or discovery well.
ConformityA surface separating younger from older rocks with no indication of erosion or other disturbance.
Confusion BlockSee impression block.
ConglomeratePoorly sorted collection of sediments, generally formed in a very high energy environment. Similar to sandstones but have much larger grains (pebbles grade 4 to 64 mm). The space between the grains may be partly or completely filled with sand grains.
ConingThe movement of a water upwards or gas downwards towards a decrease in pressure caused by producing hydrocarbons in a zone with no vertical permeability boundaries.
Connate waterThe natural brine occupying the pore spaces. Usually this water is at equilibrium with the minerals in the formation.
Connection GasThe small amount of gas that enters the wellbore when circulation is stopped to make a connection. The gas only enters the wellbore in this case when the static fluid pressure is less than the pore pressure.
Consequence (Risk)Outcome of an event.
ConsistencyA fluid’s ability to deform and flow and its general cohesion to itself.
ConsistometerA device with rotating paddles, used to check the pumpability and set time of cement slurries.
ConsolidatedAn approximate level of rock strength where sufficient cementation is present to allow the rock to remain intact during drilling and production. Often the unconfined compressive strength is greater than 1000 to 1500 psi.
ConsortiumA group of unrelated companies working on a specific venture.
Constant Choke-Pressure Kill MethodA method of killing a well where the choke is adjusted to maintain a constant casing pressure as the a water kick rises in the annulus. The method should not be used with a gas kick (will not keep a constant BHP).
ContactThe depth of the interface between the oil and water, oil and gas, or water and gas.
Contact AngleThe angle of intersection of two fluids on a given surface. Describes wetting and non-wetting behaviors.
Contaminant (cementing)Placing a material in a cement slurry (usually already in a wellbore) that purposely prevents the cement form setting so that it can be circulated out of the wellbore.
Contingency String (casing design)An “extra” string in a casing design that can be used in the event of failure to get an upper string to the correct depth.
Content (fuel)The heat value per unit of fuel expressed in Btu as determined from tests of fuel samples. Examples: Btu per pound of coal, per gallon of oil, per cubic foot of gas (AGA).
Continental MarginThe separation of emerging continents from deep sea basins.
Continental ShelfThe shallow area out from shore to a water depth of about 450’.
Contingent ResourcesThe hydrocarbons that are estimated to be potentially recoverable from known accumulations, but which are not currently considered to be commercially recoverable.
Continuous Flow Gas LiftA lift system that uses continuous injection of gas into the liquid column.
ContinuityMeasurement of a formation being present over a large area.
Continuous PhaseThe external phase in an emulsion.
ContourA curve connecting points of equal value on a map.
Contracted ReservesReserves of hydrocarbon dedicated to fill a specific contract.
Control HeadAn extension of a retrievable tool that is used to set and release the tool.
Control GasThat part of the gas stream used to actuate or operate equipment (may be rendered unusable for sale due to pressure drop, etc.).
Control LineA small diameter line, usually attached to the outside of tubing, which controls the ScSSV or other downhole tools.
Convection Heat TransferHeat transfer by gas, steam or liquid circulation. Heat transport by moving particles and the thermal energy they carry to a new location.
Convective MixingMixing created by heat transfer.
Conventional Crude OilPetroleum in liquid form capable of flowing naturally.
Conventional Energy SourcesOil, gas, coal. The source of the energy may also have bearing on the definition. Unconventional hydrocarbon energy sources include shale oil (both mature and immature), shale gas, and tight gas (ultra low permeability, usually less than 0.001 millidarcy).
Conventional GasNatural gas in a normal media, capable of flowing without other influences.
Conveyance (well work)The wireline, slickline, tubing or coiled tubing used to convey tools or equipment in a well.
COPAS (accounting)Council of petroleum accounting and shipping.
CopolymerA mixture of two or more polymers which polymerize at the same time and with some degree to linking to yield results unlike either polymer used alone.
CoreA sample of the formation, taken with a core barrel.
Core AnalysisLab work on a core sample that may yield permeability, porosity, pore size distribution, grain size, density, etc.
Core BarrelA barrel in the drilling BHA with a coring head designed to receive a rock core cut as part of core sampling operations.
Core Diameter (coiled tubing reel)The diameter of the core of the CT reel.
CorkscrewCompressional deformation of tubulars to the point where the tubing resembles a corkscrew. The condition may be temporary if the metal is not yielded past the elastic recovery point. Tubulars that are corkscrewed may be pumped through but will stick most diameters of tool strings.
CorrelateTo compare logging and core or other information and account for discrepancies.
CorridorA strip of land or water through which a concession is obtained to run pipelines, electrical power, etc.
CorrosionThe deteriorating chemical reaction of a metal with the fluids with which it is in contact.
Corrosion CouponA representative piece of metal cut to a specific size and shape that is immersed in a test bath of placed in the flow stream to enable an estimation of the active corrosion occurring in a given set of conditions.
Corrosion-ErosionEroding away of a protective film of corrosion product by the action of a process stream, exposing fresh metal which then corrodes.
Corrosion FatigueFatigue-type cracking of metal caused by repeated stresses in a corrosive environment.
Corrosion FilmFirst products of corrosion films that may form a tight, barrier film and reduce further corrosion.
Corrosion InhibitorA chemical substance or combination of substances that, when present in the environment, prevents or reduces corrosion (NACE).
Corrosion Potential (Ecorr)Potential of a corroding surface in an electrolyte relative to a reference electrode under open-circuit conditions.
Corrosion Resistant AlloyCRA, alloy intended to be resistant to general and localized corrosion of oilfield environments.
Corrosion Resistant Ring GrooveA ring groove lined with material resistant to metal-loss corrosion.
Corrosive GasA gas that attacks metal or other specified targets. Most commonly CO2 and H2S. Usually in association with water or water vapor. Oxygen can be described as a corrosive gas in some cases.
COST WellA well drilled on the continental margin to provide data for offshore leases.
Covalent BondThe combination of two of more atoms by sharing of electrons. Covalent bonds are generally stronger than other bonds.
Counterbalance WeightsThe rotating weights on a beam lift pump jack that offset the weight of the rod string.
CouplingThe connection point of jointed pipe. It may be a steel shell with female threads to which the pins are connected or a formed female connection (box) on the end of tubing.
CouponA test strip of metal used in corrosion and erosion testing.
CP (casing)Casing point.
CPSCentral power station.
CPT (corrosion)Critical pitting temperature.
CQGCrystal quartz gauge.
CrChrome. 13Cr is 13% chrome.
CRACorrosion resistant alloy.
Crack a ValveTo barely open a valve.
Cracking (refining)Breaking longer chain hydrocarbon molecules to shorter chain molecules.
Crater (blow out)A depression formed from a release of gas through loose soil at the surface or sea floor.
Cratering or SloughingCollapse of part of the formation into the wellbore during drilling or completions.
CrazingA network of checks or cracks appearing on the surface.
CreepThe slowest form of mass movement.
Creaming CurveA graph of the hydrocarbons discovered or produced in an area use to determine if new wells are improving with each new well.
Creaming of EmulsionsDensity separation state of emulsions, often where color variances are noted.
CreepThe slow movement of a solid due to an applied stress. Often very sensitive to time and rate of stress application.
Crest (geology)The top of a pay structure.
Crest (flow)The top of the water cone in (usually) a horizontal well. Compare with coning in a vertical well.
CretaceousA geological time from 65 million to 140 million years ago.
Crevice CorrosionIntensive localized electrochemical corrosion occurs within crevices when in contact with a corrosive fluid. Will accelerate after start.
CrewA group of workers on a rig.
CRI (solids handling)Cuttings reinjection.
CRI (structure)Caisson-retained island.
Critical (flow)Super sonic.
Critical Buckling LoadThe compression load that initiates buckling in the pipe.
Critical ComponentsPart identified in a system that need a higher degree of reliability or traceability.
Critical DrawdownVarious. Usually the sand free rate, but may also include a rate to achieve cleanup in special cases.
Critical FailureFailure of an equipment unit that causes and immediate cessation of the ability to perform its required function.
Critical Flow Rate (biofilm)The minimum flow rate that keeps biofilm deposits from forming on the surface of the pipe.
Critical Flow Rate (corrosion/erosion)The maximum flow rate that avoids damage to the pipe from corrosion or erosion.
Critical Flow Rate (liquids unloading)The minimum flow rate to produce liquids from a well.
Critical Flow Rate (sand production)The maximum flow rate that avoids producing sand from the formation.
Critical SaturationThe saturation of a fluid at which the fluid will begin to flow as saturation is increased.
Critical TemperatureThe temperature above which a fluid cannot be liquefied by increasing pressure.
Critical Velocity (erosion)Setting a maximum flow rate to minimize erosion corrosion.
Critical Velocity (unloading)A minimum velocity to lift liquids in gas flow.
Crooked HoleA wellbore drilled in excess of the maximum allowable dogleg.
Cross DipoleA log with the receivers located 90o to the emitter.
Cross FlowFlow between formations via a connected wellbore. Crossflow, as seen by downhole cameras, can occur with the wellbore full of fluid and the appearance of a dead well at surface.
Cross PlotTwo or more log responses or other variable records plotted on an X-, Y- axis.
CrosslinkedA polymer gel with a chemical crosslinker added to link the linear gel into a higher viscosity gel.
Crossover (gravel packing)A section of the treating string that transfers incoming flow from inside the pipe to the annulus below the crossover, and the return flow from inside the tubing to the annulus above the crossover. Straddles a packer.
Crossover SubA short section of pipe with the proper threads cut into each end to join two pieces of pipe or equipment that do not have matching connections.
Crosswell TomographyA map of the acoustic strata record between two wells where the emitter is in one well and the receiver is in the other.
CrownHigh point.
Crown BlockThe set of pulleys or sheaves at the top of the mast on a rig.
Crown LandsGovernment owned land.
Crown Plugs (subsea)The plugs above the flow T in a subsea wellhead.
Crown SaverA device that keeps the traveling block from being raised ito the crown block.
CRP (rock mechanics)Critical reservoir pressure for sanding appearance.
Crude and Crude OilA range of principally Carbon-Hydrogen chain compounds with generally straight carbon chain lengths of C1 (methane) to C60+. The straight chain materials are alkanes.
Crude Oil EquivalentA conversion of all gas forms to a comparison oil volume. Conversion factors are usually 5.6 to 6.0 mscf (depending on btu of the gas) to 1 bbl of oil.
Crush ZoneThe area of the rock adjacent to the perforation tunnel where permeability may be 50% less than initial, undamaged permeability.
CrustThe outermost crust of the earth.
CrystalA mineral with a systematic internal arrangement of ions that forms a repeating outward latticework of three dimentional units.
Crystallation TemperatureThe temperature at which the first crystal of salt appears from a brine that is being cooled.
CsCOOHCesium formate.
CSDCompensated spectral density log.
CsgCasing.
CSSCyclic steam stimulation.
CST (fluids)Centistokes. A measure of viscosity.
CST (rock)Capillary suction time.
CTSee Coiled Tubing.
CTDCoiled tubing drilling.
CTDESPCoiled tubing deployed electric submersible pump.
CTECoefficient of thermal expansion.
CTLCoiled tubing logging.
CTRControlled tension release tool. A release tool for downhole.
CTUCoiled tubing unit.
Cumulative ProductionProduction of hydrocarbon to date.
Cup PackerA packer with elastomer cups that are pushed out during fluid injection as the primary seal. Used for washing perfs and some testing. Only seals during fluid injection.
Curie PointThe temperature above which a mineral loses its magnetism.
Curing AgentA chemical substance used to initiate the hardening reaction of a resin.
Curvature (seismic)A seismic comparison method useful in finding Karsts.
Cushion (underbalance)A fluid column margin of some type. Usually well control mud weight, gas column, etc.
Cushion GasThe reservoir pressure necessary to keep gas recoverable.
CutThe fraction of a fluid in a mixture of fluids.
Cut and StripCutting the logging cable and threading it through the drill pipe when fishing for logging tools.
Cut FluidA fluid that has been contaminated by an undesirable fluid.
Cut Lip GuideA type of cut on the bottom of an overshot that, when rotated, can help center the end of a pips that is laying against the side of the hole.
Cut-Off toolGenerally a reference to a device that severs the pipe downhole by explosive, chemical, heat or mechanical action.
CutriteCarbide particles in a metal binder. Applied to the cutting surfaces of mills.
CuttingsChips of rock from the drilling process. They are circulated to the surface by the mud and separated in the screens and shaker. They are useful for identifying and correlating the formation.
CVCheck valve.
CVAR (subsea)Compliant vertical access riser.
CVPThe Group Capital Value Process, essentially the application of the stage gate decision process.
CVTChevron Texaco.
CWAClean water act, a US law.
CWI (contract)Carried working interest.
CWOPComplete well on paper exercise.
CWORCompletion and workover riser.
CWTFCentral water treatment facility.
Cycle GasGas that is separated and reinjected.
Cycle Time (drilling)Round trip time for a circulated fluid.
Cycle Time (plunger)The trip time for a plunger from dropping to recovery.
CycloneA device that separates cuttings by centrifugal motion of the fluids.
CycloniteAnother name for RDX explosive.
D&ADry and abandoned.
D&CDrilling and completion.
D/t (pipe)The OD to the pipe wall thickness.
Daily Drilling ReportThe daily report on activities, results, and shows of the past 24 hours.
Damage (formation)A general term commonly referring to an obstruction in the flow path.
Dampner or Dampener (flow line)A device in the line filled with gas that may reduce the surges of pressure pulsation or flow slugging.
DarcyA measurement of permeability (ability of fluids to flow through the rock). The relationship is an empirical law which states that the velocity of flow through porous media is directly proportional to the hydraulic gradient, assuming that the flow is laminar and inertia can be neglected.
DartA pump-down fluid separation device. May also be used to operate tools downhole by hydraulic forces.
DASData acquisition system.
Data FracA small fracture treatment, without proppant, pumped into a well to assess fracture breakdown pressure, fracture extension pressure, fluid loss coefficient, frac fluid efficiency and fracture closure time.
DatumA relative comparison point, such as the Kelly bushing, sea level or mud line.
DaughterAn atom that results from the radioactive decay of a parent atom.
Daylight TourDay working shift.
DBDump bailer.
DB&BDouble block and bleed.
DCDepth correction.
DC (drilling)Drill collar.
DCF (accounting)Discounted cash flow.
DCS (pipe)Depth control sub.
DCSDistributed control system.
DDDraw down.
DDBDrive down bailer.
DD&ADepletion depreciation and amortization.
DDCVDeep draft caisson vessel.
DDRDaily drilling report.
DEDrilling engineer.
DE (filter)Diatomaceous earth filtration unit.
De (hydraulics)Equivalent hydraulic diameter.
Dead Carbon (shale)Carbon with a type of Kerogen content that has low potential to generate hydrocarbons (generally woody carbon).
Dead Leg (pipeline)A section of pipeline that is not in use.
Dead Line (lift systems)That part of a wireline or cable that is attached to a fixed anchor point and does not move through a pulley or other mechanical device.
Dead OilCrude oil without gas. May have been degassed mechanically or by gas breakout during storage.
Dead WellA well that will not flow on its own through natural gas lift or by reservoir pressure.
DeadmanBuried anchor.
Dead TimeIn radioactive logging, the length of time that the system requires to recover after counting an event.
DeaeratorDevices used to separate gasses from liquids.
Dealloying (corrosion)Selective corrosion of one metal in an alloy.
Dean NumberFluid flow effects in spooled tubing.
De-BottleneckingA program, typically in surface facilities and lines, to remove pressure drop causing flow restrictions.
Decay RateThe rate at which a population of radioactive atoms decays into stable daughter atoms. Rate expressed in half-life of the parent isotope.
Decentralizing ArmA mechanical level that pushes a tool against the side of the well.
Decision Tree (Risk)A sequence of nodes which are either a decision or an uncertainty, and outcomes associated with each mode. The purpose of a decision tree is to define the set of scenarios and the sequence of events that guide the evaluation of risk and return.
Decline CurveThe slope of the production rate vs. cumulative time or volume measurement. The decline of a well predicts how fast it is being depleted.
DecommisionRemove from service.
Decompression Damage (gas effects on seals)When pressure is dropped rapidly, gas that has permeated the elastomers and some plastics may rupture the surface of a material when the gas expansion caused by the decompression is faster than the gas can pass through the substance. Most severe in weak tensile-strength materials.
Deconvolution (seismic)(using Werner) an automated profile-based depth estimation method derived from analysis of magnetic anomalies in sheet-like bodies. Polynomials can be simultaneously solved to estimate the depth, dip, horizontal location and susceptibility (magnetic) of the surface or structure. Basically undoing the effects of a filter.
Deep InvestigationMeasurement of formation properties far enough from the wellbore to minimize the effects of the invaded zone.
Deep Marine ChalksOften massive deposits of coccolith fragments. Usually very high porosity and limited permeability unless fractured.
Deep Penetrating ChargeA perforating charge with a liner shape designed to create a long penetration into the formation, but a smaller entrance hole in the pipe. See also Big Hole Charge.
Deep Propagation LogA log that measures the resistivity of the formation.
Deferred ProductionHydrocarbon production that is delayed due to any of several reasons, specifically well repairs, restrictions that curtail production, regulations, etc.
DeflagrationBurning, decomposition or low order detonation of explosive.
DeflectionThe total change in angle of a wellbore in a given distance.
Deflection (drilling)The amount of flex exhibited by the drill string.
DeflocculationDispersing a clump or a gathering or “flocculated” of particles. Usually accomplished by dispersants or solvent thinners.
DefoamerA foam breaking chemical.
DegasserAny device that helps remove gas from circulated fluid.
Degrees APIThe API gravity.
DehydratorA treating vessel designed to remove water from a process stream.
Delayed Gamma RayA gamma ray that is emitted from the decay of an excited state in a nuclear reaction.
Delineation WellA secondary well, after a field discovery well, drilled to help determine field extent, volume or potential rate.
DeliquificationRemoval of condensed or produced fluids from a low rate gas well.
DeliverabilityThe tested and proved ability of a well to produce.
Delta tThe sonic travel time in microseconds per foot, of a sound wave through the formation. Denser formations (generally better consolidated and cemented) have lower (faster) delta t times.
DeltasMouth of river deposits, usually fan shaped with significant variation in composition, sorting and thickness. Quality of the reservoir rock may vary widely.
Demonstrated Reserves(American Petroleum Institute) A collective term for the sum of proved and indicated reserves. Proved reserves are estimated with reasonable certainty to be recovered under current economic conditions. Indicated reserves are economic reserves in known productive reservoirs in existing fields expected to respond to improved recovery techniques where (1) an improved technique has been installed but its effect cannot yet be fully evaluated, or (2) an improved technique has not been installed but knowledge of reservoir characteristics and the results of a known technique installed in a similar situation are available for use in the estimating procedure.
DemulsifierA chemical additive, usually a surfactant, that helps break emulsions.
Dendritic DrainageA stream system that branches irregularly.
DensitometerA device used for reading the density of a flowing fluid or slurry.
DensityThe mass per volume of a substance. Density of fresh water is 8.33 pounds per gallon or 1 gram/cc.
Density Contrast (seismic)Density of one rock relative to another. The contrast can be positive or negative. Gravity anomalies within sedimentary sections can be analyzed as structural or lithologic anomalies.
Density-Depth Function (seismic)The change in density with increasing depth is often a result of compaction. Age, lithology and porosity modification are also factors.
Density LogOne of a number of logging techniques that estimate the density of the formation.
DepartureThe distance from the kelly bushing horizontally to the end of the well.
Departure CurvesGraphs that show influence of a variable on the basic measurement; e.g., temperature, hole diameter, mud resistivity, bed thickness, adjacent bed resistivity, etc.
DepletionReducing the fluid content of a formation by production of that fluid.
Depletion PlanThe primary process for Life of Field resource management. The Depletion plan sets out the framework of how Resource Management underpins efficient exploration of the resource.
Deposit AttackCorrosion occurring under or around a deposit on a surface.
Depositional EnergyRelating to the energy of the transport mechanism that carries particles into an area of deposition. Low energy environments may contain large quantities of fines where high energy environments are usually marked by larger and more consistent grain sizes.
Depositional EnvironmentThe conditions of sediment transport and deposition at the time the formations were laid down.
Depreciation, AcceleratedSee Depreciation, Liberalized.
Depreciation, Asset Depreciation RangeA system of tax depreciation which enables a corporation to choose any life falling within 20% of the designated class life for determining its annual depreciation charge. ADR requires an annual election and all depreciation records must be maintained by vintage year (From AGA).
Depreciation, Declining BalanceOne of the liberalized methods of computing depreciation (normally used for tax purposes). Under this method, the depreciation rate is stated as a fixed percentage per year and the annual charge is derived by applying the rate to the net plant balance, which is determined by subtracting the accumulated depreciation reserve (From AGA).
Depreciation, Flow ThroughAn accounting procedure under which current Net Income reflects decreases or increases in current taxes on income, arising from the use of liberalized depreciation or accelerated amortization for tax purposes instead of the straightline method. See DEPRECIATION, NORMALIZED (From AGA).
Depreciation, LiberalizedThis refers to certain approved methods of computing depreciation allowance for federal and/or state income tax purposes. These methods permit relatively larger depreciation charges during the earlier years, in contrast to the straight-line method, under which the annual charges are the same for each year. This is sometimes referred to as accelerated depreciation (From AGA).
Depreciation, NormalizedAn accounting method under which Net Income includes charges or credits equal to the decreases or increases in current taxes on income, arising from the use of liberalized depreciation or accelerated amortization for tax purposes instead of the straight-line method. The contra entries for such charges to Net Income are suspended in Balance Sheet accounts. In future years, there is a feedback of these suspended amounts to Net Income when increases in the then current taxes on income occur because liberalized depreciation or accelerated amortization was used for tax purposes in prior years (From AGA).
Depreciation, Straight LineA method of computing depreciation under which equal annual amounts are set aside for the ultimate retirement of the property at the end of its service life. For a property with an assumed 25-year life, the annual charge would be 4% per year, usually applied to the cost of the property less estimated net salvage (From AGA).
Depreciation, Sum of the YearsOne of the liberalized methods of computing depreciation, normally used for tax purposes. Under this method, the annual deduction is derived by multiplying the cost of the property less estimated net salvage, by the estimated number of years of service life remaining, and dividing the resultant product by the sum of all the digits would be 25+24+23+22+ etc. +5+4+3+2+1 or 325. A simple way to compute this figure would be to multiply the number of years by the number of years plus one and divide by 2, i.e., (25 X 26)
Depreciation, Units of ProductionA method of depreciation whereby the asset is depreciated over an estimated life expressed in units of output rather than over an estimated life expressed as a period of time (From AGA).
Depth DatumThe zero depth datum for well logging.
Depth Migration (seismic)Data processing used to shift subsurface signals to their proper depth.
Depth of InvestigationThe outer limit to which a logging tool can measure properties with a give accuracy.
DerrickThe elevated section of a rig that rises above the substructure and houses the crown block and draw works.
DerrickmanA person that works in the derrick and assists handling pipe to make up joints into the string or stand them in the derrick when breaking out joints.
Desander / DesilterDevices that typically use centrifugal flow paths to spin solids out of a drilling or circulating fluid.
DesorptionThe release of materials that have been absorbed or adsorbed in or onto a formation.
Detail LogA log recorded on a larger scale depth than the standard correlation of 1 or 2 inches per 100 ft.
Detectable LimitThe lower limit of analysis for a test of a piece of equipment for a specified measurement.
Deterministic Estimate (Risk)An estimate using a single number value. It does not account for ranges in value or probability of occurrence for the parameter.
Detonating cordExplosive wrapped with elastomer in the shape of a cord. Used to link and detonate charges in perforating guns.
DetonatorA blasting cap.
DetridalA grain of a sedimentary formation that was transported from its origin and deposited as a whole grain in the matrix of the rock.
Developed Reserves (reservoir)Developed reserves are expected to be recovered from existing wells including reserves behind pipe. Improved recovery reserves are considered developed only after the necessary equipment has been installed, or when the costs to do so are relatively minor. Developed reserves may be sub-categorized as producing or non-producing (SPE).
Development WellWells that are drilled after the discovery and appraisal wells to develop the hydrocarbon production potential of the field.
Deviated WellA well with an inclination other than zero degrees from vertical. In practice, deviated wells are usually more than about 10o from vertical.
Deviation AngleActual term is inclination - the angle from vertical in a section of a well.
Deviation SurveyA record of the deviation angle and the departure usually on a depth unit basis.
DevonianA geological time between 365 million and 405 million years ago.
Dew pointThe temperature at which liquids begin to condense from the vapor phase in a gas stream. (see also bubble point).
Dewatering (fluids separation)Separation of liquids and solids in the general sense. Also, removing water from hydrocarbon streams.
D40/D90A sorting criteria useful in screen selection.
DFDerrick floor.
DFITDiagnostic fracture injection test.
DFPDeferred production.
DG PlugA plug that is commonly set in the tubing hanger above the tubing or in tubing immediately below the wellhead for wellhead isolation.
DGLVDummy gas lift valve.
DGMKGerman Society for Petroleum and Coal Science and Technology.
DHCDownhole controller.
DHDDownhole diagnostics.
DHFCDownhole flow control.
DHPGDownhole permanent gauge.
DHSVDownhole safety valve.
DHTVMay be either downhole TV camera or a televiewer (a sonic caliper tool).
DHVDownhole video.
DHVDown Hole Video, Inc.
DiagenesisThe process of forming a sedimentary rock from the clastic grains. May also be in conjunction with several geochemical processes such as cementation reactions and chemical dissolution.
Diagenetic PorosityThe porosity formed by chemical and bacterial modification after the initial sediments were laid down.
Diamond bit or millA shaped bit body with diamonds for abrasive cutting of the formation.
DiapirA salt or other column that pierces upper layers and may form traps of obstructions to flow.
Diatomaceous EarthSilica particles from Diatom beds. Used as a filtering media and as an additive to cement.
DielectricA material that does not conduct electricity or has only a low electrical conductivity compared to a metal.
DiesA tool used to shape, form or finsih other parts.
Diesel #1A diesel fuel, C10-C14+ typically. #1 Diesel has paraffins removed for cleaner operation or cold weather use.
DIFDrill in fluid.
Differential PressureThe difference in pressure between upstream and downstream of a measurement point.
Differential SPA curve recorded as a simultaneous SP measurements from two electrodes, each serving as a reference potential for the other.
Differential StickingA common method of pipe sticking where the overbalance pressure in the wellbore pushes the tubing against the side of the wellbore in a permeable formation.
DiffusionThe random scattering of particles due to kinetic energy of the particles. Affected by viscosity, density and temperature.
Diagenetic TrapWhere rock changes produces a reservoir rock under a sealing rock.
DikeA large igneous intrusion that cuts through the sedimentary layers, creating permeability barriers.
DILDual induction log.
Dilatancy (rock)The ability of a rock to expand through micro-fractures in consolidated rocks or grain position shifts in unconsolidated rocks.
Dilatant FluidA well dispersed, high solids content liquid that has very high apparent viscosity with any applied shear.
DiluentThe fluid added to a concentrated mixture to reduce the concentration of an internal phase or reduce its viscosity.
Dimple Connector (coiled tubing)A connector with shallow holes into the body and threads on the other for attaching a BHA to coiled tubing. The end with shallow holes is slipped into the coiled tubing and a clamp-on device with set screws is used to deform the coiled tubing wall into the dimple.
DIMSDrilling Information Management System.
DipThe angle that the structural surface or bedding plane or fault surface makes with the horizontal. Measured perpendicular to the strike and in the vertical plane.
Dip LogDip meter log.
Dip MeterA log that measures the inclination of the formation beds.
Dip Slip FaultThe vertical displacement of a fault along the dip plane.
Dip TubeA tube from the intake of a pump that extends further into the liquid column of the well, to keep gas out of the pump.
Directional DrillerThe specialist that plans and executes the directional drilling plan.
Directional DrillingDrilling the wellbore in a planned angle of deviation or trajectory.
Directional PermeabilityA rock with a higher permeability along a given plane, usually created by natural fracture development, water flow that leaches the pores, depositional environment or localized reworking of the sediments.
Directional SurveyA measurement of the well path that records the inclination and azimuth of the wellbore using a compass or other device.
DirtyHigh clay content or higher natural radioactivity signature on the gamma-ray log.
DisaggregationWhen the formation breaks into grains.
DisbondA formation that comes apart or disaggregates or separation of grains.
DisconformityA change in the formation that may have been caused by ancient erosional forces. Accounts for variances in formation tops in near-by offset wells in a formation with no pay inclination.
Discontinuous Lenticular SandsLimited aerial sands.
DiscordantCutting across surrounding strata.
Discovered (reserves)The term applied to a petroleum accumulation/reservoir whose existence has been determined by its actual penetration by a well, which has also clearly demonstrated the existence of moveable petroleum by flow to the surface or at least some recovery of a sample of petroleum. Log and/or core data may suffice for proof of existence of moveable petroleum if an analogous reservoir is available for comparison. (See also “Known Accumulation”
Discovered Petroleum Initially in PlaceThat quantity of petroleum which is estimated, on a given date, to be contained in known accumulations, plus those quantities already produced therefrom. Discovered Petroleum-initially-in-place may be subdivided into Commercial and Sub-commercial categories, with the estimated potentially recoverable portion being classified as Reserves and Contingent Resources respectively (SPE).
Discovery WellThe initial well in the field that tests hydrocarbons.
DispersantAny substance that aids in breaking up a mass of individual particles, bubbles or droplets.
DispersedFluids with materials added to disperse solids or flocs.
Dispersed PhaseThe internal phase in an emulsion – i.e., the droplets or bubbles.
DispersionA mixture of a internal phase of solids, droplets or bubbles that stay relatively suspended in a continuous fluid.
Displacement (horizontal well)The distance between the wellhead and the top of a vertical line from the bottom hole location to the wellhead elevation at the surface.
Displacement (process)The set of actions used to flow a fluid or solids out of a well and replace it with another fluid system.
Displacement (volume)The volume of a wellbore occupied by fluid. When the swept volume varies from the calculated displacement, part of the wellbore may not be actively swept.
Displacement EfficiencyA measurement of how completely a flooding fluid displaces the saturated fluid in a reservoir.
Disposal WellA well into which fluids such as produced water and some liquid wastes can be injected. It is in a non hydrocarbon, non-fresh water sand and is not connected to the hydrocarbon bearing formation.
Dissimilar MetalsDifferent metals that may form an anode-cathode pair in corrosion cell conditions.
DissociationThe separation of a compound or molecule into pieces, ions, or atoms.
Dissociation PorositySecondary porosity that is created when solid materials in sediment dissolve in interstitial solutions.
Dissolved Gas (production)The solution gas associated with produced fluids.
Dissolved Gas DriveA reservoir drive mechanism in which dissolved gas from the crude oil breaks out of solution and provides energy to push the hydrocarbons toward the wellbore.
Dissolved GasOil Ratio
DistillatesA range of manufactured products from the refining processes; includes kerosene, diesel, bunker C oil, fuel oil, heating oil, etc.
Distributed Temperature LogA log of temperature along the entire length of the interval, well or flow path.
Ditch GasGas removed from the mud at the flowline by mechanical means.
DivergenceSeparation of groups of data from either other or from a norm.
Diversion (fluid treating)A method of limiting the fluid entry into a higher permeability zone and causing the fluid to flow to a lower permeability zone.
Diverter (acidizing)A material that forces acid to enter another zone by having a higher viscosity or building a filter cake.
Diverter (wellhead)A device in the flowpath at the wellhead that forces fluid to go down a pipe to a pit or tank.
Division OrderA list of interest owners and their share of revenues.
DLLDual laterolog
DLSDog leg severity.
DMDDriller’s measured depth.
DMO (seismic)Dip movement offset. The difference in arrival times at various sensors due to the dip of the surface off of which the signals are reflecting.
DMURDrilling, milling and under-reaming.
DNLDual porosity CNL.
DnVDet Norske Veritas
DOEUS Department Of Energy.
Dog HouseA crew or records shack at a lease or on a rig.
Dog LegA sudden change in the direction of the wellbore. Generally based on degrees per 100 ft.
Dog-LockA type of lock used in a profile.
DolomiteCalcium/magnesium carbonate rock. Dolomite is formed by chemical modification of a limestone.
Dolomite RhombohedrialsCrystals of dolomite in the pore space. May turn loose when acidized and become migrating fines.
DomeA symmeatrical upfold of the layers of rock in which the beds dip in all directions more or less equally from a common point; any deformation characterized by a circular local uplift.
Domestic productionProduction originating inside a specific country of reference.
DoodlebugSeismograph.
DopePipe thread dope used to lubricate and seal the threaded connection.
D.O.T. (government)Department of Transportation – a US government agency.
Double Block and BleedTwo successive plugs, each capable of holding maximum pressure, with a vent between them capable of bleeding off all pressure between the plugs. Also – a valve with two seating surfaces which, in the closed position, blocks flow from both valve ends when the cavity between the seating surfaces is vented through a bleed connection on the body cavity.
Double BoardWorking platform for the derrickman on a drilling rig.
Double Grip (packer)Slips that prevent either upward or downward movement.
Doubles (pipe)Two joints screwed together.
DoughnutA hanger, usually screwed onto the end of the top tubing joint and lowered into the slip bowl of the wellhead.
Down DipThe direction going down the tilt angle of the formation.
Down StrokeThe recovery stoke downward on a beam pump where the pump is filling with fluid by pushing the open traveling valve through the standing fluid.
DowncomerA pipe where the fluid flow path is down. Fluid return pipe.
DownholeA general term referring to subsurface equipment, tools or other items.
Downhole CameraAny of a variety of downhole cameras, including full motion video, recording memory camera, sequence sending cameras, etc. Used to get a better picture of the wellbore or a fish.
Downhole ChokeA flow bean (restriction) set in a profile near the bottom of the well. Used as a flow regulator and to take part of the pressure drop downhole to reduce the potential of hydrates.
Downhole GaugesSurface reading, downhole located gauges capable of measuring pressure, temperature and/or flow rate.
Downhole SeparationRemoval of a part of the water downhole followed by injection of the water into a disposal zone.
Downhole ShutoffA deliberate shut off of a zone by a downhole valve or other method, to prevent cross flow.
DownstreamThe transport, refining and product making part of the oil business.
DP (offshore rig)Dynamically positioned.
DP (perforating)A deep penetrating charge.
DP (reservoir)Depletion plan.
DPC (gas lift)Casing pressure at depth – the true gas weight at depth.
DPTADiaminopropanoltetraacetic acid, a calcium scale remover and solvent.
DPTDeep propagation log
DPUDownhole power unit.
DRA (flow)Drag reduction agent.
Drag (fluid flow)The force on a solid surface exerted by a fluid flowing past it.
Drag (pipe movement)Resistance to linear motion.
Drag BlocksSpring loaded blocks on a packer or other tool that contact the pipe wall, producing resistance to movement. They aid in setting of packers.
Draw WorksHoisting mechanism on a drilling rig.
DrawdownThe difference between two pressures. Completion drawdown is the pressure differential from the formation near the wellbore to the wellbore.
DRBADelaware River Basin Authority.
DressTo sharpen a bit or replace components of a tool.
Dress OffTo remove rough edges, flares, burrs, etc. from a piece of equipment prior to fishing.
Drift (geological)The rock, sand and clay moved by a glacier.
Drift (pipe gauge)The minimum id of tubing through which a standard drift tool will pass.
Drift (tool)A tool with a set diameter used to check the wellbore for clearance prior to running a tool string or piece of equipment.
Drift DiameterThe published drift diameter for a pipe that describes the diameter of a tool that can pass through the pipe when the pipe is vertical (no doglegs).
Drill BitThe rock cutting device at the bottom of the drill string.
Drill CollarA very heavy wall pipe used to add weight over the bit during drilling.
Drill CuttingsThe small chips and fines generated by drilling through a formation with a drill bit. Most of the cuttings are removed from the mud as the fluid pass through the solids control equipment (e.g., shakers, screens, cyclones, etc.,) at the surface.
Drill-In FluidThe fluid used to drill the pay zone.
Drill MotorA hydraulic or electric motor on the end of the drill string that turns the bit.
Drill OutDrilling through the cement after a primary cement job as the hole is deepened.
Drill PipeA heavy wall tubing used for drilling.
Drill Pipe Safety ValveA full opening valve with threads that match the drill pipe that can be quickly screwed onto the pipe to help control fluid flow up the tubing.
Drill StemTypically, rotating components in a drill string.
Drill StringAll the equipment in a drilling BHA plus the drill pipe.
DrillableDownhole tools and equipment that can be broken up by the bit.
Driller’s ConsoleThe control panel.
Driller’s DepthMeasured depth or the length of the pipe from top to depth.
Driller’s MethodA method of controlling a kick in which the gas is circulated out of the well using the normal weight mud controlled with backpressure of a choke. The heavier mud needed to control the formation without the choke is then circulated into the well.
DrillingThe action of placing a hole to a depth and location.
Drilling AheadContinue with drilling after stopping to check flow or other activity.
Drilling BreakA sudden increase in the ROP (rate of penetration) while drilling. May indicate a higher pressure formation, a change in lithology, a naturally fractured zone, or a poorly consolidated zone.
Drilling EfficiencyAverage distance drilled per day divided by the total number of days in a measurement cycle.
Drilling Hook and SwivelThe components below the traveling block to which the elevators are attached.
Drilling LineThe wire rope used to position tools on the floor. Also used to describe the wire rope on a cable tool rig.
Drilling MudThe fluid, water, oil or gas based, that is used to establish well control, transport cuttings to the surface, provides fluid loss control, lubricates the string and cools the bottom hole assembly.
Drilling OutDrilling out set or green cement from the casing before drilling ahead to make a deeper well.
Drilling PlatformUsually offshore; a platform from which wells can be drilled. It may be permanent (with legs grouted into the seafloor to depths of several hundred feet), anchored or dynamically positioned.
Drilling RigThe equipment at the surface used to lift and run the drilling string, provide the rotation and pump fluids down the string.
Drilling SpoolA section of the BOP that allows side ports for choke and kill lines.
Drillstem Test or DSTA controlled production of a small amount of fluid from an isolated section of the pay zone into the chamber formed by the drill pipe and a downhole valve. DST’s measure pressures, some elements of depletion and gather samples of the produced fluids.
DripCondensate liquid, or natural gasoline.
Drip GasNatural gasoline or low carbon chain liquids, condensed from the rich gas from a well.
Drip OilNatural gasoline or low carbon chain liquids, condensed from the rich gas from a well.
Drive PipeThe conductor pipe.
DRGLDrilling.
DRODBDrilling, recompletion and repair data base.
Drop BallA sized ball dropped or pumped from the surface to shift a tool downhole.
Drop Bar (perforating)A bar dropped from surface to set off a TCP gun in a near vertical well.
Dry Gas (in production)A gas stream without condensate. Note
Dry Gas (reserves)Dry Gas is a natural gas containing insufficient quantities of hydrocarbons heavier than methane to allow their commercial extraction or to require their removal in order to render the gas suitable for fuel use. (Also called Lean Gas) (SPE).
Dry Gloss Heating Value (reactions)The total energy transferred as heat in an ideal combustion reaction at standard temperature and pressure in which all water formed appears as a liquid.
Dry HoleA well that does not have or produce commercial deposits of hydrocarbons.
Dry Sieve MethodA sand particle size distribution obtained by shaking a sample of sand through a series of sieves or screens.
Dry Tree WellAn offshore well with the wellhead and access to the well at the surface.
Drying OilAn oil capable of conversion from a liquid to a solid in the presence of air.
DSDrill string.
DSDirectional survey.
DSDrill site.
DSIDipole sonic.
DSLDiesel.
DSTDrill Stem Test.
DSVDown hole safety valve.
DTSDistributed temperature sensor or survey.
D/tDiameter to thickness ratio, a common comparison value in steel pipe.
D10/D95A formation sizing criteria that shows impact of fines.
Dual completionTwo pay zones in the same well that produce up independent flow paths in the same well.
Dual Induction LogAn induction log with dual and deep measurements of resistivity. Shallow measurements are indicative of severely invaded zone and the deepest measurements are most reflective of actual formation fluids.
DUB (perforating)Dynamic underbalance perforating.
Dummy RunA wireline or tubing run into a well with a dummy piece of equipment of the same size, shape and stiffness of a valuable or unrecoverable piece of equipment to make sure the equipment can be placed.
Dummy ValveA solid body (non flowable) gas lift valve that “dummies off” a gas lift mandrel to seal the GLM or pocket.
Dump BailerA hollow tube with a flapper or other opening valve at the bottom, run on wireline to place cement or sand in a well.
Dump FloodVarious – usually allowing water to gravity feed into the annulus (without packer) or the tubing and into the formation.
DuneA deposit of sand produced by wind or running water. The dune may be massive, but usually lower energy and permeability varies.
Duplex pumpA type of pump with two, dual acting pistons.
Duplex SteelA corrosion resistant alloy with chrome and nickel as common components.
Durometer (rubber)A term used to express hardness, usually of rubbers or elastomers.
DusterA dry hole.
DutchmanA filler piece used to close a gap in piping or equipment alignment.
DV Tool (cementing)A stage tool.
DWDeep water, usually inaccessible by a fixed (non floating) platform.
DWDDeep water development
DWOP (BP)Drilling and well operations policy.
DWOPDrill well on paper exercise.
DWPDeep mater production.
DXV (subsea)Direct crossover valve.
Dynamic FlowNon steady state flow or flow with changing conditions.
Dynamic Event (propellant fracturing)Events such pressure surge or fracturing that occur over a few hundred milliseconds.
Dynamic SealA seal in a system where motion is expected in the seal or the seal area.
Dynamic Viscosity (produced fluid)The viscosity of the fluid in the reservoir at the reservoir conditions. Note – associated gas reduces the viscosity of most oils.
DynamometerA recording of the stresses in a rod string of a beam pumping unit.
DZO (seismic)Demigration to zero offset. An improvement in seismic processing over dip movement offset where signal velocity varies significantly with depth.
E&AExploration and appraisal.
E&PExploration and production.
E-LineSee electrical line.
EccentricityDecentralization of pipe in the hole. 100% eccentric is against the hole wall.
ECDEquivalent circulating density.
Echo MeterA trademarked, commercial tool that measures the height of a fluid (or solid) level by means of a reflected sound wave.
Economic InterestOwnership of part of the well.
Economic LimitWhen the revenue from the produced fluids falls below the cost of operations set by the company.
EconoPropA trademarked name for an inexpensive light weight ceramic (man made) proppant.
EcorrCorrosion potential.
ECPExternal casing packer.
ECTFEThermoplastic fluoropolymer.
eCTUElectric line coiled tubing unit.
ED (elastomers)Explosive decompression.
Edge waterWater at the sides or edges of the hydrocarbon deposit. Often causes problems because the channels that deplete the fastest are the highest permeability and water production through them can be severe. These respond well to treatment if they can be isolated.
EDP (subsea)Emergency disconnect package.
EDTAEthylene diamene tetra acetic acid.
EductorA device that through flow of a power fluid through a nozzle, creates a low pressure area useful for moving fluids.
Effective PermeabilityThe permeability of the formation matrix to a particular fluid when two or more phases are present.
Effective PorosityInterconnected, drainable porosity.
Effective Shot DensityThat number of the perforations that are open and flowing.
Effective Stress (fracturing)The principle stress less the fluid pressure.
Effective Wellbore RadiusThe theoretical radius of a wellbore that would flow the same rate as a wellbore with a fracture. Effective wellbore radius is a comparison of flow improvement related back to physical radius.
EffluentThe fluids and solids, perhaps in a mixed stream, produced from a well.
EGMElectronic Gas Measurements.
EGMBEEthylene glycol mono-butyl ether. A mutual solvent.
EGPExternal gravel pack.
EIAEnergy Information Administration.
Eight RoundA thread with 8 threads per inch.
EISEnvironmental impact statement.
EITEngineer in training.
ELElevation.
EL&PExploration, land and production.
ElasticNon-permanent structural deformation during which the amount of deformation (strain) is proportional to the applied stress (load).
Elastic DeformationDeformation of a body in the elastic range, i.e., recovery to the initial shape is possible when the stress or load is removed.
Elastic LimitThe upper range of elasticity, just before the body is permanently deformed.
ElasticityThe tendency of a body to return to its original shape and size once the stress is removed.
ElastomerA rubber or plastic material used as a seal. May occur naturally or be synthesized.
ElbowAn “L” shaped fitting in surface piping.
Electric Line or E-LineA wireline with a conductor in the middle and woven electrical braid over the conductor.
Electric LoggingA method of rock and fluid identification or evaluation that began in 1927. The first log was run by Conrad Schlumberger.
Electric RigA drilling rig where the power source is electricity provided by a generator.
Electric Submersible PumpAn ESP or dowhole artifical lift unit powered by electricity..
Electrical LogTypically a resistivity log.
Electrical Submersible Pump or ESPAn electrical powered rotating pump capable of lifting very large flow rates (>20,000 BPD).
ElectrolyteA material that, when dissolved in water, causes or increases the fluids’ electrical conductivity.
Electromotive Force Series (corrosion)A list of elements arranged according to their standard electrode potentials.
Electrostatic TreaterA separation device that uses alternating current charged plates to help break emulsions.
Elevator Bails or LinksThe bars that attach the elevators to the hook on the traveling block.
ElevatorsThe snap-around latches that couple around tubing below the pipe coupling and enables the traveling block on a rig to gab and lift the tubular string.
ELGEffluent limitation guidelines.
ELMDElectric line measured depth.
ElongationAn increase in length expressed numerically as a percent of initial length.
EMEddy current measurement for wall thickness in corrosion and wear determination.
EmbedmentProppant that has partly or completely sunk into a formation through displacement of the formation around the grain.
EmbrittlementA fatigue state of metal that may be caused by trapping atomic hydrogen in the structure of the steel. Characterized by loss of ductility. May also be caused by work hardening or other factor.
EMFElectromotive force. The force that drives electrons and creates an electric current.
ELMDElectric line measured depth.
EmpiricalObserved response, often well proven by experiences but not theoretically derived.
EmulsifierA emulsion stabilizing mechanism, usually either surface active agent, fines, viscosity and/or charge.
EmulsionA physical mixture of two or more immiscible phases.
Emulsion StabilizerA chemical or physical effect that prevents separation of two or more, normally immiscible phases. Normally surfactant, electrical charge, liquid or emulsion viscosity, or micron sized solids at the interface.
EMWEquivalent mud weight.
Encapsulated breakerBreaker in small pill-form particles that stays with the polymer and helps break the mud cake.
End of Well ReportA summary of general well data, operation data, geologic data, etc., for a particular well after the final completion step.
EndothermicA reaction that absorbs heat.
Endurance LimitThe maximum stress that a material can withstand for an infinitely large number of cycles (NACE).
Enhanced Oil RecoveryOne or more of a variety of processes that seek to improve recovery of hydrocarbon from a reservoir after the primary production phase.
Entitlement (reserves/production)Reserves consistent with the cost recovery plus profit hydrocarbons that are recoverable under the terms of the contract or lease are typically reported by the upstream contractor (SPE).
Entrained GasGas dispersed in a produced fluid.
Environmental CrackingBrittle fracture of a normally ductile material in which the corrosive effect of the environment is a cause (NACE).
EnzymeA protein based (non-living) material that can serve as a catalyst for many organic reactions.
EOBEnd of build (horizontal wellbore).
EOCEnd of curve.
EoceneA geological epoch from 38 million to 55 million years.
EolianFormed by wind.
EonThe primary division of geologic time – from oldest to youngest
EOPExtreme overbalanced perforating.
EOREnhanced oil recovery.
EOSEquation of state.
EOTEnd of tubing.
EOWREnd of well report.
EPEqualizing prong.
EPAEnvironmental Protection Agency, US pollution control enforcer.
EPCRAEmergency Planning and Community Right-to-Know Act.
EPMEquivalents per million. The epm is equal to the ppm divided by the equivalent weight.
EpochA time division of geologic time next shorter than a period.
EpoxyA resin formed by reaction of polyols with epichlorohydrin.
EPTElectromagnetic propagation tool. Measures propagation time and attenuation rate of microwave energy through the formation. Helps distinguish between oil and water.
EQMWEquivalent mud weight.
Equalizing FeatureA part of a plug that allows equalization of the pressures above and below a plug.
Equivalent Circulating DensityThe effective fluid density that the formation sees when the friction pressure on the fluids returning to surface is added to the fluid density.
Equivalent Mud WeightThe equivalent mud weight felt by the formation when circulating with a certain mud weight and holding a backpressure. A 10 lb/gal mud in a 10,000 ft well with 1000 psi backpressure would generate an equivalent mud weight of about 11.9 lb/gal.
Equivalent WeightThe atomic or formula weight of a material.
EraA division of geologic time, next shorter than the eon and larger than a period.
ERDExtended reach drilling.
ERFError function
ERFC(x)Complimentary error function = 1 – erf(x).
ErosionProgressive loss of material from a solid surface due to mechanical interaction between that surface and a fluid, a multicomponent fluid or solid particles carried within the fluid (NACE).
Erosion CorrosionCorrosion acceleration by passage of a high velocity flow or impingement of solids. May remove the thin, protective oxide film that protects exposed metal surface.
ERWExtended reach well.
ErosionWear of a material by a slurry of liquid and (usually) solids.
ES (treating)Electrostatic separator.
ES (wireline)Equalizing sleeve.
ESDEquivalent static density.
ESDEmergency shut-down.
ESDSEmergency shut down system
ESPElectrical submersible pump.
ESREquilibrium step rate test.
ESS (sand control)Expandable sand control screen.
ESS (seismic)Exploration sub salt.
ESVEmergency shut-down valve.
EthaneA two carbon chain alkane, C2H6. A gas under standard conditions of temperature and pressure.
EthanolEthyl alcohol.
Ethernet (computer)A local area network protocol standard defined by IEEE 802.3.
EthyleneA two carbon chain alkene – double bonds between the carbons and a formula of C2H4. A very common starting material for synthesis of various products.
ETP (BP)Engineering technical standards.
EU or EUESee External Upset.
Euler Method (seismic)A profile or map-based depth estimation method based on a concept that magnetic fields of structures are homogeneous functions of depth and location. This is used to satisfy Euler’s equation.
EURExpected ultimate recovery from a field.
Eutectic (brine)A mixture of substances having a minimum solidification/melting point.
EvaporiteA formation formed by the evaporation of water from shallow seas. Very low permeability.
Event (Risk)Occurrence of a particular set of circumstances.
EVXT (subsea)Enhanced vertical tree.
EVXT-DB (subsea)Enhanced vertical tree, dual bore.
EVXT-SB (subsea)Enhanced vertical tree, single bore.
Excess CementThe amount of cement over that required to cement the zone. Usually between 30% and 100% depending on hole diameter unknowns and contamination risk.
Exfoliation CorrosionLocalized and subsurface corrosion in zones often parallel to the surface that result in leaving thin layers of uncorroded metal resembling the pages of a book.
EXHT (subsea)Enhanced horizontal tree.
ExothermicChemical reactions that gives off heat.
Expandable CasingWell construction tubulars run in like conventional casing but mechanically enlarged downhole before the cement is set.
Expandable CompletionsWellbore tubulars run in like conventional completions but mechanically enlarged downhole once in place. Can include combinations of sand screens, blank pipe and annular isolation seals used in lieu of gravel packs.
Expandable HangerA combination hanger and packer run like conventional hangers for drilling liners and well completions but permanently mechanically expanded once in the well.
ExpandablesA class of pipe that can be expanded for cladding corroded or worn casing, saving room in a completion, casing open hole, sealing off perforations, etc.
Expanding CementCement with additives that promote volumetric cement expansion.
Expansion JointA device in a length of pipe that allows some pipe length expansion or contraction.
ExpectancyRemaining life.
Expected Value (Risk)The weighted average using probabilities as weights. For decisions involving uncertainty, the concept of expected value provides a rational means for selecting the best course of action and for forcasting portfolio level performance.
Expendable Gun (perforating)A gun made up of perforating charges linked together with wire or clips. The debris is not recovered on the wireline run.
ExploitationDevelopment of a producing reservoir.
ExplorationA general term covering the search for oil and gas.
Exploration WellA wildcat or well in a new area with unknown producing potential.
Explosive CutterA pipe cut-off tool composed of linear shaped charge that is designed to sever pipe. Works on the same principle as a perforating charge.
Explosive DecompressionA rapid reduction in pressure that may cause trapped gas to try to break out of rubber/elastomer seals and ruin the seals. Common at the surface but uncommon downhole.
Explosive FracturingOne of several techniques used to break the rock in the near well area. It was an early stimulation method. Fractures formed in this method are short. Although still used, its best application is in perf breakdown and overcoming some near well damage.
Explosive LimitsThe low and high range (wt %) of a combustible gas mixed in air that can be ignited at ambient pressure and temperature.
Exponential DeclineConstant percent decline of production rate over time.
Exposed GunsA perforating gun with exposed charge capsules.
Extended Reach Well or ERWA well deviated above the pay to reach further from the drill site or further into the pay formation to expose my contact area with the pay zone.
Extension WellA well drilled on the edge of the existing field that may extend the known area of the field.
External Cage ChokeA choke capable of handling high solids content flow. The external sleeve is moved over a perforated hub with high erosion resistance properties.
External Casing PackerA rubber bladder over a section of casing that is inflated, usually with cement, to give an annular seal in open hole sections. Frequently used with liners and set at intervals along the open hole.
External CutterA mechanical, chemical or explosive device that is lowered over a pipe to cut from the outside.
External Filter CakeFiltration control established on the surface of the wellbore by particles large enough to bridge on the entry of the pores.
External PhaseThe outside or continuous phase of an emulsion.
External UpsetA pipe connection with a thicker connection body than the pipe body. In an EUE, the thickness is offset to the outside diameter.
Extraction Loss (produced fluids)Loss of volume due to removal of gasses or liquids during processing.
Extraction PlantA facility for removal of liquids from gas.
Extreme Overbalance PerforatingA method of applying a very high pressure surge to the formation at the instant of perforating. Usually in excess of 1.4 psi/ft. Designed to overcome frac initiation pressure and break down each perf with a very short (<1 m) frac.
Extrusion GapRadial gap between the maximum rated casing ID and the minimum OD immediately adjacent to the packing element.
Extrusive Igneous RockA description of rock resulting from a magma breach to surface and exposed to atmospheric conditions during cooling.
EZSVA drillable bridge plug.
F (reservoir)Formation resistivity factor, dimensionless.
ɸPorosity.
F (logging)Formation factor.
F NippleA standard profile. Can accept a plug or other tools.
Face Cleat (coal)A longitudinal fracture in coal.
Face SealAllowing a flat, usually polished, face to deform an elastomer and create a seal.
FaciesThe set of all characteristics of a sedimentary rock that defines its particular environment and distinguishes it from other facies.
Facultative (bacteria)Bacteria that can survive either with or without oxygen.
FailureWhen the designed function can not longer be met.
FairwayThe best part of a reservoir. Commonly used in coal pays.
Fall-Off TestA multi-functional test that can be used to determine fracturing pressure or if the well is fractured.
False SetAn abnormal early thickening of cement which does not affect the length of time which the cement can be pumped.
Fann ViscometerA common viscometer for oil-field fluids.
Fanning Equation (or friction factor)FF = (db/2?V2) (?P/L). Where ? = density (ppg), V = avg. fluid velocity (ft/sec), ?P is pressure loss over length L (ft).
Farmer’s OilAn older term indicating the mineral owners royalty-based “share” of the oil. This was from a time when natural gas had no value.
Farm-InAn outside party paying a concession owner all or a percentage of the drilling costs of a well in order to obtain a working interest in the land or well.
Farm-OutA concession owner selling a percentage of a lease to an outside operator for drilling a well.
Fast GaugesGauges with a high sampling rate.
Fast Line (drilling)End of a braided drilling line affixed to the draw works.
Fast TaperA steep slope.
FatigueA metal failure based on weakening by flexing or cycling. The material often work hardens.
Fatigue StrengthThe maximum stress that can be sustained for a specified number of cycles without failure.
FaultWhere rock splits or ruptures with associated movement occurs on either side.
Fault PlaneThe plane or direction along which fault movement has occurred.
Fault TrapA formation that contains oil or gas that is held in place by a displaced, non permeable rock mass.
FBHPFlowing bottom hole pressure.
FBPFormation breakdown pressure,. The pressure at which the fracture initiates.
FCFluorocarbon. A aromatic resistant seal material.
FCDFracture capacity – a comparison of the conductivity of the fracture to the capacity of the formation.
FCPFinal circulating pressure.
FCS (fracturing)Fracture closure stress.
FCTA (brine)First crystal to appear.
FCVFormation control valve.
FCPFracture closure pressure. A measurement of the pressure at which the fractured formation closes. Generally determined by the change in slope of the pressure reading as leakoff gradually lessens the volume of fluid that is holding the fracture open, until the fracture walls meet and the pressure reverts to a decline to pore pressure.
FDCFormation density log.
FDCNLFormation density compensated neutron log.
FDPField development plan.
FEFacility engineer.
FeCO3Iron carbonate scale.
Fee Land (contract)Land where mineral and surface rights are controlled. Usually private lands, rather than public or government.
Feed InInflux into the well bore.
Feet of payThe thickness of a pay zone or formation, usually the gross (total) thickness.
FeldsparA silicate mineral, often modified and sometimes part of the movable particles in a formation.
Female connectionA coupling with threads on the inside.
FeOHIron hydroxide gel (a precipitate after acid spends).
FEPMFluoroelastomers (Aflas, etc.)
FERCFederal Energy Regulatory Commission (US gov. agency).
Ferric IronValence state +3 iron in solution. A very common catalyst in oil field emulsion and sludge formation. Precipitates at iron hydroxide when the pH exceeds 1.8 to 2.2 (depending on sour conditions).
FerriteBody centered cubic crystalline phases common to iron based alloys.
Ferrous IronValence state +2 iron in solution. In oil field operations, most solution iron is ferrous until oxygen is encountered. Precipitates at iron hydroxide when the pH exceeds 7 or when oxidized to ferric by contact with oxygen.
FeSxOne of several forms of iron sulfide.
FFFormation factor.
FFKMPerfluoroelastomers (Kalrez, Chemraz, etc.).
FFI (logging)Proportion of moveable fluids occupying the effective porosity.
FFMFull field model.
FgFracture gradient.
FGLRFormation GLR.
FGORFlowing gas oil ratio.
Fiber CementCement with small hair like fibers that build strength or help control fluid loss.
FieldOne or more reservoirs grouped by or related to the same general geologic structural feature or stratagraphic condition.
Field RulesThe spacing and production rules in a field or unit.
Field WeldA weld repair made in the field. Usually derates the equipment pressure or tensile rating.
Filiform CorrosionCorrosion occurring under a coating in a pattern of filaments. May resemble threads.
Filter CakeThe layer of solids stranded on the face of permeable formations by liquids driven into the rock by pressure differential towards the formation. When sized correctly the filter cake may completely stop losses.
Filter Cake Lift-OffThe act of lifting off part of the mud filter cake, at the most permeable sections of the rock, in response to flow produced by draw down.
Filter Cake Lift-Off Pressure (drilling)The inward differential pressure difference that will result in part of the filter cake being removed from the face of the formation (usually over the most permeable and higher pressured sections).
Filter MediaThe material used to make up a filter bed. Common filter media are DE, sand, various fibers, etc.
Filter PressUsually at DE filter.
FiltrateThe liquid that leaks off into the formation during fluid loss.
Filtrate ReducersMaterials that reduce the fluid loss from a wellbore fluid. May include Bentonite clays, lignite, CMC, etc.
Filtration LevelThe generally statement of the largest size particles in a fluid after passing through a filter.
Final Circulating PressureDrill pipe pressure required to circulate at the selected kill rate.
Final SetA reference to one of many expectations on when cement is sufficiently set to bear some type or level of weight.
Final StrengthThe strength of cement when the strength development with time curve ceases to change significantly.
Finding and Development CostsCapital costs from acquisition, exploration, drilling and completion costs of proved reserves.
Fines ControlAny process designed to minimize movement of otherwise mobile fines, typical size < 44 microns.
Fines MigrationMovement of small particles (usually <5 microns) through the rock pores.
Finger Board (drilling)Steel fingers mounted to the derrick into which the derrick man stores pipe that is standing in the derrick.
FingeringMovement of one fluid through another.
Fire FloodA tertiary recovery method involving injection of air into the formation and igniting the oil. Under the right conditions, the heat produced from combustion of the heavy ends that are trapped on the sand grains lowers the oil viscosity and liberates light ends.
Fischer AssayAn assay method for organics in rock by pyrolysis (burning).
FishA lost piece of equipment in the well.
Fish HookA upward turning horizontal well – usually over 90 degrees.
FisheyesLumps of undispersed polymer in suspension in the pill.
Fishing MagnetA magnet, usually run on wireline, used to recover lighter metal components from the well.
Fishing NeckA piece of equipment on most downhole tools that is designed for simple, non-rotating attachment when retrieving.
Fishing ToolsThe tools that can capture a lost item (a fish) in a well.
Fishtail BitA drag bit with no moving parts, rotated like a conventional metal drilling bit.
Fissile (rock)A fissile rock tends to break along a plane or planes that are roughly parallel to the bedding planes.
FIT (operations)Formation Integrity Test.
FIT (fracturing)Frac isolation tools.
FIVFormation isolation valve. A downhole valve that is operated by pressure cycling or other remote method.
Five Spot PatternA well placement pattern that looks like the 5-spot side on a dice cube.
Fixed ChokeA non adjustable choke that uses a flow bean for regulation.
FKMFluoro-elastomers (Viton, Fluorel, etc.).
FL (drilling/completions)Fluid loss.
FL (operations)Flow line.
FlagMarking the pipe or wireline with a paint stripe.
FlangeA common, high pressure wellhead connection, using bolt attached flange plates and metal-to-metal seals.
Flanged UpCompleted.
Flapper ValveA one-way, flow actuated valve common in safety valves, coiled tubing and fluid loss devices.
FlareA burner on a remote line used for disposal of hydrocarbons during clean-up, emergency shut downs and for disposal of small volume waste streams of mixed gasses that cannot easily or safely be separated.
Flash (pipe)The weld seam on or in a welded pipe.
Flash LiberationA sudden pressure drop that causes hydrocarbon light ends to go from a liquid to a gas.
Flash PointAn ignition temperature (given in oF) that liquid will put off enough vapors to be ignited.
Flash SetA rapid, usually unplanned, thickening of cement.
FlashingVaporization of water or light ends as pressure is released during production or processing.
FLC (completions)Fluid loss control.
FLC (operations)Field lifting cost.
FlexingPressuring and depressuring the tubing (ballooning) to remove plugs or knock scale and other debris loose from the tubing wall.
FlintA variety of chert.
Float CollarA short piece of casing run one to two joints above the end of casing. The collar contains a backpressure or check valve which stops cement from reentering the well after displacement into the annulus. It is useful to prevent channels in the cement until the cement is set.
Float ShoeSame function as a float collar but run on the end of the casing.
Float ValveThe primary, bottom hole valve in the float collar or shoe that allow the casing to self fill while running and allows the cement to pass into the annulus but helps prevent cementing U-tubing after the job. Drillable and subject to erosion wear.
FlocculationAttraction, gellation and drop out of suspended particles from a liquid.
FlocculantsMaterials used to increase visicosity. They cause colloidal particles to group into bunches or flocs.
FloodInjection of gas or water into a reservoir to drive oil towards a producing well or set of wells.
Flood PlainReservoirs that occur along ancient rivers where the rivers overflowed. Deposits are mostly silt and mud.
FloorhandA helper on the drilling floor.
FlowVery simply, movement of a fluid.
Flow-After-FlowA multipoint flow test measuring skin at each flow rate. When plotted, the intersection of the best fit line with the y-axis (skin) at zero flow rate yields the mechanical skin.
Flow Assisted CorrosionCorrosion that is accelerated by the effects of erosion removing the initial corrosion films.
Flow AssuranceA science field dealing with prevention of scales, hydrates, asphaltene and paraffin deposits and other problems that could stop flow of fluid from the subsurface, wellhead or pipeline.
Flow BackFlowing a well back after a treatment.
Flow BeanA flow restriction common in downhole chokes, surface chokes and some SSSVs.
Flow CouplingA thicker body piece of tubing above and sometimes below a tubing profile or other tool to control erosion by fluid flow.
Flow CrossA four-way connection. In a wellhead, a flow cross connects the master valve and the swab valve with two, normally horizontal, connections to the wing valves.
Flow Divider (screen)A device on the entrance to a screen to route the incoming flow more evenly across the face of the screen.
Flow EfficiencyIdeal drawdown / actual drawdown.
Flow LineThe flow connection from the wellhead to the separation facility, pipeline or storage unit.
Flow LoopA test loop of pipe in which flow characteristics are measured.
Flow PathThe subsurface course that fluids would follow as they move in a reservoir or between reservoirs.
Flow ProfileWhat the flow looks like across the cross-section of the pipe.
Flow RegimeFlow condition (e.g., mist, slug, churn, etc.) of a multiphase process stream.
Flow T or TeeA three-way connection. In a wellhead, a flow cross connects the master valve and the swab valve with the wing valve.
Flow TestA flow test designed to prove that hydrocarbon exists in the reservoir and will flow to surface. May also indicate productivity or other characteristics such as interference or boundaries.
Flow TubesTubes with a diameter slightly larger than the braded wireline or slick line that are used in the “stuffing box” on a wireline intervention to isolate the well pressure and fluid from the atmosphere. They work in combination with oil or wireline grease injection to form a hydraulic seal.
Flow WettedAny piece of a tool or the well that is wetted by the produced fluid flow.
Flowing PressureThe pressure at some datum (usually surface, FSP, or bottom hole, FBHP, measured while the well is flowing.
Flowing WellA well that flows to the surface by produced gas expansion and does not use any method of artificial lift.
FlowlineThe pipe connection between the well and the separators or tank battery.
Fluid ContactDepth of the contact point in a specific well between immiscible phases.
Fluid DensityThe mass per volume density of a fluid.
Fluid InvasionThe distance outward from the wellbore to the leading edge of the lost fluids. Varies with the permeability of the zone.
Fluid LossThe rate of loss of liquids to the formations from the fluid being circulated through the wellbore.
Fluid Loss CoefficientA measurement of fluid loss expressed in cc/min1/2
Fluid PackedLiquid filled.
Fluid PoundOr rod pound – a beam lift term where the pump is filled with gas from pump-off or too fast of an operating speed (rod speed).
Fluid Pressure GradientA measurement in the well of the pressure vs. depth. Useful for spotting liquid levels, leaks, fluid entries, etc.
Fluid SaturationThe fractional or percent amount of pore space which a specific fluid occupies.
FluidizeAdd sufficient fluid in an unconsolidated sand matrix to break cohesive bonds and lubricate grain by grain movement of sands.
FluorocarbonA seal with good resistance to aromatic fluids but susceptible to sour gas.
FLUORAZA high performance elastomer for seal assemblies.
FluoroscopeA device that uses a black light for identifying hydrocarbons on cuttings.
Flush JointA Non Upset connection in most cases.
Flush ProductionThe early, higher rate production that comes from the larger pores, fractures and vugs that empty quickly. Delivers a small, high rate flow every time the well is shut-in (recharges) and is brought back on line.
Flushed ZonePart of the rock that has been flushed with a sweep fluid. The area may have little hydrocarbons remaining.
Fly AshAsh from the burning of coal. Used as an extender in several cements and as a plug component.
Flying Leads (subsea)Flexible hydraulic hoses connected to control systems in a subsea tree.
FMEAFailure mode and effects analysis.
FMECAFailure mode and criticality effects analysis
FMIFormation micro image, a common fracture detection tool.
FMJ (control line)Ferrule metal junction.
FMWTRFormation water.
FNFishing neck.
FOFull opening.
FoamA gas in liquid emulsion. Common as a low density cleanout fluid or a frac fluid with reduced water content.
Foam BreakerOne of several materials that reduce the stability of the bubble skin in a foam and cause the foam to break.
Foam CementA cement slurry, foamed with between 40 and 60% nitrogen gas. Has a slurry density of about 7.5 to 10 lb/gal (0.9 to 1.2 g/cc).
FOCField operations center.
FoldA bend-like disruption in a rock strata such that the angle of the formation is significantly changed.
FormaldehydeAn older biocide, now rarely used.
Foot WallThe side of the fault that protrudes underneath the upper formation.
FormateOne of several low damage, low toxicity, normally high cost brine for special applications. May be one of several formation compounds.
FormationAny distinct, mapable layer.
Formation BreakdownInitiating a fracture in the formation.
Formation CompetencyThe breakdown (fracturing) pressure of a formation.
Formation DamageAn obstruction to flow. Usually a reduction of permeability.
Formation EvaluationThe analysis of formation character or properties, usually by remote logs.
Formation Gas-Oil RatioQuantity of oil dissolved in one stock tank barrel of oil at current reservoir pressure and temperature.
Formation IntegrityThe ability to resist breakup. Often taken as the fracturing point.
Formation Integrity TestA test of the fracture initiation pressure.
Formation PressureThe pressure of the fluid in the formation. The initial reservoir pressure is the pressure at discovery.
Formation ResistivityA measurement of the electrical resistivity of a formation. The measurement will be significantly affected by the type of fluid and the salinity of water based fluids within the pores of the rock.
Formation SensitivityThe tendency of a formation to react with fluids, usually filtrates from injected fluids.
Formation Volume Factor or FVFThe number of barrels of reservoir oil that shrinks to one stock tank (surface) barrel after gas breakout and light end vaporization.
Formation WaterThe connate water.
Formic AcidAn organic acid used in higher temperature wells for shallow damage removal.
FoRxo LogA focused resistivity log that uses a pad contact with the borehole wall.
FossilThe silicate replaced replica of an animal or plant.
Fossil FuelCoal, natural gas or oil.
FoulingAccumulation of deposits on a surface.
Four Point TestA flow test in which the flow rate is measured at four drawdowns to estimate how skin changes at each rate. Useful for identifying non Darcy skin or turbulent skin.
FPCSee Free Point Constant. Used in stuck pipe depth calculations.
FPHFeet per hour.
FPITFree point indicator tool.
FPPFracture propagation pressure.
FPSOFloating production, storage and offloading. An alternative to pipelines.
FPUFloating production unit.
FPWDFormation pressure while drilling.
FRAFormation rate analyser, a well performance test method.
Frac BallA technique for isolating multiple fracs using a short downhole settable ring or restriction and dropping a hard rubber ball between frac jobs. Two or more ring/ball sets can be used to stage frac a long zone.
Frac FluidThe fluid used in a fracturing treatment, may include pre and post treatment fluids.
Frac PlugA flow-through plug set after pumping a frac (between stages) in a multi-fraced well and sealed with a ball dropped from surface as the next frac stage is started.
FractionationThe process of separating natural gas into component parts or fractions such as propane, butane, ethane, etc.
Fracture AcidizingCreating a fracture in a carbonate and etching the face of the fracture to preserve flow capacity down the fracture.
Fracture Breakdown PressureThe pressure needed to initiate a fracture.
Fracture Closure PressureThe earth stresses acting to try to close a hydraulic fracture offset by the pore pressure. A measurement of the pressure at which the fractured formation closes. Generally determined by the change in slope of the pressure reading as leakoff gradually lessens the volume of fluid that is holding the fracture open, until the fracture walls meet and the pressure reverts to a decline to pore pressure.
Fracture Effective LengthNormally the propped part of the fracture that will support improved flow.
Fracture Extension PressureThe pressure necessary to extend the fracture once initiated. The fracture extension pressure may rise slightly with increasing fracture length and/or height because of friction pressure drop down the length of the fracture. Fracture roughness, fracture width and fluid viscosity also have influence on extension pressure.
Fracture Finder LogAn acoustic log that helps determine if fractures are present.
Fracture FluidsThe fluids used to fracture a well. Generally, a fracture fluid is a water based fluid with less than 0.5% total additives, most of which are common in food or household use.
Fracture Fluid EfficiencyA measurement, derived from a data frac, of the efficiency of a particular fluid in creating fracture area on a particular formation at a set of conditions.
Fracture GradientThe gradient needed to initiate a fracture.
Fracture Half LengthThe length of one wind of a fracture from the wellbore to the tip.
Fracture Initiation PressureThe pressure necessary to start a fracture from the wellbore.
Fracture NetworkThe groupings of fractures, possibly interconnected, that form a enhanced flow unit.
Fracture PackingA sand control technique coupling fracture treating (usually a tip screenout fracture) with a screen and gravel packing of the wellbore.
Fracture PadThe initial part of the fracture fluid that creates the fracture width and controls the initial fluid loss but contains no proppant.
Fracture PorosityThe porosity attributed to the natural fractures, commonly less than 2 to 4%.
Fracture Propagation PressureSame as fracture extension pressure.
Fracture Proppant Pack DensityThe loading of proppant per square foot after the fracture has been placed. Commonly between 4 and 16 lb/ft2 of fracture face.
Fracture WidthThe width of a fracture at the wellbore. Hydraulic frac width is generated by frac fluid viscosity and/or pump rate (i.e., horsepower).
FracturingA stimulation method involving injection of fluid into the well at a high enough pressure to break the rock. Fracturing “failure” of the rock is a tensile failure as the wellbore in enlarged by pressure.
Fracturing FluidsThe fluids used to fracture a well. Generally, a fracture fluid is a water based fluid with less than 0.5% total additives, most of which are common in food or household use.
FragipanDense layer of soil containing silt and sand, but no organic matter and little clay. May have extreme hardness due to compaction.
Fragmental Source Sedimentary (rock)Lithification of rock fragments.
Frangible ValvePurposely breakable valve, usually a flapper in a fluid loss device.
FRCFire retardant clothing.
Free GasGas that is not dissolved in the liquid.
Free PointA technique for estimating the highest free point in a string of stuck pipe. It is based on a differential stretch calculation with amount of pull and the free point constant (FPC).
Free Point and BackoffFree Point analysis followed by downhole unscrewing of a pipe coupling above the stuck point.
Free Point ConstantA calculation used in the stuck pipe calculation to correct for pipe wall thickness and diameter.
Free Point IndicatorA tool with strain gauges that is run on wireline and moved along the stuck pipe with successive pipe pulls until the stuck point is located.
Free Water1. the excess water that separates from a cement slurry on standing. 2. the first water that separates from the crude oil in the first stage of the separator (free water knockout or FWKO).
Free Water KnockoutThe first stage of separation in a crude that contains a large amount of water.
Freeze point (pipe movement)The depth at which the pipe is stuck.
Frequency Domain (seismic)Where the independent variable is distance and the dependent variables are strength of the signal and frequency of the signal. (A domain is a mathematical function with dependent and independent variables.)
Fresh WaterWater with less than about 600 ppm total dissolved solids. Suitable for drinking.
Fretting CorrosionDeterioration at interfaces of two metals accelerated by their relative motion.
Friable SandA sand with an unconfined compressive strength of 300 to 1000 psi. Crushable with forceps.
FrictionThe resistance to a object’s passage through a fluid (or a fluid’s passage past a stationary object). Affected by viscous resistance, density, wall contact (vessel radii).
Friction CoefficientA dimensionless value expressing the roughness of the pipe.
Friction Lock (coiled tubing)A state where the wall drag or friction is high enough to prevent further movement of the pipe.
Friction ReducerA material, usually a polymer that reduces the friction of flowing fluid in a conduit.
Front-end CostsMoney paid or costs at the start of a project (engineering, legal, contracts, etc.), before on-site activities begin.
FrontSim3D streamline model.
FrothA foam with very high internal gas volume, usually 90%+ gas. High viscosity and often very stable.
FRPFiber reinforced pipe.
FRPFailure to release packer.
FRUCOSFinal report until change of status.
FSNFailure to set in nipple/sidepocket.
FSPFailure to set packer.
FSV (completions)Formation saver valve. A check valve that prevents fluids from reaching the formation.
FTC (SSSV)Fail to close on demand.
FTHFailure to hold in nipple/sidepocket.
FTHPFlowing tubing head pressure.
FTO (SSSV)Fail to open on command.
FTPFlowing tubing pressure.
FTRFailure to release from nipple/sidepocket.
Fuel OilOne of many refined petroleum oils such as heating oil, diesel, etc.
Full Gauge HoleA wellbore drilled with a full gauge bit (maintained initial diameter).
Funnel ViscosityA viscosity measurement based on the number of seconds that it takes for 1 liter of fluid to flow through a Marsh funnel.
FuranAn organic resin, formed by polymerization reaction of furfuryl, used in consolidation, zone shut-off and water control.
Fusible Plug or LinkAn emergency shutdown device activated by fire or thermal overload. (Note
Fusible VentA pressure relief valve that opens when temperatures increases sufficiently to melt an activation linkage.
FVFlapper valve.
FVFFormation Volume Factor.
FWFresh water.
FWHPFlowing wellhead pressure.
FWHTFlowing wellhead temperature.
FWKOSee Free Water Knockout.
FWSFish and wildlife service.
GThe acceleration of gravity measured in ft/s2 or m/s2. (1G = 32 f/s2 or 9.8 m/s2.
G-functionDimensionless function used in shut-in time normalized to pumping time. It is used to analyze pressure-dependant leakoff.
G&GGeology and geophysics.
Gage JointAn older well design process of using a single joint of the heaviest wall casing in the well just below the wellhead. (Note – this restricts access of fullbore tools to all points below the joint.)
Gaging NippleA small opening in the top of a tank, allowing gaging of the contents.
GalenaLead sulfide, PbS. A mud weighting additive for high mud weights.
GallingThread damage from lack of lubrication or mismatched metals.
Galvanic AnodeSacrificial anode.
GalvanicCorrosion between two dissimilar metals - couplings, centralizers, pumps, packers, profiles – usually severe metal loss on one metal near contact point. May see galvanic loss on a single metal with current.
Galvanic SeriesA ranking of metals from the easiest corrodible (magnesium) to the most difficult.
GalvanometerA sensitive ammeter
Gamma Ray IndexA clayiness index determined from the difference between the radioactivity level of the zone of interest and that of clean rock compared to the difference between the radioactivity level in clay shale and that in the clean rock.
Gamma Ray Log or GRUses a scintillation crystal and a photomultiplier tube to measure naturally occurring and artificially induced gamma-ray radiation. The gamma-ray radiation is a signature of the formations in a well – very useful in depth control. Used in open hole or pipe and also used to spot changes in radiation (NORM scale) and radioactive tracers.
Gamma (seismic)Unit of magnetic survey map. 1 gamma = 1 nanotesla or 1 gamma = 10-5 gauss.
Gang (rig)Crew.
Gang Pusher (rig)Supervisor.
GAPGeneral allocation program.
Gap Test (perforating)A test of the sensitivity of the perforating charge to firing from a detonating cord. May be used to spot changes in charge explosive or differences in loading.
Gardner’s Equation (seismic)Empirically derived equation that describes the general relationship in rock between bulk densities (r) and acoustic velocities (v). r = 0.23v0.25.
Gas AnchorA gas separation device, usually a perforated pipe section, in a beam lift well that helps break gas out of the liquids, preventing gas entry and resultant gas lock of the pump.
Gas BusterA device that helps knock out gas from circulated well fluid.
Gas CapA zone of free gas above an oil deposit. The gas cap occurs where the oil is oversaturated with gas (past the solubility limit). When a gas cap is not present at discovery, the oil is above the bubble point.
Gas Cap DriveA reservoir drive mechanism in which gas expansion in the gas cap pushes the oil towards the wellbore.
Gas CondensateThe liquids, generally straight chain alkanes in the C2 to C6+ range, than can condense from gas when the temperature and pressure drop sufficiently low.
Gas ConingGas from a fee gas cap that goes downward toward the top perforations in response to a drawdown.
Gas CutLiquids with free gas. Usually refers to drilling or completion liquids. May indicate a kick if the gas is present in large enough quantities.
Gas DriveFlooding a oil reservoir from the top of the reservoir or an updip location, to push the oil towards a producing well.
Gas Effect (on logs)A difference in porosities caused by the compressibility of gas in porosities estimated by the formation density log and the neutron density log.
Gas Formation Volume FactorThe volume of reservoir gas resulting in one standard cubic foot.
Gas GathererThe entity that contracts with the producer to take the gas from the wellhead to the plant or market.
Gas GravityRatio of the gas density to the density of air. Equal to the ratio of molecular weight of gas to that of air (28.97).
Gas HydrateImmense deposits of natural gas tied up in clathrate structures with water. Found extensively.
Gas-In-PlaceThe original amount of gas in the reservoir before production.
Gas InjectionThe technique of injecting gas into a reservoir. It may be done for pressure maintenance, oil viscosity reduction, light end stripping or storage.
Gas Kick (drilling)An unexpected and unwanted entry of gas into the wellbore during drilling or well operations.
Gas LiftOne of the artificial lift methods that uses gas injected down the annulus and interspersed into the flowing fluids in the tubing to lessen the density and to assist in vertical flow by gas expansion.
Gas Lift DummyA solid body insert that replaces and blanks-off a gas lift mandrel pocket designed for a valve.
Gas Lift MandrelA section of pipe used in the tubing into which a gas lift valve can be inserted. The mandrel will allow communication with the annulus gas lift supply through the valve.
Gas Lift Side Pocket MandrelA type of gas lift mandrel that allows full bore passage. The valve “pocket” is on the side of the pipe.
Gas Lift ValveA pressure operated valve, placed in a gas lift mandrels at designed points in the well. The gas lift supply gas is routed through the valves into the tubing. The top valves close and the lower valves open as the static liquid level drops in the well (the well is unloaded).
Gas Lift Valve (Injection Pressure Operated Valve)Gas lift valves where injection gas enters the valve and acts on the effective bellows area, overcoming the precharge in the valve and opening the valve (the retracting bellows lifts the needle off the seat) to allow gas lift gas flow from the gas filled annulus through the seat and the reverse flow check valve, and into the tubing.
Gas Lift Valve (Production Pressure Operated Valve)Production fluid enters the valve and acts on the effective bellows area, compressing the bellows against the precharge pressure, lifting the needle off the seat and opening the valve. The injection gas then flows through the seat, through the reverse-flow check valve and into the tubing.
Gas LiquificationThe process of cooling gas to -162oC, reducing its volume by 600 fold over the gas volume at standard conditions.
Gas Lock (pump)A pump filled with gas that it cannot expel and where no further fluid will enter the pump. Common in beam lift pumps that pump off or are used in high GOR wells.
Gas Lock (facilities)A gas retention device that permits gauging the tank without loosing gas to the atmosphere.
Gas-Oil ContactThe changing contact of the gas cap and the oil below in the rock.
Gas-Oil RatioThe number of standard cubic feet of gas contained in a barrel of oil.
Gas PermeationInvasion of gas into a solid, usually an elastomer, but sometimes referring to a metal.
Gas SaturationThe fraction of the porosity in a zone that is occupied by free gas.
Gas ShowAny indication of gas in the drilling fluid or cuttings that indicates gas production from a reservoir that has been drilled.
Gas SpikingAdding gas to an injected fluid or treatment to reduce the injected water volume and provide energy for flowing the well back after the treatment.
GasificationThe production of gas from liquid or solid fuels.
GasketAny of several replaceable seals in equipment or tools.
GasolineNormally C7-C10 fuel, with a flash point of -40.
Gate ValveA valve with a sliding bar – common in the oilfield as tree valves.
Gather (seismic)A display of the input data in a stacking process designed to show all the seismic traces corresponding to the same depth.
Gathering Agreement (contract)An agreement detailing the conditions for entry of the producer's gas into the gathering system.
Gathering LineThe flow line from the well to the separator or tank battery.
Gauge (drilling)The diameter of the bit of the hole drilled by the bit when there are no washouts.
Gauge (screens)A rating where each gauge point equals 0.001”. A 12 gauge screen has 0.012” openings (about 300 microns).
Gauge CarrierA downhole tool that houses gauges.
Gauge DiameterThe OD of a bit or tool used downhole.
Gauge HoleA drilled hole with no washouts; the same diameter as the bit.
Gauge PressurePressure read by a gauge that is set to zero at atmospheric pressure.
Gauge RingA short, wireline-run tool that checks the id of a well bore.
GCGathering center.
GCIGas cap injection.
GCVGas control valve.
GDGravity drainage.
Gear ReducerA pump or motor speed reducer.
Geiger-Mueller CounterRadioactive measuring device.
GelA fluid with a higher than normal viscosity created by a gallant material such as polymer.
Gel StrengthThe ability of a fluid to suspend solids.
Gel Strength (drilling)The shear stress measured at low shear rate after the mud has set for a period of time.
GeochemistryThe branch of chemistry dealing with the specialized reactions of downhole fluids and formations.
Geologic Cross SectionVertical cross section (vertical is depth and horizontal is lateral distance) between two points through a rock section.
GeologyThe science that deals with the study of the planet earth.
GeophoneAn instrument that detects vibrations passing through the earth’s crust.
GeophysicistUsually a professional involved with application of physics to geology, e.g., seismic interpreter.
GeophysicsThe science of the physical properties of the earth.
GeopressuredOverpresured zone.
Geo-steeringUsing the formation data generated by a measurement while drilling system to assist in drilling a wellbore to a specific target in the formation.
Geothermal energyThe heat of the earth, usually from produced natural steam, heat recovered from circulated water or direct heat-to-energy conversion (on-going research).
Geothermal GradientThe gradient reflecting the amount of temperature rise as the well depth increases. Normally about 1.1 to 1.8o F per 100 ft of true vertical depth increase.
Geothermal WellsThe wells that produce geothermal energy (heat).
Geronimo Line (rig)A safety slide or a line from the derrickman’s platform to the ground, used in an emergency.
GHGGreen house gasses.
GIIPGas initially in place.
GilsoniteAn asphaltic drilling fluid loss additive.
GISGlobal information system.
GIVGas injection valve.
GJGigajoule; 1,000,000,000 joules.
GL (datum)Ground level.
GL (lift)Gas lift.
Glacial DriftGeneral term for debris and stones transported by glaciers.
GLADSoftware package, gas lift assisted design.
GlandA seal around a moving rod.
Glass DiskOften a rupture disk to allow a well to flow after it is broken by a dropped bar.
GLL (subsea)Guidelineless.
GLMGas lift mandrel.
GLRGas / liquid ratio.
GLVGas lift valve.
GlycolA hydrate inhibitor or freeze-up preventer.
Glycol DehydratorsEquipment for removal of water from natural gas.
GneissA coarse, metamorphic rock with some parallel alignment of granular minerals and alternate bands of flaky or elongate minerals.
GNFTGas no-flow test.
Go DevilVarious. A wireline cutter. A cleanout pig. A sleeve, etc.
GOCGas / oil contact
Gooseneck (coiled tubing)The CT guide arch over the injection head.
GORGas / oil ratio. May refer to a solution GOR or total GOR.
GOSGulf of Suez.
GPFGas production facility.
GPGGrains per gallon.
GP/GL (subsea)Guide post guide line.
GPMGallons per minute.
GPRGravel pack replacement
GPSGlobal positioning system.
GRGamma ray log.
GrabenA block of the formation that has slid downward between two faults.
Graded Production Acreage (GPA)A term that expresses the producability of a part of the reservoir for purposes of comparing one producing area to another.
GradientChange in pressure or temperature per unit depth.
Gradiomanometer (well logging)A device that measures the density of fluids along a fluid column.
Gradiometer (seismic)A device that measures an electric field at multiple points at the same time. The gradient is the difference in measured values per unit of distance between the measuring points.
Grain (fluid loss additive)Literally grain or animal feed that is circulated with mud to act as a identifiable marker.
Grain (formation)A small piece of the formation composed of a single piece of sand.
Grain DensityThe density of the rock components, without the effect of porosity.
GrainstoneAn often high permeability limestone where large grains are in contact. Only high perm if fines are absent.
Grand SlamA combination of logs or a computational procedure for calculating the depth of invasion and the resistivity of both invaded and uncontaminated zones, based on a dual-induction-laterolog and a proximity log or microlaterolog.
GraniteCommon igneous rock. No effective permeability.
Granite washA sandstone with a large percent of weathered granite grains.
GrappleA spring like device, resembling a interlocking finger puzzle that allows a round work piece to slide through the ID when in compression, but grips the work piece (or fish) when a tension load is applied. Common in overshot fishing devices.
GravelLarge, well sorted and consistently sized sand used to hold back a soft formation.
Gravel PackA sand control completion that uses a larger gravel to stop the formation sand and a screen to stop the gravel.
Gravel Pack Evaluation ToolUses porosity, density and/or tracer tools to determine presence of gravel and placement of gravel type between the screen and the hole or casing.
Gravel Pack LogA neutron-type device that evaluates the packing completeness or condition of the gravel pack. The log is useful for estimating voids in the pack.
Gravel ReserveThe amount of gravel above the top perf, after the job, in a well with deviation less than about 50o.
GravimeterAn instrument that measures differences in the gravitational attraction. Particularly useful in finding salt domes.
GravimeterA device that measures the local gravitational pull. Gravimeters are useful for determining small changes in the gravity. Very useful for detecting salt domes.
GraviometerDevice that records the specific gravity of a fluid.
Gravity (API)The specific gravity of a fluid in API units, where fresh water is 10. Lighter gravity crude has higher API numbers.
Gravity AnomalyDifference between theoretical calculated and observed terrestrial gravity; excess gravity us positive and deficiency is negative.
Gravity DrainageThe movements in a reservoir driven by gravity.
Gravity MeterA device that measures gravity changes over a specific area.
Gravity Unit (seismic)An acceleration unit (gu) used in gravity measurement. 1 milligal = 10 gu.
Gravity SpecificGravity of a fluid expressed as a ratio of a standard fluid. For liquids, the standard is fresh water. For gases, the standard is air.
Gravity SurveyA exploration method that uses an instrument to measure the intensity of the earth’s gravity. Areas with unusual readings may indicate traps or structures that could contain hydrocarbons.
Gray ShaleAn indeterminate description of a shale with lower carbon content than a “black shale”.
GraywackeA sandstone, characterized by angular-shaped grains of quartz and feldspar set in a matrix of fine grains. May have high hardness.
Grease InjectorA pressure control method for forming a pressure seal around braded line and electric line. Grease is injected between special tubes in a high pressure housing. The tubes are slightly larger than the line and grease seals the remaining area.
Green CementUncured cement.
GRIGas Research Institute.
Grind OutA shake out of solids, centrifuged or otherwise separated from the produced or circulated fluids.
Gripper BlocksThe contacting blocks on a coiled tubing injector that grip and move the coiled tubing.
GRNGamma ray neutron.
Gross AcresThe total acres in which the company owns an interest.
Gross PayThe total thickness of the pay zone, whether or not it is productive.
Gross ProductionTotal production. Has been used as total fluids produced. Has also been used as cumulative hydrocarbon production.
Ground BedAnodes buried in the earth to supply cathodic protection to equipment.
Ground WaterWater subject to recharge from surface water accumulation.
GroutUsually cement, water and some additives used to fill a void. May also be bentonite and water.
Growth FaultA fault that is created in an actively forming basin. It is often parallel to the shore line when created.
GRPGlass reinforced plastic.
GSA common inside fishing neck design. Also a series of running tools.
GscmGiga standard cubic meters (one billion standard cubic meters).
GSOGas shut-off.
GTLGas to liquids. A conversion of gas to a liquefied state by compression and cooling. Also, a conversion of gas by chemical methods to an easily transportable liquid hydrocarbon of a more stable, longer chain.
GTS (well testing)Gas to surface.
GTWGas to wire. Generally converting the gas from a small field to electricity at the well site and transporting the power by the electrical grid.
Guard LogA formation resistivity tool that involves the use of a guard tool.
Guard ToolA tool that produces the effect of one elongated current electrode from which current flows radially in all directions to a distant current-return electrode. The output from the tool can be focused to improve logging resolution in thin beds.
GuarA natural polymer from the guar plant. Common in fracturing fluid gellation.
Guide RingA protective cylinder or ring to guide downhole tools past casing obstructions.
Guide ShoeA short section of casing with a rounded nose of a drillable material and a port through the center to allow circulation.
GumPolymer gellants.
GumboSticky, reactive shale formation.
GunPerforating gun.
Gun BarrelA vertical separator vessel.
Gun the PitsMix the pits.
Gunk PlugCement (or some clays) and diesel oil dispersion that thickens when water is contacted.
GusherA well drilled into a high pressure formation that results in an immediate surge towards the surface. In the days of cable tools with minimum fluid (hydrostatic) head, the formation fluids often flowed to surface when the pay zone was penetrated.
Guy Wire (rigging)A support wire or cable used to stabilize a mast on a rig or other structure.
GVGate valve.
GWCGas water contact.
GWPCGround Water Protection Council.
GypSee gypsum.
Gypsum or GypA common form of calcium sulfate precipitate or scale. CaSO4-H2O.
Gyroscopic SurveyA survey of a wellbore that measures its position and trajectory.
hThickness (or pay height).
H crossover or profileA profile with circulation port.
hjLayer thickness
H2SHydrogen sulfide.
HadianThe oldest eon in earth’s history. Extends from the origin of earth to about 3.9 billion years ago.
Hairy IlliteA fibrous form of illite, also described as spider-web illite. The hairs or fibers randomly project into the pore space. In most cases, the clay is not overly reactive with water but the fibers do act as a trap for migrating particles.
Half-LifeThe amount of time required for one half of the population of radioactive atoms to decay.
Half MuleshoeA pipe end cut on a diagonal to ease the string through restrictions or guide tools through.
HaliteSodium chloride, NaCl.
Hall PlotA test of injectivity that is useful for establishing formation behavior during pumping.
Hammer UpConnect unions on treating iron.
Hand-Over DocumentThe document containing operational and test data used to transfer custody of a well from drilling to operations or production after completion or from production to drilling when repairs are needed.
Hang FireAn unplanned delayed firing of explosives after the initiation attempt - various causes.
Hang RodsSuspending sucker rods in the derrick from rod hangers.
HangerA mechanical device that suspends all or part of the weight from a tubular string, transferring the load to the well head and the earth.
Hanger PlugA plug placed below the BOP prior to a pressure test.
Hanging Wall BlockThe body of rock that lies above an inclined fault plane.
HAPHazardous Air Pollutant.
Hard Shut-inTo close in a flowing well with the BOP with the choke line closed.
Hard WaterWater with a high mineral content.
Hardness (metal)Measure of the resistance encountered in pressing a steel ball into the metal.
Hardness (mineral)The resistance of a mineral to scratching . Determined by the Mohs scale.
Hardness (water)Ion content of water.
HardpanThe relatively hard layer of soil just below ground surface.
HatchThe opening on a tank.
HAZHeat affected zone. The area around a weld or other area in the steel that has been modified by heat and, as a result, is more subject to some forms of corrosion.
HazardA condition or object that has the potential to cause harm risk is the probability of an event happening times the impact of its occurrence on operations. (Impact is the effect on conditions or people if the hazard is realized (occurs) in practice and potential is the likelihood that the impact will occur.)
HAZOPHazardous operations.
HBPHeld by production, a leasehold kept in force by production.
HClSee hydrochloric acid.
HClO2Chlorine dioxide, a bacteria killer.
HCPV (reservoir)Hydrocarbon pore volume.
HDPEHigh density polyethylene plastic
HESee Hydrogen Embrittlement.
Heading (logging)The information on the well at the top of the log.
Heading (well flow)The flow of slugs of fluids (unstable behavior).
Heat Affected ZoneHAZ, the metal adjacent to a weld or other heated area that has been altered by the heating.
Heat Transfer CoefficientCoefficient describing the total resistance to heat loss from a producing pipe to its surroundings. Includes heat loss by conduction, convection and radiation.
Heater TreaterA separator that uses heat to speed the separation of emulsions.
Heating OilOil used for residential heating.
Heave (geology)The horizontal displacement (travel) of a fault.
Heave (ship)The vertical motion of a vessel.
HeavingPartial or full collapse of the wellbore by particles of shale.
Heavy OilLower gravity, often higher viscosity oils. Normally less than 28o API gravity.
HECHydroxyl ethyl cellulose, a synthetic polymer.
HeelThe area of pay closest to the casing in a highly deviated well.
HEGFHigh energy gas fracturing.
HEGSHigh energy gas stimulation.
Held by ProductionKeeping an oil and gas lease in effect by producing the well.
Helical BucklingA buckling characterized by maximum wall contact. Takes the form of a wound spring.
HematiteA natural deposit of iron oxide.
Henry HubA pipeline interchange/delivery point. Used as a benchmark in gas futures for natural gas pricing.
HESHalliburton Energy Services.
Hesitation SqueezeA cement squeeze technique where the cement is squeezed into a channel or leak at a low rate, then allowed to sit and dehydrate by leakoff, before again raising the pressure. The action gradually builds a dehydrated cement node that blocks the channel.
HeterogeneitiesDifferences.
HeterogeneousRock with differences in texture, permeability, porosity or other factors.
HexafluorosilicatesA byproduct and precipitant of the HF – silica reaction.
HFHydrofluoric acid.
HHpHydraulic horsepower.
High Angle WellA highly deviated well.
High AnticlinalTop part of the structure, expected to be the best place to encounter accumulation of hydrocarbons.
High Density Basement (seismic)The deepest, thick, high density rock that serves as a density contrast in an area.
High Pressure Water CleaningCleaning at less than 5,000 psi water pressure.
High Rate Water PackA sand control operation in which gravel is injected into a well where a screen has been placed. The pressure of the injection is usually at or near the fracture pressure of the reservoir and a pressure packing of all perforations ensues. Some perf breakdown occurs. The amount of gravel placed is about 40 to 75 lbs/ft of perfs.
High Sulfur OilUsually an oil with more than 1% sulfur.
Hindered SettlingA flow region in a near vertical well, in which rising fluid or gas hinders the fall rate of liquids of solids, enabling flow from the well.
Hinge FaultA fault along which there is increasing offset or separation along the strike of the fault plane. Measured from the initial point of separation.
Hipp TripperA brand name of a tool used to deliver rapid impact stokes to a small BHA downhole. Operated by fluid flow. Usually run on CT.
HIPPS (offshore)High integrity pressure protection system.
HLNHydraulic landing nipple.
HMSVHydraulic multi-service valve.
HMXHigher temperature perforation charge explosive. A modified RDX.
HNBRHydrogenated nitrile (bunadiene rubber).
HNSVery high temperature perforation charge explosive; hexanitrostilbene.
HoistTo lift. Also the equipment used to lift.
Holdup (flow)The volume fraction of a specific fluid in the upward moving stream.
Hole CleaningTransporting drill cuttings or fill to surface.
Hole OpenerA larger device (usually of a fixed diameter) that enlarges the wellbore to a diameter equal to or less than the upper casing drift). Compare to an under-reamer or watermelon mill or string mill.
HolidayA small hole in a coating.
Hollow CarrierA perforating gun that surrounds the charges and contains much of the shock of the detonation.
HoloceneAn epoch of geologic time from present to 10,000 years ago.
Hook (drilling rig)The hook on the traveling block from which the elevators are suspended.
Hook LoadThe actual weight of a pipe string measured at the surface; affected by buoyancy, friction and other factors in the wellbore.
Hook Wall PackerPackers equipped with drag blocks or springs so rotation of the pipe unlatches the slips and sets the packer.
Hooke’s LawA statement of elastic deformation, where strain (deformation) is proportional to stress (applied stress).
HopperMixing chamber where dry components can be evenly mixed with liquids. The dry materials are introduced at the bottom of the hopper through a nozzle.
HorizonA specific sedimentary layer across a study plane.
Horizontal DrillingA well drilled in a manner to reach an angle of 90 degrees relative to a level plane at its departure point at the surface. In practice, the horizontal section of most horizontal wells vary several degrees.
Horizontal treeA subsea production tree with a horizontal valve arrangement to the side of the tubing hanger, permitting direct access to the tubing and tubing hanger without having to remove the tree during a workover.
Horizontal WellFor a strict definition, a 90o deviated well. Actually the well covers a range of “highly” deviated wells (80o to >90o). In the strictest terms, the deviation is measured as 90o from vertical, but tilting bedding planes may make the deviation to the bedding planes a different judgment.
Horner PlotA type of build up pressure test plot. The Horner plot uses a recording of the pressure during pressure build-up to predict its virgin reservoir pressure. The slope (m) of the extrapolated line reflects the nature of the reservoir rock and the fluids flowing through the rock.
Horse HeadThe head of a beam lift pump jack, onto which the bridle to the yoke and polish rod attaches.
HorstA block of the formation that has been raised between two faults.
Hostile Environment (well)High temperature, deep, high pressure or highly corrosive or erosive producing environments (e.g.
Hot OilA technique of injecting or circulating heated crude oil from the surface to help remove paraffin deposits. It is usually only effective for shallow depths when circulated.
Hot Spot (mantle)An area in the upper mantle from which magma rises. A hot spot can endure for 10 million years or more.
Hot Spot (shale)A section of the formation with high gamma ray readings (usually above about 200 SPI units).
Hot StabA penetration under pressure.
Hot TapA method of attaching a valve or port to a pressurized line without removing the pressure.
Hot WorkOperations requiring welding, cutting, grinding, burning, etc.
HP (facilities)High pressure facilities and lines.
HP (incident)A high potential incident.
HP (well)High pressure facilities or separator train.
HPGHydroxyl propyl guar; a chemically modified guar.
HPHTHigh pressure, high temperature. HPHT is where the undisturbed bottom hole temp at prospective reservoir depth or total depth is greater than 300oF or 150oC, and either the maximum anticipated pore pressure of any porous formation to be drilled through exceeds a hydrostatic gradient of 0.8 psi/ft, or a well requiring pressure control equipment with a rated working pressure in excess of 10000 psi.
HPLTHigh pressure, low temperature. Identification of the problem zone for hydrate formation.
HRWPSee high rate water pack.
HSHigh sulfur.
HSEHealth, safety and environment.
HSFOHigh sulfur fuel oil.
HSP (lift)Hydraulic submersible pump
HSP (fracturing)High strength proppant.
HTHPHigh temperature, high pressure.
HCHughes Christensen.
HUDHold up depth.
Huff and PuffA tertiary recovery operation, consisting of first injecting steam, followed by flowing the well back to recover oil that has had its viscosity reduced by application of the heat.
HWDPHeavy weight drill pipe.
HWHR (subsea)Hot water hydrate removal.
HWOHydraulic workover, usually working under pressure. Some HWO units are set up with pipe handling capacity as are snubbing units.
HWUHydraulic workover unit.
HXT (subsea)Horizontal tree.
HYDHydraulic.
HydrateA clathrate type molecule (cage) of gas and water that forms in a certain range of temperature and pressure in wells. In flow lines, hydrates are a problem in deep-water sub sea wellheads and flow lines, but also seen in some nearly dry, onshore gas wells. In-situ hydrates are a potential natural gas resource.
Hydrate SuppressantsMaterials that lower the formation temperature of hydrate molecules.
HydrationInclusion of water into the structure of a material.
Hydraulic CentralizerA downhole tool centralizer that is engaged by raising hydraulic pressure.
Hydraulic DisconnectA disconnect, usually in a BHA that is activated by hydraulic pressure.
Hydraulic DiversionA diversion technique for injecting fluids into separate zones without added diverters. Limited numbers of perforations or set obstructions in the wellbore can build pressure at higher rates and cause diverting to lower permeability or damaged zones.
Hydraulic FractureA fracture creased by hydraulic pressure – usually intentional.
Hydraulic Hammer EffectAn effect, also known as water hammer, in which a pressure wave can be generated behind a rapidly closed valve. The pressure wave travels at sonic speed, reflecting off of the pipe end or the bottom of the well and returning to the valve. If the valve is closed before the wave returns, a hydraulic impact is produced on the valve. Extreme cases are seen with slam closures of sub surface safety valves. Much smaller effects may be produced in front of the valve in a few cases.
Hydraulic HeadPressure exerted by a column of liquid.
Hydraulic IsolationPartial isolation without using a direct seal between the device and the flow path. Efficiency depends on fluid viscosity, clearance and flow rate.
Hydrostatic pressurePressure created by a column of fluid that expresses uniform pressure in all dirrectins at a specific depth and fluid composition above the measurement point.
Hydraulic PumpAn artificial lift system that is powered by injected fluid (usually water), that powers a pump similar to the rotating pump used in electrical submersible pumps.
Hydraulic Set PackerPacker set by hydraulic pressure.
Hydraulic Well WorkoverA snubbing job in which the well is workover without killing the well with fluid. Usually accomplished by multiple barriers that seal on the tubulars.
Hydraulic Window (drilling)The allowable effective fluid density difference between the fracturing pressure and the pressures exerted b a fluid that are needed to control formation flow and the wellbore.
HydraulicsA general term referring to how fluids move and unloads cuttings, etc. in a well. Most common in drilling to insure claring and effective pressure control.
HydrilA manufacturer of BOP and other well equipment. Also a common term for a section of the BOP stack that utilizes a large rubber “donut” that can seal on irregular surfaces or even on itself.
HydrocarbonA compound formed essentially of carbon and hydrogen.
Hydrochloric AcidThe most common oilfield stimulation acid. A mixture of hydrogen chloride gas in water. Useful for removing calcium scale, some mud and cement damage and very shallow stimulation of formations with some calcium in the flow path.
HydrocycloneA cone shaped device for separating fluids and the solids dispersed in fluids.
Hydrofluoric AcidAn acid that reacts with clays. Very harmful to humans in concentrated form.
Hydrogen BlisteringThe formation of cavities just below the surface in a metal. Growth of the near-surface blisters may result in bulges in the metal.
Hydrogen EmbrittlementA corrosion mechanism in which atomic hydrogen enters between the grains of the steel, and causes the steel to become very brittle.
Hydrogen Induced CrackingStep-wise internal cracks that connect hydrogen blisters.
Hydrogen SulfideA toxic, corrosive, colorless gas with the characteristic smell of rotten eggs in low concentration. An acid gas.
Hydrogen Sulfide CrackingMinute cracking just under a metal’s surface caused by exposure to hydrogen sulfide gas.
HydrometerAn instrument that is dropped in a liquid to measure its specific gravity.
HydrophilicHaving affinity for water.
HydrophobicRepels water.
HydrophoneA pressure sensitive receiver that transforms sound to electrical signals that may be recorded.
Hydroset ToolA tool that is set by hydraulic pressure.
HydrostaticThe pressure exerted by a column of a single density fluid. For a non-compressible fluid the pressure (in psi) at any depth = 0.052 x depth x fluid density in lb/gal.
HydroxideCompounds having the OH ion. Bases or caustics.
HygroscopicAbsorbing water from the air.
Hyperbolic DeclineVariable rate of decline over the life of the well.
IAInner annulus.
IADCInternational Association of Drilling Contractors.
IAMIntegrated asset modeling.
IAPInner annulus pressure.
IAxOAInner annulus to outer annulus.
IBPInflatable bridge plug.
ICInner casing.
iChokeInjection choke model. A model that helps identify critical junctures in injection support.
ICOTAInternational Coiled Tubing Operators Association.
ICPInflatable casing packer.
ICPInside casing gravel pack.
ICPInitial circulating pressure.
ICV (injection)Injection control valve.
ICV (completion)Internal control valve.
IDInside diameter.
ID Drift (of pipe)The OD of the drift that will pass through the tube.
IDmMinimum ID.
IDnNominal ID.
Ideal GasA theoretical gas that perfectly obeys PV=RT/m, where V is the specific volume, T is the absolute temperature, R is the universal gas constant, and m is the molecular weight.
IEEEInstitute of Electrical and Electronics Engineers.
IEMInvert emulsion mud.
IFPIntegrated field planning.
IFTInterfacial tension.
IGLRInjection gas lift ratio.
Igneous RockSolidified molten rock. Specifically granites, etc.
IGPInside casing gravel pack where no gravel is placed into the perforations.
IGRF (seismic)International Geomagnetic Reference Field.
II (injection well)Injectivity index. ILD (logging)
IlliteA clay type of varying form and composition. Rarely water sensitive. May occur in unusual cases as a fiberous deposit that can act as a particle trap.
ILM (logging)Medium induction log.
SFLU (logging)Spherically focused resistivity log. Measures the resistivity of the flushed zone (Rxo). In a hydrocarbon zone, the curve may report higher resistivity than deep (ILD) or medium (ILM) induction curves because the flushed zone contains mud filtrate and residual hydrocarbons.
IM Standard (BP)Integrity management standard.
ImbibitionAbsorption and adsorption of fluids into the pores of the rock.
IMFIntermediate manifold facilities.
Immature OilYoung crude or crude that has not been thermally “processed” by heat to generate lighter ends (short carbon chains) and gas.
Impact (in risk analysis)Impact (or consequence) is the effect on conditions or people if the hazard is realized (occurs) in practice and probability is the likelihood that the impact will occur. Risk is a function of probability and impact (consequence).
ImpedanceTotal opposition (resistance, capacitance and inductance), expressed in Ohms, to the flow of current.
ImpellerThe rotating pump component that drives the fluid in a centrifugal pump.
ImpermeableRock with passages so small that no effective flow can take place. Note
Impressed CurrentA corrosion control mechanism in which a small charge is used to oppose the electrical current generated by a corrosion cell. The current reduces metal loss at the anode.
Impression BlockA soft lead flat end or cone bottom on a steel tool. The impression block can give ideas on what it is set down upon. Usually run via slickline and set down once to get an imprint. Also derisively called a confusion block.
Impression PackerAn inflatable packer with a soft rubber shell. It is inflated in an interval and then deflated; the rubber shell is a reverse cast of the imperfections in the well. Used to confirm split pipe or perforation density.
Improved Oil Recovery or IORAny of various methods, chiefly reservoir drive mechanisms and enhanced recover techniques, designed to improve the flow of hydrocarbons from the reservoir to the wellbore or to recover more oil after the primary and secondary methods (water and gas floods) are uneconomic.
Impulse-Fracture TestingAn injection-type test with a goal of estimating reservoir parameters.
Inc (drilling)Inclination or the deviation of the well from vertical.
Inclination (wellbore)The measurement of a wells deviation from vertical. When used with fluids, a positive number indicates upflow and a negative number may represent downflow.
Inclusion (corrosion)A nonmetallic phase such as an oxide, sulfide, or silicate particle in a metal.
Incompatible WatersWaters, which, when mixed, may cause a precipitate.
IndependentTypically a non-integrated oil or natural gas company, usually active in a few sectors of the industry.
Index FossilsFossils specific to a certain geologic time.
Indexing ToolA tool that operates by pipe rotation or reciprocation.
Indicator (chemical)A chemical in a titration reaction that changes color at a certain pH.
Indicator (mechanical load)A dial or gauge.
Induced Spectral Gamma Ray LogAn activation log.
Induction LogOpen-hole log that measures resistance difference between formation and wellbore fluids to various depths in the formation.
InertA general term meaning non-reactive with the materials with which it contacts.
Infant FailureAn early failure; often related to poor design, candidate selection or installation problems.
Infill DrillingAdding new wells in an existing field within the original well patterns to accelerate recovery or to test recovery methods.
Infinite Acting ReservoirA reservoir that acts during a short term test as if it had no boundaries.
Inflatable PackerA device with metal slats or cords woven around a rubber bladder with an elastomer cover designed to inflate in the wellbore and provide isolation.
Inflow Performance RelationshipThe relationship between reservoir or pore pressure, flowing bottom hole pressure, and production rate. Can be calculated from reservoir properties (reservoir pressure, permeability, skin) or can be a curve fitted to experimental data from the well.
InfluxInflow.
InhibitorA chemical that slows a reaction between a reactive fluid and a material. Specifically, acid corrosion inhibitors slow the reaction of acids on steels.
Inhibitor IntensifierA chemical that assists the corrosion inhibitor in slowing corrosion in harsh conditions.
Inhibitor TruckA special truck equipped with a small pump and an inhibitor checmical tank used to treat wells on a scheduled basis.
Initial Circulating PressureThe pump pressure required when a shut-in well that has taken a kick is circulated after initially opening the well.
Initial Gel StrengthThe maximum reading from a direct reading viscometer (e.g., Fann VG meter), after the fluid has set for ten seconds.
Initial PotentialFlow rate, often from a short test, measured during a test at or just before completion.
Initial Reservoir PressureThe pore pressure in a reservoir at the time of discovery.
Injection GasGas injected into the reservoir to maintain pressure.
Injection LogA downhole recording or log that shows where fluids are leaving the well bore. It is used to establish injection profile and to check for leaks and crossflow.
Injection Pressure Operated Valve (gas lift)Gas lift valves where injection gas enters the valve and acts on the effective bellows area, overcoming the precharge in the valve and opening the valve (the retracting bellows lifts the needle off the seat) to allow gas lift gas flow from the gas filled annulus through the seat and the reverse flow check valve, and into the tubing.
Injection ValveA downhole valve in an injection well designed to prevent backflow if the injection is stopped.
Injection WellA well either specifically drilled, or, more likely, a poor producer that is converted to inject fluids to stabilize the decline of pressure in a productive zone. An injector is required to have a pressure connection to the pay and to a producing well. Water is typically injected at the base of the pay or, in a gas well, or gas is injected into the gas cap.
Injection-Withdrawal RatioThe ratio of the rate of injection to rate of production. A target may be as high as 1.0, although it is seldom achieved.
Injectivity IndexSlope of inflow performance relationship for injection. Bbl/psi or m3/bar.
Injector Head (coiled tubing)Coiled tubing handling device that provides pulling and injection power. Usually powered by two to four motors that transmit the forces to the coil through chains equipped with specially shaped couplers.
Inland Barge RigA structure consisting on a barge to which drilling equipment is attached for the pumpose of drilling in shallow water. The barge is usually sunk to drill.
Insert pumpA pump run on a sucker rod string and set in a pump barrel, then powered with the sucker rod pump.
Inside Blowout PreventerA valve installed inside the drill stem to prevent flow up the inside of the pipe.
In-SituIn place or inside the formation.
In-situ Coal GasificationGasification of an underground coal seam by injection of air.
In-Situ CombustionBurning a small part of the hydrocarbon to provide heat to reduce the viscosity of thermally crack the heavier ends. See Fire Flood.
In-situ stressThe stresses on the formation imposed by the overlying overburden and tectonic forces. The stresses are at least partially offset by the fluids in the pores of the formation.
Instrument HangerA piece of downhole equipment from which gauges and instruments can be suspended.
Insulated FlangeA flange with plastic gasket and bolt isolation devices to stop electrical conductance.
Insulated TubingOne of several tubing configurations designed to reduce heat loss from the produced fluids.
Intangible Drilling CostsThat part of the drilling and completion expenses that have no practical salvage value.
IntegratedA firm that operates in both the upstream and downstream areas of the energy industry.
Integrity ManagementAll phases of management of the well pressure seal integrity as a principal, critical objective.
IntensifierA pressure multiplier device use to assist pumping in high pressure well work.
Intercrystalline corrosionCorrosion along the grain boundaries of a metal.
Interface TreatmentA fluid diversion technique using density of the fluid to place fluids or other materials at a specific location in the well.
Interference (perforating)A perforating gun effect in which the firing of charges overlap slightly with the effect of one charge affecting the development of a jet in another with the result of reduced penetration.
Intergranular CorrosionCorrosion along the grain boundaries of a metal.
Intermediate Base OilOils with API gravity between 25 and 30.
Intermediate CasingOften a casing string or liner run to isolate a zone between the surface casing and the final production casing.
Intermittent Lift or FlowGas lift where gas is periodically injected into the fluid column.
IntermitterA time cycle controller that controls gas injection to improve lift.
Internal CutterA mechanical, chemical or explosive device capable of severing the pipe from the inside.
Internal Filter CakeFiltration control by particles smaller than the pore bridging size that invade the pores and bridge within the pore throats. Often very difficult to remove.
Internal Rate of ReturnThe interest yield expected from an investment based as a percentage.
Internal UpsetA pipe connection with a smaller I.D. than the pipe but a consistent O.D.
Interstitial WaterWater within the pores.
InterventionIn a well work sense, usually a non-rig well entry using wireline or CT intervention where the well head remains attached. Rigs may be used. Compare to workover.
IntrusionAn igneous rock body, which when molten, forced its way into a surrounding rock. Salt intrusions are also possible.
Invaded ZoneThe part of the rock next to the wellbore into which wellbore fluid has leaked.
Invasion (drilling or workover)Movement of one fluid into a permeable zone.
Inverse Modeling (seismic)A modeling technique for 2D or 3D seismic where density, susceptibility or geologic data is calculated or matched to an observed gravity or magnetic field.
Invert EmulsionAn emulsion that has swapped the internal phase to the external phase.
Invert MudWater-in-oil emulsion muds. There may be as much as 50% brine in the liquid.
IOGCCInterstate Oil and Gas Compact Commission.
Ion ExchangeIon exchange (cation or anion) where scaling or water hardening minerals such as calcium and magnesium are removed by substitution for sodium.
Ion MillingA focused ion beam useful in preparing SEM samples of rocks to gain much clearer pictures of pore structures.
Ionic BondA bond formed by an atom that has a strong tendency to loose electrons with an atom with a strong tendency to accept electrons.
IP (facilities)Intermediate pressure separator or separator train.
IP (technology)Intellectual property.
IPAIsopropyl alcohol.
IPAAIndependent Petroleum Association of America.
IPC (field capacity)Installed production capacity including injectivity.
IPLIntegrated porosity logging.
IPRInflow performance relationship. The relationship that shows inflow as a function of drawdown. Changes with time.
IPTTInterval pressure transient test.
IRInfra-Red.
IRISIntelligent remote implementation system.
Iron ControlChemicals that control the precipitation of iron from solution.
Iron HydroxideA brown, gelatinous precipitate that comes out of a spent acid solution when the acid spends completely or when the Ferrous Iron (+2) in solution at pH > 1.8 oxidizes to Ferric iron (+3).
Iron ReducerA chemical that helps reduce the valiance state of iron from iron+3 (ferric) to iron +2 (ferrous) in non sour applications. Helps prevent sludges that are triggered by iron and asphaltic crude in combination with salt water or acid. May also help prevent iron precipitation in sweet wells.
Iron RoughneckA pipe connection device that sits on the rig floor or is suspended just above the floor. It combines lead and backup tongs with a integral spinning table to spin the top joint during make-up or break-out.
Iron ScalesIron carbonate, iron sulfide and other forms of scale deposits containing iron.
Irreducible Water SaturationThe fraction of the pore space occupied by water when the hydrocarbon content is at maximum. This level of water can only be reduced below this level by flow of very dry gas that evaporates the water. Rewetting of a core with saturation below the irreducible water point may sharply reduce native state permeability to gas.
ISAInstrument Society of America.
IsenthalpicA constant heat loss/gain applied to a calculation and a temperature or pressure can be adjusted to meet this new heat content (around fluid equilibrium considerations).
ISIPInitial shut-in pressure. Used to isolate the formation fracturing or injection effect from the friction effects.
ISISIntegrated subsurface information surveillance.
ISOInternational Organization for Standardization, a network of national standards institutes of 146 countries, based in Geneva, Switzerland.
Isobar mapA map that shows points of similar pressure in a field.
Isochronal testA multi-rate drawdown and build-up test with different drawdowns of the same duration but buildups reaching stabilization.
IsochroneAt the same time.
IsopachA map that shows contours between points of equal formation thickness. It may also show depth of the zone.
IsoproponalIsopropyl alcohol.
IsosaturationMap showing equal points of a specific fluid saturation.
IsotopeOne of several forms of an element, all having the same number of protons but differing in the number of neutrons.
IsothermalTaking place at constant temperature.
IsotropicNo variation in properties with direction.
ISPIntermediate strength proppant.
ISRSInternational safety rating system.
ISSSVInjection subsurface safety valve.
IUSee Internal Upset.
IUDInstantaneous underbalance device.
IVICVInfinitely variable internal control valve.
IWOCS (subsea)Integrated workover control system.
JProductivity index.
J ProfileA profile design (less common than F, S, and X). The F allows circulation with the annulus. Used in place of a sliding sleeve, but does present a restriction.
J-SlotA pin and groove assembly that keeps a tool in the unset position while running and then can be worked or “Jayed” to operate the tool. Common in retrievable packers and liner hangers.
Jack (beam lift)Usually a pump jack, operating the rods in a lift and fall motion.
Jack Knife RigA rig with a folding mast that can be lowered and raised relatively quickly.
Jack-Up RigAn offshore rig with retractable steel legs that can be placed on the ocean floor and raise the rig above the water line.
Jacket (platform)The steel support structure from the sea floor to the top sides.
JarA device run on slickline, coiled tubing, tubing or drill pipe that will sharply increase the impact force of the conveyance when trying to retrieve a stuck tool or equipment.
Jar AcceleratorA hydraulic tool used in combination with a jar to increase the impact of the jar on the fish.
Jerk Line (drilling rig)A cable from the tongs through a pulley in the mast and to the cat head.
Jet ChargeA shaped charge used in perforating.
Jet Cone MixerA mixer that introduces additives to a moving fluid stream though use of the low pressure formed with fluid passage through a nozzle. An “on-the-fly” mixing device.
Jet CutterA radial shaped charge (explosive) cutter for pipe.
Jet FuelHigh quality, kerosene-like fuel.
Jet MixerA type of mixer for cement that uses air pressure to propel the dry cement into the flowing water.
Jet NozzleA nozzle through which fluid is pumped to produce an impact force. Used in jetting tools and bits. These nozzle often have a designed shape to maximize impact.
Jet PerforatingShaped charge perforating.
Jet PumpAn artificial lift device that uses the flow of a power fluid through a nozzle to create a low pressure area that draws well fluids into the chamber and assists in lift the fluids to the surface.
JettingInjecting fluid at high pressure against a target, often with fluid focused through a nozzle tool.
JOAJoint operating agreement.
Joint (geological)A large, generally planar fracture through a rock across which there has been no movement.
Joint (pipe length)A section of tubular.
Joint (connection)The tubular connection.
Joint Operating AgreementA written agreement that sets the terms under which a property will be developed by the working interest owners.
Joint VentureA project in which two or more parties are involved. Funding may be in direct money or work-in-kind.
Joule-Thompson EffectWhen a real (not ideal) gas expands, the temperature of the gas drops. During passage of a gas through a choke, the internal energy is transferred to kinetic energy with a corresponding reduction in temperature as velocity increases. The effect for natural gas is approximately 7o F for every 100 psi pressure reduction.
Journal BearingA bearing on a rotating shaft.
JRAJob risk assessment.
JRCJet Research Center.
JSAJob safety analysis.
JT (gas)Joule Thompson.
JugGeophone.
Junction (multilateral)The intersection of the lateral and the mother-bore when two or more laterals are drilled in a multilateral well, or when a single kick-off lateral is drilled from a vertical well. The junction may be unsealed or sealed and may or may not hold pressure.
JunkDebris in the well.
Junk BasketMay also be called a Jet Basket
Junk MillA rough, sturdy mill for grinding up odd shaped materials in the well.
Junk RetrieverJunk basket.
JurassicA geologic time period 140 to 200 million years ago.
K (viscosity)The consistency index, is the shear stress or viscosity of the fluid at one sec-1 shear rate. An increasing K raises the effective annular viscosity, increases hole cleaning capacity.
kPermeability
K ValveStorm Choke.
KALREZA brand name for a high temperature seal.
KaoliniteA clay type marked by platelet like deposits in the authogenic form. Usually not water sensitive but may have occasional loose attachment to the host grain.
KarstA topography formed when groundwater forms pockets or caves below or in a structure (usually limestone), allowing some of that structure to drop (e.g., create sinkholes). The complete cycle occurs over geologic time.
KBKelly bushing on a rig with a rotary table. A depth datum.
Kbbl/d1000 barrels per day.
KClPotassium chloride salt.
KCOOHPotassium formate.
KellyThe main rotating shaft on a rotary drilling rig that connects to and turns the drill string.
Kelly BushingThe bushing that directly transmits torque from the rotary table to the kelly.
Kelly CockThe valve on the Kelly.
Kelly DownWhen the kelly has reached the rotart table and a joint of drill pipe must be added.
Kelly Saver SubA short threaded sub that is made up to the kelly and to which the drill string is connected. The connections are made to the sub, saving wear on the kelly threads.
Kelly SpinnerA pneumatic device fitted to the top of the kelly that can spin the kelly.
KerogenAn initial stage of oil that never developed completely into crude. Typical of oil shales.
Kerogen Type 1Liptinite; (usually lacustrine in origin) has a high hydrogen to carbon ratio and a low oxygen to carbon ratio. Oil prone with a high yield – up to 80%.
Kerogen Type IIExinite; (naphthenic) has an intermediate hydrogen to carbon and oxygen to carbon ratio. Usually formed from marine organic matter (planton) in a reducing environment. Oil and gas prone with yields of 40 to 60%.
Kerogen Type IIIVitrinite; has a low hydrogen to carbon and high oxygen to carbon ratio. Usually dry, low quality gas prone with low yields. Source is terrestrial vascular plants. Humic coal precursor.
Kerogen Type IVInertinite; very low in hydrogen, principally a dead carbon. No oil or gas generating gas potential.
KeroseneA medium range (C9-C16), straight chain blend of hydrocarbons. Flash point is about 60oC (140oF). Boiling point is 174o to 288oC. Density is 0.747 to 0.775 g/cc.
KEVLARAn extremely strong fiber, common in composites.
KeyseatA out of round bore hole worn to the side, often with the side of the drill pipe in a crooked hole, that looks like a key hole. Keyseats create problems with passage of tool joints and larger pipe that does not bend as easily as smaller diameter pipe.
khThe permeability times the height; a measure of formation conductivity.
khHorizontal permeability.
KickAn unwanted flow of fluids from a formation into the wellbore. Can happen during drilling, completions or interventions.
Kick-Off PointThe point at which a rapid change of deviation is made in a vertical well.
Kick Off Pressure (gas lift)The gas injection pressure available for unloading fluids from a gas lifted well down to the last valve.
Kickover ToolA fishing tool that decentralizes the retrieving tool. Commonly used in gas lift.
KillA term used to describe various methods to stop flow from a well. Commonly pumping a kill weight fluid into a well to create an overbalance into the formation.
Kill and Block ValveA downhole valve in the tubing string used to isolate the string and allow a kill without having fluid on the formation.
Kill FluidA liquid with a density sufficient so that a full column of the fluid would control the well and prevent fluid entry into the wellbore from any exposed formation.
Kill LinesFlow lines to the BOP stack, entering below the pipe rams, through which kill weight fluids can be pumped.
Kill PillA pill with fluid loss control materials selected to stop losses in the well. A kill weight pill is a fluid with a density high enough to control the well.
Kill SpoolA kill line port located between the shear ram and the slip ram on a BOP.
Kill Weight FluidThe density of a full column of fluid when the density of that fluid is just high enough to prevent pore fluid flow.
KiloKilogram, 1000 grams.
KilojouleAbout a BTU (British thermal unit). Used to express the heat content of gas.
KilopascalKPa, 1000 Pascal, 6.9 kPa per psi, 1000 psi = 6900 kPa.
Kinematic ViscosityThe ratio of the viscosity to the density using consistent units. Same behavior as in a Marsh Funnel.
Kinetic Hydrate InhibitorAn inhibitor that prevents solid hydrate plugs.
Kinley CaliperA multi-finger caliper for determining casing ID condition.
KJKnuckle Joint.
kj (rock)Permeability of a layer.
Kl/d1000 liters per day.
KitchenA source rock in with sufficient heat and other inputs to produce hydrocarbons.
Klinkenberg PermeabilityA method of correcting permeability measurements to account for gas not adhering to the walls of rock pores as does water. Gas permeabilities are usually higher than liquid permeabilities by up to one order of magnitude, especially in dry cores.
KMKerr McGee
KnockoutA separator used to remove easily removed or excess gas or water from the produced fluid stream.
Knuckle JointA flex joint in a tool string that allows alignment with a target not in the same plane.
KOPKick-off point.
KOTKick over tool.
KPKill pill.
kPaKilopascal, 6.9 kPa per psi, 1000 psi = 6900 kPa.
KPIKey performance indicator.
KrgRelative permeability to gas.
Kriging (seismic)The geostatistical method of applying known values in one sample to produce an unbiased estimate of values in another.
KroRelative permeability to oil.
KrwRelative permeability to water.
KTOne thousand metric tons.
Kuff (process)The partly broken emulsion layer between water and oil in a separator.
kvVertical permeability.
Kwm (drilling)Kill weight mud.
LACTLease automatic custody transfer unit. A calibrated measurement device used as an official sales point for crude oil transfer into a second party pipeline.
Lag TimeThe time it takes for drill cuttings to be carried to surface from the bottom of the well.
Lagoonal DepositsRegionally extensive deposits along the shores of ancient seas. Permeability varies with energy of deposition (amount of residual silt).
Lamellar CorrosionLocalized and subsurface corrosion in zones often parallel to the surface that result in leaving thin layers of uncorroded metal resembling the pages of a book.
Laminar FlowFluid flowing at a lower rate with elements of the fluid flowing in fixed streamlines. Laminar friction is a function of NRe (Reynolds number). For laminar flow, the Fanning fracition factor = 16/NRe.
Laminated SandsSandstone deposits in layers, often with very different permeabilities and frequently found with barriers to vertical flow.
Laminations (geological texture)Parallel layers less than 1 cm thick.
LAN (computer)Local area network.
Land CasingInstalling casing to the casing set point.
LandmanA person who negotiates with the land or mineral rights owner to secure a lease to drill.
Landing NippleA nipple profile that contains a specific profile with a lock and a polished bore for sealing.
Langelier IndexA calculated saturation index for calcium carbonate, useful in scaling predictions.
Langmuir Isotherm (gas adsorption)The relationship of pressure to the amount of adsorption of gas to an organic surface.
LAP (packer)Leakage across packer elements.
LapWhere the top of the liner comes up inside the upper casing string.
Laplace’ LawThe larger the vessel radius, the larger the wall tension required to withstand a given internal pressure. A spherical vessel will have half of the wall tension of a cylindrical vessel for a set vessel radius and internal pressure.
LaserLight with a narrow spectral width. Light Amplification by Stimulated Emission of Radiation.
Laser DistributionA % by volume distribution of the particle sizes in a sample.
LatchOne of several a downhole coupling mechanisms that hold the string to a predetermined load before releasing. Useful for confirming depth and attachment when the string is snapped into or out of a latch.
Latch OnTo connect the elevators to the tubing.
Lateral (wellbore)An indefinite term, usually meaning one or more departures from a mother bore. May be used in some areas to mean a high angle well bore.
Lateral lengthThe length of the lateral part of the well, usually in the pay zone. The departure length is the horizontal distance from the surface penetration point to the furthest distance reached by the drill bit.
Lateral (load)A sideways load.
LaterlogAn electrical log. Formation resistivity measurement with specific conductive muds.
LatexA organic cement additive that provides some strength in set cement and fluid loss control in the slurry.
LavaMagma that comes to the earth’s surface.
Law of Capture (hydrocarbon movement)A legal concept, valid in some places, that since oil (and gas) are mobile fluids, that they are not owned until they are produced.
LayerA distinct segment in a vertical stack of formation sequences. Often with areal extent.
Laying Down PipeTo disassemble the drill string into individual joints and lay it down on the pipe racks.
LCALeakoff control acid.
LCMLost circulation material.
LCPLeakage in closed position.
LCTDLast crystal to dissolve.
LDLay down.
LDC (transport)Long distance carrier.
LDFNLay down for night.
LDHI (hydrates)Low dosage hydrate inhibitor.
LDPELow density polyethylene.
LDS (wellhead)Lock down screws.
Lead CementThe first part of the cement slurry injected – often contaminated during the flow by mixing with mud from the walls of the pipe or the formation.
Lead Lines (pipeline)The lines from a well to a battery. Also called gathering lines.
Leak Off RateThe fluid lost from the well expressed in volume per time.
Leak-Off TestLOT, a drilling test. A LOT is intended to determine the point of leak-off. Compare to FIT.
Lean GasA near dry gas, containing only a trace of condensate.
Lease (drilling)A legal document granting the right to prospect, drill, complete and produce hydrocarbons on a tract of land.
Lease HoundA person that acquires leases and resells them to a drilling company.
Lease SetbackThe minimum distance away from a lease boundary that a well may be drilled.
Least Principal StressMinimum principal stress. Hydraulic fractures form perpendicular to this stress.
LELLower explosive limit.
LensA permeable, often small sedimentary deposit bordered by impermeable rock.
LevelwindA device in a coiled tubing reel control that aids in controlling spooling of the CT.
LIBLead impression block.
Lift CostThe cost of lifting or flowing fluids from a well to the facilities. Often used as a benchmark for efficiency.
Lift CurveTubing performance curve.
Lifting FrameA device on which the CT injector may sit that can be hydraulically raised to allow access to the BHA below the CT connector. Takes the place of a crane.
Lifting CostThe operating expenses of producing fluids to the surface.
Lifting SubThe short pipe section that screws into the top of the tubing hanger and is then latched onto by the elevators to manipulate the tubing string.
Lift-Off Pressure (mud)The differential pressure across the mud cake from formation towards the wellbore that will cause some of the mud filter cake to lift off the face of the formation and to re-establish permeability.
Light CrudeVarying definition, typically an API gravity of 30o or 33o up to 40o.
Light EndsHydrocarbon liquids with lower boiling points that may flash off when pressure is released.
Light Weight CementA cement with a slurry density less than the normal approximate density of 16 lb/gal (1.92 g/cc) density. Normally in the range of 11 to 14 lb/gal (1.32 to 1.68 g/cc).
LigniteVery young coal. Moderate to low energy yield.
LigosulfonatesA multipurpose additive base derived as a byproduct from paper manufacturing. Used as gellants, fluid loss, drilling additives, etc.
LIHLeft in hole.
LILLog-inject-log.
Limited EntryPenetrating or perforating only part of the pay zone. Usually done to control water or gas entry or to assist in ball sealer action in selective treatments.
Line DriveUsing a line of injectors to drive fluid preferentially along a given path.
Linear Darcy LawThe Darcy equation describing linear movement of fluids in laminar flow through a porous media.
Linear GelAn uncrosslinked polymer gel. Typical polymers are guar, HPG, CMC, HEC, etc.
Liner (casing)A partial string of pipe that does not run back to surface. Liners may or may not be cemented.
Liner (perforating charge)The inner liner over the propellant in a perforating charge, most often made of pressed, powdered copper mixture or drawn or stamped from copper sheet. The liner deforms as the charge is fired and its mass is added to that of the jet from the charge.
Liner (sand control)A perforated, drilled or slotted liner for formation control or to preserve wellbore access.
Liner HangerA packer-like hanger with slips suitable for hanging liner weights. May or may not incorporate a seal.
Liner LapThe top of a liner, specifically the interval between the liner top and the shoe of the previous casing.
Liner Tie-BackA string of casing, usually of the same size, used tie a set liner back to surface.
Liquefied Natural Gas or LNGMethane that has been compressed and cooled to the liquefaction point for shipping.
Liquefied Petroleum Gas or LPGLight ends, usually C3 and C4 gasses liquefied for storage and transport.
Liquid HoldupWhen gas is slipping by the liquids, emptying only a part of the liquids in the well and leaving a portion of the liquid in the wellbore.
Liquid LevelThe depth in a well where the standing or percolating level is located.
LithificationProcess of changes that produce rock from sediments.
Litho-Density LogMeasures the bulk density of the formation. Useful to estimate lithology.
Lithofacies MapA map of subsurface changes in formation physical properties.
Lithologic LogA chart of the physical properties of the formations; specifically rock composition, texture, porosity and type, etc.
LithologyRock composition and type; limestone, sandstone, etc.
LithosphereOuter layer of the earth including the crust and the uppermost mantle.
Lithostatic PressureOverburden pressure of rocks at a depth.
Live Carbon (shale)Carbon with a type of Kerogen content that has a high potential to generate hydrocarbons.
Live OilProduced oil before removal of associated gas.
Live Well WorkoverA workover done without killing the well (with wellhead pressure and proper barriers).
LLD (logging)Deep laterlog resistivity.
LLRTLiquid level leak test.
LLS (logging)Shallow laterlog resistivity.
LMRPLower Marine Riser Package.
LNFT-IALiquid, no flow test, inside annulus.
LNGSee liquefied natural gas.
LO (reservoir fluid)Live oil.
Load CellA device based on strain gauge technology that helps measure the surface weight of coiled tubing.
Load FluidThe fluid that is injected into a well.
LockA mechanism to hold a plug in a profile.
LoessDeposits of windborne dust.
LogA systematic recording of data from a well.
Log HeaderThe information section at the top of a printed well log.
Log-Inject-LogA production or injection well logging technique where the zones is logged for water saturation, oil saturation or temperature, followed by fluid injection, followed by another logging pass. Data available include changes in saturations, quantitative/qualitative determination of injection location and amount of temperature charge, etc.
Logged DepthTotal depth or measured depth.
Logging While DrillingA technique using a suite of logs that are part of the drilling BHA. The formation properties are measured while drilling (although 40 to 60 feet back from the bit) and the information is pulsed to the surface.
Long Radius WellA description of well deviation change at about 2o to 6o per 100 ft.
Long StringIn a side-by-side dual completion, the tubing string that connects the deeper zone to the surface.
LOP (rock mechanics)Leak off point. The departure from the straight line of a limit test on a wellbore. Usually from at leakoff test after casing is set and before drilling ahead.
LOP (production)Loss of production.
LosalLow salt or fresher water.
Lost CirculationDuring circulation, when less fluid returns to the surface than was injected into the well. Severe lost circulation is the loss of all returns.
Lost Circulation Control Agent or LCAAny of a number of materials that control the loss of fluids to the formation. See Filter Cake.
Lost Circulation Materials or LCMSame as lost circulation control materials.
Lost Circulation ZoneA high permeability zone that takes fluids from the wellbore and the conventional filter cake building materials have no effect on fluid losses.
Lost PipeAny pipe lost in the hole.
Lost ReturnsLoss of returning fluid during circulation of a well.
LOT (drilling)Leakoff test, a drilling test. A LOT is intended to determine the point of leak-off. Compare to FIT.
Low Alloy SteelSteel with less than about 5% alloying additives.
Low Carbon SteelSteel with less than 0.30% carbon and no other alloys.
Low Energy System (geologic)A depositional environment where to deposited sediments are poorly sorted and can have a large proportion of very fine particles.
Low Pressure SqueezeA cement squeeze technique with a final squeeze pressure below the formation fracturing pressure.
Low Pressure Water CleaningCleaning at less than 5,000 psi water pressure.
Low Solids MudMud with a low suspended solids quantity. It may be formulated with a brine with high density created by dissolved salt.
Lower CompletionThe part of the completion below the packer.
Lower Crown Plug (subsea)A plug that fits in the bore of a subsea tree, usually below the tubing hanger, to serve as the primary barrier against reservoir pressure.
Lower Kelly ValveA near full-opening valve installed just below the kelly. It has the same outside diameter as the tool joints.
LP (facilities)Low pressure separator or separator train.
LPGLiquefied petroleum gas.
LPS (downhole gauge)Loss of pressure signal.
LPSLow pressure separator.
LPSALaser particle size analysis.
LPSDLaser particle size distribution.
LPT (downhole gauge)Loss of pressure and temperature signal.
LRPLower riser package.
LSLow sulfur.
LSA (scale)Low specific activity scale. Low radioactivity scale.
LSFOLow sulfur fuel oil.
LSOBMLow solids oil base mud.
LTA (seals)Leakage to annulus.
LTALost time accident.
LT&CLong thread and coupled, a connection description.
LTBSLiner tie back sleeve.
LTOBMLow toxicity oil based mud.
LTRMLong term reservoir management.
LTSLow temperature separation.
LTS (downhole gauge)Loss of temperature signal.
LTSILong term shut-in.
LUBLubricator.
LubricantsMaterials that reduce torque and drag. May be oil, synthetic (polymer) liquids, graphite, glycols, glycerines, etc.
LubricatorA pressurized shell, mounted above the BOP or master valve, which houses the tool string when entering a live well.
LubricityLubrication properties of a given drilling mud.
LWDSee Logging While Drilling.
LWLLow water loss.
LWRPLower workover riser package.
LyohilicAn easily suspended colloid. Having an affinity for the suspending medium.
m (logging)Cementation exponent.
M3Cubic meter. 0.16 barrels. (6.28 barrels per meter.)
MAASPMaximum allowable annular surface pressure.
Macaroni StringA small diameter string, usually attached to the outside of the tubing, used to place inhibitors and other chemicals downhole. May also be used to describe any small tubing.
MagmaMolten rock (lava) that crystallizes into an igneous rock.
Magnetic Basement (seismic)Usually a crystalline unconformity on which a non-magnetic sedimentary rock sequence has been deposited.
MagnetometerInstrument used to measure the intensity and variances of the magnetic fields in the earth.
Main BoreMotherbore or main wellbore from which a lateral bore is drilled.
MajorTypically a large operator, usually a multinational oil company that is usually a large producer in several areas of the world.
Make A TripThe round trip of pulling the drill string from a well and returning it to bottom. Usually done to change or check the bit or to change the BHA.
Make HoleDrill.
Make-UpScrew pipe joints together.
Make Up TongsSpecialized wrenches used for making up pipe connections.
Male CouplingThe part of a connection with threads on the outside.
MalteneA cyclic compound associated with asphaltenes that helps keep asphaltene platelets in suspension.
Managed Pressure DrillingAn adaptive drilling process used to precisely control the annular pressure profile throughout the wellbore (IADC definition).
MandrelA round bar or tube (i.e., as in a packer) around which other parts are mounted.
ManifoldA junction or center for connecting several pipes and selectively routing the flow.
MantleThe middle layer of the earth, laying just below the crust and composed of relatively high density rock.
MarasealA Marathon Oil water/zone control chemical. For matrix shut-off.
MarbleA metamorphic rock composed largely of calcite.
MarcitA Marathon Oil water/zone control chemical. For fracture shut-off.
Mare’s Tail (process facility)A frayed rope-line strand inserted in a flow line before a separator that aids in separation of entrained droplets in a flowing liquid.
Marginal FieldA field at the edge of commercial viability.
Marginally ConsolidatedFormation with an unconfined compressive strength of less than 300 psi. Can be crush with fingers.
Marine RiserAn outer steel shell that connects a drill ship, jackup or floater to the well template on the ocean floor. The drill string is run through the riser and the returning mud and cutting flow u the drill pipe / riser annulus.
Marker (circulation)A material such as a dye, sand, grain, etc., that can be recognized as the fluid is circulated. Useful for determining swept volume of the hole.
Marker (formation)An easily identified formation that is used to identify the start of a rock sequence. In the wellbore, a marker is a material placed in the circulating fluid that can be easily seen when the fluid returns to surface – helps identify the swept volume of the wellbore.
Marker FossilsFossils specific to a particular age.
Marsh FunnelA funnel shaped device of specific volume and shape and outlet that is used to quickly estimate the viscosity of the drilling mud by the time it takes a funnel volume to flow out of the funnel. The Marsh funnel viscosity is reported as the number of seconds required for a given fluid to flow 1 quart through the funnel.
MartensiteA hard carbon supersaturated iron characterized by needle-like microstructure.
MASPMaximum allowable surface pressure.
Mast (rig up)A portable derrick, usually a single unit that can be quickly raised.
Master BushingA device that fits into the rotary table to accommodate the slips and drive the kelly bushing.
Master ValveThe main shut-in valve on the well.
Material Safety Data SheetA description of the HSE data for a marketed product.
MatrixThe physical structure of a clastic rock.
Matrix AcidizingAcidizing a rock below the fracturing pressure, either to reduce the formation damage or to improve the initial permeability.
MAWPMaximum allowable working pressure.
Maximum Allowable Working PressureThe maximum pressure to which a surface vessel can be operated or the maximum pressure during treating to which a well should be exposed.
Maximum Efficient RateThe maximum rate that a field can be produced or drawn down in pressure without undue stranding of oil that could be lost during more rapid production. Setting the MER required knowledge of fluid and rock properties and well design throughout the formation.
Maximum Principal StressThe direction of greatest earth stress in a reservoir. Hydraulic fractures are parallel to this stress.
MaxIPThe largest production volume for a month, divided by the number of days in that month.
MbalMaterial balance calculation of fluid production.
MBDThousands of barrels per day.
MBPDThousands of barrels per day.
MBE (reservoir)Material balance equation.
MBE (heavy oil)Matrix breakthrough event.
MBTMethylene blue test.
Mcf1000 ft3, usually measured at a specific set of conditions.
MCSMaster control station.
mD (frequently shown incorrectly as md)Millidarcy, 1/1000th of a Darcy.
MDMeasured depth – the along hole measurement of depth of the well. As opposed to true vertical depth (TVD).
MDRTMeasured depth relative to the rotary table.
MDTModular formation dynamics tester.
Meandering StreamA stream that transverses relatively flat land, ultimately creating different channels in response to floods and sediment build up.
Measured DepthDepth measurement of a wellbore as measured along the drill pipe without respect for vertical penetration.
Measurement While DrillingDownhole logging while drilling. “Logging While Drilling” is one form of "measurement while drilling" - to differentiate it from mud logging, wireline logging, etc. See Logging While Drilling.
Mechanical FilterA strainer type filter that is specifically for removal of larger particles in a liquid stream.
Mechanical Integrity TestA regular pressure test on an injection well to assure the integrity of the isolation seal.
Mechanical Jar (wireline tools)A device used to provide a short space of free wireline travel before solidly connecting to the BHA in a string. Used in fishing.
Medium RadiusA description of well deviation change at about 8o per 100 ft.
MEGMonoethylene glycol. A hydrate inhibitor.
Memory LogsUsually slickline or CT logs that record data electronically and are downloaded later.
Memory ToolAny downhole tool that records the information rather than transmitting the data back to surface.
MeniscusA phenomena between a liquid and a solid surface created by adhesion and cohesion forces. The meniscus may be upward where adhesion forces are stronger than cohesion or downward when cohesion forces are stronger.
MeOHMethyl alcohol.
MEORMicrobial enhanced oil recovery.
MERMaximum efficient recovery or rate.
MercaptanA class of compounds containing carbon, hydrogen and sulfur. The shorter chain materials are used as an odor marker in natural gas.
Mercury Pore Measurement or PorosimetryMercury is injected at step-wise increasing pressures where large pore fill first, followed by smaller pores at successfully higher pressures. Volumes injected at different pressures indicate the pore size distribution.
MeshA measurement of particle size based on the openings per inch in a screen.
MeshriteA sand control screen made from steel wool trapped between two perforated or slotted liners.
MesozoicA geologic time era from 65 million to 250 million years ago.
Metal-to-Metal SealA seal in a pipe joint, flapper seal or other area based entirely on the fit or the deformation of one metal surface against another.
MetallizingCoating of a surface with metal.
MetamorphicChange produced in a rock to another state by temperature, pressure, time or chemical influence.
Meter FactorA correction factor applied to a meter to increase measurement accuracy in a range.
Meter SlippageRelated to the amount of fluid that slips by a meter without being accurately recorded.
MethaneCH4. or natural gas.. The simplest alkane.
MethanolMethyl alcohol, a common hydrate inhibitor.
MetoceanA contraction of the words 'meterology' and 'oceanology' referring to the waves, winds and currents conditions that affect offshore operations.
Metric TonApproximately 7.4 bbls of 36o API crude.
MFCTMulti-finger caliper tool.
MFEA trademark for a repeat formation tester.
MFPManifold flowing pressure.
MFTManifold flowing temperature.
mGal (seismic)Milligal.
MGIMiscible gas injection.
MGLMean ground level.
MIMove in (as in equipment).
MI (flooding)Miscible injection.
MicaA silica mineral, often present as ultra thin flakes and sometimes mobile.
MicelleAn association or grouping of molecules in suspension.
Micro CementCement with very small particle size.
Microbeads or MicroballoonsSmall, hollow ceramic or glass beads used as a lightening agent for special, ultra light weight cements.
MicrogelsLumps of non dispersed polymer.
MicrolaterlogA pad contact micro resistivity log. Useful for assessing the flushed zone fluid in contact with the pad.
Micro LogA special resistivity tool that measures the resistivity of the mud cake on one curve and the resistivity of the fluids in the formation, but near the wellbore, on a different curve. Separation between the curves is an indication of permeability since mud cake builds on permeable zones.
MicroorganismsMicroscopic living organisms such as protozoa, bacteria, viruses, algae and fungi.
Micro-SeismicThe small energy emissions from small feature tectonic events, including production of fluids from a reservoir and the resultant transfer of overburden to the matrix of the reservoir.
MicroemulsionAn emulsion with very tiny, highly dispersed bubbles. May be very stable and highly viscous when the internal phase is high (>75%).
MicronOne millionth of a meter. ?m.
Micron RatingA rating of the opening in a screen (or in a filter less accurately). A micron is approximately 1/25400th of an inch.
MicropolishingA very smooth finish on the interior walls of a pipe to reduce friction during fluid flow.
MicroporosityVery small pores created by high surface area, authogenic clay deposits. May trap water in structure and indicate higher Sw.
MicroseismicA method of tracking a fracture by listening for the sounds of shear fracturing in the formation during the hydraulic fracturing process.
MicroseismA weak vibration of the ground that can be detected by seismographs and caused by wind, waves or human activity but not earthquakes.
Middle DistillatesRefinery products in the middle distillation range of refined products
Midstream (operations)The area between upstream and downstream operations. Usually includes pipelines.
Migration (seismic)A computation applied to seismic data that returns reflection events (signals) to their origin in the subsurface.
Migration (fluids)The movement of fluids, generally away from a source rock through permeable layers towards a trap or vent.
MillA cutting tool used to grind up metal, dress off a fish, or open up a window for a kick-off.
Mill ScaleAn iron oxide on the pipe walls that is formed during pipe manufacture.
MilliPrefix meaning one thousandth.
Millidarcy1/1000th of a Darcy.
Milligal (seismic)Unit of acceleration used in gravity measurement. 1 Gal= 1,000 milligal. 1 Gal = 1 cm/sec2. 1 milligal = 10 gravity units.
MillingRemoving a blockage, fish or casing wall by drilling with a metal-cutting device to gain access to the area beyond.
Millout Extension (packer)A large diameter tube below the packer where a grab will deploy when the packer is being milled out.
Mils Per YearA corrosion, abrasion or erosion measure of penetration through the walls of the measured material. MPY reports the material loss as an average across a surface and does not accurately reflect penetration by localized pitting.
MineralA compound of generally known composition and structure involving naturally occurring silica-based formulations. Minerals are natural compounds formed by geologic processes.
MineraloidA natural compound that does not meet the stricter mineral definitions.
Mineral RightsThe ownership of the in-place (in the reservoir) hydrocarbon.
Minerals Management ServiceMMS, a US government agency that oversees minerals production from US federal lands.
Mini FracSee Data Frac.
Minimum Bend RadiusThe minimum radius (R) that a pipe with a tube OD (D) can be bend around and remain in the elastic region. R= E(D/2)/Sy. (R is in inches). E=30x106 psi.
Minimum Principal StressLeast principle stress in a rock. Hydraulic fractures form perpendicular to this stress.
MioceneAn epoch of time from 5.3 to 25 million years ago.
MIRMaximum injection rate.
MIRUMove in, rig up.
MiscibleFluid phases that mix together without forming a distinct boundary.
Miscible Gas DriveInjection of a large volume of gas from an injection well where the gas is designed to lower the viscosity of the oil and help displace it towards the wellbore.
MisfireIn perforating; fail to fire the perforating gun.
MississippianA geologic period of time from 320 to 265 million years ago.
Mist FlowA flow regime where droplets of liquids are entrained in the gas flow.
MITSee Mechanical Integrity Test.
MIT-IAMechanical integrity test – inside annulus.
MitigationAn action taken to reduce the impact or consequences of an event.
MIT- OAMechanical integrity test – outer annulus.
MIT-TMechanical integrity test – tubing.
Mixed Layer ClaysTypically mixtures of illite and smectite or other clays. These may or may not be water sensitive.
Mixing TankA preporation tank for gel, mud, treating chemicals, etc.
MJMegajoule. 1,000,000 joules.
MLMulti-lateral.
MLTMud line temperature
MMblsMillion barrels.
MMcfMillion standard feet of gas.
MMHMixed metal hydroxide
MMOMixed metal oxides.
MMSUS Minerals Management Service.
MMscf (gas volume)Millions of standard cubic feet.
mremMillirem (a radiation dose or exposure unit).
mrem/yrMillirem per year.
Mobility RatioA comparison of the ability of a fluid to move through another fluid or to displace the fluid.
MobilizeTransport to the location.
MOCManagement of change – a process to understand all the implications of a change to a procedure.
Model D PackerA trademarked name for a very common packer.
Modified Isochronal TestA multi-rate drawdown and build-up test with different drawdown pressures but the same duration.
MODUMobile Offshore Drilling Unit.
Modular Perforating GunA set of hollow carrier guns that can be run with wireline and stacked in the well before being fired.
Modulus of ElasticityStress over strain. A measure of stiffness or Young’s Modulus (E). Rocks are ? to 12 x 106 psi and mild steel is 30 x 106 psi. Modulus refers to stress at a predetermined level of elongation, usually at 100% elongation. The higher the modulus of a compound, the more apt it is to recover from loading or localized force and the better is its resistance to extrusion.
MOEMillout extension.
Mohr-CoulombA plotted relationship that predicts shear stress levels at various envelopes of effective normal stress.
Mohs ScaleA ten point scale of mineral hardness. The levels are keyed to the minerals
Monkey BoardThe spot where the derrick man works.
MonoboreA tubular string all the same diameter. Some monobore definitions exclude profiles and some do not.
MonoclineA simple fold with an otherwise uniform dip, in local steepening strata. All strata are inclined in the same direction.
MonolayerA full layer of proppant, only one proppant thick.
Monte Carlo Risk AssessmentA method of assessment that helps identify the risk in data analysis or sampling.
MontmorilloniteA water reactive clay mineral, now called smectite, a common component of bentonite.
Moon PoolAn open shaft in a deep-sea drilling vessel, usually located in the center of the hull, through which the drilling takes place.
MOP (LWD)Mud operated pulse.
Mosquito BillA siphon tune on a downhole pump.
MotherboreThe main well bore from which a lateral well bore is drilled.
Mouse HoleA hole in the rig floor designed to hold a joint of pipe. The rat hole (a term also used for the borehole below the pay zone) holds the Kelly when it has to be disconnected.
Moveout (seismic)The difference in arrival times of reflected seismic data at different detectors.
MPaMegapascals, 1 million Pascals.
MPDManaged pressure drilling.
MPLTMemory production logging tool.
MPYMills per year, a measurement of corrosion.
msMillisecond, equal to 1/1000 of a second.
MSAMethane sulfonic acid.
MSA (regulations)Mine safety act.
MSCF (gas volume)Thousand standard feet.
MSDSMaterials safety data sheet.
MSFL (logging)Microspherically focused log resistivity .
MSVMulti-service valve.
MTManifold temperature.
MTBEMethyl tertiary butyl ether.
MTBFMean time between failures, a measure of reliability.
MTRMotor.
MTTFMean time to failure
MUMake up.
MudDrilling mud. Usually a slurry of weighting and fluid-loss control solids in a liquid.
Mud AcidAn inexact term, usually meaning a mixture of hydrochloric (HCl) and hydrofluoric acid (HF), HCL/HF. HF will dissolve some silicates and some of the components of drilling mud.
Mud AnchorA enlarged area that promotes solids settling prior to a fluid entering the pump.
Mud Balance (fluid density)A simple scale with a cup and bar with a sliding weight that, when used with a pedestal mount, will give the density of mud, cement or brines. See also Pressurized Mud Balance.
Mud CakeThe filter cake on the formation formed by dehydration of the solids as the liquid part of the mud (filtrate) leaks off into the formation.
Mud CupA graduated cup used to sample mud and fill the Marsh funnel.
Mud DensityThe specific gravity of the mud expressed in lb/gal, kg/m3, etc.
Mud Displacement FlushA sequence of washes, dispersants, carrying fluids and spacers designed to remove mud and mud cake from the annulus prior to cementing and completion.
Mud EngineerPerson in charge of building the mud (mixing) and compositional checks.
Mud FiltrateThe liquid part of the mud that invades the formation after the particles are stranded at the surface of the formation.
Mud Flow Through ScreensA laboratory test that flows drilling fluids through screens to check for plugging potential on cleanup.
Mud LogA record of information on mud or cuttings that are circulated to the surface.
Mud LossLoss of whole mud to the formation.
Mud LoggerThe person who monitors the mud for hydrocarbon shows, y use of chemical analysis, microscopic examination or instrumentation.
Mud MotorA hydraulic powered motor used on the drilling sting or coiled tubing to provide rotation.
Mud PitThe primary storage tank for drilling mud.
Mud Pit Level Indicator and AlarmThe indicator system that reports the level of mud in the tank. Useful for losses and kick indications.
Mud PulseA pressure pulse in the mud system. Some downhole tools can be controlled by mud pulses and some data is transmitted from bottom hole to the surface via pressure pulses.
Mud PumpPrimary mud circulation pumps on the rig.
Mud TracerA material such a grain, dye, flakes or other material that can be circulated with the mud to track how quickly and to what extent the hole is circulated.
Mud UpIncreasing the density of the mud.
Mud WeightMud density.
MudstoneSedimentary rocks that consist of particles finer than sand grade (less than 0.0625 mm) and include both silt and clay grade material. Also called shales.
Mule ShoeA bias cut across the pipe or tool body on the end to aid in entering restricted openings.
Multicomponent SeismicA survey conducted using 3-component geophones for sensing seismic reflections in the vertical, horizontal, and crossline directions (3-C). In the marine environment, a hydrophone is included to acquire 4-component (4-C) data.
Multi-Finger CaliperA diameter measuring device that uses many small blade-like fingers to track and record the shape and imperfections of the ID of a pipe.
Multi-LateralMore than one producing wellbore from a single wellbore or mother bore.
Multi-Phase FlowTwo or more flowing phases. This often severely complicates pumping, flow prediction and measurement. .
Multiple CompletionHaving multiple and often separate completions into different producing pays but in the same wellbore. The completions may be concentric or side-by-side where the pays are not to be commingled or stacked where the flow is to be commingled.
Multi-PointingWhen two or more gas lift valves are flowing gas at once.
Multi-Stage CementingUsing more than one stage of cement to get more complete cement coverage of the annulus.
Mutual SolventA chemical that have some common solvency for both water and oil materials. See EGMBE.
MWMud weight.
MWDSee measurement while drilling or logging while drilling.
MWPMaximum working pressure.
MWPTMeasurent while perforating tool.
MylarPolyester film.
Mysid ShrimpA species of shrimp used to test toxicity of chemicals in sea water.
MZMultizone.
n (logging)Saturation exponent.
n (viscosity)Power law component. As n decreases from 1, the fluid becomes more shear thinning. Reducing n produces more non-Newtonian behavior.
NACENational Association of Corrosion Engineers.
NaClSodium chloride salt. Halite.
NanometerOne billionth of a meter.
Nanotesla (seismic)The units in which magnetic survey maps are contoured. 1 nanotesla = 10-9 tesla. 1 nanotesla = 10-9 weber/m2. 1 nanotesla = 10-1 lines/m2. 1 nanotesla = 10-5 lines/cm2. 1 nanotesla = 10-5 gauss, 1 nanotesla = 1 gamma.
NaOHSodium hydroxide.
NaphthaAn aromatic solvent with highly-variable quality. Often has a described carbon range in the C7 to C10 area.
Naphthalene Base OilOil with API gravity of less than 25.
Naphthalene FlakesA common diverter. It can sublime, or go directly from a solid to a gas.
Native State CoreA core preserved as close as possible to reservoir conditions with effort made to keep all hydrocarbons in place.
Natural ClaysNatural occurring clays as opposed to commercially formulated clays.
Natural CompletionA completion that is not stimulated.
Natural FractureA fracture in the rock created by geologic events such as uplift.
Natural GasMethane, CH4; plus some short chain hydrocarbons (ethane, propane, butane) that may be in gasseous state at standard conditions.
Natural Gas LiquidsThe portion of the natual gas compounds that liquify at surface conditions.
Natural GasolineCondensate liquids.
Natural SeepA naturally occurring hydrocarbon seep to surface. (There are over 1100 known seeps in North America.)
Naturally Flowing WellA well that can flow to the surface unassisted.
Naturally Occurring Radioactive MaterialNORM scale, usually barium or strontium sulfate scale with very low level radiation from atoms of uranium, thorium and potassium in the matrix of the scale.
NBRNitrile butadiene rubber. The most widely used elastomers in the oil field.
NDNipple down. Disassemble.
NDTNon destructive testing.
Near Wellbore DamageDamage to the permeability occurring within the first few feet away from the wellbore.
Neat CementCement slurry without additives.
NEBNation energy board for Canada.
NECNational electric code (US).
Needle and Seat ChokeAn adjustable common choke for clean (no solids) production flow.
Needle ValveA low volume, small orifice, high pressure bleed valve.
NEONeoprene. A ball covering and seal type.
NEPANational Environmental Policy Act.
NeriticMarine zone; the environment between low tide and the continental shelf.
NESHAPsNational Emission Standards for Hazardous Air Pollutants.
Net AcresThe total of the company’s fractional interest in the gross acreage position.
Net BackThe amount of money received per barrel of oil equivalent produced after subtracting operating and administrative costs, and royalties.
Net PayThe most productive part of the pay zone.
Net Pay CutoffThe lower level to the permeability, porosity or saturation in what is considered net pay.
Net ProductionThe company’s share of the production after royalties and partners shares are removed.
Net Profits InterestA share of the production as calculated from the net profits of the operation.
Net Revenue InterestThat part of the proceeds less royalty payments.
Net-To-Gross RatioThe ratio of the net pay to the gross pay.
Network FracturesOpening up secondary natural fractures that may be orthogonal to the planar fracture.
NETLNational Energy Technology Laboratory.
Neutral PointThe theoretical point in pipe length that accounts for the effects of buoyancy.
Neutralization (processing)Neutralizing acid production (sour gas) with sweetening agents, etc.
Neutralization (stimulation)Raising the pH of the backflowed acid to the neutral point.
Neutron CaptureA measurement in which a target, either a formation of an injected fluid adsorbs natural or generated neutrons.
Neutron LogA log whose source emits neutrons into the formation. Neutrons interact with hydrogen nuclei resulting in an energy loss that is converted to neutron porosity. All hydrocarbons and water contain hydrogen, but the formation usually does not. The amount of hydrogen in the gas affects the reading, so gas filled porosity shows a lower log porosity than oil or water filled porosity.
Newtonian FluidA fluid whose shear force and response is directly proportional to shear rate. Yield point is zero.
NFTNo flow test.
NGLNatural gas liquids.
NGVNatural gas vehicle.
NH4ClAmmonium chloride.
Night ToolpusherAn assistant toolpusher. Also known as a tour pusher.
Nipple (tubular string)A short piece of pipe, usually with a profile shape in the ID. Nipple profiles are used in tubular strings to provide places to set plugs.
Nipple DownTake apart or tear down a piece of a equipment such as a wellhead.
Nipple ProfileThe specific shape of the nipple, usually an accepted profile such as a F, X, J, S, etc.
Nipple ProtectorA sleeve that fits inside of a profile to protect the polished bore and the latch recess.
Nipple UpConstruct or put together a piece of equipment such as a wellhead.
NIRNear infared.
NITRNitrile
NitrideA metal surface treatment that improves abrasion and wear resistance.
Nitrified FluidA stimulation fluid with dispersed nitrogen gas, usually at several hundred cubit feet per barrel.
NitrileElastomer base material with resistance to oil.
Nitro ShotAn old stimulation process that involved lowering nitroglycerine canisters into a well and detonating.
Nitrogen CushionA cushion of nitrogen gas placed on top of a liquid column to reduce the downhole pressure. Also use in the annulus for an expansion cushion in the event of annular fluid expansion.
Nitrogen KickoffBringing a well on with nitrogen lift to get the initial flow rate or to get it to steady state flow. Commonly used after workovers to jet back heavy brines until the hydrocarbons with associated gas flow into the well and begin natural production.
Nitrogen LiftShort term use of nitrogen to kick a well off, i.e., establish flow.
NitrileA common seal materials with good resistance for oil but poor resistance to aromatics.
NLLNeutron lifetime log.
Nm3Normal cubic meters.
NMO (seismic)Normal moveout offset. Difference in arrival times of reflected signals at different detectors caused by source variance and detector separations.
NMRNuclear magnetic resonance log. Can show the difference in water, oil and gas movable fluids.
No GoA profile ring in the tubing with a very small opening that allows flow but stops any equipment or tool from passing through the restriction. May be small I.D. or pinned.
Nodal AnalysisA pressure drop vs. flow study, using a computer program that compares flow performance at various “nodes” along the flow path.
Nodding DonkeyA rod pump surface unit – pump jack.
NodeA reference point in the well.
NOELNo-observed-effect level
Noise LogA sound recording downhole. Best performance of noise logs is with gas flow. Gas flow can be heard to about 10 actual ft3/D (Note – not standard ft3/day). At very low gas flow rates (q<400 actual ft3/D), gas flow can be estimated from millivolts of noise between the 200-Hz and 600-Hz frequencies
Nolte G-functionA dimensionless measure of time often used in analyzing pressure behavior during the hydraulic fracturing process.
Nolte-Smith PlotA log-log plot that is very useful in predicting when the fracture is in tip-screen-out mode and whether the fracture is being widened or height growth is occurring.
Nominal (in filtration)An approximation of a filter’s ability to remove particles of a certain size or larger. Often does not perform at this level until a filter bed of particles builds up on the upstream side of the filter.
Non Associated GasNatural gas, not initially dissolved in oil, produced from a reservoir.
Non Conductive MudUsually oil base or an oil external mud which will not conduct electrical charge. Many logs cannot be run in these muds.
Non Conventional GasGas in unusual reservoirs, e.g., hydrates, coal beds, low permeability, etc.
Non Darcy FlowA flow regime departing from the laminar flow region where Darcy flow is measurable. Generally turbulence.
Non DispersedA fluid without thinners or dispersants.
Non EmulsifierA material, usually a surfactant that prevents emulsions.
Non Marking SlipsSpecial slips for make up tongs that do not mark 13Cr pipe.
Non NewtonianA fluid with a viscosity that does not produce a linear shear stress-shear stress graph.
Non-Producing ReservesReserves subcategorized as non-producing include shut-in and behind-pipe reserves. Shut-in reserves are expected to be recovered from (1) completion intervals which are open at the time of the estimate, but which have not started producing, (2) wells which were shut-in for market conditions or pipeline connections, or (3) wells not capable of production for mechanical reasons. (SPE).
Non-Stress Preferred Fracture PlaneA fracture that is driven in a direction other than perpendicular to the least principle stress. Common in explosive fracturing events.
Non Upset or NU ConnectionA pipe connection with consistent I.D> and O.D. with the pipe. The connection walls are thin and weaker than EU or IU connections. Used in flush joint liners and wash pipes.
Non Selective NippleA profile cannot pass another plug. Usually only one non-selective profile is used – at the bottom of a well.
NonclasticSedimentary rocks not composed of fragments of pre-existing rocks or minerals. Usually called crystalline.
NonconformityAn unconformity that separates profoundly different rock types, such as sedimentary rocks from metamorphic.
Nonionic SurfactantA surfactant with no preferential charge.
NORMA naturally occurring radioactive scale. Usually Barium Sulfate scale with Uranium or Radium atoms substituted into the lattice structure. Can be detected downhole with a gamma ray log.
Normal CirculationCirculation down the tubing and up the annulus.
Normal FaultA fault with mostly vertical movement.
Normalizing (pipe)Heating a steel pipe to a temperature above the alloy transformation temperature range and holding at the temperature for long enough to remove stored stressed from handling, forming or other fabrication.
Normally PressuredA formation with a pore pressure the same as a sea water gradient (0.46 psi/ft).
NORSOKNorsk Sokkels Konkurranseposisjon.
North Sea BrentCrude oil from the Brent field often quoted as a price benchmark.
NOxNitrogen oxides.
NozzleA shaped orifice for directing fluid flow.
NPDNorwegian Petroleum Directorate.
NPDESNatural Pollution Discharge Elimination System.
NPHNaphtha.
NPTNon productive time.
NRNo returns, mud logging term.
NReReynold’s number.
NRV (flow line)Non return valve.
NRWONon rig workover.
NTANitrilotriacetic acid, a chelant.
NTELNo-toxic-effect level
NTUNephelometric turbidity unit, a unit used in measuring water quality. An instrument called a nephelometer (from a Greek word meaning "cloudy") measures turbidity directly by comparing the amount of light transmitted straight through a water sample with the amount scattered at an angle of 90° to one side; the ratio determines the turbidity in NTU's. NTU measurements can be confused by the base color of the water from stains that may not create damage in the rock.
NU (pipe)See Non Upset.
NU (repairs)Nipple up. Put back together.
Nuclear LogRadioactivity log.
NYDECNew York State Department of Environmental Conservation.
NylonA polyamide material.
O3Ozone.
O-RingA circular seal with a circular cross section.
OA (logging)Oxygen activation.
OA (well design)Outer annulus.
OAPOuter annulus pressure.
OBROil
Observation WellA well with primary purpose of monitoring fluid movement or other reservoir function.
ObsidianDark, volcanic glass.
OCOperating center.
OCOuter casing.
OBSOcean bottom seismic.
Observation WellWells used for instrumentation or mechanical observations of a reservoir.
OCSOuter continental shelf.
OCS OrdersRules and regulations from US Minerals Management Service (MMS)
OctaneAn eight carbon chain hydrocarbon in the paraffinic oil series.
OCTGOil country tubular goods.
ODOutside diameter.
OD/IDOutside diameter/inside diameter, usually used in reference to pipe dimension, and a factor in pressure stability of the pipe.
Off -pattern WellA well outside the normal drilling/production pattern.
Offset WellA well drilled next to another. Sometimes refers to neighboring wells of different operators.
Offshore WellA well that has it’s wellhead location offshore, either on a platform or on the sea floor as a subsea well.
Offshore PlatformA fixed, moored, or dynamically positioned platform for hydrocarbon production or handling operations offshore.
OFPOpen flow potential.
OGIPOriginal gas in place.
OGLVOperating gas lift valve.
OGPInternational Association of Oil and Gas Producers.
OHOpen hole.
OHFPOpen hole frac pack. Frac packing in an open hole.
OHGPOpen hole gravel pack.
OhmElectrical unit of resistance. One ohm is the the resistance through which a potential of one volt will maintain a current of one ampere.
Ohm’s LawE=IR, I=E/R, or R=E/I, the current "I" in a circuit is directly proportional to the voltage "E", and inversely proportional to the resistance "R".
Oil Based MudA mud in which the external, liquid phase is oil.
Oil ColumnVertical thickness of an oil accumulation above an oil/water contact.
Oil Emulsion MudA predominately oil phase drilling mud with trace water (<10%) as an additive or a contaminant. Oil as the continuous or external phase. Note
Oilfield ServicesThe support services involved in constructing, stimulating, producing and repairing a well.
Oil-In-PlaceThe oil in place at any time in the reservoir. The original oil in place is OOIP.
Oil-in-Water EmulsionA common oilfield emulsion where oil droplets (the internal phase) are suspended and surrounded by the water (the continuous or external phase).
Oil JarA jarring tool, capable of very large impacts that is cocked and then triggered by oil moving through an orifice.
Oil PoolA porous rock reservoir that contains oil.
Oil RunThe oil production or transfer during a specific time period.
Oil SandPayzone, usually produces oil in economic quantities.
Oil Saturation (reservoir)The fraction of the porosity of a zone occupied by oil.
Oil SaverA seal arrangement on top of a wireline lubricator that prevents loss of oil or gas to the atmosphere.
Oil ShaleA mudrock or mudstone, composed of a large amount of kerogen or similar deposit, which will yield oil only when refined.
Oil-Water ContactLocal boundary between the oil and the bottom water. OW Contact may vary in the field depending on individual drawdowns and local variations in vertical permeability.
Oil Wet RockRock coated with an oil in direct with the rock and attracted by natural surfactant properties.
Oil ZoneA formation from which oil might be produced.
OIMOperations installation manager.
OIPOil in place.
OIWOil in water.
OJOil jar.
OJTOn the job training.
Oleofinic HydrocarbonHydrocarbons that contain one or more double or triple bonds.
OligoceneAn epoch in time from 25 to 28 million years ago.
On-PumpNo longer flowing naturally.
On StructureAt or near the top of the structure that forms the reservoir trap or cap rock.
On-The-Fly (in mixing)Generally used as an addition method of adding materials to the fluid being pumped without recirculation.
OOC (North Sea)Offshore Operators Committee.
OOIPOriginal oil in place.
OOSOut of service.
OoliteSpheres of calcium carbonate precipitated from connate water.
OPAOil pollution act.
OP (gas lift)Opening pressure of a gas lift valve at depth.
OPECOrganization of Petroleum Exporting Countries. (1983 list
Open Flow PotentialThe maximum potential rate from the well if all back pressure was removed.
Open FormationA productive interval, open to the wellbore.
Open Hole CompletionsA completion without casing.
Open-Hole FishingAttempts to retrieve pipe of tools lost in the open hole.
Open Hole Gravel PackA sand control completion for high permeability soft sand formations where the small amount of area offered by the perforations is a restriction on what the formation can deliver to the wellbore.
Open Hole LogOne of a suite of logs commonly run in a well before it is cased.
Open Hole PackerAn inflatable or other packer that can seal in an open hole environment.
Open Hole PerforatingShooting an open hole section of the well for stimulation.
Open ShoeA external annulus ( production by surface casing for example, in which the cement behind the production pipe has not been brought up into the casing by casing annulus. The annulus is open to the formation into which the outer string has been set.
Opening RatioThe ratio of the pressure required to open the preventer to the pressure under the rams.
Operating Gas Lift ValveThe operating valve (open and flowing) in a gas lift system.
OperatorThe company who makes the decisions and is responsible for drilling, completing, operating and repairing the well.
OPEXOperation expenditures. Generally repair or maintenance expenses.
OrdovicianA geologic time period from 425 million to 500 million years ago.
ORFOffshore receiving facility.
Organic AcidAn organic acid such as acetic, formic, etc., that has the characteristic COOH- group.
Organic DepositA deposit in the flow path that is chiefly organic in composition – typically paraffin (wax), asphaltene, tar, or other organic material.
Organic TheoryThe most widely accepted theory to explain the generation of hydrocarbons. As organic materials are buried, heat and pressure transform them into hydrocarbons over geologic time.
OreA mineral deposit rich enough to be mined commercially.
Oriented PerforatingPerforating to align the charge penetration direction with a feature like the fracture plane or to miss an adjacent string of pipe.
Orifice MeterA single phase flow meter, primarily for gas that measures the pressure drop created by the hole as gas is flowed.
Orifice PlatePart of a orifice metering system. A plate with a hole through which a single phase flow produces a pressure drop.
Orifice (gas lift)A set diameter passage. (Not really a valve).
Original Gas in PlaceOGP or OGIP, the entire volume of gas contained in a reservoir, whether or not it is currently recoverable with state of the art technology or ability to produce.
OrogenyA period (geologic) of mountain building.
Orphan WellsWells for which the operators cannot be located.
OSOvershot.
OSHAOccupational safety and health administration, US government agency.
OsmosisMovement of a solvent through a semipermeable membrane (plastic, polymer or living cell) into a solution of higher solute (dissolved salt) concentration that tends to equalize the concentrations of solute on the two sides of the membrane.
OTCOffshore Technology Conference.
Ottawa SandA high quality, widely available mined sand used for gravel packing and fracture proppant.
OutcropWhere a formation surfaces.
Outer Continental Shelf (MMS)All submerged lands seaward and outside the area of lands beneath navigable waters. Lands beneath navigable waters are interpreted as extending from the coastline 3 nautical miles into the Atlantic Ocean, the Pacific Ocean, the Arctic Ocean, and the Gulf of Mexico excluding the coastal waters off Texas and western Florida. Lands beneath navigable waters are interpreted as extending from the coastline 3 marine leagues into the Gulf of Mexico off Texas and western Florida.
OutgassingBreakout of gas from a liquid, normally at the point where the pressure has declined sufficiently to allow solution gas to be released as bubbles.
OvalityA change in tube roundness. Ovality in percent = (Dmax-Dmin)/Dnominal x 100.
Ovality Limit (CT)A limit placed on coiled tubing, usually in % ovality, after which the CT may not be used in deep wells or in well operations outside of completion hangoffs.
OverbalanceWhere the pressure in the wellbore in higher than the pressure in the reservoir.
OverburdenThe sediment weight pressing down on the formation. Usually about 1 psi/ft.
OverflushThe fluid that is pumped after the last reactive or active part of a stimulation to displace the stimulation down to (displacement) or into (overflush) the formation.
OverlapThe section of a concentric liner or casing installation where both strings are cemented.
OverliftOver production, beyond the allotment or contract volume, that must be accounted for in a contract.
OverpullThe load applied when pulling equipment that is in excess of the actual string weight.
Overriding Royalty Interest (contract)A royalty interest that may be retained by a third party as payment or investment. This interest normally bears no part of the drilling and completion expenses of the well.
OvershotA fishing tool designed to slip over the fish and grasp the outside.
OverthrustAn area of earth shift common to mountainous regions in which strata are shoved upwards creating highly titled reservoirs.
OWCOil water contact.
OWROil
Oxbow LakeA crescent-shaped body of generally isolated water, cut off from a meandering stream as the stream changed its course.
OxidizersReactants that oxidize, e.g., bleach and sodium persulfate. Also, a compound that releases oxygen.
Oxygen Activation SurveyA log that detects compounds with oxygen such as water. Often used to detect channels behind pipe.
Oxygen Index (shale)(OI, mg CO2/g TOC) a measurement of the percent of oxygen needed to support reaction.
P&APlug and abandonment.
P&IDProcess and instrument diagram.
P WavePrimary or compression wave. A seismic body wave that involves particle motion, alternating compression and expansion. It is the fastest seismic wave.
PALProducer, artificial lift.
P/Z PlotA plot of P/Z vs. cumulative production that indicates compartmentalization if not a straight line.
Pack-OffA seal between or around equipment to isolate pressure or areas within the well. .
PackerA device that forms a seal between two chambers of the well. Packers may be equipped with slips that anchors the packer and stops movement under high pressure.
Packer Bore ReceptacleA removable PBR anchored into the top of a packer.
Packer ElementsElastomer seals on a packer.
Packer FluidThe fluid left in the annulus behind the packer. It may help offset pressure in the tubing or help reduce thermal losses.
Packer MillingRemoval of a permanent packer.
Packer Squeeze CementingIsolating a cement injection site between a packer and a plug prior to squeezing.
Packerless CompletionsA completion with no packer. Common where ever gas has to be kept away from ESPs and rod rumps.
Packing (seals)Seals around a moving shaft or other equipment.
Packing ElementSeal that blocks fluid communication.
PackoffA seal formed in the tubing or around the top of a screen or packer to isolate a flow path.
Packing offA collection of materials including cutting and/or fill that dehydrates or is held by pressure and stops to circulation of fluid in a wellbore.
PACVPressure activated circulating valve.
PadA volume of fluid, without proppant, injected in front of a frac job to establish frac width.
Paddle Blender or MixerA mixing chamber, usually in a small tank or pod that uses a rotating paddle to mix the fluid and the additives.
PAL (log)Pipe analysis log.
PAL (lift)Producer, artifical lift.
PaleoceneA geologic time period from 250 to 570 million years ago.
PaleontologyThe study of fossils. Useful for dating and identifying rocks.
PaleozicAn era of geologic time lasting from 570 million years ago to 245 million years ago.
ParaffinNormal or straight carbon chain alkanes with carbon chain lengths of C18+. The alkanes in this range solidify at temperatures from 80oF to over 200oF. Paraffin is amorphous but may appear to have structure in slow growth examples.
Paraffin base oilOil with API gravity greater than 30.
Paraffin Scraper or ScratcherA wireline tool to remove paraffin deposits.
ParentA radioactive element whose decay produces stable daughter elements.
Parted Rods (beam lift)A sucker rod string that has broken or come apart in the well.
Partial CompletionWhere only part of the pay zone is completed. Generally used to control coning of a fluid or to select the origin of the fracture in a stimulation.
Partial MonolayerA layer of proppant with gaps between the grains. High capacity but weak.
Partial PenetrationDrilling only part way through a reservoir (near vertical wells).
Partial PressureFor CO2 corrosion potential; the mole fraction of the gas times the total pressure.
Particle DistributionA sieve or laser analysis of the particle sizes in a sand.
Particulate MatterPM, a particle of solid or liquid matter (soot, dust, mist, etc.).
Parts Per Million or PPMUnit weight of the solute per million unit weights of the solution. A small correction factor is needed to convert to mg/liter.
PascalA unit of pressure equal to 1/100,000 of a bar.
Passivation (corrosion)Reduction of the anodic reaction rate.
PassiveA condition when the metal shows a marked decrease in corrosion rate.
Patch (tubular)An in-place, downhole repair of part of a tubing string.
Pattern Water FloodA series of injection and production wells in a regular arrangement.
Pay ZoneHydrocarbon producing interval.
PayoffWhen the well has produced sufficient net revenue to pay the cost of drilling and equipping the well.
PayoutThe point where the capital cost have been earned.
PBPump bailer.
Pb (reservoir fluids)Saturation pressure or bubble point pressure.
PBRSee Polished Bore Receptacle.
PBTDPlug back total depth.
PBUPressure build up.
PCProduction casing.
PCL (SSSV)Pemature valve closure.
PCPProgressive cavity pump.
PCPPermanent completion perforating.
PCT (brine)Pressure crystallization temperature.
PCT (tool)Production combination tool.
PCT (brine)Pressure crystallization temperature.
PD (gas lift)Bellows gas pressure at 60oF.
PD (reserves)Proved developed.
PDCPoly crystalline diamond compact drill bit or cutter.
PDC LogPerforating depth control log.
PDGPermanent downhole gauge.
PDHGPermanent downhole gauge.
PDNP (reserves)Proved developed non producing.
PDPProfessional development plan.
PDMPositive displacement motor.
PEPetroleum engineer or production engineer.
PE (plastic)Polyethylene.
PeatA organic deposit, which, with time and burial stresses would become coal.
PEEKPolyetheretherketone, (Victrex, Arlon)
PEIProduction efficiency improvement
Penetration Rate (drilling or well cleanout)A rate, measured in distance per time or the penetration of a bit or cleanout sub through a formation or a deposit.
PennsylvanianA geologic time period from 290 to 320 million years ago.
Penny FracA frac that grows up and outward.
PentaneA five carbon chain alkane. Used in the lab to check for asphaltenes (precipitates them).
PeptizeDisperse into a colloid.
Perched Water TableA water saturated area that lies within a zone of aeration.
Percussion Hammer (drilling)A device that delivers rapid thrust or blows to the assembly containing the drill bit.
PERFPetroleum Environmental Research Forum.
Perforated CompletionA completion where the well is cased and cemented and then perforated in the zone of interest.
Perforated LinerA liner with holes drilled for fluid entry. Not usually for sand control but may be useful for increasing hole stability or access.
Perforating ChargeA shaped explosive charge used for penetrating casing and cement.
Perforating DebrisPieces of charge cases, loading tubes, and alignment equipment generated by firing the gun. They may or may not be left in the well.
Perforating DensityShots per unit length.
Perforating Depth ControlThe process by which a perforating gun is lined up to fire at the correct depth.
Perforating GunA carrier for shaped charge explosives that punches holes through the casing and cement and into the formation. Guns may be run on wireline or tubing.
PerforationA hole made through the casing and cement and into the formation. It has a characteristic entrance hole and penetration. It is the flow path from the formation to the wellbore in a cased and cemented completion.
Perforation BreakdownThe fracturing of a perforation tunnel. Often used to bypass damage or increase permeability.
Perforation CarrotA piece of the copper liner that forms a cylindrical slug.
Perforation Crush ZoneThe area of crushed rock surrounding the perforation. Usually 30 to 70% of initial permeability and ?” or about 1cm thick.
Perforation DensityThe number of perforations per unit length of pipe in an interval.
Perforation Entry HoleThe diameter of the hole in the first string of pipe penetrated by the perforator.
Perforation PenetrationThe total depth of penetration including the casing thickness, the cement and the formation.
Perforation PhasingThe angle between the shots. The phasing can have an impact on pipe strength, formation strength and productivity.
Perforation PrepackingPacking the perforation with gravel to prevent tunnel collapse.
Perforation Shot DensityThe number of perforations per foot or per meter.
PerformNodal analysis program.
PeriodA geologic time scale that is less than an era and greater than an epoch.
PermafrostA type and structure of frozen soil found in a new cold areas of the world. May extend to depths in excess of 1000 meters.
Permanent PackerA reliable packer designed and intended to be left in place for a long period of time that seals and holds pressure or resists movement from both directions.
Permeability or kA measurement of the ability of a fluid to flow through a rock.
Permeability BarrierA barrier to movement of a fluid through the rock. This may be a change in the rock where the pores are no longer connected or even present, or secondary mineral growth that filling in the pore throats and natural fractures. In one sense, a permeability barrier may be another rock that acts as a seal.
Permeability ContrastA comparison of permeabilities of a fracture proppant and the formation.
Permeability CorrelationA mathematical permeability correlation, normally based on porosity and rock type.
PermeationMovement of gas to and through an elastomer.
PermianA geologic time period from 250 to 290 million years ago.
PESProduction engineering supervisor.
Petal Basket (cementing)A attachment to tubing or a plug that looks like an upside down umbrella. It helps hold cement or sand as a plug is started. It has metal ribs and a tough fabric between the ribs.
Petal Basket Flowmeter (logging)A petal basket that reroutes all the fluid over the diameter of the wellbore into a single flow stream near the middle so an accurate measurement with a flowmeter can be made.
PETNA low temperature explosive used in perforating charges.
PetrochemicalsChemicals derived from oil or gas.
PetroleumLatin origin is rock oil.
PetrophysicsThe study of reservoir rocks and their reactions.
PfFriction pressure – may be annulus or tubing.
PFOPressure fall off test – a common injector test or a test after pumping in.
PhHydrostatic pressure.
pHThe negative logarithm of the hydrogen ion activity. pH = -log10 (aH+) Measurement of acid (<7), basic (>7), neutral = 7. pH measures the acifdity or alkalinity of water.
PhaseA homogeneous body of material that differs in properties from other phases (immiscible) – e.g., gas, liquid, solid.
Phi?, porosity
Phosphate EstersDerivatives of phosphoric acid and alcohols. Used for scale inhibitors in process flow.
PhosphonatesOrganophosphorus compounds that form the basis for many scale inhibitors that are squeezed into a formation and provide long term protection.
PHPAAcrylamide polymer mud.
PIThe productivity Index, usually measured in bbl/day/psi of drawdown.
Pick (seismic)A selected event on a seismic record.
Pick Up WeightThe surface weight measurement when pulling a pipe string or wireline out of the hole. Includes both string weight and frictional drag.
Pickett PlotA log-log plot of resistivity (x-axis) vs. porosity. Helps determine which zones contain hydrocarbon.
PickleA chemical treatment of the tubulars to remove pipe dope, mill scale and mud or cement residue.
PIDPerforation Inflow Diagnostic.
PIE (BP)A pressure transient data base.
PigA flow line clearing device, pumped through the line with normal flow.
PillA volume of gelled fluid mixed for a specific purpose. A fluid loss pill for example.
PilotA small scale test or trial used to assess the feasibility of a process to a reservoir or field.
Pilot HoleA small (sometimes) diameter hole drilled through a pay zone to determine the pay top and bottom or various contacts, before the main well position is selected. May also use a pilot hole to better control influx rate.
Pilot MillA step-diameter mill that makes a pilot hole then enlarges it with the upper diameter.
Pin (in pipe)The male end of the connector.
Pin (in wireline tools)A small piece of steel, brass, aluminum bar stock that is designed to break on a certain impact or pressure load and enable another tool function.
PINC (DOI)Potential Incident of Non Compliance
Pinch OutLoss of permeability in a reservoir rock. Often so severe that the pinch out becomes a barrier or a seal.
PinjBottom-hole injection pressure.
Pinnacle ReefA conical shaped reef-type deposit, usually with good permeability and pososity.
PIPTrademarked name for a pin point injection packer.
Pip TagA radioactive tag or marker in the casing threads or the perforation that can quickly and positively be found wit h a gamma ray log.
Pipe DopeA lubricant, anti-gall and sealer applied to the pin threads when making a connection in the pipe.
Pipe HeavyA hydraulic workover/snubbing tubing running term – when the weight of the pipe is sufficient to pull the pipe into a well against the surface pressure.
Pipe Lay DownRemoving pipe from the well or from standing in the derrick and laying in on the pipe racks away from the rig.
Pipe LightHydraulic workover/snubbing tubing running term – when the weight of the pipe is not sufficient to pull the pipe into a well against the surface pressure and additional force (snubbing) is required.
Pipe RackStorage racks.
Pipe RampAn angled ramp or track for bringing pipe from the rack to the rig floor.
Pipe RamsThe rams in a BOP that seal around the pipe diameter for which they were sized.
Pipe TongsTools used in making up pipe connections.
Pipe UpsetAn increased diameter of the pipe body which allows for a thicker coupling and an increased diameter at the coupling.
PipelineThe principle underground transport of produced gas and oil.
Pipeline Quality OilOil with the BS&W removed and the contaminates brought within the contract specifications.
Pipeline gasProduced gas within pipeline spec and under sufficient pressure to enter the pipeline against the pressure of the fluid in the pipeline.
Pipe UpsetThe thicker part of a pipe where threads are machined for the coupling.
PISSPump in spinner survey.
PISTLPump in spinner temperature log.
PITAPerforation inflow test analysis.
PITPacker integrity test. Pressure testing the tubing/casing annulus to insure isolation.
PITPressure integrity test.
Pit (drilling)A temporary (earlier use) or permanent containment for circulated fluids.
Pit LevelThe level of mud in the pits.
Pitch (drilling)Deviation from a horizontal plane. Down is negative and up is positive.
PitmanThe connecting rod from the rotating counterweights to the beam on a beam lift pumping unit.
Pitot tubeA small tube used for sensing pressures in a flowing stream.
PITSPump in temperature survey.
PittingExtremely localized attack that results in holes in the metal. Will accelerate after start.
Pitting Resistance Equivalent NumberA relative measure of a material’s pitting resistance in corrosive service.
PJPetajoules. 1,000,000,000,000,000 joules. 1 kilojoule = 0.9478 BTU.
PJTHAPrejob task hazard analysis.
PkrPacker.
PLPipeline.
Placer DepositA deposit of heavy or durable minerals found where runoff water slows.
PlanktonicFree floating bacteria.
Plastic DeformationA stress level, beyond the elastic limit, that produces yielding in tubulars.
Plastic FluidA complex, non-Newtonian fluid whose shear force is not proportional to the shear rate. Pressure is necessary to start circulation of the static fluid. Main low rate flow is plug flow. Yield point is greater than zero.
Plastic ViscosityAn absolute flow property indicating the flow resistance of certain types of fluids. A measurement of shear stress.
PlateauThe best producing time of a field, before decline of total production rate begins.
PlatformAn offshore structure from which a well may be drilled or produced.
PlayA pay zone or set of pay zones with proven commercial reserves.
PlayaA dry lake basin found in a desert.
PLCProgrammable logic controller.
PLET (subsea)Pipeline end terminal.
PLTProduction logging tool.
PlugAny device, object or material that blocks a flow passage.
Plug and AbandonP&A. Setting cement and mechanical plugs to seal off pays, potential leak points, fresh water zones and the surface.
Plug and CageA type of choke that is suitable for high volume and can stand some solids.
Plug and Seat ChokeA high volume flow choke.
Plug BackTo set a plug (usually permanent) in a wellbore, giving a new bottom.
Plug Back DepthThe depth of the well to the top of the last permanent plug.
Plug Container or Dropper (cementing)The housing with valves and bails that controls the position and dropping of the plugs used in cementing.
Plug FlowFluid moves as a unit.
Plug ValveA high pressure valve with a rotatable plug that allows or denies flow.
Plunger (gas wells)A tool that is dropped without attachment through the tubing and standing water in the well, then seals against the tubing using the pressure of the incoming gas to raise the plunger and the water above it to the surface. A very common Deliquification tool.
Plunger (beam lift)The traveling bar in beam lift pump internals.
Plutonic igneous (rock)Magna extruded into overlying rock that is not exposed to atmospheric conditions during cooling.
PMParticulate matter.
PM10Particulate matter having a size diameter of less than 10 millionths of a meter (10 micro-meters).
PM2.5Particulate mater having a size diameter of less than 2.5 micro-meters.
PMACSPortable measurement, alarm and control system.
PML (perforating)Powdered metal liner.
PNCPulsed neutron capture.
PNGPipeline natural gas.
PNIDProcess and instrument diagram.
PNLPulsed neutron log.
Pocket (drilling)Old term for rat hole.
Pocket (gas lift)A receiving orifice for a gas lift valve in the gas lift mandrel.
Pod MixerA tank with an agitation system used to more precisely mix components during a job.
POEPolyoxyethylenated – a common surfactant group.
POHPull out of the hole. Also POOH.
Poiseuille’s Law (flow)In the example or laminar flow for Newtonian fluids, the volume flow rate is given by the pressure differential (inlet to outlet) divided by the viscous resistance. This resistance depends on fluid viscosity and the length but is dominated by dependence on the fourth power of the radius.
Poisson’s RatioAs a rock is compressed axially, the ratio of longitudinal compressive strain to the transverse extension strain (length change over width change). Always between the range of 0 to 0.5.
Polished BoreA slightly smaller I.D. that the tubing above it in a tool or profile that allows a set of seals to provide isolation.
Polished Bore ReceptacleA polished bore, typical in a packer to accept the seal assembly on the end of tubing.
Polished NippleA polished nipple is run below blast joints to allow a pack-off set point when by-passing a damaged joint.
Polished RodA surface rod pup joint that slides through the stuffing box on a beam pumped well. The part is highly polished and generally chrome plated. It must not be exposed to HCl acid.
Polished Rod Clamp (beam lift)A device that fastens the polished rod to the bridle.
PolyacrylamideA polymer with a very stable carbon chain. A good friction reducer in small amounts, but the polymer may cause formation damage. Can be used to gel acid, but the polymer will not break.
PolyesterResin formed by condensation of polybasic and monobasic acids with polyhydric alcohols.
PolymerA synthetic or man made gelling agent that increases viscosity and helps control leakoff.
PolymorphA mineral that is identical to another mineral in chemical composition but differs from it in chemical structure.
Pony RodA short rod for spacing out a rod string.
POP (plug)Pump open plug.
POP (production)Put on production.
Poppet ValveA type of valve common on early subsurface safety valves, where higher than expected flow through an orifice can move a round ball onto a sealing surface and stops the flow.
POOHPull out of the hole.
PoolGenerally a petroleum containing reservoir or group of reservoirs.
Pooled UnitUnit created by combining separate mineral interests under the pooling clause of lease or agreement.
Poorly SortedA comparison of sand grain sizes in a formation where there are a broad range of coarse to fine particles.
POPPut on production.
POP (downhole)Pump-out plug.
PoreThe opening within the rock. Interconnected porosity is linked together and results in permeability.
Pore pressure gradientThe formation or reservoir pressure divided by the depth.
Pore Size DistributionA range of the pore sizes plotted against frequency of that size. Mercury is injected at step-wise increasing pressures where large pore fill first, followed by smaller pores at successfully higher pressures. Volumes injected at different pressures indicate the pore size distribution.
Pore ThroatThe connection between the pores, often a fraction of the pore size and an obvious restriction.
PorosityThe percentage of the rock volume that is not rock grains and could be occupied by fluids. Pores may or may not be connected.
ɸPorosity
Porosity CutoffThe lower limit of porosity that identifies a proven productive part of a particular formation.
Porosity ExponentThe exponent, m, in relating formation factor to porosity in the Archie equation, F = 1/ɸm
Port PlugThe sealing plug over a charge on a reusable perforating gun.
Potable WaterWater suitable for human consumption.
Ported NippleA nipple profile with an accessible side port to the annulus.
Portland CementA general class of cement that encompasses the most common cements used in construction and the oil field.
Portland Cement ClinkerHard, approximate marble-sized nodules of calcium silicates and other additives that are the feed stock for making cement.
Positive ChokeTypically a non adjustable choke using a flow bean.
Possible ReservesPossible reserves are those unproved reserves which analysis of geological and engineering data suggests are less likely to be recoverable than probable reserves. In this context, when probabilistic methods are used, there should be at least a 10% probability that the quantities actually recovered will equal or exceed the sum of estimated proved, plus probable, plus possible reserves. In general, possible reserves may include (1) reserves which, based on geological interpretations, could possibly exist beyond areas classified as probable, (2) reserves in formations that appear to be petroleum bearing, based on log and core analysis but may not be productive at commercial rates, (3) incremental reserves attributed to infill drilling that are subject to technical uncertainty, (4) reserves attributed to improved recovery methods when (a) a project or pilot is planned, but not in operation and (b) rock, fluid, and reservoir characteristics are such that a reasonable doubt exists that the project will be commercial, and (5) reserves in an area of the formation that appears to be separated from the proved area by faulting and geological interpretation indicates the subject area is structurally lower than the proved area. Often referred to as P3 (SPE).
Possum BellyAn enlarged section of a tank for settling solids.
Pottable waterDrinkable water.
Potassium ChlorideA salt commonly used in brines to reduce or prevent clay swelling in the formation.
Potassium Chloride SubstituteGenerally salt and/or surfactant materials designed to simulate the effect of potassium chloride in preventing clay swelling. Substitutes may work in the wellbore but generally fail in the formation where severe swelling conditions exist.
Potassium K40One of the natural isotopes that as a trace element may incorporate into the matrix of naturally forming barium or strontium sulfate scale and make it a very low level radioactive material (NORM scale).
Potential (electrical)Difference in electrical power level.
Potential (risk analysis)Actually probability - the likelihood that the impact will occur. Impact (or consequence) is the effect on conditions or people if the hazard is realized (occurs) in practice and probability is the likelihood that the impact will occur. Risk is a function of probability and impact (consequence).
Pour PointThe lowest temperature that a hydrocarbon fluid can be flowed before gelling or turning solid. Related to pumpability.
Power FluidA fluid, usually dead oil or water, pumped downhole to operate a pump.
Power Law FluidA description of the flow properties (viscosity) of a fluid. Power law fluids are characterized by decreasing viscosity with increasing shear.
Power Swivel (drilling and workovers)A rig floor tool that can rotate a string.
Power TongsHydraulic power make up tools suspended above the rig floor.
PozzlinA silica cement additive.
PPPulling prong.
PP (formation)Pore pressure.
PPBParts per billion or pounds per barrel depending on the use.
PPEPersonal protective equipment.
PPGPounds per gallon. Usually used as a measure of additive, slurry or cleanout. Actually it is pounds of proppant in a gallon volume with liquid added to make up the gallon “space”.
PPGAPounds per gallon added. See PPG.
PPMParts per million.
PPPOT-TPositive pressure pack-off test – tubing.
PPSPolyphenylene sulfide (e.g., Ryton)
PPTBPounds per thousand barrels.
PRPressure.
Pr (reservoir)Reservoir pressure.
PREPitting resistance equivalent number.
PrecambrianThe geologic time from 570 million years ago to be beginning of the earth. Most rocks in this period have no hydrocarbons.
PrecipitatedA solid material that drops out of an over saturated solution. Usually driven by an upset of equilibrium.
Precipitation HardeningHardening caused by precipitation of a material (specific element or alloy) from a supersaturated solution.
Precipitation PointThe calculated solubility point of an ion in solution (scale/brine stability calculations).
PrecisionThe number of significant decimals expressed in a measurement.
Prehydrated (clay or polymer)Already wetted to make easier to disperse and fully wet.
Prepacked ScreenA sand control screen that uses a captured gravel or resin coated gravel to assist in restraining formation sand or gravel packing gravel.
Prepacking (perfs)Packing the perforations with gravel to prevent tunnel collapse.
Prescient (Risk)Foreknowledge of events. Human anticipation of the course of events.
Present Net ValuePNV; the current time value of an income stream that extends into the future. Various calculation methods and interest rates have been applied.
Preserved CoreCore removed from the formation and preserved by sealing or freezing to prevent drying or other altering of the rock or fluids.
PressureForce per unit area exerted by a fluid.
Pressure BombA downhole device used to collect reservoir samples at pressure.
Pressure BuildupThe rate at which pressure builds up after a flow period. It is related to permeability, fluid viscosity, pressure differential, hole volume, zone thickness and time.
Pressure Dependent PermeabilityThe permeability that increases as driving pressure increases, such as opening fractures wider at higher pressure.
Pressure DepletionA method of producing a reservoir when water drive is not available. Also a condition that exists when the gas pressure is drawn down before the oil is recovered.
Pressure Dependent PermeabilityModifications to the character of the rock through the matrix or natural fractures, where the permeability is a function of the pressure applied to the rock through fluid pressure or earth stresses.
Pressure FalloffThe rate at which pressure decreases at the end of an injection. Related to rock permeability, and to fracture closure stresses when above the fracture point.
Pressure GradientChange in pressure with depth.
Pressure Integrity TestA pressure test of a vessel formed by the entire well or a part of the well. It usually measures the ability of a pressure vessel to hold pressure without leaking at a given pressure.
Pressure Relief ValveA mechanical valve that opens at a preset pressure to relive pressure in a vessel.
Pressure Transient TestAn analysis of well flow using a test that shuts the well in following a flow period and measures the rate or pressure build-up.
Pressure TraverseCalculation of well pressure vs. depth by integrating the pressure gradient for increments of pipe length (MD).
Pressurized Mud Balance (fluid density)A cup and bar with a sliding weight, similar to a Mud Balance, but also having a screw on top with a slide valve through which a small amount of fluid could be added under pressure, collapsing the air dispersed in the fluid. Better accuracy than an unpressurized mud balance.
PrimacordA detonating cord for perforating guns.
PrimacyA right granted to states by the US government that allows state agencies to implement programs with federal oversight. Usually, states develop their own set of regulations to meet a specific goal.
Primary CementingThe first attempt at creating a cement seal in the annulus.
Primary CompletionThe first completion in a well.
Primary Natural FracturesNatural fractures oriented along the same plane as the preferred fracture direction, i.e., perpendicular to minimum principle stress.
Primary ProductionThe oil recovered before pressure maintenance (flooding).
Primary RecoveryThe amount of the reserves recovered by primary production, i.e., without injected fluid pressure support.
Primary TermThe period of time which a lease is effective without being renewed.
Prime MoverThe main type of power source for an application.
Primer CordDetonation cord for explosives. Primacord is a trademarked name for detonation cord. Normally used in a perforating gun.
Probabilistic Estimate (Risk)The probabilistic (risk weighted) approach of estimating recognizes that, in the real world, there are uncertainties associated with each project component. As such, for each component, there exists probabilities of occurrence within a range of possible values. Likewise, for the total project estimate (Being an accumulation of individual components defined by a mathematical mode), there exist probabilities of occurrence within a range of possible values. An estimate using a range of numbers with associated probabilities of occurrence for each of the components or, at least, for each of the components that have substantive certainty.
ProbabilityThe likelihood that the impact or event will occur. Impact (or consequence) is the effect on conditions or people if the hazard is realized (occurs) in practice and probability is the likelihood that the impact will occur. Risk is a function of probability and impact (consequence). With discrete data, it is determined by taking the number of occurrences for the particular type of event being considered and dividing that by the total number of outcomes for the event. Expressed as a deterministic value (quantative single value, or, high, medium, low, etc.) or as a range of values – i.e., uncertainty – that is represented by a probability distribution.
Probability Distribution (Risk)A mathematical relationship between the values and the associated probabilities for a variable across the entire range of possible values for that variable. Typically, probability distributions are displayed as frequency or cumulative frequency plots.
Probable ReservesProbable reserves are those unproved reserves which analysis of geological and engineering data suggests are more likely than not to be recoverable. In this context, when probabilistic methods are used, there should be at least a 50% probability that the quantities actually recovered will equal or exceed the sum of estimated proved plus probable reserves. In general, probable reserves may include (1) reserves anticipated to be proved by normal step-out drilling where sub-surface control is inadequate to classify these reserves as proved, (2) reserves in formations that appear to be productive, based on well log characteristics, but lack core data or definitive tests and which are not analogous to producing or proved reservoirs in the area, (3) incremental reserves attributable to infill drilling that could have been classified as proved if closer statutory spacing had been approved at the time of the estimate, (4) reserves attributable to improved recovery methods that have been established by repeated commercially successful applications when (a) a project or pilot is planned, but not in operation and (b) rock, fluid, and reservoir characteristics appear favorable for commercial application, (5) reserves in an area of the formation that appears to be separated from the proved area by faulting and the geologic interpretation indicates the subject area is structurally higher than the proved area, (6) reserves attributable to a future workover, treatment, re-treatment, change of equipment, or other mechanical procedures, where such procedure has not been proved successful in wells which exhibit similar behavior in analogous reservoirs, and (7) incremental reserves in proved reservoirs where an alternative interpretation of performance or volumetric data indicates more reserves than can be classified as proved. Often referred to as P2 (SPE).
Produced Gas-Oil-RatioTotal gas (solution + free) production divided by the oil production volume. Excludes gas lift gas.
Produced WaterWater, ranging from fresh to salty, produced with the hydrocarbons as a result of pressure drawdown and flow through the formation.
Producing HorizonThe depth or zone in which the well is being currently produced.
Producing WellA well that produces hydrocarbon in commercial quantities. .
Production CasingThe innermost casing string that straddles and isolates the producing interval.
Production ChemistA chemist that specializes in hydrocarbon flow and emulsion separation problems.
Production IndexJ or PI. A measure of a well’s ability to flow. Applies above the bubble point.
Production Index (Shale)An indication of source rock potential measured by the conversion of kerogen into free hydrocarbons (PI, S1/(S1+S2))
Production LogA technique in which the entry points and the amount of fluid entering the wellbore are identified.
Production MaintenanceThe operations necessary to optimize recovery and keep production as high as practical.
Production PackerAny packer that forms a seal between tubing and annulus during production.
Production Pressure Operated Valve (gas lift)Production fluid enters the valve and acts on the effective bellows area, compressing the bellows against the precharge pressure, lifting the needle off the seat and opening the valve. The injection gas then flows through the seat, through the reverse-flow check valve and into the tubing.
Production RigA mobile servicing or workover unit.
Production SeparatorA vessel through which production passes and the multi-phase fluids are broken and separated.
Production Technical LimitsThe maximum potential from the best achievable production practices.
Production TestA monitored flow test.
Production TreeThe pressure and flow control tree on a producing well.
Production Tubing StringThe primary flow path from the pay to the surface.
Production Wing ValveThe valve on the flow cross that controls the exit point as produced fluids flow from the tree.
Productivity IndexA comparison of the productivity of a completion to the productivity of an ideal, undamaged open hole. Labeled PI or J.
Productivity OptimizationComparison of processes, products or operators by comparison to the rest of the operators in an area.
ProfileA machined design in a short piece of tubing or casing that allows a plug to set, anchor and seal.
PropaneAn alkane with a 3 carbon chain.
PropellantA gas generating charge of explosive that is used for perf breakdown.
ProppantsWell sorted and consistently sized sand or man-made materials that are injected with the frac fluid to hold the fracture faces apart after pressure is released.
ProrationingAllocation of production among commingled reservoirs according to reservoir production characteristics, tests, etc.
ProspectA location where a well is to be drilled.
ProsperNodal analysis program.
Protection StringA string of casing used when drilling a well to protect an outer string of pipe from drill string contact or to protect a zone.
Proved ReservesProved reserves are those quantities of petroleum which, by analysis of geological and engineering data, can be estimated with reasonable certainty to be commercially recoverable, from a given date forward, from known reservoirs and under current economic conditions, operating methods, and government regulations. Proved reserves can be categorized as development or undeveloped. If deterministic methods are used, the term reasonable certainty is intended to express a high degree of confidence that the quantities will be recovered. If probabilistic methods are used, there should be at least a 90% probability that the quantities actually recovered will equal or exceed the estimate. Often referred to as P1, sometimes referred to as “proven” (Reserve definitions are from SPE).
Proved Undeveloped ReservesProved Undeveloped Reserves are those Proved Reserves that are expected to be recovered from future wells and facilities, including future improved recovery projects which are anticipated with a high degree of certainty in reservoirs which have previously shown favorable response to improved recovery projects. (See Undeveloped) (SPE).
Proved Developed ReservesProved Developed Reserves are those Proved Reserves that can be expected to be recovered through existing wells and facilities and by existing operating methods. Improved recovery reserves can be considered as Proved Developed Reserves only after an improved recovery project has been installed and favorable response has occurred or is expected with a reasonable degree of certainty. (See Developed Reserves) (SPE). Developed reserves are expected to be recovered from existing wells, including reserves behind pipe. Improved recovery reserves are considered developed only after the necessary equipment has been installed, or when the costs to do so are relatively minor. Developed reserves may be sub-categorized as producing or non-producing. (SPE).
ProducingReserves subcategorized as producing are expected to be recovered from completion intervals which are open and producing at the time of the estimate. Improved recovery reserves are considered producing only after the improved recovery project is in operation. (SPE).
Non-producingReserves subcategorized as non-producing include shut-in and behind-pipe reserves. Shut-in reserves are expected to be recovered from (1) completion intervals which are open at the time of the estimate, but which have not started producing, (2) wells which were shut-in for market conditions or pipeline connections, or (3) wells not capable of production for mechanical reasons. (SPE).
Behind-pipe reservesAre expected to be recovered from zones in existing wells, which will require additional completion work or future re-completion prior to the start of production (SPE).Proximity Log pad contact tool that measures resistivity.
PRPPremature release of packer.
PRVPressure relief valve.
PsPressure at the surface.
PSPump station.
PS Wave (seismic)Seismic energy that has traveled partly as a P-wave and then as an S-wave; having been converted on reflection at an interface.
PSAPressure setting assembly. A E-line tool used to set downhole tools. Normally uses a gas propellant charge.
PSASVPressure shut annular standing valve.
PSC (contract)Production sharing contract.
PSC (gas lift)Closing pressure at surface for a gas lift valve.
PSDParticle size distribution.
Pseudogravity (seismic)A magnetic gravity field expression that is measured at or transformed to the magnetic pole. Susceptibility values are converted to density values and expressed as a vertical integration.
Pseudoplastic fluidA complex non-Newtonian fluid without thixotrophy. Flow starts with pressure but apparent viscosity decreases instantaneously with increasing rate of shear.
PSIPounds per square inch.
PSIAPounds per square inch absolute.
PSIGPounds per square foot gauge.
PSLProduct specification level. A rating for wellheads.
PSO (gas lift)Surface opening pressure of the gas lift valve.
PSPPremature setting of packer.
PSVProduction swab valve.
PSVPressure safety valve.
PT (gas lift)Tubing pressure.
PT (skills)Petroleum technologist or technician.
PT (subsea)Pressure temperature.
PT (well test)Pressure test.
PTFEPolytetrafluoroethylene, (e.g., TEFLON ).
PTRO (gas lift)Test rack opening pressure for a gas lift valve.
PTLProduction technical limits.
PTSPressure temperature survey.
PUPick up.
Public LandsAny land owned by the government in the US. May compare to Crown or Federal lands in other countries.
PUD (reserves)Proved undeveloped.
Puddle JobA cement job done by spotting a column of cement then lowering a liner into the cement slurry.
Pulling Unit (rig)A well servicing rig used specifically for pulling rods and tubing.
Pulse Echo ToolVarious forms of a tool for bond evaluation, usually an ultra sonic emitter and detector.
Pulsed Neutron LogA cased-hole log capable of distinguishing between water and hydrocarbons.
Pump Barrel (beam lift)The tube through which the plunger of a rod pump reciprocates.
Pump Down ToolAny tool that is pumped down the well by injected fluid.
Pump EfficiencyThe output of the pump at stated conditions divided by the ideal output.
Pump JackThe main rocking unit of a rod pumped well. Older uses were in central power units.
Pump OffPumping all the fluid out of the wellbore to the point where free gas enters the pump.
Pump-Open PlugA plug that is opened by pressure that is used for well suspensions.
Pump Out PlugA plug run on a work string that is being snubbed into a well that can be pumped out when the tubing is landed.
Pump Through PlugA plug that permits pumping into a well but stops backflow of the well.
Pump TrucksPumping units used in bullheading, circulating or other operations involving liquid and foam pumping.
PumpabilityA measurement of a fluids capability to be pumped. Usually refers to cement slurry and is also called the thickening time.
Pumping TeeA Tee fitting in the top of a rod pumped well. The side ort allows the pumped fluids to flow into the surface lines.
Puncher ChargeA specially designed perforating charge that is designed to punch through only one string of pipe and not damage the outer string. Useful for establishing a circulation path in a well with collapsed or plugged tubing prior to killing the well.
Pup JointA short section of casing or tubing used as a depth identifier to a collar locator log or used at the top of the well when spacing out a string prior to hanging the string.
Purple KA fire extinguished powder.
Push PillA gelled pill designed for piston-like fluid displacement.
PV (drilling fluids)Plastic viscosity.
PV (PVT analysis)Pressure-Volume method.
PV (rock)Pore volume.
PVC (gas lift)Closing pressure at depth for a gas lift valve.
PVC (plastic)Polyvinyl chloride.
PVDFThermoplastic fluoropolymer.
PVTPressure volume temperature data for fluids.
PWProduced water.
PWIProduced water injection.
PWRIProduced water re-injection.
PWTProduced water treatment.
PyroclasticsParticles (to chucks) of molten igneous rock ejected from a volcanic vent during an eruption.
PyrobitumenA hard, native asphalt within the pores. Does not ordinarily move or enter into reaction.
PyrolysisDestructive distillation that involves decomposition of coal, woody materials, petroleum, etc., by heating in the absence of air.
PYXA very high temperature perforating explosive.
qFlow rate.
QA/QCQuality assurance and quality control.
QN NippleA high pressure (10,000 to 15,000 psi) profile. N signifies that it is a no go design.
qoFlow rate or initial flow rate.
QRAQualitative risk assessment.
Quality (foam stimulation fluid)The percent of the total volume that the internal phase comprises.
Quality (product)A product providing utility without variability (Taguchi).
QuaternaryA geologic time period from present to 2 million years ago.
QuartzSiO2 mineral with a variety of crystal shapes.
Quench CrackA crack in steel resulting from stresses produced during transformation from austentite to martensite.
Quench HardeningHeat treating requiring austenitization followed by cooling, under conditions that austenite turns into martensite.
R&RRead and record.
R&WReservoir and wells.
R/PReserves to production ratio.
RA (logging)Radioactive.
RabbitA drift dropped through tubulars on the rig floor before joint make up.
RackA pipe storage rack.
Racking Back PipeTo stand pipe in the derrick.
RADRadioactive densiometer. Fluid density measuring device.
Radial Darcy LawThe Darcy equation describing radial movement of fluids in laminar flow through a porous media.
Radial Stress (tubular)Stresses inward and outward along the tubing radius.
Radiant Heat TransferHeat transfer without convection or conduction. Sunshine is radiant heat.
Radioactive LogAny log with a radioactive source, e.g., Neutron Porosity and Formation Density. A Gamma Ray log detects naturally occurring radioactivity and does not emit.
Radioactive TaggingApplying a washable or non-washable radioactive tracer to equipment or proppant to allow tracking of position of the tagged item in the well. Can be used to determine if radioactive tagged sand entered the formation at a specific set of perforations.
Radioactive TracerA very low strength radioactive isotope used to tag water or other fluid for tracing the path of fluid in the reservoir or in a well.
Radioactive Tracer LogA log device that emits a burst of tracer and tracks its movement. May “see” a foot or so outside casing in good circumstances. Normal for injection wells.
Radiographic Inspection (pipe inspection)X-ray inspection.
RadioisotopeAn unstable isotope of an element that decays spontaneously, emitting radiation.
RadiolarianA class of one cell marine animals with siliceous skeletons.
RadionuclideAn unstable form of an element that emits nuclear radiation through radioactive decay.
RadiumR226, one of the natural isotopes that as a trace element may incorporate into the matrix of naturally forming barium or strontium sulfate scale and make it a very low level radioactive material (NORM scale).
Radius of CurvatureThe radius of the guide arch, reel or bend through which a pipe is moved.
Radius of InvestigationDepth of investigation of a tool or logging process.
Rag PumpA rod pump with extremely loose tolerances (an loose seals) that may be temporarily run in a well to pump fluid that contains sand. Used for clean-ups after a fracture treatment.
RamOne of the hydraulically actuated rams in a blow out preventer (blind, shear, pipe or slip).
Range of Load (beam lift)The difference in the peak load at the polished rod on the upstroke and the minimum load on the downstroke.
Range 1 TubularA pipe 16 to 25 ft in length.
Range 2 TubularA pipe 25 to 34 ft in length.
Range 3 TubularA pipe 34 to 48 ft in length.
Rank WildcatAn exploratory well drilled in a basin where no other wells (or too few wells to define the basin) have been drilled. (Some areas use a specific distance between wells).
RAPPS (subsea)Riser annulus pressure protection system.
RAPPS (policies)Reasonable and prudent practices for stabilization.
RaspA wireline-run, round, rough file like device useful for scraping hard deposits on tubing walls.
Rat Hole (well)The hole below the pay zone. Commonly drilled to drop off perforating guns or as a gathering or sump area for liquids to separate from gas prior to being pumped out of the well.
Rat Hole (drilling rig)The hole through the rig floor where the kelly can be stored when it has to be disconnected.
Rate Dependent SkinA skin value that increases with flow rate. Generally recognized as a turbulence induced skin.
Rate of PenetrationThe speed of a drill bit or a clean-out nozzle in penetrating a formation or a wellbore deposit.
Rate Sensitive (damage)A term describing a resistance to flow that increases exponentially with flow and may disappear when the flow rate is dropped.
Ratio of Specific HeatsThermodynamic comparison (k = cp/cv) of the ratio of a specific heat (k) at a constant pressure (cp) to a specific heat at a constant volume (cv). The ratio range for most gasses is 1.2 to 1.4.
Raw Natural GasGas as it is produced from the reservoir. Raw gas may contain methane, heavier hydrocarbons and other nonhydrocarbon gasses such as CO2, H2S, nitrogen or helium.
R-BOPRotating BOP.
RBReservoir barrels.
RBPRetrievable bridge plug.
RCARoot cause analysis.
RCFARoot cause failure analysis
RCMRecirculating mixer.
RCRARecourse Conservation and Recovery Act.
RCPResin coated proppant.
RCSResin coated sand.
RCSSPResin coated sand slurry pack.
RCTRadial cutting torch, a tubing cutting tool that uses thermite plasma.
RDRig down.
RDDK (valve)A Weatherford valve, retrievable dummy dump valve. It is a valve that is placed in a standard gas lift mandrel and has a fracture rod for pressure shearing (then has a check valve to prevent tubing to casing communication). It can be used to displace the completion fluid from the "A" annulus during the completion. It can later be pulled like a regular GLV and replaced with a dummy or live valve.
RDFNRig down for night.
RDMORig down, move off or out.
RDTReservoir description tool.
RDXPerforating charge explosive. Cyclotrimethaylenetrinitramine.
reReservoir drainage radius.
REReservoir engineer.
Real Time GaugeA downhole, surface readable gauge.
ReamerA hole enlargement tool to open up a open hole or a window through the casing.
ReaveTear apart.
RECIPReciprocate.
ReciprocateTo move a pipe up and down. Usually done to help remove mud or cuttings during well cleanup or placement of cement.
Recirculating MixerAny mixing device that circulates the fluid through one or more tanks with the intent of more evenly blending the fluid.
Reciprocating PumpA piston pump.
ReclamationRestoring land to its pre-development condition, or to a condition specified by regulations..
RecompleteTo move the primary completion from one zone to another. May involve reperforating, running other tubulars or setting a new packer.
Recoverable Gas Lift GasThe gas lift gas produced from a well that is transferred into the pipeline.
Recoverable OilThe percentage of hydrocarbons that can be recovered from the formation under planned production methods. Often depends strongly on the revenue received from the oil and the operating cost.
Recoverable ReservesThe portion of reserves that can be recovered by currently available technologies.
Recovery EfficiencyThe percent of the initial in-place hydrocarbon that can be recovered in the project.
Recovery FactorThe percentage of the hydrocarbon in place that can be produced with each production plan: primary, secondary, and tertiary
RecrystallizationThe growth of new mineral grains in a rock at the expense of existing grains which supply the material for the new grains.
REDRestriction enhancement drill (under reamer).
Re-DressTo re-equip a tool to be run back into the well.
Reduction (chemical)Gain of electrons in a reaction.
Reduction-To-Equator (seismic)A mathematical transformation of the total magnetic intensity field at its observed inclination (I) and declination (D) to that of the magnetic equator. I=0o.
Reduction-To-Pole (seismic)A mathematical transformation of the total magnetic intensity field at its observed inclination (I) and declination (D) to that of the north magnetic pole. I=90o, D=0.
Reciprocating pumpPump with an up and down stroke or motion.
RecompletionAction that changes the equipment or intake point in a well.
ReefCoral reef built deposits. Among the highest permeability reservoirs because of connected voids if there has not been extensive chemical modification.
ReelA take up real for hose, coiled tubing or cable.
Re-EntryActions taken to enter a well after it has been plugged or otherwise isolated.
Re-entry SpoolAn upper tree connection profile that allows remote connection of a tree running tool.
Reeve (rigging)String wire or cable through a pulley.
Reference PointThe point on the logging tool that is the depth reference.
RefinerA company involved in upgrading hydrocarbons to saleable products.
RefractureTo fracture a zone after the initial attempt. Refracs may be to correct a problem during the initial frac or to expose new pay after stresses in the rock have been modified by production.
ReFrac EfficiencyThe ratio between the production of the well (or the initial or max production) to the production after the well is refractured.
Regional Gravity Field (seismic)Long wavelength component of field density variations that are usually deeper than general exploration interest.
Relative PermeabilityThe permeability to a specific fluid based on permeability at 100% saturation of that fluid, when two or more fluids occupy the pore space. The relative permeability may change with changing fluid saturation.
Relative Permeability ModifiersChemicals that attempt to change the permeability of a pore if another fluid tries to flow. A common approach in water control but with very mixed results.
Release SubA part of the BHA designed to separate on rate, pull or a ball drop.
ReliabilityThe ability to perform a design function at a specified set of conditions over a target time period.
Relief ValveA valve in a pressurized system that is set to open and relieve pressure at a certain pressure level.
Relief WellA close offset well drilled to intersect a well that is flowing out of control and cannot be killed with conventional methods.
Remedial CementingRepair cementing.
Remotely Operated VehicleUsually an unmanned diving vehicle that performs repairs or maintenance on a subsea well.
Repeat Formation TesterA tool that isolates small sections of the pay and removes fluid samples and takes pressures.
Repeat SectionA section of a log that is repeated.
RepeaterAn electronic device which receives, amplifies and transmits the signal.
Reporting LimitThe lowest required reporting level for a material.
Reserve ExtensionAny added reserves to an already described reservoir, due to drilling, testing, production, etc., that establishes new data on reserves or production limits outside the previously known limits of the reservoir(s).
Reserve PitTank or pit for used/discarded mud, or a secondary mud supply.
ReservesA calculation of the amount of hydrocarbon reserves that are in the formation. Proven reserves have a very high degree of recovery with wells in place and techniques that are proven.
Reserves to Production RatioR/P, ratio of size of the field to the annual production capacity of that field. The R/P is used to estimate the field’s productive life.
Reserves, 1PProved reserves.
Reserves, 2PProved plus probable reserves.
Reserves, 3PProved, probable plus possible reserves.
Reserves, Behind PipeBehind-pipe reserves are expected to be recovered from zones in existing wells, which will require additional completion work or future re-completion prior to the start of production (SPE).Proximity Log
Reserves, DevelopedDeveloped reserves are expected to be recovered from existing wells, including reserves behind pipe. Improved recovery reserves are considered developed only after the necessary equipment has been installed, or when the costs to do so are relatively minor. Developed reserves may be sub-categorized as producing or non-producing. (SPE).
Reserves, EntitlementReserves consistent with the cost recovery plus profit hydrocarbons that are recoverable under the terms of the contract or lease are typically reported by the upstream contractor (SPE).
Reserves, ExtensionAny added reserves to an already described reservoir, due to drilling, testing, production, etc., that establishes new data on reserves or production limits outside the previously known limits of the reservoir(s).
Reserves, Non ProducingReserves subcategorized as non-producing include shut-in and behind-pipe reserves. Shut-in reserves are expected to be recovered from (1) completion intervals which are open at the time of the estimate, but which have not started producing, (2) wells which were shut-in for market conditions or pipeline connections, or (3) wells not capable of production for mechanical reasons. (SPE).
Reserves, ProducingReserves subcategorized as producing are expected to be recovered from completion intervals which are open and producing at the time of the estimate. Improved recovery reserves are considered producing only after the improved recovery project is in operation. (SPE).
Reserves, PossiblePossible reserves are those unproved reserves which analysis of geological and engineering data suggests are less likely to be recoverable than probable reserves. In this context, when probabilistic methods are used, there should be at least a 10% probability that the quantities actually recovered will equal or exceed the sum of estimated proved, plus probable, plus possible reserves. In general, possible reserves may include (1) reserves which, based on geological interpretations, could possibly exist beyond areas classified as probable, (2) reserves in formations that appear to be petroleum bearing, based on log and core analysis but may not be productive at commercial rates, (3) incremental reserves attributed to infill drilling that are subject to technical uncertainty, (4) reserves attributed to improved recovery methods when (a) a project or pilot is planned, but not in operation and (b) rock, fluid, and reservoir characteristics are such that a reasonable doubt exists that the project will be commercial, and (5) reserves in an area of the formation that appears to be separated from the proved area by faulting and geological interpretation indicates the subject area is structurally lower than the proved area. Often referred to as P3 (SPE).
Reserves, ProbableProbable reserves are those unproved reserves which analysis of geological and engineering data suggests are more likely than not to be recoverable. In this context, when probabilistic methods are used, there should be at least a 50% probability that the quantities actually recovered will equal or exceed the sum of estimated proved plus probable reserves. In general, probable reserves may include (1) reserves anticipated to be proved by normal step-out drilling where sub-surface control is inadequate to classify these reserves as proved, (2) reserves in formations that appear to be productive, based on well log characteristics, but lack core data or definitive tests and which are not analogous to producing or proved reservoirs in the area, (3) incremental reserves attributable to infill drilling that could have been classified as proved if closer statutory spacing had been approved at the time of the estimate, (4) reserves attributable to improved recovery methods that have been established by repeated commercially successful applications when (a) a project or pilot is planned, but not in operation and (b) rock, fluid, and reservoir characteristics appear favorable for commercial application, (5) reserves in an area of the formation that appears to be separated from the proved area by faulting and the geologic interpretation indicates the subject area is structurally higher than the proved area, (6) reserves attributable to a future workover, treatment, re-treatment, change of equipment, or other mechanical procedures, where such procedure has not been proved successful in wells which exhibit similar behavior in analogous reservoirs, and (7) incremental reserves in proved reservoirs where an alternative interpretation of performance or volumetric data indicates more reserves than can be classified as proved. Often referred to as P2 (SPE).
Reserves, ProvedProved reserves are those quantities of petroleum which, by analysis of geological and engineering data, can be estimated with reasonable certainty to be commercially recoverable, from a given date forward, from known reservoirs and under current economic conditions, operating methods, and government regulations. Proved reserves can be categorized as development or undeveloped. If deterministic methods are used, the term reasonable certainty is intended to express a high degree of confidence that the quantities will be recovered. If probabilistic methods are used, there should be at least a 90% probability that the quantities actually recovered will equal or exceed the estimate. Often referred to as P1, sometimes referred to as “proven” (Reserve definitions are from SPE).
Reserves, Proved DevelopedProved Developed Reserves are those Proved Reserves that can be expected to be recovered through existing wells and facilities and by existing operating methods. Improved recovery reserves can be considered as Proved Developed Reserves only after an improved recovery project has been installed and favorable response has occurred or is expected with a reasonable degree of certainty. (See Developed Reserves) (SPE)
Reserves, Proved UndevelopedProved Undeveloped Reserves are those Proved Reserves that are expected to be recovered from future wells and facilities, including future improved recovery projects which are anticipated with a high degree of certainty in reservoirs which have previously shown favorable response to improved recovery projects. (See Undeveloped) (SPE).
Reserves, RecoverableThe portion of reserves that can be recovered by currently available technologies.
Reserves, UndevelopedUndeveloped reserves are expected to be recovered
Reserves, UnprovedUnproved reserves are based on geologic and/or engineering data similar to that used in estimates of proved reserves; but technical, contractual, economic, or regulatory uncertainties preclude such reserves being classified as proved. Unproved reserves may be further classified as probable reserves and possible reserves. Unproved reserves may be estimated assuming future economic conditions different from those prevailing at the time of the estimate. The effect of possible future improvements in economic conditions and technological developments can be expressed by allocating appropriate quantities of reserves to the probable and possible classifications (SPE).
ReservoirAn independent hydrocarbon holding rock.
Reservoir Drive MethodOne of several reservoir drive methods including volumetric, depletion, gravity, gas cap, solution gas expansion, water drive, etc.
Reservoir EnergyThe driving force in the reservoir, usually gas cap, dissolved gas, water drive, gravity, or compaction of sediments.
Reservoir PressureThe pore pressure in the reservoir, usually at current value unless otherwise specified.
Reservoir RockA rock containing porosity, permeability, sufficient hydrocarbon accumulation and a sealing mechanism to form a reservoir from which commercial flows of hydrocarbons can be produced.
Residence TimeA reference to the amount of time that a given volume of fluid spends in a location. Related to fluid holdup and separation. Used in both surface separators and mud removal times.
Residual BendA permanent deformation in metal caused by taking the stress loading past the maximum elastic point.
Residual Gravity Field (seismic)Short wavelength component of field density variations within high density basement and/or low density overburden. Anomalies in the residual field are usually of interest in general exploration.
Residual WaterConnate water that will not be displaced. See also Irreducible Water.
Resieved SandA sand that has been run through sieves a second time to remove fines and course particles.
Resin Coated SandFrac sand that has been coated with a bonding or non-bonding sand.
Resin ConsolidationUsing an injected plastic to increase the grain-to-grain bond strength in the formation.
Resin (asphaltene micelle)A cyclic material that, along with maltenes, helps keep asphaltenes tied up a micelles in suspension.
Resin (sand control)One of several plastic compositions.
ResistivityMeasurement of a substance (or rock) to resist the flow of electric charge. Opposite of Conductance.
Resistivity LogOne of various logs that measure some component of resistivity.
Restoring ForceForce exerted by a centralizer against the casing to keep it away from the wellbore wall.
Retained InterestA fractional interest in a project retained by a previous owner.
RetarderA chemical that slows a reaction. In cementing, retarders slow the set time of the cement and prolong the pumpability of the cement.
Retention TimeThe time, based on the separator volume and shape and the fluid flow rate that produced fluids spend in a separator. It is based on the time needed to separate an emulsion.
Retrievable Bridge PlugA retrievable plug set in a non-profile segment of the downhole pipe string.
Retrievable PackerA non-permanent packer meant to be retrieved.
Retrieving ToolA tool used to locate, equalize and retrieve a plug or orther settable downhole device.
Retrograde CondensateCondensate that precipitates in the pore space of the rock in a previously dry gas (single phase) reservoir as the pressure drops below the dew point. The building condensate severely reduces the permeability to gas.
Return PermeabilityThe comparison of permeability after testing with the additive compared to initial permeability.
ReturnsFluids and solids flowing out of a well during circulating.
REVReverse.
Rev DustFriction reducing material composed of very small particles. Also used in lab tests to simulate mud cutting fines.
Reverse CirculateCirculating down the annulus and up the tubing.
Reverse OsmosisA semipermeable membrane that will allow water to pass but not salt. Salt water is pressured into the face of the membrane, the water passes through but the salt cannot pass. The filter has be be backwashed regularly to remove the accumulated salt. The process is relatively slow.
Reverse OutRemoving gravel or cement by shifting the packer or opening the sleeve and circulating out of a well by reverse circulating.
Revs (engine)Revolutions per minute.
Reynolds NumberAn experimental number used in fluid flow to predict the flow velocity at which the flow regime moves from laminar flow through a transition range and into turbulent flow. It is the dimensionless ratio of inertial forces to viscous forces in flowing fluids. It may be viewed as a ratio of the shear stress due to turbulence to the shear stress due to viscosity. Flow with a Reynolds number less than 2000-4000 is laminar flow; that with a Reynolds number greater than 2000-4000 is turbulent flow.
RFRecovery factor.
RFIRequest for Information; similar to a contracts tender, but has less strict legal constraints.
RFPRequest for proposal.
RFQRequest for quote.
RFTSee Repeat Formation Tester.
RFVRadial flow valve.
RH (pipe)Right hand thread.
RheologyThe study of the deformation and flow of matter. Real fluids include non-elastic solids, non-Newtonian fluids and viscoelastic substances. The added materials that provide viscosity range from clays to polymers to complex surfactant chemistry.
Rich GasMethane gas containing other low carbon chain alkanes such as ethane, propane and butane.
RigTypically a well drilling or service unit capable of pulling and running joined tubing.
Rig DownDisassemble the equipment that was placed around a well for a specific work operation.
Rig UpAssemble equipment at the wellsite for work on a well.
Right Angle SetA term usually meaning flash setting of a cement or other material. May be intended or unintended.
Rigid CentralizerA centralizer with ribs that do not bow or flex.
RiglessWithout a drilling or workover rig (may involve a wireline unit, snubbing unit, or coiled tubing unit).
RIHRunning pipe in the hole.
Ring GasketsA not re-usable, metal-to-metal seal. Used between spools of a wellhead and in other equipment such as flanges.
RiprapMaterials (boards, rocks, etc.) arranged to mark a walkway or a barrier.
RiserPipe through which liquid travels upward.
RiskThe probability of an event happening times the impact of its occurrence on operations. (Impact is the effect on conditions or people if the hazard is realized (occurs) in practice and potential is the likelihood that the impact will occur.)
Risk AnalysisA decision making tool that allows examination of the level and significance of workplace risk for humans, equipment, weather, operations or other conditions. Determines the probability of risk occurring, the impact the risk will have and how to mitigate the risk.
Risk AssessmentThe process of identifying and evaluating the technical and non-technical risks associated with a project. It includes the amount or degree of potential danger perceived (by an assessor) when determining a course of action to accomplish a given task. Risk assessment may be qualitative or quantitative.
Risk PremiumThe additional financial return which shareholders expect to be earned in order to compensate for taking additional risk.
Risk WeightedResult of impacting one or more potential outcomes from an uncertainty assessment with risk. Risks might take the form of specific losses (i.e., costs), the impact of the failure (failure to achieve a goal), or other representation. Risk weighting is expressed in a risk-weighted value such as Net Risk-Weighted Value, and Economic Risk-Weighted-Resource Value, other number of risk weighted parameters, and/or by impacting the Y-axis (probability) intercept of a cumulative-frequency curve on a cumulative frequency plot.
River FracA description of a large volume water frac (ungelled water) where proppant sand is pumped at 1/4 to 1/2 lb/gal. Normally at very high rates (25 to 50+ bpm). For very low permeability, non water sensitive formations.
RKBReference Kelly bushing or rotary Kelly bushing.
Rmf (logging)Resistivity of the mud filtrate.
ROCEReturn on capital employed.
Rock DensityRanges from 125 to 200 lb/ft3
Rock MechanicsThe study of mechanical rock behaviors under changing loads and stresses.
Rock PropertiesProperties that describe the physical state of a rock; porosity, permeability, UCS, density, etc.
Rock Shear StrengthThe stress level at which rock fails under shearing or distorting load. Generally the same as compressive strength.
Rock SaltA diverter that is used in acids. Best for high permeability and fractures.
RockingPressuring up with supply gas and then opening the well. This works for wells without packers where the annulus can be used as a pressure charge chamber. When a well has a packer, the effect may also work if the liquids are pushed into the formation and then brough back with the extra gas for lift.
Rockwell HardnessHardness measuring scales relating penetration of a small indentation ball to ultimate yield strength, used to establish steel harness. Rockwell C scale is used in determination of metal hardness limit to control stress chloride cracking.
Rod BoxThe female coupling on sucker rods.
Rod PoundA beam lift term where the pump is filled with gas from pump-off or too fast of an operating speed (rod speed).
Rod PumpA beam lift artificial lift method. Useful for low rate wells (to 1200 BPD) of moderate depth (to 12,000 ft). One of the few lift systems to be able to remove all but a gas gradient of back pressure from the reservoir.
Rod StringThe string of sucker rods used in beam pumping a well.
Rod WiperA wiper placed over the drill pipe to wipe off excess mud as they are pulled from the well.
ROIReturn on investment.
Roll-On Connector (coiled tubing)A type of connector (with grooves around its diameter on one end and threads on the other) is slipped inside the coiled tubing and the wall of the coiled tubing is deformed by a roller-type device into the grooves, securely connecting the BHA to the coiled tubing.
Roller Cone BitA bit with multiple rotating cones that bring cutters into contact with the formation as the string is rotated.
Roller StemWireline stem with wheels to reduce sliding friction in highly deviated wells.
Rolling the TanksCirculating the contents of a surface tank.
Roof RockA layer of dense (sealing) rock above a permeable strata.
Root Cause (in failures)The most basic reason for a failure.
ROPRate of penetration.
ROPEReally overbalanced perforating, see EOP or extreme overbalanced perforating.
Rope SocketThe connection of the wireline to a threaded
RopingSand and proppant falling through a vertical pipe faster than the downflow of fluid during placement of propping. Bridging may occur.
Rotary BushingThe drive bushing on the rotary table that turns the kelly.
Rotary DrillingA rig that spins a drill string with a bit on bottom.
Rotary HoseThe connection from the mud pump to the stand pipe. Also called the mud hose or kelly hose.
Rotary SpeedString RPM.
Rotary SteerableA deviation drilling method where the BHA is turned through a steerable component at the bottom of the well that directs the path of the bit.
Rotary TableThe assembly of gears and connections that spins the kelly.
Rotating HeadA circulating connection that allows pipe rotation. Used in cementing with non top-drive rigs.
Rotating ROPThe rate of penetrating while rotating the pipe.
Rotor (PDM motor)The rotating shaft in a PDM motor.
RoughneckA member of the rig crew.
RoughnessThe interior surface metal roughness of a pipe. Rough pipes have higher friction.
Round TripPulling a string of pipe from a well and returning to bottom.
RoustaboutGeneral laborer in the field.
ROVRemote operated vehicle, usually an unmanned underwater work vehicle.
RoyaltyA percent interest paid to the mineral owner on the value of fluids produced from a lease.
Royalty OilThe mineral owners share of production, taken in oil rather than in cash.
RP (policy)Recommended practice.
RPM (string rotation)Revolutions per minute.
RPMRelative permeability modifier.
RQReportable quantity.
RSMDResumed.
RSS (drilling)Rotary steerable system
Rt (logging)True formation resistivity.
RTDResistive thermal device, used for temperature measurement.
RTE (seismic)Reduction-To-Equator.
RTG (perforating)Retrievable thru-tubing gun.
RTJRing tool joint or ring tool joint flange.
RTNSReturns.
RTP (seismic)Reduction-To-Pole.
RTSReady to service; time for a service company to be on location.
RTTGPRe-enterable through tubing gravel pack system.
RTTSA brand name for a retrievable squeeze tool. Retrievable, test, treat, squeeze.
RTURemote telemetry unit.
RURig up.
RubblizeBreak up the formation into pieces to improve the flow path.
RugoseRoughness of a hole.
RugosityA measurement of roughness of the surface of a passage.
Run InGo into the hole.
Run TicketA record of the oil moved from a storage tank or through a pipeline to custody of another company.
Runaway (coiled tubing)Uncontrolled run-in of coiled tubing into a wellbore.
Running SqueezeA cement squeeze that injects cement until a resistance is built.
Running ToolA tool used to run and set a plug or other device.
Rupture DiskA frangible seal that can isolate a section of a well while the tubing is isolated and then be broken to bring in the well.
Rw (logging)Resistivity of the formation water at the formation temperature.
rwWellbore radius.
RWORig workover.
Rxo (logging)Shallow formation reistivity, usually of the flushed zone, from a very shallow reading device.
S1, S2, S3Rock evaluation pyrolysis parameters.
S-LineSlick line.
S ProfileA standard profile. Can accept a plug or other tools.
S-RiserS-shaped flow line off wing valve.
S-Shaped WellA well path that starts vertical, then is deviated to reach a target before being turned near vertical again to drop through the pay zone.
S WaveSecondary wave, shear wave, transverse wave. A seismic body wave that involves particle motion from side to side, perpendicular to the direction of wave propagation. S-waves are slower than P-waves and cannot travel through liquid.
Sack (cement)94 lb of dry cement.
Sacrificial AnodeA metal slug, lower in the electromotive series than steel that is hard wired to the casing and buried in a bed of wet soil or below the surface of the water. The corrosion cell in the well then transfers the current to the new anode and the steel in the well is protected. Common offshore.
SaddleA pipe fitting made in parts to weld or clamp onto a line to create a junction.
Saddle BearingA bearing that allows the walking beam to move atop the Sampson post in a beam lift pump.
Safeing OutSecuring a well such that the well is not capable of flowing hydrocarbons to surface.
Safety ClampA clamp for flush joint pipe. Also any clamp for securing pipe above the rotary table, even when the slips are set.
Safety FactorThe derating factor applied to a pressure test limit or weight limit to set a maximum operating load condition.
Safety HeadBOP.
Safety JointA joint above a piece of equipment that is designed to fail and allow recovery of the upper string.
Safety ReleaseA section in a downhole tool string than can be actuated by ball or pressure to allow recovery of the pipe string if the tool is stuck.
Safety SlideThe line from the derrickman’s platform to the ground, used in an emergency. Also called a Geronimo line.
Safety ValveVarious. Generally used in describing a surface or subsurface safety valve.
SagSettling of particles in a fluid.
SAGDSteam assisted gravity drainage.
Sail AngleThe planned inclination of the tangent section of a directional well. In a horizontal well if would be 90 deg (+/- 10 deg), in a build and hold or S well it would be the tangent section, in a slant well it would be the inclination throughout.
SalamanderVarious, usually a heater.
Sales GasVarious, but generally the gas send to the pipeline after dehydrating, stripping and sweetening.
Saline waterWater that generally is considered unsuitable for human consumption or for irrigation because of its high content of dissolved solids. Commonly expressed as milligrams per liter (mg/L) of dissolved solids, with 35,000 mg/L defined as equivalent to sea water, slightly saline as 1,000 - 3,000 mg/L, moderately saline as 3,000 - 10,000 mg/L, very saline as 10,000 - 35,000 mg/L, and brine has more than 35,000 mg/L (after USGS, 1984).
SalinityOne of many tests that measures, either directly or indirectly, the concentration of salt in a sample of water.
Salinity GradientA plot of increasing salinity with depth to spot anomolies such as uplift and migration paths.
Salinity LogA type of log that measures salinity by use of gamma ray emission measurements from collisions of neutrons with chloride ions.
Salt (brine)Specifically sodium chloride, but also may be a generic term for most water soluble salts.
Salt Bed StorageStorage of fluids in a chamber mined or leached out of a salt deposit.
Salt Bridging MaterialRock salt or granulated salt sized to construct a filter cake to control fluid loss.
Salt CavernAn underground cavern, developed usually by solution mining, for storage of gas or liquid products.
Salt DomeA usually large movement or intrusion of salt that gradually flows through the rock. Can create reservoir traps and can create casing collapse problems.
Salt Water (production)Any non-fresh water flow. Saturated NaCl brine has a density of 9.9 lb/gal.
SaltationA particle movement method where the particle is carried in a series of short hops along a flow path.
Sample LogA record of rock cuttings (and some properties) that is made as the rock is being drilled.
Sample RateThe rate that data or samples are taken per unit of time.
Sampson PostThe uprights on a beam lift (rod) pump jack that hold the bearing housings.
SAMSensor activated module.
Sand (formation)Specifically a sandstone, but also used in some texts as a general term for the pay zone.
Sand BailerA slickline tool used to place or remove sand or similar small grains from a wellbore.
Sand ConsolidationOne of various methods of consolidating the grains of an unconsolidated or weakly consolidated formation. Typically resin consolidation (epoxy, furan or phenol-formaldehyde), but may also include sodium silicate, coking, and mineral or metal precipitates.
Sand ControlOne of various mechanisms for controlling formation sand movement during fluid production from a weakly consolidated sandstone.
Sand Control ScreenA sand restraining device that is a mesh or wire wrapped screen wound over a base pipe with holes.
Sand FracA propped hydraulic fracture.
Sand Free Rate (production)The maximum production flow rate that a weakly consolidated pay zone will produce without producing sand.
Sand LineThe braided line on a rig, normally used for lifting and deploying tools. May also be used in some instances downhole.
Sand Line DrillA chisel-like tool run on the rig’s sand line to break up junk or stuck tools downhole.
Sand ProductionFree grains of sand pulled loose by flow, brittle failure or formation disaggregation and produced with the hydrocarbon production.
Sand ScreenA downhole screen designed to stop sand production before the flow enters the pump or tubing.
Sand TrapA surface vessel in the production line with the specific task or capturing sand before the production goes through a point where the sand may damage equipment.
SandfaceThe downhole completion interface.
Sanding BackLaying a sand plug over the lower perfs to cover and protect them form another operation.
Sand/Shale Ratio MapA map that uses contours to show the ratio of sand to shale in a formation. Useful for determining clean sand trends and permeability channels.
SandstoneGranular sedimentary rocks with grain sizes between 0.0625 and 2mm. The pore space where hydrocarbons may be held is between the grains.
Sandy ServiceA rating indicating improved performance in erosive environments.
SARASuperfund Amendments and Reporting Act.
SASStand alone screen completion
Satellite FieldAn adjacent field to larger, host, field facilities.
Satellite WellAn offshore well that is separate from the main group of wells but in the same field. May be a subsea well or a single platform well with a flow line tie back.
Saturated SolutionA solution containing the maximum concentration of a specific ion that it will hold at a certain temperature and pressure without precipitating.
Saturation (reservoir)The fraction of the effective porosity filled with a specific fluid.
Saturation ExponentThe exponent, n, in the water saturation term in the equation that relates resistivity to water saturation.
Saturation PressurePressure at which vapor and liquid are in equilibrium. For oils, equal to the bubble point. For condensates, the dew point.
Saucier CriteriaA gravel sizing method that takes the 50% intercept of a cumulative percent retained of the formation sand against a log particle size; then multiplies by 6 to get the median gravel size for the pack.
Saver Sub (drill string)A threaded coupling under the kelly to which the joints of drill sting are make up. Save wear on the kelly threads.
SBHPStatic bottom hole pressure. May also be called shut-in bottom hole pressure.
SBHTStatic bottom hole temperature.
SBMSynthetic oil based mud.
SBR (elastomer)Copolymer of stryene and butadiene.
Scab LinerA casing or tubing repair technique that uses a packer at the top and bottom with a smaller diameter pipe in-between to isolate a breach in the pipe or seal off old perfs. Also used for a liner set in open hole to isolate an unstable zone or loss zone, rather than to increase the pressure containment capability of the well.
SCADA SystemSupervisory Control And Data Acquisition, a data gathering system.
ScaleOne of several mineral precipitates that crystallize out of waters at or above the saturation of the ions.
Scale ConverterA chemical that converts an acid insoluble scale to a acid soluble material.
Scale DissolverA product that chemically dissolves scale.
Scale InhibitorA chemical that prevents scale from forming in scale mineral saturated produced waters.
Scale Inhibition SqueezePlacement of a scale inhibitor chemical by injecting it into the formation. The material may absorb, adsorb or precipitate.
Scale PredictionPrediction of where in the wellbore that scale minerals are oversaturated in solution and could form scale. Not necessarily where scale will form.
Scaled OffPlugged by scale.
Scallop GunA hollow carrier perforating gun with relief ports drilled part way through the gun body to provide an exit point for the perforation charge and to provide a recess to minimize damage from the burr that forms around the exit hole in the perforating gun.
ScavengerA material that takes another material out of solution or the flow stream. Among most common are oxygen and H2S scavengers.
SCBASelf contained breathing apparatus.
SCC (corrosion)Stress Chloride Cracking.
SCC (sand control)Sand control completion.
scfStandard cubic foot, a measurement at standard conditions of gas volume.
ScfmStandard cubic foot per minute.
SchistA crystalline metamorphic rock that can be split into think layers because of the bedded mineral arrangements.
Scintillation DetectorA device that measures radiation output (Geiger counter).
SCM (subsea)Subsea control module.
SCRAMSSurface controlled reservoir analysis and management system.
ScraperA device used to remove downhole deposits.
ScratcherA device with bristles or wires that is used to remove mud cake, soft deposits, etc.
SCSFSSurface controlled selective flow system.
SCLSlickline collar locator.
Scorpion PlotA graph or the production performance of wells against the cost of operations to achieve that production – particularly useful for comparing the effectiveness of workovers.
ScourRemoval of part of sea bed by current, storm or ice.
ScoutA person that reports on competitor leasing and drilling activity.
Scout TicketA brief report on well information from drilling through initial completion.
SCPSustained casing pressure.
SCR (alternate)Steel catenary riser.
SCR (completions)Subsea completion riser.
ScraperA device that cuts through paraffin, asphaltenes, etc. inside the pipe. Run on wireline.
Scratchers (cementing)Mechanical methods of physically removing mud cake from the borehole wall.
ScreenA sand exclusion device.
Screen AnalysisParticle size distribution of a sand sample made by running the sample through a set of screens.
Screen CentralizerA blade type centralizer, usually mounted at the connection, which holds the screen off the casing wall to assist in gravel packing and flow.
Screen Only CompletionA completion that uses a screen without a gravel pack, allowing the formation to cave in around the screen.
Screen OutTo dehydrate a sand slurry to a point where the sand is no longer moveable.
Screen TableA platform and handling system to make up screens without damaging the screens.
Screening EffectThe tendency of proppants to segregate in the fluids due to density effects when the fluid velocities drop below turbulence.
Screenless FracA sand control method where the sand is held in place with closure pressure, resin or other methods and no screen is run.
Screw Port Gun (perforating)A reusable, reloadable perforating gun with port plugs over the perforating charges.
ScrubRemoval of components (gas, liquids or solids) from the methane achieved by surface equipment (scrubbers).
ScrubberA reactor that removes various components from produced gas.
ScSSVSurface controlled subsurface safety valve.
ScSSV Leak Rate (acceptable to pass)< 900 scf/hr.
SCVFSurface casing vent flow.
SDShut down.
SDFNShut-down for the night.
SDR (downhole gauge)Signal drift.
SDRSize diameter ratio, a common measurement in plastic liner pipe.
SDVShut down valve.
SDWASafe Water Drinking Act.
Sea Water Composition (ASTM.D1141)19359 mg/l chloride; 2702 mg/l sulfate; 142 mg/l bicarbonate; 11155 mg/l sodium + potassium; 1297 mg/l magnesium; 408 mg/l calcium; TDS = 35169 mg/l; pH = 8.2.
Sea Water Composition (typical)PH 8.0; Oxygen 6-8 ppm; Sodium 11,000 ppm; potassium 380 ppm; calcium 400 ppm; magnesium 1,300 ppm; Chloride 19,000 ppm; sulfate 2600 ppm; carbonate 142 ppm. Sea water composition may be fresher near rivers and melting ice caps, and more concentrated near desert areas.
Sea Water Density65 lb/ft3 or 8.68 lb/gal (1.04 g/cc).
Seal (geologic)A rock seal that is sufficiently impermeable to prevent leakage of hydrocarbons from a trap.
Seal (mechanical)A elastomer or metal-to-metal device that isolates one pressure region from another.
Seal AssemblyA short section with external seals on the end of tubing to stab into a polished bore receptacle and achieve a seal. The seal assembly may be allowed move in the PBR when tubing temperature and/or pressure changes.
Seal Bore ExtensionA seal bore receptacle below the packer. Used where a longer seal assembly is needed.
Seal Bore PackerA packer with the seal bore through the body of the packer.
Seal RamA ram in the BOP that seals around the pipe.
Seal SwellingA reaction of an elastomer seal by absorbing gas or a liquid and increasing its volume. May or may not be detrimental.
Seal-TiteA trademarked name of a leak stopping material.
Sealing FaultA fault that effectively seals a compartment.
Seating NippleA machined profile in a heavy wall short tubing section that allows a plug to be set and the seal on the plug to effectively isolate the well.
Secondary CementingAn inexact term. Any cementing after the primary cement job. Rarely used.
Secondary FracturesUsually another set of natural fractures in the pay oriented at some angle to the primary natural fractures.
Secondary PorosityNon intergranular porosity such as fractures, vugs, etc. that may contribute sharply to permeability but may not significantly raise the porosity level.
Secondary RecoveryA recovery improvement process such as water flooding or gas flooding.
Section (US land)640 acres.
SedimentaryDeposit made up of pieces of other rocks.
Sedimentary BasinA specific geographical basin of sedimentary rocks.
SeedingIntroducing very small particles in the liquid that accelerate the development of scale or other precipitates.
Seep (natural flow)A natural site, generally small, where water or oil percolates slowly to the land surface or into a stream, lake or ocean.
SeismicAn exploration technique that can find structures and potential reservoir traps by reflecting sound waves from the rock strata. [Seismic acquisition (2-D, 3-D, 4-D) – seismic data are used to map subsurface formations. A 2-D survey reveals a cross section of the subsurface. In a 3-D survey, seismic data are collected in the inline and crossline directions to create a three-dimensional image of the subsurface. In a 4-D or time-lapse 3-D survey, 3-D surveys are repeated over time to track fluid movement in the reservoir. (from Baker Hughes).
Seismic Lines“shock” waves from an event (explosive, tectonic, impact, etc.) that travel through the earth and reflect off of subsurface structures (rocks) in the same manner as sound echos and water waves and ripples.
SeismographA device that records vibrations (natural or man-made) in the earth. With interpretation, the data can give information on buried strata.
Selective FiringA perforating gun initiation that can sequentially fire charges at two or more depths on a single gun run.
Selective ProfileA profile design that can be used at several places in the same string. A plug must pass through the profile and be pulled back into the profile to set.
Self Potential LogSee Spontaneous Potential Log or SP.
SEMScanning electron microscope.
Semi-SubmersibleA rig supported by attached pontoons.
Separation (fluid treating)Processes related to separation of gas, water and hydrocarbons.
SeparatorA production treating vessel designed to facilitate the separation of gas, oil, and/or water from a produced fluid stream
Separator PressureThe pressure at which the separator is operated. This pressure is a direct backpressure on the well.
SepioliteClay mineral used in drilling fluid. Like attapulgite, it creates viscosity by mechanical interference with the clay particles rather by electrochemical forces.
SequestrationTo tie up ions into a complex micelle or molecule and prevent or slow precipitation of materials.
Service WellA well that is used for purposes other than production.
SessileAttached masses of bacterial colonies.
Set BackPulling tubing and stand back in the vertical racks on the rig.
Set CasingThe actions involved with running casing and cementing it in place.
Set PipeRun casing and cement. General term that means to start the completion on a well.
Set-Through CompletionA completion with casing set through the interval and cemented.
Set TimeTime for cement (usually construction cement) to become rigid. Pumping time and strength development terms are usually used for downhole cementing.
Settling TankA surface vessel where solids are allowed to settle out of a produced or circulated fluid stream.
Set UpGel or harden as in cement.
SgGas saturation.
SGRSpectral gamma ray tool.
Shake-Out TestsSolids production test accomplished by taking samples of the produced fluids and centrifuging to separate the solids.
ShakerA piece of drilling equipment, usually with a vibrating screen, where drill cuttings are removed from the flowing mud.
ShaleA common sedimentary rock with porosity but little matrix permeability. Shales are one of the petroleum source rocks. Shales usually consist of particles finer than sand grade (less than 0.0625 mm) and include both silt and clay grade material.
Shale Control InhibitorMaterials that slow or prevent the mechanical or chemical disaggregation of shale. These materials include inorganic salts and some organic compounds.
Shale GasMethane gas stored in a shale. May be in the pore space, adsorbed to the mineral or rock surfaces, or as free gas in the natural fractures.
Shale OilCan be either a immature oil phase, often called Kerogen, or actual oil in the crocks of pores of a shale.
Shale ShakerA solids separation piece of equipment on a drilling rig that uses vibrating screens to remove solids from the returning mud.
Shaped ChargeA shaped explosive charge for perforating steel pipe.
Shear DilationThe small movement in a newly fractured formation that results from the formation unloading build in streses.
Shear JointA joint above a piece of equipment that is designed to fail and allow recovery of the upper string.
Shear LoadA loading at a diagonal to the structure.
Shear Modulus (G)Shear stress over angle of deformation.
Shear PinA pin in a tool (brass, steel or aluminum) that is designed to shear or break at a certain pressure that enables a tool function.
Shear RamA ram in the BOP that shears off the pipe.
Shear RateThe rate of shearing of a fluid during a viscosity measurement. The rate of movement between plates.
Shear StrengthThe minimum shear stress that will produce permanent deformation of the fluid (gel breaking).
Shear Stress (viscosity)The force required to move a given area of fluid. Units are Newtons per sq. meter.
Shear ThinningA fluid that when sheared, reduces viscosity.
Shear WaveS wave.
Shearing The PinAn impact or pressure load that shears the pin in a downhole tool and allows another tool function.
SheathA jacket or armour, often around a logging cable, a gauge cable, or a pump cable.
SheaveA grooved pulley.
SheenA visually apparent oil layer on water. Depending on the hydrocarbon type, sheens can develop with as little as 50 to 100 ppm.
Sheet SandA thick sand body without significant vertical or areal barriers.
ShieldedMetallic foil or multiwire screen mesh that is used to prevent electromagnetic fields from penetrating or exiting a transmission cable.
Shifting A SleeveOpening or closing a sliding sleeve.
ShmaxMaximum stress direction.
ShminMinimum stress direction.
Shock AbsorberA mechanical dampener above a perforating gun that attenuates some of the acceleration force created by firing the gun.
Shoe (casing)The end of the casing, usually called a guide shoe than helps insert the casing through the drilled hole.
Shoe JointThe casing joint containing the cement float.
Shoe TestA test of the cement seal at the shoe.
Shoe TrackThe space between the casing guide shoe and the cement float collar that traps cement contaminated by the top plug displacement.
Shoestring SandsNarrow strands of sandstone formation, often from stream deposits.
Shoot Fluid LevelUse a sonic depth measurement device to find the fluid level in a well.
Shooting NippleSurface equipment used for quick access to the wellbore.
Shooting the WellSetting off charges downhole to rubblize the formation and create a stimulation.
Shootoff (pipe recovery)Separating a pipe string with a explosive cutter.
Shootoff (perforating)Comparison of shaped charge performance in surface targets.
Shore Hardness (plastics)A plastics hardness scale. As hardness increases, abrasion resistance tends to increase for some plastics while impact resistance may decline.
Shore’s HardnessElastomer rating system.
Short RadiusVertical to horizontal direction change in < 40 ft vertical travel (approximately 2.2o per foot).
Short String (dual completion)Generally the string leading to the upper completion in a side-by-side dual completion.
Short TripPulling the pipe up the hole several stands and returning to bottom. May be used to check for fill or to clear cuttings out of a section of the well.
Shot DensityNumber of perforations per unit length.
Shot Hole (completions)A wellbore where an explosive such as nitroglycerin has been exploded.
Shot Hole (seismic)A shallow wellbore filled with explosives and shot as a seismic signal.
Shot PointLocation of initial seismic signal.
ShoulderA surface on a downhole tool on which an upper tool or piece of equipment will stop.
Shoulder OffSet a seal stack all the way down so the locator shoulder on the stinger contacts the packer.
ShowCuttings or returning fluids with a hydrocarbon content above normal background level.
SHR (subsea)Subsea hybrid riser.
Shrimp (testing)Mycid shrimp used for toxicity tests.
Shrinkage FactorThe amount to which a reservoir barrel of oil shrinks when gases are removed at surface. Reciprocal of the formation volume factor.
ShroudA device that directs fluids across a downhole pump motor for cooling or directs gas away from the liquid intake.
Shunt TubeAn Alternate Path for gravel packing slurry that routes the flow around a well bore bridge out during gravel packing.
Shut-inStop a well from flowing and close the valves.
Shut-in Casing PressureThe pressure on the annulus side when the well is shut-in.
Shut-in PressureThe pressure at a datum when the well is not flowing. The shut in pressure is usually either surface shut-in pressure or bottom hole shut-in pressure.
Shut-in Tubing pressureThe pressure on the annulus when the well is shut-in.
SIShut in.
SIBHPShut in bottom hole pressure.
SICPShut in casing pressure.
Side-By-Side CompletionA single bore-hole completion where there are distinct surface-to-zone tubing strings with isolation from each other.
Side Pocket MandrelA short, full diameter passage tubing sub with a pocket reachable from the inside where gas lift valves or chemical injection valves can be placed by wireline.
SideriteIron carbonate.
SidetrackA second (or higher) attempt to drill a wellbore after the first wellbore has been junked. This saves re-drilling the top part of the hole but requires drop back to a smaller wellbore size in the sidetrack. Also can be a second wellbore.
Sidewall CoreA core sample removed from the open hole bore hole wall by an explosive device or rotary drilled with a small tool.
SIDPPShut in drill pipe pressure.
Sieve DistributionA % by weight distribution of the particle sizes in a sample.
Significant Wave HeightCommon measure of ocean wave conditions, approximately equal to the average of the highest one-third of the waves.
Silica FlourVery fine mesh sand used as additives and fluid loss.
Silica Gel (drier)A desiccant for removal of water vapor from gas.
Silica Sand (cementing)A high purity sand of specific size (0.088mm to 0.210mm) used in cement slurries to add weight.
Sill (rock)Horizontal intrusion of igneous rock.
SiltSmall sediment, usually 2 to 74 micron (200 mesh) particles.
Silt Stabilized EmulsionAn emulsion, usually breakable only with solvent that is stabilized by silt accumulation at the surface of the bubbles or droplets.
SilurianA geologic period of time between 40 and 425 million years ago.
SIMOPsSimultaneous operations.
SimulfracTwo or more wells simultaneously fractured to achieve benefits of pressure diversion of fracturing within the formation.
Single Pole Unit or RigA well servicing unit that consists of but one steel tube.
Sink HoleA depression in the ground at surface caused by collapse of a cave roof.
Sinker BarA weight stem on a wireline tool assembly.
SinusoidalA repeating shape like a sine wave. May be applied to pipe buckling.
SIPShut in pressure.
Siphon StringSee velocity string.
SITHPShut in tubing head pressure.
SITPShut in tubing pressure.
SIWHPShut-in well head pressure.
Sized SaltA salt with a range of sized designed to achieve a low permeability filter cake.
SkidMove a well to a close-by locations with minimum rig down of equipment.
SkinA dimensionless estimation of obstruction to flow. An undamaged well would have a skin of zero. A damaged well has a positive skin above zero and a stimulated well has a negative skin.
Skin DamageSee Formation Damage.
Skin FracA fracture treatment designed to bypass skin damage.
SLSee Slick Line.
Slack-Off WeightThe weight reading when the pipe is entering the well. Compared to the pick-up weight to estimate the friction.
SlateMetamorphic shale rock with fractures or cleavage planes.
SLBSchlumberger.
SLD (wireline)Slick line depth.
Slick JointA pipe section, usually on the bottom of a BHA that is a straight pipe.
Slick LineSmall solid wire used for rapid, economic placement and retrieval of small equipment in a well. Comes in several sizes; 0.072”, 0.082”, 0.092”, 0.108”, 0.125”, etc.
Slick WaterA water base fluid with only a very small amount of a polymer added to give friction reduction benefit.
Sliding ROPThe rate of penetrating while sliding the pipe (not drilling) in a horizontal).
Sliding SleeveA downhole piece of equipment in a tubing string that allows flow from annulus to tubing. Usually opened and closed by wireline.
Sliding TimeThe time spend sliding the drill pipe along the wellbore when leaving or re-entering a well.
Slim HoleA smaller well. Thought to be cheaper to drill, but much more expensive to repair or workover and often limited on fluid flow rate potential.
Slime FormerA type of bacteria that forms a slick surface.
Slip and CutTo remove a segment of wireline by pulling wire through the system from the reel, removing the wire that is worn or heavily used in normal operation of the wireline system.
Slip JointA tubular joint that allows tubing movement.
Slip RamAn element of the BOP that grips and holds the pipe in place.
Slip Stop (wireline)A wireline set plug with slips and seals much like a small packer.
SlippageWhere two phases travel in the same direction but at different velocities.
SlipsDevices (usually containing steel teeth) that hold the pipe. Capable of suspending heavy pipe string loads.
SLMSlick line measurement.
Slotted LinerA casing joint with regular pattern slots of a specific phasing, width and length. Used as a simple sand control method.
Sloughing (shale)Movement of large amounts of shale material into the wellbore, usually caused by chemical reaction or earth shift forces. Typically as clumps of particles.
Sloughing ShaleA shale, usually in the wellbore, that increases size (swells) or casts of particles by reacting with brine or water.
Slow TaperA shallow bevel or angle that is not steep.
SludgeA very viscous, usually solids stabilized emulsion. Often triggered by ferric iron and an asphaltenic oil after an acid job.
SluffSloughing particles into the well.
Slug (Drilling)A volume of heavier or more viscous mud that is routed through the circulation system to assist in cleaning, fluid loss, etc.
SlugA volume of gas or liquids that moves through the well and the production facility. A well that flows alternating volumes of water and gas is slugging.
Slug FlowFlow of distinct volumes of gas and liquid, often signaling unstable behavior.
SlurryA mixture of a liquid and solids.
Slurry PackingGravel packing with a gel.
Sm3Standard cubic meter.
Smart PigA pigging device that incorporates instrumentation to measure properties of the pipe (corrosion, wear, etc.).
SmectiteA clay that exhibits water swelling and fines dissociation problems when it occurs in authogenic form and is reactive with the flowing fluid. Smectite clays such as bentonite generate viscosity by forming a colloid suspension in water.
SNAPNodal analysis program.
Snell’s Law (seismic)An expression to predict change of direction of a wave crossing the boundary between two isotropic (no variation in properties with direction) media.
Snubbing (pipe running)Forcing pipe into a well against the effects of wellhead pressure.
Snubbing BasketThe snubbing unit control location.
Snubbing JobA job where the well is workover without killing the well. Usually accomplished by multiple barriers that seal on the tubulars.
Snubbing StackA set of pipe seal and blind rams used in the snubbing operation.
SO2Sulfur dioxide.
SoOil saturation.
SoakAllowing a solvent to be in contact with a deposit for a period of time.
Soap StickA foamer for removing water from a gas well, placed in the form of a solid stick.
SOCScreen only completion.
Soda AshSodium carbonate.
Sodium BicarbonateUsed for treating cement contamination and calcium contamination in muds.
Sodium SilicateWater glass, used in sealing permeability channels.
Soft WaterWater with low calcium and magnesium content.
Soil MechanicsThe rock mechanics related study of unconsolidated and poorly consolidated sands.
Solid Body CentralizerA centralizer with a rigid, solid body with straight or curved veins that hold the pipe off the wall and allow flow. Used in deviated wells and with heavy pipe strings.
Solid WasteAny solid or semisolid material intended for disposal.
Solution GasThe natural gas that is dissolved in a crude oil.
Solution Gas DriveA drive mechanism where a drop in pressure releases gas from the oil that helps drive the oil towards the wellbore. It is a poor recovery mechanism.
Solution GORThe solution GOR of the oil as it resides in the reservoir.
SolventA substance that will dissolve a solid. In the oil field, oil based solvents may range from xylene for asphaltenes and sludges, to kerosene and diesel/xylene mixtures for paraffins.
SonalogA commercial tool that measures the fluid depth in a well by use of a reflecting sound wave.
SondeA term usually referring to a logging instrument.
Sonic Amplitude LogA log that measures the sonic amplitude of a formation to a sound wave. The log is used to locate fractures.
Sonic CaliperA wellbore caliper, useful in larger wellbores and washouts that uses sound through thin liquids to map the wellbore.
Sonic LogA sonic log measures the interval travel time (delta t) of compression sound waves moving through one foot of a formation (milliseconds/ft). If matrix velocity is known, porosity can be calculated since sound waves travel slower in porous media (travel slower in less dense materials such as fluids). Sonic logs are used for porosity determination, pressure determination in shale, as a correlation log, and a gas detector.
SOPStandard operating procedures.
SORStatement of requirements.
SorptionThe processes of absorption and adsorption.
SortingA relative comparison of the formation to determine if there is a large difference between the size of the largest articles and the size of the smallest particles.
SOSShear out sub.
Source PotentialAbility of a source rock to yield hydrocarbons to a reservoir rock.
Source RocksGenerally fine grain rocks such as shales or carbonates that can yield hydrocarbons.
SourH2S containing.
Sour CrudeCrude oil that contains more than 1% total sulfur content. Typically applied as a label to oils with sour smell.
Sour GasGas rich in hydrogen sulfide, H2S.
Sour ServiceDefined in NACE MR-0175/ISO 15156 as exposure to oilfield environments that contain H2S and can cause cracking of materials by the mechanisms addressed by NACE MR-0175/ISO 15156.
Sour Service RatingA classification of materials that predicts satisfactory performance in hydrogen sulfide.
Source RockThe rock in which hydrocarbons form.
SOVScreened orifice valve.
SOxSulfur oxides.
SPSpontaneous potential log.
SPA (BP)Single point of accountability.
Space Domain (seismic)A function where distance is the independent variable and another factor (magnetic, density, amplitude) is the dependent variable.
Space OutUsing short pieces of pipe to property position the top of the string to hang off while keeping the bottom of the string in the correct position and with the correct tension.
Space Out Joint (drilling)The joint of drill pipe used to prevent a tool joint from being in the BOP body (across a ram face).
Spacer (pumping)A fluid used between two fluids to prevent contamination.
SpacingThe distance between well producing in the same reservoir. The spacing is actually the area they drain (e.g., 320, 160 or 40 acres).
Spaghetti StringVery small pipe.
SpallingThe chipping, fragmentation, separation or disbonding of a surface in response to pressure, mechanical or chemical influence.
Spang JarA mechanical jar, used commonly on wireline.
SpargeUsing a jet of air or water to stir the contents of a tank.
SPCCSpill prevention control and countermeasures.
SPESociety of Petroleum Engineers.
SpearA fishing tool that is designed to enter an opening of a fish and grip the ID.
Specific GravityThe ratio of the density of a substance to the density of a comparison material, usually at a specific temperature and pressure.
Specific HeatThe heat required to raise one unit mass of a substance by one degree.
Specific WeightThe weight of a volume per unit of volume.
Spectral Gamma RayA gamma ray tool capable of spotting the different isotopes used in tracers.
Spectral Gamma Ray ImageGamma ray tool which splits the spectral range into three parts
Spf (perforating)Shots per foot.
SpiderA round device that holds the slips when supporting a string of drill pipe on a rig.
Spill Point (reservoir)In a trap, the low point under which hydrocarbons will escape when the trap is full.
Spinner LogA production log that uses a propeller-like spinner to measure changes in fluid velocity in sections of the well.
Spinning ChainA chain moved by a counterweight or winch to assist in making up drill pipe joints.
Spiral-Grooved Drill CollarA drill collar with spiraled grooves down its length to improve circulation of fluids in close clearance well bores.
SpiralizerA brand name of a spiral shaped solid body centralizer for casing and screens.
Split EstateWhen mineral rights and surface rights are owned by separate entities.
Split ShotA linear explosive cutter that is designed the cut linearly through the pin and box connection during pipe recovery.
Split Skirt (milling tool)A slot in a mill or other tool to assist with alignment, cleaning or entry.
SPM (drilling)Strokes per minute. A count of pump strokes times pump volume times plunger # times pump efficiency estimates volume pumped.
Spm (perforating)Shots per meter.
SPOCSingle point of contact.
Spontaneous Potential Log or SPOne of the oldest and simplest logs. Measures voltage between formations and the fluid in the wellbore. Potential differences arise due to the differences between salinity of the formation and the wellbore fluids. SP is used for qualitative permeability, reservoir quality evaluation, Rw calculations and zone shaliness estimation.
Spot MarketA market for short term transactions of specific volumes of product without a long term commitment.
Spotting FluidPlacing fluid at a specific place in the wellbore.
Spread CostThe total cost for a rig, crews and all equipment that goes with operation of the rig for that job.
SpudTo begin drilling.
Spud DateThe date that drilling operations commenced and were reported to the governing regulatory body.
Spud MudMud used to drill from the surface to a depth where a more technical mud is needed.
Spurt LossThe initial loss of fluids from a mud or frac fluid, before the walk cake can be formed.
SPWLASociety of Petrophysicists and Well Log Analysts.
Squeeze CementingA cementing repair technique involving injecting cementing under pressure to fill channels in the primary cementing treatment.
Squeeze Treating or JobA designed technique where a treatment is squeezed into a specific zone.
Squeeze PackerA millable retainer for squeeze cementing.
SRBCSusquehanna River Basin Commission.
SRBSulfate reducing bacteria.
SRDShort radius Drilling.
SrSO4Strontium sulfate.
SRTSpill response team.
SSSubsea.
SSSliding sleeve.
SSCStress sulfide cracking. Occurs when metal is in tension and exposed to H2S and water. Generates atomic hydrogen. Hydrogen moves between grains of the metal. Reduces metal ductility.
SSDSubsea disconnect used during drilling a subsea well in case the floating rig moves to an extreme that begins to threaten the shear resistance of the riser or the drill string.
SSIVSub surface (or subsea) isolation valve. Often placed in offshore pipelines within a few hundred meters of the facility to give an emergency stop point in the event of a line rupture or fire.
SSPStatic spontaneous potential.
SSTTSubsea test tree.
SSSVSubsurface safety valve.
SSVSurface safety valve (subsurface safety valve is SSSV)
STSidetracked.
StabInsert the seal stack or stinger into the polished bore receptacle.
Stabilizers (drilling)Near gauge diameter joints that stabilize the drilling BHA.
ST&CShort thread and coupled, a connection description.
Stack (seismic)A composite of traces from different seismic records.
Stage Tool (cementing)A alternate path device that allows access into the annulus when shifted. Used in two stage cementing operations to pump the upper job.
Staged CementingSequenced cement jobs that are placed through different entry points into the annulus. Undertaken to place a higher cement column in the annulus when the fracturing gradient of the exposed formations will not tolerate a full column of cement.
Stall (fluid powered motors)A condition in which the motor stops rotating when more force is required to rotate the shaft than the motor can produce.
StandSee stand of pipe.
Stand-by-TimeThe cost of a piece of equipment or a crew to wait when a job is postpones.
Stand of PipeThe number of joints of pipe that can be pulled and stood back at one time by the rig, e.g., doubles or triples.
Stand OffThe distance from the tool to the wall of the hole.
Stand PipeA vertical pipe on the derrick used for routing injected fluid flow.
Standing ValveThe fixed position valve at the bottom of a beam lift pump.
StandoffThe clearance from casing to the tool face.
StandpipeThe pipe in the derrick that delivers mud to the kelly hose.
Stationary Block (drilling)The crown block on a drilling rig.
Stationary slipsThe non-moving slips in a snubbing stack.
Standard Blue BarrelBbl – the measurement of a barrel (42 gal) of oil originated by Standard Oil Company (their “standard” barrel was pained blue).
Static Bottom Hole PressureThe bottom hole pressure when the well has been shut-in and the well stabilized.
Static Fluid LevelThe depth below the surface to where the reservoir fluids will rise by pore pressure.
Static PressureThe pressure when the well is not flowing. Can be surface static pressure or bottom hole static pressure.
Static SealSeal where no motion is present.
Stator (PDM motor)The stationary rubber element of a PDM motor.
STBStock tank barrel.
Steam FloodA tertiary oil recovery method involving injection of steam into the reservoir to reduce the oil viscosity.
Steerable Motor (drilling)A downhole drilling motor with a bent housing that can turn a well’s direction in addition to turning the bit.
Stem (wireline)A weight bar.
Step Out WellA well beyond the current boundaries of a known field.
Step Rate Breakdown TestAn injection test, plotted pressure against injection rate, where a curve deflection and change of slope indicates the fracture breakdown pressure.
Stretch Target (Risk)An exceptional outcome that a team will strive for but will probably not achieve.
STG (subsea)Seal test gauge.
Stick PlotDip meter results.
StimplanA fracturing design simulator from NSI, Inc.
StimulationAny effort to increase production from a well by the improvement of natural or damaged flowing capability.
Stinger (well control)A hollow, tapered rod hooked to the boom of an oil fire fighting crane. Mud can be pumped through the stinger once it has been stabbed into the remains of a wellhead.
Stinger (well tubular)A short prong that slides into a tool. Often a seal assembly.
StM3Stock tank cubic meter.
STOStock tank oil.
Stock Tank BarrelOne barrel of stabilized or dead oil at the surface after the gas has escaped.
Stock Tank ConditionsAtmospheric pressure of 14.696 psi and temperature of 60F (16C).
STOOIPStock tank oil originally in place.
Stop-cockingTemporarily shut in and re-open well. Shut-in forces free gas into solution and some liquid back into the formation. Opening the well allows gas to breakout of liquids and the formation and lift liquids.
Storm ChokeA flow controlled shut-in device to control flow in the event of loss of surface well control. Must be reset periodically. Replaced by ScSSVs.
STPStandard temperature and pressure.
StraddleA downhole device that isolates a zone, a wellbore or a piece of equipment.
Straddle PackerA twin sealing element device with a perforated nipple in between. It is used to selectively inject fluids into a part of the zone.
Straight HoleAn essentially straight hole with less than 5o total deviation from surface to bottom hole and dogleg severity less than 3o/100 ft.
StrainE = delta L / L.
Strain GaugeA electronic “Wheatstone-type bridge” element than may form the measurement basis for a load cell or other strain measurement application. The device measures changes in electrical resistance produced by changes in load.
StrapMeasure the fluid level in a storage tank.
Stratification (logging)The sequence of unlike formations penetrated by the borehole.
Stratified FlowA flow regime in a highly deviated or horizontal well where the fluids are segregated by density.
Stratigraphic TrapA reservoir capable of holding fluids created by decreases in porosity, permeability or disappearance of the reservoir.
StratigraphyThe succession and age relationship of layered rocks.
Stray CurrentThe difference in potential between the earth and the well. Measured and minimized before explosive operations may proceed. Also a measure of corrosion potential.
Stray Current CorrosionExtraneous electrical current in earth. Point of arrival is cathode - departure point is anode.
Stream BedA moderate to low energy deposit with permeability streaks where energy was higher. May be very limited in extent and volume.
StressSigma, ?, is the force exerted on an object.
Stress CageA shallow zone of (usually) higher strength surrounding a perforation, cavity or the bore hole, caused by explosive effects or other pressure factors and possibly related to the mechanics of work hardening.
Stress Chloride CrackingA corrosion form generated by high chloride brine contact.
Stress Corrosion Cracking / Stress CorrosionOccurs in metal that is subject to both stress and a corrosive environment. May start at a “stress riser” like a wrench mark or packer slip mark.
Stress CrackAn external or internal crack in steel or other material caused by the environment and/or the loads on the material.
Stress ReliefControlled heating of material to predetermined temperature for the purpose of reducing any residual stresses.
Stress RiserA disturbance in the metal structure caused by impact or a wrench mark or penetration of slips that is a likely location for increased corrosion or some failures such as hardening or local fatigue.
StriationA group of roughly parallel marks.
StrikeThe compass direction of a feature such as a flood plane or fault.
Strike-Slip FaultA tectonically induced failure of a section of a formation with the result that one block of the formation moves horizontally to the formation.
String MillA mill that cuts to the side, opening up windows or cutting out restrictions.
String ShotOne to four strands of explosive detonating cord suspended by wireline in a well and exploded to “rattle” the pipe and drop scale and debris from the sides of the pipe. Used frequently in back-off operations (unscrewing a pipe joint downhole).
Stringing UpThe act of threading the drilling line through the pulleys or sheaves of the traveling block and the crown block. One line is connected to the derrick and the other to the winch or hoisting drum.
Strip (processing)Removing light hydrocarbons (C2+) from the gas before sale.
Strip GunA perforating gun where the charges are mounted on the strip. The strip is recovered after firing.
Strip OverA recovery method, or less frequently, a wire installation method using pipe.
StripperThe seal at the top of the BOP around coiled tubing or pipe during snubbing.
Stripper RubberThe elastomer element that completes the seal in a stripper unit.
Stripper WellA marginal productivity well, usually less than about 10 barrels per day in onshore US fields.
Stripping (pipe running)Holding back on a pipe as it is run into the well.
Strokes Per Minute (Drilling)The number of strokes that a mud pump makes in one minute. SPM times time times pumper chamber volume equals volume displaced. Can be compared to volume recovered.
Strokes Per Minute (Beam Lift)The number of rod strokes per minute of the beam ift unit. Set by depth, viscosity of fluid, gas content, weight of fluid supported, etc.
STRONGERState Review of Oil and Natural Gas Environmental Regulation, Inc.
Structural CasingConductor casing string.
Structural GeologyThe study of the geological processes that formed the earth’s crust, mountains, etc.
Structural MapA diagram using contour lines to connect the elevation of similar depth points in a formation.
Structural Model (seismic)2D or 2-1/2D, a gravity or magnetic structural model is a density and/or susceptibility model of given or assumed geology in a system. The modeling can be to represent lithologic layers as equi-density and/or equi-susceptability layers or blocks. The layers are contrast boundaries. Best fit where high contrasts exist in nature.
Structural TrapA combination of a formation structure feature such as a fault with a sealing mechanism that forms a place where oil accumulates or is “trapped”.
Stuffing BoxA device using an elastomer seal (and sometime oil or grease injection) that provides a pressure barrier around a moving tubular or wireline.
Stuck Pipe (drilling)Refers to drill pipe stuck in the hole from differential sticking or bridging.
STV (subsea)Seal test valve.
StyoliteA pressure dissolution feature in a layered reservoir, often a vertical permeability barrier.
Suction PitA steel tank containing mud, where the input line to the mud pump originates.
SubA short section of pipe, used to describe tools or to solve space-out gaps.
Sub Critical (flow)Sub sonic.
SubductionThe sinking of an oceanic plate edge as a result of collision of a less dense plate.
SublimationThe process by which matter passes passed from a solid directly to a gaseous state.
Submersible Electrical PumpSee ESP
Submersible RigA large rig supported and stabilized by underwater pontoons.
SubsaltFormations located below a salt layer.
Subsea CompletionA subsea well.
Subsea WellA well with the wellhead and significant control mechanisms located on the sea floor.
SubsidenceCompaction of a zone (vertical height shrinkage) created by compaction of the matrix after some load supporting fluids have been produced.
Subsurface Controlled Subsurface Safety ValveA downhole safety valve designed to close when the flow rate reaches a preset level as measured by a pressure drop across a valve.
Subsurface Safety Valve or SSSVA downhole safety valve designed to shut the well in case of surface damage to the wellhead.
Sucker RodA string or solid or hollow tubular that is moved by a pump jack at the surface to operate a rod pump at the bottom of the well.
Sugar Water (cementing)A contaminate water that will prevent cement slurry from setting.
Suicide SqueezeA cement squeeze involving injecting into a lower perforation, separated by a packer from an upper perforation while trying to fill a channel.
Sulfamic AcidA dry acid derivative of sulfuric which is used in very minor acid jobs in the form of acid sticks dropped into the well.
SulfateOne of several minerals containing sulfur ions bonded to oxygen atoms.
SulfideOne of several minerals containing sulfur ions bonded to metal ions.
Sulfate Resistance (cement)The ability of set cement to resist deterioration in contact with water containing sulfate ions.
Sulfide Stress CrackingCracking of a metal under the combined action of tensile stress and corrosion in the presence of water and hydrogen sulfide (a form of hydrogen stress cracking) (NACE).
SumpA low area, usually the area below the perfs.
Sump PackerA bottom packer, commonly used to locate the bottom of a screen assembly in a sand control completion.
SuperchargingElevating the near wellbore pressure of a formation through leak-off of wellbore fluids during drilling, completion or workover.
Super SaturatedA condition where the liquid is over saturated with incompatible ions or one ion concentration is above the saturation point. Usually a result of cooling a undersaturated fluid below the saturation point without a sufficient upset to start the precipitation growth.
SURFSubsea, umbilicals, riser, flowline.
Surface Active AgentsSurfactants that exhibit an effect on water or oil by changing fluid properties at the interface of the fluid. May be emulsifiers, demulsifiers, surface tension lowering , flocculants, deflocculants, wetting agents, etc.
Surface CasingThe casing string that protects the fresh water supply. It is always cemented across the water zone and usually extends to surface.
Surface Controlled Subsurface Safety Valve or ScSSVA safety valve controlled from the surface through hydraulic or electrical power.
Surface RoughnessA consideration in fluid friction calculations. A pipe with a polished surface may have 1/10th the friction and flow 10 to 25% more fluid at the same pressure drop (depending on pipe diameter), than a pipe with a corroded or heavily fouled surface.
Surface TensionA measurement of the difficulty of moving a fluid past another fluid (see interfacial tension). The resistance is created by the cohesion forces between the liquid molecules. The forces make it more difficult to pass fluids past a surface. Surface tension is measured in dyne/cm. Untreated water is 72.8 dynes/cm at 20oC. Ethyl Alcohol is 22.3 and mercury is 465.
SurfactantA chemical that is attracted to the surface of a fluid and modifies the properties such as surface tension.
Surge ToolA downhole tool that is used to create a sudden pressure decrease at a spot in the well.
Surging (pipe movement)A pressure higher than the hydrostatic column, below the BHA produced by rapid movement of pipe into the well. Maximized in cases with large diameter tools, high viscosity and high pipe speeds. May cause fracturing. Opposite of swabbing.
Surging (flow)Opening the well to flow against a significantly underbalanced fluid column. A perf cleaning technique.
Susceptibility (seismic)A measure of the degree to which a rock can be magnetized. It is defined as the ratio (k) of the intensity of magnetization (I) to the magnetic field (H) projected into the rock.
SuspendTemporarily discontinue operations.
SWSea water.
SwWater saturation.
Sw/So (logging)Movable hydrocarbon index.
Swa (logging)Water saturation of the uninvaded zone.
SWDSalt water disposal.
SwirrIrreducible water saturation.
SwabReducing the well pressure below the swab tool by rapid upward movement of a tool or equipment in a wellbore. Swabbing may be intentional using a wireline swab cup tool to lift water or unintentional by fast movement of a pipe or wireline conveyed, large diameter tool such as a packer.
Swab ValveThe valve at the top of the tree, above the flow cross or flow Tee. The lubricator for interventions may be attached above this valve or the valve may be removed to fit a larger lubricator.
SwageA smooth faced tool that is used to try to re-round ovaled tubing.
SwarfMilling debris from cutting steel.
SWCSide wall core.
SWC (corrosion)Stepwise cracking. Cracking that connects hydrogen-induced cracks on adjacent planes in steel.
Swcor (logging)Corrected water saturation of the uninvaded zone.
SWDSalt water disposal
SWDASolid Waste Disposal Act.
SweepA displacement. In the reservoir a sweep is displacement of a hydrocarbon fluid from a reservoir rock by a flooding fluid. In the wellbore, a sweep is a viscous pill circulated around to help clear the wellbore of cuttings or debris.
Sweep EfficiencyThe percentage of original oil in place displaced from a formation by a flooding fluid.
Sweep PillA spacer designed to pick up and transport particles from the well.
Sweep SpotThe part of a field that has the best production characteristics (permeability, porosity, hydrocarbon saturation, pressure, etc.).
SweetAbsence of hydrogen sulfide, H2S.
SweeteningRemoving H2S from a hydrocarbon stream.
Swell PackerA packer whose seal elements swell in a hydrocarbon, establishing a seal between packer body and casing.
Swept Volume (circulating)The amount of the wellbore that is circulated by fluid (describes the hold-up and upswept volume).
SWI (logging)Initial water saturation.
Swivel (drilling)The connection between the traveling block and the hook that allows torque release and rotation.
SWOPStandard workover procedure.
SWR (subsea)Subsea wellhead array.
Swr (logging)Water saturation of the uninvaded zone.
SynclineA down-fold in the rock where the sides tilt upwards. Opposite of a trap.
Synthetic CrudeOil formed by a chemical process that converts coal or shale to liquids.
Synthetic Oil Based MudA mud with the oil component replaced by a lower toxicity oil such as mineral oil.
SXSacks.
Sxo (logging)Water saturation of the flushed zone.
SynclineA set of rocks that are bent downward.
SyncrudeSynthetic crude upgraded from mined hydrocarbon.
SyngasSynthetically prepared natural gas.
SyneresisDehydration of a gelled fluid.
tTime
t (pipe)Wall thickness
T-SealA specialized seal shape.
TA or T/ATemporarily suspended (abandoned).
T&CThreaded and coupled.
T&D (drilling)Torque and drag.
TachehydriteA precipitate of sulfate minerals following acidizing with strong hydrochloric acid.
Tadpole PlotA plot of dipmeter or drift where the dip angle or displacement is plotted vs. depth as a displacement of the dot. Also called a vector plot.
TAG (perforating gun)Throw away gun or scallop gun.
TagTo touch the top of a tool, fill, water, etc., with wireline, tubing or CT tool.
Tag LineA small rope attached to a load being lifted by a crane that allows a person on the ground to help guide or place the load.
TAI (shale)Thermal alteration index; an estimate of how maturation has altered the source rock in the creation of hydrocarbons.
Tail CementThe last of the cement slurry, generally the highest strength cement designed to be left across the casing shoe.
Tail GasResidue gas, as from a sulfur recovery unit.
Tail PipeThe tubing below the packer.
Tailing RodsThe act of laying down a rod string when pulling a sucker rod pumped well.
Tall OilA fatty acid drilling additive.
TallyMeasuring and recording the length of all pipe and downhole equipment.
TalusA pile of rock fragments at the base of a cliff from which they have broken off.
TAMLTechnical Advancement of Multi-Laterals. An industry group that has defined multi-lateral junction levels and terminology.
TampThe pressure, exerted by packing or a fluid column above an explosive charge that helps contain or focus the energy of the explosive or propellant.
TANTotal acid number. Measurement of natural organic acididity in a compound such as oil.
Tangible Costs (Drilling)Items of well construction that have salvage value, ordinarily capitalized on taxes.
Tangential Stress (tubing)Stresses around the body of the tubing (Hoop Stresses).
Tangential WaveAn S wave.
Tank BatteryA storage and separation location for oil.
Tank BottomsThe near solid or highly viscous residuals at the bottom of an oil storage tank, generally composed of a large amount of paraffins, silt, heavy ends, etc.
Tank FarmA group of supply or storage tanks.
TAPTrapped annular pressure.
TapA valve on a line.
TapCutting of threads in a hole.
TAPSTrans Alaska pipeline system.
Taper TapA spear-like fishing device with threads to engage ID threaded fish.
Tapered BowlA two piece fitting placed in the master bushing to hold the slips.
Tapered MillA mill with a gradual concave or convex taper designed to enlarge the wellbore.
Tapered StringA tubing string with more than one tubing size. Normally the smallest pipe is on bottom with larger sizes toward the top. The sizes are set to minimize flowing friction and keep the velocity above the critical level to lift fluid.
TarA deposit of very long carbon chain alkanes. May be associated with asphaltenes.
Tar SandsA deposit of heavy oil, usually with API gravity less than about 18o. May have sand content of 50%.
Target (Risk)A preferred outcome from an activity.
Tettle TailA reference mark, also a minute mark.
TBNTotal base number, a reserve alkalinity number.
TCTime constant.
TCF (gas lift)Temperature correlation factor.
tcf (reserves)Trillion (one million million) cubic feet.
TCPTubing conveyed perforating.
TCP (chemical additive)Tri Crecyl Phosphate, a defoamer.
TCTTrue crystallization temperature.
TDTotal depth measurement or pipe length to the depth. Used for displacement calculations.
TDHTotal dynamic head.
TDRMTop down reservoir modeling/modeling.
TDSTotal dissolved solids in a quantity of liquid.
TDTThermal decay time log.
Technical LimitA benchmarking comparison to determine how much better a process or a piece of equipment can be improved.
Technically Recoverable ResourcesThe amount of the resource that is estimated to be recovered by current or proposed technologies.
Tectonic ForceAny one of several insitu or earth stress forces. May include classic plate tectonics, salt flows, thrust forces, faults, folds, etc. Can be either near-field or far-field.
Tectonic MapA geologic map showing the structure of the earth’s crust.
TEGTriethylene glycol.
TELTubing end locator.
TelemetryConversion of a logging tool measurement to a signal suitable for transmission to the surface.
Telescoping MastA portable mast composed of sections nestled inside one another and raised with a winch or a hydraulic cylinder.
TeleviewerBorehole televiewer, a sonic tool that creates a sound reflectance picture of the wellbore.
Tell Tale (gravel packing)An upper or lower screen in a gel packing gravel pack. Use to spot annular fill up by pressure rise.
Tell Tale ScreenShort screens used at the top and bottom of older gravel packing assemblies to help determine where the gravel is within the screen by casing annulus during packing.
Telluric CurrentsNatural earth currents originating as result of variations in the earth’s magnetic currents.
Temperature GradientThe rate of increase of temperature per unit of depth. Varies in the world with geothermal activity. Usually between 1.1 and 2.2+ oF/100 ft.
Temperature LogA measurement of temperatures along the wellbore. Useful for determining temperatures at any point, static and circulating temperature and tops of cement column. May also be used to locate the top of a fracture if run soon after the frac.
Temperature Stability AgentsProducts that increase the temperature stability of a material, usually a drilling or workover fluid above its normal expected range.
Temperature SurveyRepeated, regular measurement of temperatures along a unit of depth in a well.
Temporarily abandonedA well where operations are suspended; i.e., shut-in while awaiting repairs, pipe line engineering analysis, etc., but not permanently abandoned.
Ten RoundTen threads per inch.
Tender (ship)A support barge, boat or ship that supplies support to a rig or production facility.
Tensile ExtensionThe stretching of a material in pure tension.
Tensile StrengthThe greatest lengthwise stress that a substance can bear without failure.
Tension Set PackerA packer set by pulling and holding tension in the tubing.
TEORThermal enhanced oil recovery.
TertiaryA geologic period 2 million to 65 million years ago.
Tertiary RecoveryAn enhanced recovery process that goes beyond water or gas flooding. It may involve steam, fire, chemicals, miscible gases, bacteria or other techniques.
Test PillAn encapsulated radioactive material that serves as a portable source of gamma radiation for tool calibration.
Test SeparatorA smaller separator than the main production separator, used for regular production tests to measure oil, gas and water rates on a well.
TFE (elastomer)Teflon.
TFETotal, Final, Elf.
TFLThrough the flow line, a mechanism for well service where the tools are pumped downhole through the flow lines.
TGTrip gas, mud logging term.
TGLRTotal gas lift ratio.
TGSTight gas sands.
THAIToe to heel air injection.
THD (subsea)Tubing hanger.
ThermA measure of heat content, where one therm = 100,000 btus.
Thermal Decay LogA series of temperature log runs before, during and a sequence of temperature logs to spot channels, and differences in temperature heat up or cool down.
Thermal DecompositionBreaking down by thermal destruction of the molecule.
Thermal ExpansionExpansion of the volume (length & diameter) of an object as it is heated. In tubing, heat increases lengthen the tube or increase axial stress.
Thermal MaturityA measurement of the processing of kerogen towards dry methane gas. Usually expressed at Vitronite reflection percent. Vro <0.6 is a immature oil, 0.6 to 1.0 is a oil with dissolved gas, 1.0 to 1.3 is wet gas and >1.4 is dry gas. Vro over values of about 4.o are a reflection of all hydrocarbons being cooked off.
Thermal RecoveryAn enhanced oil recovery process that uses heat to reduce oil viscosity.
Thermogenic gasNatural thermal cracking of sedimentary organic material to oil and gas (C14 isotope is absent).
Thermos FlaskA container used on logging tools to give temporary protection from the downhole temperature.
THIThreshold hydrate inhibitor.
Thickening TimeThe time that a cement slurry will remain pumpable at temperature and pressure.
ThiefTo remove a sample from a tank for analysis.
Thief ZoneA high permeability streak that serve as a loss site for wellbore fluids.
Thin SectionA section of the formation, forcibly impregnated with epoxy and sliced thin enough to examine with a light from the opposite side.
ThinnersMaterials that change the relationship between solids and viscosity of a fluid to lower the gel strength, yield point, yield strength or viscosity as it affected by solids.
ThixotropicFluid property of being a semi-solid gel at rest and liquid when pumped. Thixotropic fluids decrease in viscosity with time at shear.
ThoriumTh232, one of the natural isotopes that as a trace element may incorporate into the matrix of naturally forming barium or strontium sulfate scale and make it a very low level radioactive material (NORM scale).
THPTubing head pressure.
Thread Gauge or Thread FormA pattern template for identifying a specific thread type.
Thread ProtectorPlastic or metal storage couplings that are screwed onto a stored tubing string, protecting the threads from impact and sometimes corrosion.
Three-D or 3-D seismicSeismic maps that show detail in three directions. A network or grid of values that models a geologic surface or structure as a surface of density contrast (gravity), or susceptibility (magnetic).
Threshold VelocityA limit flow velocity for a specific fluid, either minimum or maximum, that would accomplish a task. Threshold Velocities are usually minimums to promote liquid lift in a gas well, or a minimum velocity to keep a pipe surface clean.
ThrottlingControlling flow with a reduced orifice.
Through the Flow LineTFL, a completion or repair technique that depends on pumping the tools or equipment into a flow line and down the well.
Through TubingEntering a well for a completion or repair by entering the well without removing the wellhead or the tubing string. Usually done under pressure.
Through Tubing GunA perforating gun small enough to be run and recovered through the tubing.
ThroughputThe amount of a material that moves through a plant in a set time.
ThrowA fault’s vertical displacement.
Throw the chainTo jump the spinning chain from the box end of the joint to the pin end of the joint after the connection has been stabbed. The chain is pulled by a rope from the cat-head to tighten the joint.
Thrust FaultA type of reverse fault in which the inclination of the plane of the fault is not highly deviated.
THSTubing hanger setting.
THTTubing head temperature.
TieA structure, bed or identifiable rock feature that allows correlation of depth control in an area.
Tie-BackTo connect a downhole liner to the surface with a casing of similar size.
TIFLTubing integrity fluid level.
Tiger TankA tank for holding treating or flowed back fluids.
Tight FormationNon specific term meaning lower permeability.
Tight GasNatural gas held in reservoirs of low permeability that cannot be accessed in an economically reasonable time by natural flow methods. Hydraulic fracturing is required to create formation exposure sufficient to produce the gas.
Tight HoleAn exploration well or other project where information is not released to the public.
Tight SandLow permeability formation.
Tight SpotA restricted place in the bore hole, caused by wall cake, dog leg, deviation change or other factor.
TIHTrip in hole.
Tip Screen OutA fracture treatment, common where high fracture flow conductivity is needed. Very high pressures and very high proppant loadings are applied near the end of a fracture treatment where the tip of the fracture has stopped growing due to bridging of proppant at the fracture dip because of dehydration (frac fluid leakoff).
TIVTubing isolation valve.
TIWTexas Iron Works (manufacturer).
TJTerajoules. 1,000,000,000,000 joules. 1 kilojoule = 0.9478 BTU.
TKVTubing kill valve.
TLPTension leg platform.
TLVThreshold limit value.
Tmax (shale)The temperature in shale maturity at which maximum hydrocarbon release occurs.
TMDTotal measured depth.
TNTank.
TNLTubing nipple locator.
TOCTop of cement.
TOC (shale)Total organic carbon in wt%.
ToeThe far end of a highly deviated well.
TOHTrip out of hole.
TOL (casing string)Top of liner.
TolueneAn aromatic (cyclic) 6-carbon ring compound with 7 carbons and 3 triple bonds. A very powerful solvent for oil, tar and asphaltenes.
TomographyThree dimensional display of seismic velocity in a well or area.
TongsA wrench, hand or power, suspended above the rig floor to make or break pipe connections.
TOOHTrip out of the hole.
Tool JointA pipe connection.
Tool PusherOn-site rig manager. Often there is a rig manager that looks after the rig (office position usually) and between 2 and 4 tool pushers)
Top DriveA rig with the pipe rotation mechanism in the traveling block section. Usually does not use a Kelly.
Top JobA cement repair job done by running a tube down an annulus and cementing to surface.
Top KillA dynamic kill procedure, used in low pressure wells, good for a short period of time. A typical top kill is to pump 5 bbl of fluid in the tubing, offsetting the tubing pressure as the fluid falls. The well must be monitored for pressure or flow and the pump truck usually stays connected in the event that another fluid pill is necessary.
Top LeaseA separate lease to a shallower part of the strata.
Top PlugIn cementing, the last plug pumped in cementing with the two plug system. It isolates the displacement fluid and cement slurry. It helps keep the heavy cement slurry from reversing or U-tubing back into the wellbore while the cement slurry is still unset.
Topographic MapA surface elevation map.
Top-Set CompletionA completion with the casing set and cemented above the pay. Usually an open hole pay zone.
TopsidesPlatform equipment – facilities.
Tornado ChartA resistivity log plot showing the different investigation results based on depth of fluid invasion.
TorpedoThe connection joining the electric line logging cable and the electrical bridle at the reel.
TorqueResistance to rotation of a string. The turning force applied to the string to cause it to rotate.
Torsion testerA slickline tester used to spot slickline fatigue and embrittlement before the run.
TortuosityA description of the hindrance caused to flowing fluids as they attempt to enter the wellbore from a fracture or the formation. Also used to describe the deviation of the wellbore from a smooth path.
Total DepthThe maximum depth of a well measured along the wellbore.
Total Dissolved SolidsTDS, conductivity test of ions in the water. The combined dry weight of dissolved materials, both organic and inorganic, expressed in ppm that are contained in the water.
Total GORGOR that includes solution and free gas from the reservoir.
TOTPTurn over to production.
Tour(often pronounced as tower) a shift worked by the crew.
Township36 sections of land, usually laid out as a square. Along with the section number and the Range, the Township is a way of describing the location of a well.
ToxicityThe degree to which a chemical is poisonous to the plant or animal life in specified surroundings.
TPTail pipe – pipe below the packer.
TPTubing pressure.
TPC (lift)Tubing performance curve. A tubing specific relationship that is plotted with the IPR curve to select the tubing size for the well.
TPC (production)Theoretical production capacity.
TPHTotal petroleum hydrocarbon.
TPI (pipe and connection)Threads per inch.
TPSVTerminal particle settling velocity.
tpyTons per year.
Trace Element (analysis)An element found only in minor amounts (usually less than 1.0 mg/l).
TraceabilityThe ability to trace the components of a product through out the supply and manufacturing system from raw material to finished and installed product.
Tracer (injector)Chemicals placed in the flow stream of an injector to determine that the water takes from an injector to the producing wells.
Tracer Log (fluid movement)A log that uses radioactive tracer to monitor fluid movement in the wellbore or measure losses from the wellbore.
Tracer Log (fracturing)A log that uses a spectral gamma ray and multiple marked sand tracers to analyze proppant placement.
TrackA recording of one measurement from a log.
TractorAn electrically or hydraulically powered downhole tool with driven wheels or slip and hydraulic extension capability that can pull a tool string along a highly deviated well.
TransientA short lived state. Generally used describing reservoirs during production as pressure is progressively drawn down near the wellbore and slowly permeates the rock outward.
Transition Zone (flow)A zone where the flow type or saturation changes due to gas breakout, gas expansion, shear or turbulence.
Transitional SpacerA fluid that separates two incompatible fluids during well cleanout and prepares the wellbore for the next fluid.
TransmissibilityA measure of the conductivity of the formation corrected for the viscosity of the flowing fluid. kh/mu.
Traveling BlockThe block of sheaves or pulleys that moves with the pipe during running or pulling.
Traveling ValveThe valve at the top of the pump in a beam pump.
TreaterA separator vessel.
Treating FluidThe fluids used in a kill, stimulation, cleanout, etc.
Treating IronTemporary surface piping rigged up for a stimulation or well kill operation.
Tree CapA blind flange over a valve at the top of the tree.
Tree SaverAn isolation device commonly used in fracturing to protect the tree from pressure and proppant erosion.
Trench MagnetA magnet in the return trough from wellhead to shaker that removes suspended metal particles from the fluid.
TrendAn indefinite term normally used to identify a producing formation over a large area of production.
TRIToxics Release Inventory.
TriassicA geologic time from 200 million to 250 million years ago.
TriaxialAxial, radial and tangential stress testing.
Thribble (old drilling term)A triple, or three joints of pipe screwed together.
TripPulling all pipe from the well and rerunning the pipe to bottom.
Trip GasGas that enters the wellbore during a trip of the drilling string. May be due to swabbing and/or lowering the mud equivalent circulating density during pump shutdowns.
Trip InRun in the hole with tubing or drill pipe.
Trip MarginAny mud density over the amount needed to balance the formation with a static mud column. Related to overbalance.
Trip OutPull a string of tubing or drill pipe out of the hole.
Trip TankA smaller tank that holds the fluids form running or pulling a string of pipe. Because of its smaller volume, it is used to quickly spot incoming kicks or fluid losses.
TripleThree joints of pipe screwed together.
Triplex PumpA pump with three cylinders.
Tripping InRunning pipe into the well.
Tripping OutPulling pipe from the well.
TRSCSSSVTubing retrievable surface controlled subsurface safety valve. May also be referred to as a ScSSV or DHSV.
TRSSSVTubing retrievable subsurface safety valve.
TST (geologic)True stratagraphic thickness.
True Vertical Depth or TVDThe vertical depth from the surface to the depth of interest. Used for formation comparison and calculation of hydraulic pressures.
TSOTip screenout.
TSRTubing Seal Bore Receptacle
TSSTotal suspended solids in a quantity of liquid.
TSTM (flow measurement)Too small to measure.
TTThrough tubing.
TTDThrough tubing drilling.
TTFWOTime to first workover.
TTGPThrough tubing gravel packing.
TTP (perforating)Through tubing perforating.
TTP (tubular)Tubing tail plug.
TTRThrough tubing retrievable.
TTRDThrough tubing rotary drilling.
TubingTypically the smaller, inner string of pipe in a well that is primarily used for a fluid flow path.
Tubing AnchorA packer-like device without seals that keeps the tubing from moving. Common in rod pumped wells.
Tubing Bonnet (wellhead)The spool or hanger receiver in the wellhead, above which the master valve is the primary control.
Tubing BowlA section in a part of the wellhead that accommodates the tubing hanger.
Tubing ConveyedMovement of any tool via the tubing string.
Tubing End LocatorA wireline device that indicates when the end of tubing is reached.
Tubing HangerA slip set or donut that suspends and holds the top of the tubing in the wellhead.
Tubing HeadA flanged spool containing the tubing bowl where the tubing hanger will set and seal.
Tubing PressureThe pressure on the tubing during either flow or shut-in.
Tubing PumpA beam lift pump where the barrel of the pump is attached to the tubing.
Tubing RetrievableAny equipment pulled with the tubing string.
Tubing SpiderThe holder for the slips on a rig. Suspends the tubing during connection make-up.
Tubing TailEnd of tubing.
Tubing ValveA gas lift valve controlled by pressure in the tubing.
Tubingless CompletionA low cost completion or multiple completion in which the tubing strings are cemented directly in the hole. There is no outer casing. Due to the small tubing diameters, potential to repair or re-enter the well for repairs is limited.
TuggerA winch line or other device that can pull equipment into place.
Tungsten CarbideA hard, abrasion resistant compound used in cutting tools such as mills and bits.
TurbidityA measurement of fluid clarity. Suspended solids and color in water reduces light transmission. Turbidity is a comparison of the amount of light that passes through a trial fluid compared to a clear sample.
Turbine MotorA motor spun by injected fluid moving past vanes affixed to the rotor.
Turbo DrillA turbine motor for drilling.
Turbulent FlowNon laminar flow, usually above a Reynolds number of about 3000. The Blasius equation estimates the friction factor for NRe values less than 100,000 as fB = 0.0791 / NRe0.25.
Turner EquationAn equation that predicts the minimum gas flow to lift liquids in wells above 1000 psi flowing pressure.
Turnkey (drilling)A type of a drilling contract. Once it meant the entire job, beginning to end, and often to ready-to-produce for a set price, however, the term has numerous meanings as defined by individual contracts.
Turner EquationsEquations for deliquification of a well at operating pressures greater than 1000 psi.
TurntableRotary table.
TVDTrue Vertical Depth.
TVDTRTrue vertical depth from the rotary table.
TWC (core)Thick walled cylinder.
TWC (flow path)Two way check.
TWC (pipe)Thick walled compression strength.
Twinning (flow lines)Adding an extra flow line with the same path to increase capacity.
Twinning (wellbore)Using a single slot on a platform to house two wellbores, with independent controls, that are drilled to different parts of the reservoir.
Twist-OffTo separate the drill string during rotation, usually from excess torque.
Two BarrierA operating philosophy and sometimes a requirement that calls for having two barriers to flow from a well. Most appropriate for active drilling, workover or intervention. May not be appropriate for all production wells but is appropriate for wells with a higher risk factors concerning safety or environmental.
TxIATubing by inside annulus.
Type CurveA method of analysis of well behavior by matching the problem curve to curves draw from known conditions.
μViscosity
U-TubeA fluid flow path that has a low spot. In a well, the U-tube is represented by the tubing and the annulus with the bottom of tubing as the low spot. Where two different density fluids are involved, the effect is that the lower density fluid will be pushed higher on its side by the higher density fluid on the other side.
UBUnderbalance.
UBDUnderbalance drilling.
UBIUltrasonic borehole imager.
UBOUnderbalance operations.
UCSUnconfined compressive strength, a measure of the formation strength form compressive tests on core.
UICUnderground injection control.
ULCCUltra-large crude carrier
Ultimate StrengthThe maximum stress that a material can withstand.
Ultrahigh-Pressure Water JettingWater jetting at pressures over 25,000 psi.
UltrasonicVery high frequency sonic signals used in measuring distance, surface imperfections or even metal thicknesses.
Ultraviolet DisinfectationA process using ultraviolet (UV) light to kill bacteria and viruses.
UmbilicalA control line attached to a remove piece of equipment, usually a subsea wellhead, to provide hydraulic or electrical control, or inject small amounts of chemicals.
UMVUpper master valve.
Unassociated gasGas that occurs without association to oil.
UncertaintyThe amount of possible inaccuracy.
Uncertainty (Risk)A reflection of the measured or perceived possible range of outcomes associated with an event or process. Uncertainty can be expressed as deterministic quantitative value, a qualitative value, or as a probability distribution that combines a range of quantitative coefficients with the likelihood that any value in the range will occur.
Uncertainty Assessment (Risk)The process of combining uncertainties, as with a Monte Carlo Simulation, to generate output parameters that are represented by probability distributions. No involvement of risk is implied. Example
UnconformityA geologic aged erosional removal from the top of a formation. Reservoir rocks below this surface may contain hydrocarbon deposits if the unconformity acts as a seal.
Unconsolidated formationFormations with insufficient cementing agents between the grains to stop movement of individual grains when fluid flows through the formation. Usually less than 2 to 10 psi compressive strength.
Unconventional ResourcesHydrocarbon from unconventional and more difficult to produce resources such as (hydrocarbon) shale gas, shale oil, heavy and viscous oil, hydrates, tight gas, etc.
Under ReamerA tool with downhole deployable arms and cutters that allow a larger hole to be drilled below a smaller opening.
UnderbalanceWhen the pressure exerted by the column of fluid in the wellbore is less than the pore pressure in the formation.
Underbalance DrillingDrilling with a pressure in the wellbore that is lower than the pressure in the formation.
Underbalance Drilling Level 0IADC-UBO term. Performance enhancement only; no zones containing hydrocarbons.
Underbalance Drilling Level 1IADC-UBO term. Well incapable of flow to surface.
Underbalance Drilling Level 2IADC-UBO term. Well capable of natural flow to surface, but conventional well kill methods are enabled, and limited consequences are possible in case of catastrophic equipment failure.
Underbalance Drilling Level 3IADC-UBO term. Geothermal and non-hydrocarbon production. Maximum shut-in pressures are less than UBD equipment's operating pressure rating. Catastrophic failure has immediate, serious consequences.
Underbalance Drilling Level 4IADC-UBO term. Hydrocarbon production. Maximum shut-in pressures are less than UBD equipment's operating pressure rating. Catastrophic failure has immediate, serious consequences.
Underbalance Drilling Level 5IADC-UBO term. Maximum projected surface pressures exceed UBO equipment's operating pressure rating, but are below BOP stack rating. Catastrophic failure has immediate, serious consequences.
Underbalanced PerforatingPerforating the well when the pressure in the wellbore is less than the pressure in the formation.
Under-deposit CorrosionA corrosion deposit occurring under a scale or bacterial deposition and thus not treatable by corrosion inhibitiors that are not designed for the purpose.
Undergauge holeAny part of a wellbore drilled with a worn bit.
Underground BlowoutAn uncontrolled and unintentional flow of fluids from one formation to another, generally when one or more well barriers have been breached.
UnderliftUnder production, short of the allotment or contract volume, that must be accounted for in a contract.
Under-ReamEnlarge an existing borehole by a special bit that opens to a diameter larger than running diameter by hydraulic or mechanical method, or by use of a bi-center bit.
Under TravelWhen the travel of the rod string at the pump (bottom of the well), is less than the surface rod travel.
Undersaturated OilAn oil with less gas than its solubility capacity.
Undeveloped ReservesUndeveloped reserves are expected to be recovered expenditure is required to (a) recomplete an existing well or (b) install production or transportation facilities for primary or improved recovery projects (SPE).
Undeveloped AcreageLease acreage on which wells have not been completed to a point of testing or allowing production.
Undiscovered Petroleum Initially in PlaceThat quantity of hydrocarbons estimated yet to be discovered.
Undisturbed ZoneWhere the zone still has the natural connate fluids.
UndulatingA well path that rises and falls over its length.
Unit OperatorThe oil company identified as the operator in a unitized field.
UnitizeForm an operating unit with a operating company from a group of wells in the same field.
UnloadingLightening of a fluid column, usually by adding gas, until the fluid flows out of the well.
Unloading ValveGenerally a downhole valve that, when opened, permits circulation.
Unproved ReservesUnproved reserves are based on geologic and/or engineering data similar to that used in estimates of proved reserves; but technical, contractual, economic, or regulatory uncertainties preclude such reserves being classified as proved. Unproved reserves may be further classified as probable reserves and possible reserves. Unproved reserves may be estimated assuming future economic conditions different from those prevailing at the time of the estimate. The effect of possible future improvements in economic conditions and technological developments can be expressed by allocating appropriate quantities of reserves to the probable and possible classifications (SPE).
Unsteady StateNon constant, in fluid flow a condition marked by changing flow properties.
Unweighted FluidThe base fluid without added salts or solids.
uoOil viscosity.
Up DipIn an upward direction in a tilting formation.
Updip WellA well located higher in the structure.
Up SteamIn the fluid path before the point of interest.
UpliftVertical movement of a formation to a shallower depth than when it was deposited.
Upper CompletionThe part of the completion above the packer.
Upper Crown Plug (subsea)A plug that fits in the bore of a subsea tree to serve as the secondary barrier against reservoir pressure.
Upper Kelly CockA valve at the top of the kelly that can be closed in the event of a inside tubing kick or high pressures.
Upset (chemical)In a produced fluid stream, an upset is when chemical or physical reactions create precipitates or emulsions.
Upset (mechanical)An enlargement in the string, usually for cutting threads. May be internal or external upset.
Upset ConnectionA pipe connection with thicker wall area at the coupling. An external upset is thicker to the outside with a consistent I.D. with the pipe and is called an EU or EUE. A connection upset to the inside (smaller ID but consistent O.D.) is an IU.
UpstreamThe oil producing end of the business.
UraniumU238, one of the natural isotopes that as a trace element may incorporate into the matrix of naturally forming barium or strontium sulfate scale and make it a very low level radioactive material (NORM scale).
URUnder-reamer.
USDWUnderground source of drinking water.
USGSUnited States Geololgical Survey, a US government agency.
USIUltrasonic imager.
USITA brand name for ultrasonic inspection tool, a corrosion damage monitoring device.
UTMUniversal transverse mercator. An orienting/origin defining system used in surveys.
UVUltraviolet.
V-BeltA drive belt with a trapezoidal cross section.
V-Door (Vee Door)An opening at floow level in the side of the rig to facilitate bringing in pipe.
V-G MeterFann viscosimeter.
V-StackA seal stack of chevron type seals.
ValveAny of several valves
Van der Waals ForceAttraction created by the weak electrostatic forces of distributed charge in a polar molecule. Even though the water molecule as a whole is neutral, the polarity or the molecule leads to attraction between individual molecules from slight negative and positive centers. This enters into effects of viscosity and surface tension.
VAPEXVapor assisted petroleum extraction.
Vapor PressureThe pressure exerted by the gas phase (vaporized liquid) in equilibrium with the system conditions.
Vapor Recovery UnitA device that removes mists and vapors from gas in a tank or enclosure.
Variable Bore RamsA ram element in a BOP that will fit more than one size of pipe. Commonly a ram element that can seal around the pipe body or the coupling.
Variable Speed DriveA mechanism that allows the motor speed and power to optimally match the requirements of a pump.
VASPS (subsea)Vertical annular separation production system.
Vee-DoorThe opening in the rig framework that allows pipe to be pulled upright from the catwalk.
Velocity Gradient (seismic)Usually the vertical velocity gradient, i.e., the rate of change of velocity of sound traveling through rock with depth. Normally, it refers to seismic velocity at seismic frequencies, i.e., smoothly varying (rather than rapidly varying, as with a sonic log). With respect to material being sheared, velocity gradient is the change (dv) in relative velocity (v) between parallel planes with respect to the change (dz) in perpendicular distance (z) throughout the depth of the material. Velocity gradient has the same dimensions as rate of shear, which is reciprocal seconds.
Velocity Safety ValveA valve specially dressed for a particular well and kept current with maximum flow potential that can shut in the well if surface control is lost. Also called a storm choke – an early subsurface safety valve.
Velocity StackA long tube used in well fire fighting operations to move all the fluids and the fire up above the damaged wellhead. May also be used to put out the fire in some cases.
Velocity StringA small diameter tubing string, often coiled tubing that is suspended inside the existing production tubing. By occupying part of the flow path space, the velocity of the produced fluid is increased and the potential to lift water from the well is increased.
VentRelease gas pressure.
Vent ScreenA length of tubing with a screen at each end, intended to be installed through tubing and half of the assembly covered with gravel. A common repair for a breached screen. Generally low rate.
VenturiA shaped nozzle.
VerificationTool surface operational check.
Vertical DepthVertical extent of a depth measurement.
Vertical Tree (subsea)A subsea tree with the master valve above the tubing hanger.
VibroseisA seismic survey where the energy is generated by vibrators attached to large truck-mounted plates at the surface
VIPA finite difference reservoir simulator that replaced GCOMP.
Virgin PressureThe pore pressure at discovery.
VIS or VISCViscosity.
ViscosityA measurement of the internal resistance of a fluid to flow against itself. Expressed as the ratio of shear stress to shear rate.
ViscosifiersAny material that increases the viscosity of a fluid.
VITVacuum insulated tubing.
VitonA brand name of a common fluorocarbon elastomer common in seals. Aromatic fluid resistant.
Vitrinite ReflectanceA measure of shale maturity based on whether it has generated hydrocarbons. The value is in units of reflectance, in % Ro with values of 0 to >3.
VIV (riser)Velocity induced vibration.
VLCCVery large crude carrier
VLVValve.
VMEVon Mise’s Equivalent. – a method of calculating triaxial stress.
VOCVolatile organic carbon.
VoidsHoles, blanks spots or empty areas.
Volatile oilEasily evaporated oil, usually above a gravity of 40o API.
Volumetric DriveA reservoir drive mechanism provided by the expansion of solution gas in the oil.
VMEVon Mises Equivalent.
Vortex Shedding (marine)A form of hydrodynamic loading of deep water structures that may lock into a structure’s natural vibration frequency. May include loop currents.
Vreeland EffectA dynamic force. Most common is suddenly stopping a traveling casing string. May cause a pipe joint to separate.
VRUVapor recovery unit.
VSDVariable speed drive.
VSPVertical seismic profile> Run in a single wellbore. Helps correlate logs with seismic data.
VugA large open pore feature. May be associated with chemical dissolution of part of the matrix over geologic time.
VXT (subsea)Vertical subsea tree.
W/CWater cut.
W/VWing valve on a wellhead.
WAGWater-alternating-gas; a tertiary drive mechanism using alternating injections of water and gas.
Wait and Weigh MethodA method of controlling kicks in which the weight of the kill weight mud is calculated by the difference between the difference of casing and tubing pressure and the volume of fluid increase; followed by injection of the kill weight mud to displace the lighter weight mud and the kick in a single circulation.
Waiting on Cement or WOCThe time spent waiting on cement to reach sufficient strength to proceed with operations.
Walking Beam (beam lift)The main moving beam in a beam lift pump.
Walking SqueezeA cement squeeze under the fracture pressure, trying to build pressure slowly. Typical in fracture sealing.
Walking WashPlacement of a fluid in the wellbore with coiled tubing where the fluid is spotted at the bottom of the zone and the CT is withdrawn at the same rate the hole is filled.
Wall CakeFilter cake.
Wall HookA device at the bottom of an overshot for centering the upward looking end of pipe that may be laying against the casing. The hook may resemble a finger or strip of metal pointing clockwise and used with pipe rotation to surround and center the pipe.
Wall StuckUsually differential sticking (by overbalance), but may also include effect of friction and mud cake adhesion to the tubing or drill string.
WARIWalk around rig inspection.
Wash OverA recovery process in which a larger pipe is used with circulation to surround and capture a pipe stuck in sand or cuttings. Circulation is critical to washing the sand from around the fish. Can be used with normal or reverse circulation.
Wash PipeA nonupset pipe with an O.D. close enough to the I.D. of an inner pipe to cause hydraulic diversion. Used inside a screen during gravel packing to direct flow and gravel to the bottom of the screen and effect a tighter pack. Developing hydraulic diversion benefits with a wash pipe usually requires that the washpipe OD be at least 80% or the outer pipe or screen’s ID.
WashingForced circulation of fluid through the perfed interval with the intent of generating communication between perforations or intervals.
Washout (drilling)Flow cutting of equipment downhole.
Washout (formation)An enlarged area of the wellbore caused by removal of formation grains during drilling or circulation.
Washover OperationUsing a overshot tool and circulation to remove debris above and from around a fish and grip the fish with the overshot.
Washover PipeA recovery tool that fits over the OD of the lost pipe.
Waste WaterWater with any home or industrial waste.
Wasting AssetsAssets that will lose or are losing their value.
Water Base Emulsion or MudMud with water as the external phase. May contain clays, polymers, or even an internal oil phase.
Water BlockA relative permeability problem usually occurring in a gas zone. Highest potential formations for water blocks are low pressure gas sands (<0.25 psi/ft pore pressure), with small pore throats (<10 microns), lower permeability (<100 md), and when using water that has a surface tension about 50 dyne/cm.
Water ConingMovement of water upward into oil strata in response to production of oil and lower reservoir pressures. May be localized in areas of high vertical permeability.
Water CushionA level of water in a string to be used for flowback to generate an initial damping back pressure.
Water CutThe amount of water in percent in a produced fluid stream.
Water Disposal WellA well where produced water is injected back into a deep, usually depleted zone but one that is not connected to the producing pay zones.
Water DriveA reservoir drive mechanism where an aquifer provides pressure support and pushes towards the low pressure area around the well, driving the oil ahead of it.
Water FloodPurposely injecting water below and/or into the reservoir to drive the oil towards the producing wellbore. This is a secondary recovery mechanism.
Water FracA fracturing treatment using ungelled water.
Water HammerA sharp, sometimes very high force and pressure load that is created when a valve is closed too rapidly in a flowing stream. The major force occurs behind the valve. Most common in a production well when sudden closure (slam closure) of a subsurface safety valve can create a load of over 50,000 lbs force in the tubing tensile/compressive loading. In an injector, the water hammer effects of a rapid shut-in are lower, but some effects may be seen on the formation.
Water-in-Oil EmulsionWater droplets suspended in a continuous oil phase.
Water Injector WellA well used to inject water into a reservoir to maintain pressure or to drive hydrocarbons towards producing wells.
Water Mellon MillA string mill, designed to enlarge the hole.
Water of CondensationThe water initially in vapor phase within a gas that condenses out when gas cools. Usually 1 to 2 bbls per million scf.
Water PackA gravel packing treatment using ungelled water as the carrier fluid.
Water Table (drilling)The top of the drilling mast where the crown or stationary block rests.
Water Table (water supply)The upper level of groundwater.
Water WetA surface condition in which he coating chemicals show an attraction preference for water.
WatershedAll lands that drain runoff water into a specific area.
Wave TrainResponse of an elastic formation to an acoustic energy impulse.
WaxParaffin, C18+ alkane fraction.
Wax BeadsA diverting agent.
WBMWater based mud.
WBS (rock strength)Wellbore stability.
WBS (seismic)Wellbore seismic.
WCWater cut.
WCL (SSSV)Well to control line communication.
Weak Link (coiled tubing)A weak point at the top of the BHA, designed to separate before the tubing fails if the BHA becomes stuck.
Weak Point (wireline or CT)A designed weak point, usually right about the fishing neck on the tool that is designed to separate when excess tension or axial loads are applied.
Wear BushingA part surrounding the drill string designed to wear instead of more expensive components of the rotary train.
Weather WindowPeriod of time during which weather conditions favorable for operations will or may exist.
Weathered (mineral)A chemically altered mineral that has lost some definition of the lattice or crystal shape. May be more unstable or more reactive.
Weave Screens (sand control)Screens where the filtration layer is largely layers of woven screenwire.
WeevilAn inexperienced worker.
WEGSee Wireline Entry Guide.
Weight (tubing)The weight of a particular tubing size, grade and weight on a weight per pound basis. Includes the weight of the coupling.
Weight BarSame as a weight stem, a bar used mainly to add weight in a wireline BHA.
Weight IndicatorA string weight measurement device that can report the weight on the string at any time.
Weight StemA weight bar in a wireline tool BHA.
Weight UpIncrease fluid density.
Weighting MaterialsSolids added to increase density in a fluid.
Well CleanupRemoval of solids, completion fluid, sand workover fluids by production.
Well CompletionThat processes involved, after drilling, is properly isolate pressures and fluids, and then stimulate or restrain the formations so that hydrocarbons can be produced with minimum amounts of extraneous fluids.
Well ConstructionThe drilling and completion steps prior to production.
Well ControlUsing barriers to prevent unwanted flow of hydrocarbons to surface.
Well InterferenceThe change in pressure or flow rate in one well caused by production in another.
Well OperationThe act of producing the well with all the efforts involved in bringing the well on-line, keeping it flowing and shutting it in.
Well PatrollerA cleanup tool that helps remove debris from a well.
Well ProductivityThe tested ability of a well to produce hydrocarbons.
Well ProgramThe well drilling and completion or repair procedure.
Well Pulling HoistA unit used for retrieval of completion strings and accessories.
Well SortedA measurement of the comparison of large to fine grains. A well sorted formation has a narrow size range between the smallest and the largest particles.
WellboreIn drilling, the drilled hole.
Wellbore CleanoutA treatment designed to remove damage or debris from the wellbore and the perforations.
Wellbore DiagramThe drawing of the well and its equipment showing depths, sizes, grades, and specific equipment.
Wellbore ScreenoutAn early time frac failure when the frac width is too small and the fracture proppant bridges off on the fracture.
Wellbore Storage EffectThe after flow, created by wellbore volume, into a wellbore after the surface valve has been closed.
Wellbore Wash (chemical treating)A solvent or acid wash of the wellbore with minimum leakoff into the matrix.
WellheadThe mechanical connection between the tree and the casing. May house tubular hangers, annular access valves. It is connected to the casing by welding, threads, hydraulic forming or set screws.
WetWater bearing with little hydrocarbon.
Wet CombustionInjecting air and water into a reservoir during a fireflood.
Wet GasA hydrocarbon gas with heavier ends (C2+).
Wet Gloss Heating Value (reactions)The total energy transferred as heat in an ideal combustion reaction of a water saturated gas at a standard temperature and pressure in which all water formed appears as a liquid.
Wet OilOil with a water content above specification.
Wet ShoeA casing shoe with poor cement support.
WETSWellwork evaluation tracking system.
WettabilityThe measurement of the wetting phase currently on a formation. Wetting is driven by the fluid or the surfactants in the fluid in contact with the surface.
Wetted SurfaceAny surface in contact with the flowing fluids in a well.
Wetting FluidThe fluid that coats a mineral surface; usually either oil wet or water wet.
WFWater flood.
WFWellhead flange. The flange on the first cemented string of casing to which the BOP is bolted during drilling and on which the wellhead is built after drilling.
WFRVWater flood regulation valve.
WFTWireline formation tester or wireline formation testing.
WGWire grab.
WHE (wells)Well head equipment.
WHFPWell head flowing pressure.
WhipstockA hardened steel ramp along which a mill turns as it cuts a hole in the side of the casing to start a sidetrack or lateral wellbore.
White OilShorter chain hydrocarbon liquids, generally after refining.
Whole CoreA core as drilled from the reservoir and not separated into smaller cores.
WHPWell head pressure.
WHTWellhead temperature.
WickersBroken or frayed strands of braided line or E-Line.
WildcatA well in a previously undrilled area. An exploratory well.
WIMSWorkover Information Management System data base.
Window (casing)An exit point of a lateral from a mother bore, generally a hole cut in the side of the casing to allow sidetracking the well. Can also be where the entire section of the casing is removed.
Window (hydraulic)The allowable effective fluid density difference between the fracturing pressure and the pressures exerted by a fluid that are needed to control formation flow and the wellbore.
Wing ValveA valve located at the tree, above the master valve, on the flow line.
WIOWorking interest owners.
WIOPWell integrity operations procedure.
Wiper PlugA pumpable plug with flexible cup-like extensions that seal and isolate the fluid behind the plug from the fluid in front.
WirelineA term encompassing slickline, electric line and braided line operations.
Wireline Entry GuideA small fitting on the end of a tubing string that is shaped to allow easier entry of logging tools when pulled back into the tubing from the wellbore below.
Wireline FeelerA fishing tool used to find and catch wireline in preparation for fishing the line.
Wireline Formation TesterA formation fluid sampling device.
Wireline PreventorA BOP for wireline operations.
Wireline RetrievableTools or equipment retrievable with a wireline trip.
Wireline ToolsTools specifically designed to operate on wireline conveyance. May be either for slickline (non electrical signal conducting) or for electric line.
Wire Wrapped ScreenA sand control screen with a shaped wire wound to achieve a set opening size (within tolerance) around a perforated base pipe.
Whirl (drilling)A detrimental condition where a bit bites into a part of the hole off center and forms a pivot point that creates impact of the bit and some of the string with the borehole wall.
WITWell isolation tool.
WLMWireline measurement.
WLMDWireline measured depth.
WML (perforating)Wrapped metal liner.
WOWorkover
WOBWeight on bit.
Wobble Ring (gas lift)Lock ring that anchors the gas lift valve in the side pocket mandrel.
WOCWaiting on cement or water oil contact
WOEWaiting on engineering.
WOOWaiting on orders.
WORWater oil contact
Work BasketThe basket on a snubbing unit where the operator stands.
Work HardeningA metal deterioration in which the metal becomes progressively harder and more brittle with repeated application of load.
Work StringA special, often large string of tubulars that are used during the completion of the well. Usually higher pressure capacity or allow higher weights than the production tubing.
Working InterestAn interest in an oil and natural gas lease that gives the owner of the interest the right to drill for and produce oil and natural gas on the leased acreage and requires the owner to pay a share of the costs of drilling and production operations.
Working PressureThe pressure rating that continuous operations may take place at the set conditions and fluids. Examples – e.g., WP set at 80% of rated burst for new pipe, 70% for used pipe, 50% for welded or damaged pipe.
Working WindowA section, usually pressurized and capable of being opened, below a coiled tubing injector where larger tool can be added or removed to the CT BHA.
WorkoverRepairing a well. Usually implies opening the well and running in with a tubing string. May or may not involve killing the well and may or may not involve a conventional rig.
Workover RigA servicing rig designed to run and pull tubing. It usually has some capacity to mill or drill.
WormAn inexperienced worker.
WormholeA channel created by acid reacting along a high permeability streak.
WOSWest of Shetlands.
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