Oil and gas terminology · MLC-0103

Oil and gas terms: D (313)

• DamageA reduction in the permeability of a reservoir rock near the wellbore, hindering the flow of oil or gas into...
• Damaged zoneThe region of the reservoir rock immediately surrounding the wellbore that has experienced a reduction in...
• DampingThe reduction in amplitude of seismic waves as they propagate through the Earth. This energy loss occurs due...
• DarcyA unit of intrinsic permeability, representing the ability of a porous medium to transmit fluids. One darcy...
• Darcy unitsA system of units commonly used in reservoir engineering for permeability, flow rate, and pressure gradient...
• DartA small plug with a sealing element that is dropped or pumped down the string to land on a seat. In cementing...
• Data analyticsThe process of inspecting, cleansing, transforming, and modeling data with the goal of discovering useful...
• Data augmentationA set of techniques used to increase the amount of data by adding slightly modified copies of existing data...
• Data centerA dedicated facility that houses computer systems and associated components, such as telecommunications and...
• Data miningThe process of discovering patterns and insights from large datasets using statistical methods, machine...
• Data rateThe speed at which digital information is transmitted from a downhole logging tool to the surface acquisition...
• DatumA reference surface or plane to which elevations or depths are measured and corrected in seismic data...
• Datum correctionA set of adjustments applied to raw seismic or gravity data to remove the effects of elevation and...
• Datum levelA reference depth or elevation used as a common base for pressure measurements in a well or reservoir. All...
• Day rateA common contractual payment structure in the drilling industry where the drilling contractor is paid a fixed...
• Daylight tourThe work shift on a drilling rig that occurs during daytime hours, also known as the dayshift. On rigs with...
• dBA decibel, a logarithmic unit used to express the ratio of two values of a physical quantity, such as power...
• DDA drilling detergent added to a drilling fluid to reduce surface tension and counteract the sticking...
• DEA unitA diethanolamine (DEA) unit is a gas processing facility that removes acid gases, primarily hydrogen sulfide...
• Dead oilCrude oil that contains very little or no dissolved natural gas, resulting in a low gas-oil ratio (GOR) and...
• Dean-Stark extractionA laboratory method used to determine the water and oil content of core samples by distillation. The sample...
• DecibelA logarithmic unit used to express the ratio of two values of a physical quantity, typically power or...
• DecollementA detachment fault or zone of décollement, where a block of overlying rock has slid over an underlying block...
• DeconvolutionA seismic data processing technique designed to remove the effects of the seismic source wavelet and...
• Deep inductionA wireline logging measurement that provides a resistivity reading from a volume of rock far from the...
• Deep learningA subfield of machine learning that uses artificial neural networks with multiple layers (deep neural...
• Deep penetrating chargeA type of shaped charge specifically designed to create a long, narrow perforation tunnel deep into the...
• Deep seismic soundingA geophysical method using seismic refraction and wide-angle reflection to investigate the structure of the...
• Deep towA method of deploying geophysical sensors, such as magnetometers, side-scan sonar, or sub-bottom profilers...
• Deepwater playAn exploration or development setting offshore in water deeper than about 300 metres (1,000 feet), where...
• Deflector flowmeterA production logging flowmeter, also called a diverter flowmeter, that uses a basket or inflatable element to...
• DeflocculantA chemical additive used in drilling fluids to reduce the attractive forces between clay particles...
• DeflocculateTo disperse aggregated clay particles within a drilling fluid by neutralizing their electrical charges...
• Deflocculated mudA drilling fluid treated with chemical deflocculants to reduce the attractive forces between clay particles...
• DeflocculationThe chemical process of dispersing clay particles in a drilling fluid by neutralizing their positive charges...
• DefoamerA chemical additive used in drilling fluids to prevent or break down foam formation. Foam can interfere with...
• Defoaming platesInternal components within separation vessels designed to break down foam that forms on the surface of...
• DegasserA piece of solids control equipment that removes entrained gases, such as methane, carbon dioxide, or...
• Degree APIA measure of the density of crude oil or condensate, developed by the American Petroleum Institute (API). It...
• DehydrateTo remove water, typically in vapor form, from a gas or liquid stream in production facilities. This process...
• DehydrationThe removal of water from a drilling fluid system or from its components. This process can involve the...
• DehydratorA piece of equipment used to remove water vapor from natural gas or liquid hydrocarbon streams. Common types...
• Delay rentalAn annual payment made by a lessee to a lessor to maintain an oil and gas lease in force during its primary...
• Deliverability testA well test in which a gas or oil well is flowed at several stabilized rates while the corresponding flowing...
• DeltaA landform created by the deposition of sediment at the mouth of a river where it enters a slower-moving or...
• Delta rhoThe density correction applied to the bulk density measurement of a gamma-gamma density tool, which...
• Delta tThe time interval between successive samples in a digitized seismic trace, representing the sampling rate of...
• Delta t stretchAn erroneously long transit time on a sonic log, produced when the received signal is weak and the tool's...
• DeltaicRelating to or formed in a delta environment, characterized by the deposition of sediments carried by a river...
• DemulsifierA chemical additive designed to break emulsions by separating the dispersed phase from the continuous phase...
• DensimeterAn instrument used to measure the density (mass per unit volume) of a fluid, such as drilling mud, cement...
• DensitometerAn instrument that provides a continuous, real-time measurement of the density of a fluid flowing through a...
• DensityA measure of mass per unit volume of a substance, expressed in units such as grams per cubic centimeter or...
• Density contrastThe difference in bulk density between a body and its surroundings or between adjacent rock layers. In...
• Density currentA gravity-driven flow of fluid that moves through another fluid due to a difference in density. In geology...
• Density measurementThe determination of the bulk density of a formation using a logging tool that emits gamma rays into the rock...
• Density profileA plot or model showing how the bulk density of subsurface rocks varies with depth. This profile is typically...
• Departure curveA set of charts used to correct raw well log measurements for environmental effects that distort the tool's...
• DephasingThe process by which nuclear magnetic moments, initially aligned by a magnetic field, lose their coherent...
• Depleted zoneA section of a reservoir whose pressure has fallen well below its original value because fluids were produced...
• DepletionThe process of reducing the average reservoir pressure and the amount of hydrocarbons in place due to...
• Deployment systemEquipment and procedure for running a toolstring too long for the lubricator into a live, pressurized well in...
• DepocenterA localized area within a sedimentary basin where the maximum thickness of a particular stratigraphic unit or...
• DepositAn accumulation of sediment, mineral matter, or organic material laid down by natural processes such as...
• Depositional energyThe kinetic energy of the geological agent, such as water or wind, responsible for transporting and...
• Depositional environmentThe specific set of physical, chemical, and biological conditions under which sediments accumulate and are...
• Depositional systemA three-dimensional assemblage of genetically related sedimentary facies that were formed within a specific...
• Depth controlThe process of accurately measuring and managing the position of downhole tools and equipment relative to...
• Depth conversionThe process of transforming seismic reflection data from the domain of two-way travel time to the domain of...
• Depth correlationThe process of aligning the measured depth of a wireline logging tool with the known depths of geological...
• Depth datumA fixed reference point or surface from which all depths in a wellbore are measured. This can be the rotary...
• Depth mapA contour map that illustrates the subsurface topography of a specific geological horizon, showing its true...
• Depth markA magnetic mark placed on a wireline logging cable at regular intervals to serve as a reference for depth...
• Depth matchedDescribing two or more well logs or data sets that have been adjusted so that corresponding features align at...
• Depth matchingThe process of correlating and adjusting depth measurements from multiple data sources to a single...
• Depth migrationA seismic imaging technique that repositions reflected seismic energy to its true subsurface location in...
• Depth of invasionThe radial distance that drilling fluid filtrate penetrates into a permeable formation from the borehole...
• Depth of investigationThe radial distance into the formation from the borehole wall that a logging tool measures. This distance...
• Depth referenceA fixed, identifiable point in or near a wellbore from which all vertical depth measurements are made. Common...
• Depth reference pointA precisely defined and consistently used datum from which all depth measurements in a wellbore are taken...
• Depth sectionA two-dimensional cross-section of the Earth's subsurface, where the vertical axis represents true depth...
• Depth wheelA calibrated wheel that measures the length of wireline or coiled tubing deployed into a wellbore. It...
• Depth-derivedDescribing a borehole-compensated sonic measurement in which a transit-time reading is stored and averaged...
• Derivative logsWell logs that are mathematically derived from primary log measurements, often by calculating the rate of...
• DerrickA large, load-bearing structure on a drilling rig that supports the crown block, traveling block, and drill...
• Derrick floorThe elevated platform at the base of the derrick where the drilling crew operates the drilling equipment. It...
• DerrickmanA member of the drilling crew who works on the derrick floor or in the derrick, primarily responsible for...
• DesanderA piece of solids control equipment that uses one or more hydrocyclones to remove sand-sized particles from...
• DesiccantA substance that absorbs or adsorbs water vapor from a gas or liquid stream, used in dehydration processes...
• DesilterA hydrocyclone unit designed to remove silt-sized solid particles from drilling fluid. It uses centrifugal...
• DesulfurizeTo remove sulfur compounds, such as hydrogen sulfide (H2S) and mercaptans, from crude oil, natural gas, or...
• Detail logA well log plotted at an expanded depth scale so the formation can be examined in fine detail, in contrast...
• Detectable limitThe lowest concentration or quantity of a substance or signal that an analytical method or instrument can...
• DetectorA device used to sense and record physical phenomena, such as seismic waves, electromagnetic fields, or...
• DetergencyThe ability of a substance, typically a surfactant solution, to remove oil or other contaminants from a solid...
• DeterminismThe principle that the future state of a system is entirely determined by its present state, with no element...
• Deterministic deconvolutionA seismic processing technique that aims to remove the effects of the seismic source wavelet from the...
• Deterministic methodsModeling approaches that produce a single, unique outcome or model based on a given set of input data and...
• DetonateTo initiate a rapid, self-sustaining chemical reaction in an explosive material that propagates at supersonic...
• Detonating cordA flexible cord containing a core of high explosive, used to transmit a detonation wave along the length of a...
• DetonatorA small explosive device used to initiate the detonation of a larger, less sensitive explosive charge, such...
• DetritalDescribing rock fragments or mineral grains that have been derived from the physical disintegration of...
• DetritusLoose, unconsolidated fragments of rock, minerals, or organic matter that have been weathered and eroded from...
• DevelopmentThe phase of an oil and gas project that follows exploration and appraisal, involving the planning, design...
• Deviated drillingThe practice of drilling a wellbore at an angle from the vertical, allowing access to hydrocarbon reservoirs...
• Deviated holeA wellbore that intentionally departs from a vertical path to reach a target reservoir located away from the...
• DeviationThe angle or direction by which a wellbore departs from a vertical path, often measured from the vertical...
• Deviation surveyA series of measurements taken at intervals along a wellbore to determine its inclination and azimuth. These...
• DewateringThe process of removing water from drilling fluid or drill cuttings to reduce their volume and facilitate...
• DewpointThe temperature at which a gas, at a constant pressure, begins to condense into a liquid. In enhanced oil...
• DextralDescribing the sense of movement along a strike-slip fault where the block on the opposite side of the fault...
• DiagenesisThe collective physical, chemical, and biological changes that occur in sedimentary rocks after deposition...
• DiageneticRelating to the physical, chemical, and biological alterations that sediments undergo after deposition and...
• Diagenetic porosityPorosity in a sedimentary rock that has been created or modified by diagenetic processes after initial...
• Diameter of invasionThe diameter of the cylindrical zone around the borehole axis that drilling fluid filtrate has invaded...
• Diameter of investigationThe effective radial distance from the borehole that a logging tool's measurement represents. This parameter...
• Diamond bitA drill bit that uses industrial diamonds as the cutting elements to penetrate rock formations. These bits...
• DiapirA dome-shaped or anticlinal structure formed when a mobile, ductile material, such as salt or shale, pierces...
• DiatomA single-celled alga that secretes a hard, porous cell wall made of silica, known as a frustule. These...
• DiatomaceousDescribing a sedimentary rock, sediment, or earth composed primarily of the fossilized siliceous shells of...
• DiatomiteA soft, friable, and porous sedimentary rock composed primarily of the fossilized remains of diatoms, which...
• Dichromate saltA salt containing hexavalent chromium, such as sodium dichromate or potassium dichromate, that was added to...
• DielectricA material that is an electrical insulator and can store electrical energy when an external electric field is...
• Dielectric constantA dimensionless measure of how strongly a material polarizes in an electric field, equal to its permittivity...
• Dielectric permittivityA measure of a material's ability to store electrical energy when subjected to an electric field, indicating...
• Dielectric propagation logA formation evaluation measurement that determines the dielectric constant of the formation by measuring the...
• Dielectric resistivityThe resistivity value derived from a dielectric (electromagnetic propagation) logging tool, which measures...
• Diesel-oil mudA type of oil-based drilling fluid where diesel fuel serves as the continuous phase, with emulsified water...
• Diesel-oil plugA lost-circulation pill made by slurrying dry bentonite in diesel oil, sometimes with cement added, which...
• Difference mapA map created by subtracting the grid values of one data set from another on a point-by-point basis, used to...
• Differential compactionThe uneven reduction in volume of sedimentary layers due to varying degrees of overburden pressure and...
• Differential pressureThe difference between the hydrostatic pressure of the drilling fluid column in the wellbore and the fluid...
• Differential pressure stickingA condition where the drill string becomes stuck against the wellbore wall due to a pressure imbalance. This...
• Differential SPA spontaneous potential measurement taken between two electrodes placed close together in the borehole...
• Differential spectrumAn NMR logging method for identifying fluids that subtracts the T2 distribution acquired with a short...
• Differential stickingThe immobilization of the drill string against the wellbore wall when a section of pipe contacts a permeable...
• Differential temperature logA record of the temperature difference between two sensors, typically spaced a few feet apart, as they are...
• Difficult to disperseDescribing a well cement that is not easily dispersed by a dispersant additive, so the viscosity of its...
• Difficult to disperse in saltDescribing a well cement that is not easily dispersed by a dispersant additive when the slurry is mixed with...
• DiffractionThe phenomenon where waves bend, spread out, and interfere as they pass around an obstacle or through an...
• Diffraction stackA specialized seismic imaging product created by isolating and stacking only the diffraction energy from the...
• DiffusionThe process by which particles or energy spread out from an area of higher concentration to an area of lower...
• Diffusion equationA partial differential equation that describes the movement of substances or properties, such as heat, mass...
• Diffusion modelsA class of generative artificial intelligence models that learn to create new data samples by reversing a...
• Diffusion relaxationThe shortening of the transverse relaxation time T2 of a fluid caused by molecules diffusing through a...
• Digital twinA virtual replica of a physical asset, process, or system, created using real-time data from sensors and...
• DikeA tabular body of igneous rock that cuts across the layering or fabric of the surrounding rock. Dikes form...
• DilatancyThe phenomenon where the volume of a granular material, such as rock, increases when it is subjected to shear...
• Dilatancy theoryA hypothesis proposing that changes in rock volume due to dilatancy, particularly before an earthquake, can...
• DilatationThe change in volume per unit volume of a material, representing its volumetric strain. In geophysics, it...
• Dilatational waveA seismic wave in which the particle motion is parallel to the direction of wave propagation, causing...
• DiluentA lighter hydrocarbon liquid, such as naphtha or condensate, added to heavy crude oil or bitumen to reduce...
• DilutionThe process of adding a base fluid, typically water or oil, to a drilling fluid to reduce the concentration...
• Dilution waterWater added to a water-based drilling fluid to reduce its density, viscosity, or solids content. This is a...
• Dim spotA localized decrease in the amplitude of a seismic reflection, which can indicate the presence of...
• DipThe angle at which a planar geological feature, such as a bedding plane, fault, or vein, is inclined from the...
• Dip correctionA calculation applied to well log data to convert measured, or apparent, formation bed thickness to true...
• Dip faultA fault whose strike runs in the direction of dip of the strata it cuts, so that it crosses the strike of the...
• Dip moveoutA prestack processing step that corrects for the dip dependence of normal moveout, so that reflections from...
• Dip tubeA tube extending from the top of a vessel or tank down into the liquid contents, used for sampling, level...
• DipoleA pair of equal and opposite charges or poles separated by a small distance, creating an electric or magnetic...
• Dipole fieldA magnetic or electric field generated by two equal and opposite poles or charges separated by a small...
• Dipping bedA sedimentary rock layer that is inclined at an angle to the horizontal, rather than lying flat. This...
• Direct emulsifierA chemical additive that promotes the formation of an oil-in-water emulsion, where oil droplets are dispersed...
• Direct hydrocarbon typingThe use of nuclear magnetic resonance logging to identify the type of hydrocarbon in the pore space directly...
• Direct-indicating viscometerAn instrument that measures the shear stress of a fluid at several specific shear rates, allowing for direct...
• Directional drillerA specialist responsible for guiding the drill bit along a predetermined trajectory to reach a specific...
• Directional drillingThe practice of intentionally deviating a wellbore from a vertical path to reach a subsurface target that is...
• Directional permeabilityThe property of a porous medium where permeability varies with the direction of fluid flow, meaning the ease...
• Directional surveyA series of measurements taken at intervals along a wellbore to determine its precise trajectory from the...
• Directional variogramsGeostatistical tools used to quantify the spatial continuity or correlation of a reservoir property, such as...
• Directional wellA wellbore drilled at an angle from the vertical to reach a target reservoir that is not directly beneath the...
• DirectivityThe directional dependence of the radiation pattern of a seismic source or the sensitivity pattern of a...
• DirtyDescribing a reservoir rock that contains a high proportion of clay minerals or other non-hydrocarbon...
• DisbondingThe separation of a coating or lining from the substrate material it was applied to. In the oil and gas...
• DisconformityAn unconformity where the sedimentary layers above and below the erosional surface are parallel. It...
• DiscontinuityA break or interruption in the continuity of a geological formation or physical property within the Earth...
• DisharmonicDescribing folds or structural deformation where the style and geometry of folding vary significantly between...
• DispersantA chemical additive that deflocculates clay particles in a water-based drilling fluid, reducing viscosity and...
• Dispersed bubble flowA multiphase flow regime in a wellbore where gas is present as small, discrete bubbles uniformly distributed...
• Dispersed clayClay minerals distributed throughout the pore space of a sedimentary rock, rather than being concentrated in...
• DispersionThe phenomenon where the velocity of a wave depends on its frequency, causing different frequency components...
• DisplacementThe distance and direction of movement of one block of rock relative to another along a fault plane. It is a...
• Displacement efficiencyThe fraction of oil displaced from the pore spaces of a reservoir rock by an injected fluid, relative to the...
• Displacement fluidA fluid used to push another fluid out of a wellbore or pipeline, typically during cementing operations or...
• Displacement frontThe moving interface between the injected fluid and the reservoir fluid during an enhanced oil recovery...
• Disposal wellA well used to inject produced water, drilling fluids, or other non-hazardous industrial waste fluids into...
• Dissolved solidsMineral salts and other compounds that are completely dissolved in the aqueous phase of a drilling fluid...
• Distillation extractionA laboratory method used to separate and quantify the oil and water content from a core sample. The sample is...
• DistortionAny alteration or deformation of seismic wave characteristics, such as amplitude, phase, or waveform, as they...
• Distributed temperature logA logging technique that measures temperature along the entire length of an optical fiber cable permanently...
• DistributionThe statistical pattern describing how values of a particular reservoir property, such as porosity...
• Diurnal variationA regular, daily fluctuation in the Earth's magnetic field, primarily caused by solar radiation affecting the...
• DivergenceThe spreading out of seismic wave energy as it propagates away from its source, causing a reduction in...
• DiversionThe technique of temporarily blocking off high-permeability or previously treated zones within a reservoir to...
• DiverterA low-pressure system used to direct wellbore fluids away from the rig floor during the initial stages of...
• Diverter flowmeterA flowmeter for production or injection wells in which an inflatable or umbrella-style diverter forces the...
• Diverting agentA chemical or particulate material added to a treatment fluid to temporarily block fluid flow into highly...
• Division orderA legal document that instructs a purchaser of oil or gas on how to distribute proceeds from production among...
• Dix formulaAn equation used in seismic processing to calculate interval velocities from root-mean-square (RMS)...
• DMOAn acronym for Dip Moveout, a seismic data processing technique that corrects for the smearing effect of...
• Dog collarA safety clamp fitted around the body of a perforating gun, drill collar or other tubular so the string stays...
• DoghouseA small, portable cabin located on the rig floor, serving as an office and shelter for the driller and other...
• DoglegAn abrupt change in the direction or inclination of a wellbore, creating a bend or curve in the drilled path...
• DolomiteA carbonate mineral composed of calcium magnesium carbonate, CaMg(CO3)2, or a sedimentary rock primarily made...
• DolomitizationThe diagenetic process by which limestone, composed primarily of calcite, is converted into dolomite through...
• DolostoneA sedimentary rock primarily composed of the mineral dolomite, containing at least 50% dolomite by weight. It...
• DomainA specific range or space in which data or a physical phenomenon is observed, measured, or analyzed. In...
• Domainal fabricA rock fabric or spatial structure made up of several domains superimposed on one another, usually differing...
• Domainal structureA structure built from several domains laid over one another, each of differing size or wavelength, rather...
• DomeA geological structure characterized by upwardly convex, roughly circular or elliptical strata that dip away...
• DoodlebuggerA colloquial name for a person who works as a field technician or geophysicist on a seismic acquisition crew...
• DopeA specialized thread compound or lubricant applied to the threaded connections of drill pipe, casing, and...
• Dosing pumpA positive displacement pump designed to inject precise and controlled volumes of chemicals or additives into...
• Double block-and-bleedA valve configuration that provides a positive shutoff of fluid flow by using two in-line block valves with a...
• Double descentA phenomenon observed in machine learning where model performance initially improves with increasing model...
• Double refractionThe splitting of a single incident light ray into two distinct rays as it passes through an anisotropic...
• Down dipThe direction that is directly down the steepest angle of a tilted geologic surface, such as a bedding plane...
• Down lapA seismic reflection pattern where younger, overlying strata terminate progressively downwards against an...
• DowndipThe direction that is directly down the steepest angle of a tilted geologic surface, such as a bedding plane...
• Downhole gaugeAn instrument run into a wellbore to measure and record pressure and temperature data under reservoir...
• Downhole receiverA sensor deployed within a borehole to detect seismic waves that have traveled through the subsurface. These...
• Downhole safety valve (DSV)A subsurface valve installed in the tubing string of a producing well, designed to automatically shut off...
• Downhole sensorsElectronic devices installed within the wellbore to measure parameters such as pressure, temperature, and...
• Downhole sourceA device lowered into a borehole to generate seismic energy for subsurface imaging. This source can be an air...
• DownlapA seismic reflection pattern where younger, overlying strata terminate progressively downwards against an...
• DownstreamThe sector of the oil and gas industry that includes the refining of crude oil, processing of natural gas...
• Downstream pipelineA pipeline located after a processing plant, refinery or other reference point in the direction of flow...
• DownstrokeThe downward movement of the sucker rod string and pump plunger in a rod pumping cycle. During the downstroke...
• Downward continuationA mathematical process used in potential field geophysics to estimate the gravity or magnetic field at a...
• Draeger tubeA glass tube containing a chemical reagent that changes color when exposed to specific gases, used for rapid...
• Drag bitA type of drill bit that cuts rock by scraping or shearing action, rather than by crushing or grinding. It...
• Dräger tubeA sealed glass tube containing a chemical reagent that reacts with specific gases, producing a color change...
• Drain holeA wellbore drilled horizontally or at a high angle from a vertical or deviated well, designed to increase the...
• DrainageThe process where a non-wetting fluid displaces a wetting fluid from the pore spaces of a rock, such as oil...
• Drainage areaThe subsurface region from which a well produces hydrocarbons, encompassing the portion of the reservoir that...
• Drainage volumeThe volume of reservoir rock from which fluids flow toward a single well during production. Its size and...
• Drained testA laboratory test in rock or soil mechanics where a sample is subjected to stress slowly enough to allow pore...
• DrainholeA wellbore drilled horizontally or at a high angle from a vertical or deviated well, designed to increase the...
• DrapeThe deformation of sedimentary layers over an underlying topographic high, such as a fault block or a reef...
• DrawdownThe difference between the static reservoir pressure and the flowing bottomhole pressure in a producing well...
• Drawdown testA well test conducted by flowing a well at a constant rate and monitoring the decrease in bottomhole pressure...
• DrawworksThe primary hoisting mechanism on a drilling rig, consisting of a large drum around which the drilling line...
• DriftThe angle by which a wellbore departs from vertical, measured in degrees from the vertical axis. In tubular...
• Drill bitA cutting tool attached to the end of the drill string that grinds, scrapes, or shears rock to create a...
• Drill collarA heavy, thick-walled steel pipe that provides weight on bit for drilling and maintains tension in the drill...
• Drill solidsFinely ground rock particles generated during the drilling process that become suspended in the drilling...
• Drillable packerA downhole device that isolates zones in a wellbore, designed to be drilled out after its purpose is served...
• Drilled solidsFragments of rock and formation material that are cut by the drill bit and circulated to the surface by the...
• DrillerThe individual on a drilling rig who operates the drilling machinery, including the drawworks, rotary table...
• Driller's depthThe measurement of the depth of a wellbore as recorded by the driller at the rig floor. This depth is...
• Drill-in fluidA specialized drilling fluid designed to minimize formation damage while drilling through the reservoir...
• Drilling breakA sudden and noticeable increase in the rate of penetration (ROP) during drilling, indicating a change in the...
• Drilling contractorA company that owns and operates drilling rigs and provides drilling services to oil and gas exploration and...
• Drilling crewThe team of workers on a drilling rig responsible for the physical execution of drilling operations. This...
• Drilling detergentA chemical additive used in drilling fluids to reduce surface tension and improve the wetting properties of...
• Drilling fluidA circulating fluid, typically a mixture of liquids and solids, used to facilitate the drilling of a...
• Drilling foremanThe drilling contractor's senior supervisor on location, also called the toolpusher, who is responsible for...
• Drilling mudA circulating fluid, also called drilling fluid, used in rotary drilling to perform several functions...
• Drilling procedureA detailed, sequential plan outlining all operations required to construct a well from spud to completion. It...
• Drilling programA detailed plan that outlines all aspects of drilling a well, including geological objectives, well design...
• Drilling rateThe speed at which the drill bit deepens the wellbore, also known as the rate of penetration (ROP). It is...
• Drilling rigA large, complex machine assembly used to bore wells into the earth's surface to extract oil, natural gas, or...
• Drilling riserA large-diameter pipe that connects a subsea blowout preventer (BOP) stack on the seabed to a floating...
• Drilling-fluid engineerA specialist responsible for the design, maintenance, and management of the drilling fluid system on a rig...
• Drillpipe conveyedA method of deploying logging tools into a wellbore by attaching them to the end of the drill string instead...
• DrillshipA self-propelled offshore drilling vessel equipped with a drilling rig positioned over a moonpool in its...
• DrillstemThe entire column of pipe and specialized components extending from the surface rotary equipment down to the...
• Drillstem testA temporary completion of a well or an openhole interval to evaluate the productivity of a...
• DrillstringThe entire assembly of tubulars and tools that transmits power from the rig to the drill bit at the bottom of...
• DripA low point in a natural gas pipeline where condensed liquids, such as water or natural gas liquids...
• Drip accumulatorA vessel installed at a low point in a natural gas pipeline to collect condensed liquids, such as water and...
• DroopA characteristic of a pressure regulator or control system where the outlet pressure or controlled variable...
• Drop ballA spherical device pumped downhole with fluid to actuate a tool or isolate a wellbore section. It lands in a...
• Drop barA heavy, cylindrical weight dropped from the surface into the wellbore to mechanically activate a downhole...
• Drop subA sub in a tubing-conveyed perforating string that releases the guns after firing so they fall into the...
• Dropoff gunA perforating gun assembly that is released from the tubing after firing and falls to the bottom of the well...
• DropoutA sudden and temporary loss of signal or data in a recording system, often caused by equipment malfunction...
• Dry bedA dehydration system that uses a solid desiccant, such as molecular sieves, silica gel, or activated alumina...
• Dry combustionAn in situ combustion process where air or an oxygen-enriched gas is injected into a heavy oil reservoir to...
• Dry forward combustionAn in-situ combustion process where air is injected into a reservoir, igniting the crude oil and creating a...
• Dry gasNatural gas that consists almost entirely of methane, with very low concentrations of heavier hydrocarbons...
• Dry holeA well that does not produce hydrocarbons in commercial quantities, or one that is drilled and found to be...
• Dry oilCrude oil that contains very little to no water, typically less than 0.5% by volume. This condition is...
• Dry rockA rock sample or formation whose pore space contains only air or a vacuum, with no water, oil, or gas...
• Dry-bed dehydratorA type of dehydration unit that removes water vapor from natural gas using solid desiccants like molecular...
• DSSDeep Seismic Sounding, a geophysical technique that uses controlled seismic sources and widely spaced...
• DSTA temporary completion of a wellbore to evaluate a specific formation's ability to produce hydrocarbons. It...
• DST pressure chartA graphical record of downhole pressure versus time measured during a drillstem test (DST). The chart is...
• Dual completionA well completion method that allows two different producing zones in a single wellbore to produce...
• Dual inductionA wireline logging tool that provides two simultaneous induction resistivity measurements with different...
• Dual waterA model used in petrophysics to account for the electrical conductivity of both free formation water and...
• Dual-permeability reservoirA reservoir model for naturally fractured or layered formations in which two interacting systems, a...
• Dual-porosity reservoirA reservoir model that describes formations with two distinct pore systems, such as fractured carbonates or...
• Due diligenceThe process of conducting a thorough investigation and review of a potential investment or acquisition to...
• Dummy valveA blank or non-functional valve installed in a side pocket mandrel within a gas lift string, used to...
• Dump bailerA wireline-conveyed tool used to deliver cement, sand, or other granular materials to a specific depth in a...
• Duplex pumpA positive displacement pump featuring two pistons or plungers that operate in parallel, providing a more...
• DusterAn exploratory or development well that has failed to encounter commercially viable quantities of...
• Dye penetrant inspectionA non-destructive testing method used to detect surface-breaking discontinuities, such as cracks, pores, and...
• DykeA tabular body of igneous rock that cuts across the layering or fabric of the surrounding rock. Dykes form...
• Dynamic correctionAn adjustment applied to seismic reflection data to account for variations in the travel time of seismic...
• Dynamic filter pressA laboratory device used to measure the filtration properties of drilling fluids under simulated downhole...
• Dynamic filtrationFluid loss of a mud into a permeable formation while the mud is flowing past the face, so that the filter...
• Dynamic fluid levelThe depth from the surface to the top of the liquid in a well's casing annulus while the well is actively...
• Dynamic miscibilityThe condition where two fluids, initially immiscible, achieve miscibility through mass transfer and...
• Dynamic positioningA computer-controlled system that automatically maintains a vessel's position and heading using its own...
• Dynamic rangeThe ratio of the largest to the smallest signal amplitude that a geophysical recording system can accurately...
• Dynamic sealA type of seal designed to prevent fluid leakage between two surfaces that are in relative motion. These...
• Dynamic-aging testA laboratory procedure that simulates the thermal and mechanical stresses a drilling fluid experiences...
• DynamiteAn explosive material historically and sometimes currently used as a seismic energy source, particularly in...
• DynamometerAn instrument used to analyze the performance of a sucker-rod pumping system by measuring the load and...
• Dynamometer cardA graphical plot of load versus displacement for a sucker rod pumping unit, recorded by a dynamometer. This...

313 of 4,468 terms in Oil and gas terminology (MLC-0103). Request the full dataset.