Discover the IHRDC Energy Glossary_beta

daily feedstock

The volume of raw material a plant consumes each day.

daily injection

The volume put into storage or the reservoir each day.

daily inspection

The operator round covering the checks that must be made every shift.

daily sendout

The volume a terminal or storage facility delivers each day.

daily sendout requirements

The average amount of gas that an LDC must deliver to its customers daily.

daily stand-up

The short daily meeting where the team coordinates and surfaces impediments.

daisy-chain

A wiring scheme in which the hot and/or ground leads for multiple controllers are connected through each other.

damage

Any impairment to production arising in the reservoir, the near-wellbore rock, the perforations, the gravel pack or the production system.

damaged zone

The region around the wellbore whose permeability has been reduced by drilling, cementing or completion fluids.

dampener

A gas or liquid-charged, chambered device that minimizes the ef¬fects of pulsation.

damper

A device consisting of one or more blades that can be adjusted to control air flow in a fan or ventilation system.

damping

Any action that reduces the output of, or response to, sudden changes or high frequencies. In process control, adjusting the time between signal transmissions to eliminate electrical and mechanical noise, which suppresses oscillations in the process variable and slows its response to control output changes.

damping (electrical)

The process of preventing an instrument's pointer from oscillating above and below the measured value.

damping magnet

A permanent magnet used in an induction disc element that produces a fixed drag on the disc so that the disc turns at a constant speed.

dangerous conflict

Conflict that has moved from the issue to the person, and will not resolve itself.

DAP (Delivered At Place)

The seller delivers to a named place, ready for unloading, bearing risk until arrival.

DAQ

Data Acquisition.

darcy

A unit of permeability defined as that which permits a fluid of one centipoise viscosity to flow at a rate of one cubic centimeter per second through a porous medium with a cross-sectional area of one square centimeter under a pressure gradient of one atmosphere per centimeter.

darcy law

The relation making flow rate proportional to pressure gradient and permeability and inverse to viscosity.

dark fermentation

Bacterial hydrogen production without light, unlike photobiological routes.

dart

A device dropped or pumped down a tubing or coiled tubing string to actuate a downhole tool.

dashboard

A consolidated display of current measures for monitoring at a glance.

data acquisition board

A plug-in printed circuit board that allows standard PCs to process input data from a variety of sensors.

data analysis

Examining data to extract something that supports a decision.

data analytics

The examination of large datasets to extract patterns, trends and conclusions that support a decision.

data augmentation

Expanding a training set by generating modified copies of existing examples.

data centre site selection

Choosing a location on power, connectivity, climate, jurisdiction and risk exposure.

data classification

Labeling data by sensitivity so controls can be applied proportionately.

data collection method

How the data was gathered, which determines what conclusions it can support.

data ethics

The obligations governing what may be collected and inferred about people.

data files

One of two main types of PLC files, in which the current states of inputs, outputs, timers, counters, numbers, etc. are stored.

data governance

The ownership, standards and controls determining how data is defined, secured and used.

data highway 485

An Allen-Bradley peer network for connecting members of the SLC-500 family, PCs, and low-end HMIS together.

data highway plus

An Allen-Bradley peer network for connecting members of the PLC-5 family, PCs, and high-end HMIS together.

data integration

Joining data from separate systems so it can be analyzed together.

data leakage prevention (DLP)

Controls detecting and blocking sensitive data leaving the organization.

data logger

Portable equipment typically used by maintenance personnel to take and store readings on-field equipment.

data management

The disciplines controlling how data is stored, secured and made available.

data mining

Searching large datasets for patterns and relationships that were not being looked for specifically.

data plate

A metal plate attached to a forklift that provides important information such as the forklift's rated lifting capacity, weight and required clearances or other limitations.

data precision

Data precision refers to the closeness of two, or more, measurements to each other.

data privacy

The individual's right to control how information about them is collected and used.

data quality

Whether data is accurate, complete and timely enough to be relied upon for decisions.

data rate

The rate at which measurements are transmitted from a downhole tool to surface.

data retention and destruction

How long data is kept and how it is disposed of, driven by law as much as by preference.

Data Rights Management (DRM)

Controls that stay attached to a file and restrict what a recipient can do with it.

data visualization

Presenting data so the pattern is visible to a decision-maker.

data-driven recruitment

Selecting and sourcing on evidence rather than on impression.

database security

Protecting stored data through access control, encryption and monitoring.

dated brent

The assessment of physical North Sea cargoes with assigned loading dates, the main global benchmark.

datum

An agreed reference value or surface — sea level, a benchmark elevation, a chosen depth — to which other measurements are corrected.

datum correction

A time shift applied to seismic traces to place sources and receivers on a common datum plane below the weathered layer.

datum line

The zero point to which a liquid level measurement is referenced.

datum plate

A reference point, located near the bottom of a tank, for use in measuring liquid levels.

datuming

Shifting data to a common reference level so sections can be compared.

daughter product, daughter isotope, daughter nuclide

A daughter product, daughter isotope or daughter nuclide is the remaining nuclide left over from radioactive decay.

Davenport-Kim three-stage model

Framing the problem, solving it analytically, then communicating and acting on the result.

day rate

The daily charge for a drilling rig with its crew and specified equipment, under a contract where the operator carries the drilling risk.

daylight tour

The drilling crew shift beginning around dawn.

dB

Decibel — a logarithmic ratio of two power or amplitude levels, one tenth of a bel.

DC bus

A section of an AC inverter controller that serves as a reservoir of electrical energy.

DCS

Distributed Control System. A computerized network that gathers industrial process input information, makes calculations, and transmits instructions to output devices to maintain a process at desired conditions. System control is distributed across hundreds or thousands of inputs and outputs, including variable speed drives.

DD

Drilling detergent — a surfactant added to stop shale and clay sticking to the bit and bottomhole assembly.

de-aeration

The process of removing air and non-condensable gases from condensate to decrease the amount of oxygen that is dissolved in the water.

de-aerator

A type of open feedwater heater in which steam and condensate mix together while also removing air and non-condensable gases from the condensate or water.

de-aerator storage tank

A storage tank, often located below a de-aerator, that holds de-aerated feedwater to supply the demands of the feedwater system, if needed. Also called a feedwater storage tank.

de-asphalting unit

A unit that separates recoverable oil from asphalt materials contained in pitch, or bottoms.

de-energize

Remove power from a circuit or device.

de-ethanization

Removing ethane from a natural gas liquids stream so the remainder meets propane specification.

de-ethanizer

The fractionation column separating ethane from heavier natural gas liquids.

de-ethanizer/absorber

A tower in a cracked gas plant that receives unstabilized cat-cracked gasoline and compressed noncondensed gases from the gas recovery system. Ethanes and lighter components are removed from the top of the tower. The bottoms product is the feed stream to the debutanizer.

de-isobutanizer

See Isostripper.

de-methanizer column

The column separating methane from heavier components in gas processing.

de-propanizer column

The column separating propane from butane and heavier components.

DEA unit

A gas treating system that circulates diethanolamine to absorb hydrogen sulfide and carbon dioxide from a gas stream, then regenerates the solvent.

dead oil

Dead oil is an oil that contains no dissolved gas or a relatively thick oil or residue that has lost its volatile components.

dead time

The time interval between when a control input or output changes and when the process or system begins to respond to that change.

dead weight tester

An instrument used to check the accuracy of the static element during an orifice meter witnessing.

deadweight

The total weight a ship can carry, including cargo, fuel and stores.

deadweight tonnage

The total weight a ship can carry, including cargo, fuel, stores and crew.

deaerator

A device on the LACT unit which removes free gas and air from the oil.

Deal Making Negotiation (DMN)

Negotiating to create a new agreement rather than settle a dispute.

deal profit

The realized gain on a completed transaction after all associated costs.

deal profitability

What a single transaction earned after freight, financing, losses and hedging costs.

Dean-Stark extraction

A distillation method for measuring core fluid saturations, in which a solvent boils water out of the sample and the recovered water is read off.

debit and credit

The two sides of every entry, whose meaning depends on the account type.

debottlenecking

Removing the single constraint that limits throughput, usually far cheaper than new capacity.

debrief

The structured discussion after an exercise, where the learning is actually extracted.

debris flow

A dense downslope flow of poorly sorted sediment, depositing chaotic unsorted rock.

debt service

The scheduled interest and principal payments a project must meet.

Debt Service Cover Ratio (DSCR)

Cash available in a period divided by debt service due, tested each period.

debt tenor

How long the loan runs, which for project finance must fit the asset's producing life.

debutanizer

A tower in a cracked gas plant that separates butanes and lighter components from heavier components in a feedstream. The bottoms product is stabilized cat-cracked gasoline.

Decade of Gas

Nigeria's policy of developing gas for domestic industry and power through the 2020s.

decanter

An auxiliary vessel used to separate two immiscible liquids on the basis of differences in density, or a vessel in an azeotropic distillation system where overhead product separates into two liquid phases.

decanting

Drawing off the clear upper liquid after solids or a denser phase have settled.

decarbonization

Reducing the carbon dioxide emitted per unit of energy or output.

decarbonization roadmap

A dated sequence of actions taking an organization from present emissions to its target.

decarbonize

Remove carbon dioxide from an activity's output, by fuel switching, efficiency or capture.

deceleration

Slowing down at a controlled rate.

deceleration ramp

The time it takes for a variable speed drive to slow down from a preset speed.

deceptive advertising

Marketing that misleads about a product's nature, price or performance.

decibel

One tenth of a bel: a logarithmic unit comparing two signal intensities, and the practical unit for sound and gain.

decimal numbering system

The numbering system based on powers of ten.

decimal places

The places to the right of the decimal point in a decimal number.

decimal point

The period in a decimal number that separates the whole place values from the fractional place values.

decision gate presentation

The case a team makes to the review board to secure approval for the next phase.

decision review board

The panel to which a team presents at a gate for the decision to proceed.

decision tree analysis

Mapping sequential choices and chance outcomes to value the decision, not just the project.

declaration of inspection (DOl)

A list of requirements that must be completed before a barge transfer is performed.

declination

The angle between magnetic and true north, which must be applied to every magnetic survey.

decline curve

The observed fall in a well's rate over time, extrapolated to forecast remaining recovery.

declutch lever

A device that places a motor operator clutch in the manual, or handwheel, position; a clutch operating lever.

decollement

A low-angle fault surface, usually following a mechanically weak layer, that detaches deformed rock above from less deformed rock below.

decommissioning

Shutting down, cleaning and removing facilities and wells at the end of field life.

decommissioning a tank

The process of taking a storage tank out of service.

decompose

To break down chemically, as organic matter to kerogen or a polymer under heat.

decomposition

Breaking a large item into pieces small enough to estimate and complete.

decontamination

The removal of hazardous substances from employees and their equipment to the extent necessary to preclude the occurrence of foreseeable adverse health effects.

deconvolution

A processing step that removes the effect of the source wavelet and the earth filter, sharpening the wavelet and attenuating short-period multiples.

deconvolved

Processed to remove the source wavelet and sharpen resolution.

decoupling capacitor

A compensation capacitor used to bypass power supply AC frequency variations around an op amp circuit to the ground.

deep conversion coking

The refinery configuration achieving the highest conversion of residue to light products.

deep induction

The deepest-reading curve of an induction tool, designed to measure true formation resistivity beyond the invaded zone while keeping usable vertical resolution.

deep learning

Machine learning using neural networks of many layers, which learn their own features rather than being given them.

deep offshore

Offshore operations in deep water, requiring floating rather than fixed facilities.

deep penetrating charge

A shaped charge designed for a long perforation tunnel, so the perforation reaches past the drilling-damaged zone.

deep resistivity

Resistivity read far enough from the borehole to represent undisturbed formation.

deep seismic sounding

A long-offset seismic profile recorded to image the lower crust, the Moho and the upper mantle.

deep tow

Marine acquisition with the source or receivers towed well below the surface, closer to the target and away from surface noise.

deepwater

Offshore operations in water too deep for fixed platforms, typically beyond 500 meters.

deepwater drilling

Drilling in water depths needing floating rigs and subsea equipment.

deepwater play

Exploration in water depths beyond about 200 m, past the edge of the continental shelf.

deepwater project

A development in water too deep for fixed structures.

default and termination

The breaches that entitle a party to end the contract, and the process for doing so.

defect

A characteristic of a product, such as color, shape, or size that does not match the desired or design specifications.

defective product

A product that is unusable because it has one or more defects.

defensive driving

Driving to avoid an accident in spite of adverse road, traffic, weather, vehicle, light or glare conditions, or the incorrect actions of other drivers.

deferred income tax

Tax arising from timing differences between accounting profit and taxable profit.

Define, Measure, Analyze, Improve, Control

The five DMAIC phases, taken in order and gated.

definitive cost

The firm estimate produced once engineering is substantially complete.

deflector

Plate breaking the momentum of an incoming stream so it does not shear the liquid surface.

deflector flowmeter

A flowmeter that diverts the whole stream through its spinner using a basket or a partially inflated packer.

deflocculant

A thinner that disperses flocculated clay and lowers the viscosity and gel strength of a mud.

deflocculate

To break up flocculated clay structure with a thinner, reducing a suspension's viscosity.

deflocculated mud

A clay mud whose viscosity has been reduced by a chemical that separates the clay platelets from each other.

deflocculation

The dispersal of flocculated clay structure, lowering viscosity and gel strength.

defoamer

An additive that breaks foam by lowering the surface tension of the bubble film so trapped gas escapes.

defoamers

Additives that break foam in drilling fluid so density can be measured and pumps prime.

defoaming

Breaking foam so that density can be measured and pumps can prime.

defoaming plates

Inclined parallel plates or tubes in a separator that give foam bubbles a surface to coalesce against and collapse.

degasser

Surface equipment that strips entrained gas out of drilling mud before it is pumped back down the hole.

degradation

Breaking down the chemical composition of amine due to high temperatures.

degradation product

A compound formed as a solvent or oil breaks down, usually corrosive and always accumulating.

degree API

The API gravity scale for liquid density, defined so that lighter oils have higher numbers and water sits at 10 degrees.

degrees A.P.I.

Unit of measurement that indicates the gravity or weight of oil.

dehumidifier

A device that removes moisture from air.

dehydrate

To remove water from a substance — crude oil, natural gas or natural gas liquids.

dehydrating

Removing water from a gas or liquid stream.

dehydration

The removal of water from a substance, such as natural gas or glycol.

dehydration system

The equipment removing water from gas or liquid to meet specification.

dehydration unit

The plant section removing water from gas to meet dew point specification.

dehydrator

The vessel in which water vapor is removed from gas, usually by counter-current contact with glycol.

dehydrogenation

A reforming reaction in which hydrogen is removed and a naphthene is converted to an aromatic.

dekatherm

A unit of heat energy equal to a million British thermal units, used in gas contracts.

Delaware Basin

The western, deeper and more productive sub-basin of the Permian.

delay drilling payments

An annual payment made to a property owner, typically determined by the size of the property, paid in advance of oil and gas drilling activities.

delayed coker

The unit thermally cracking residue into lighter products and petroleum coke.

delayed gamma rays

Delayed gamma rays are the gamma rays given off by the daughter product.

delayed start

A defensive driving technique used when starting up at a stop sign or traffic light. It involves counting to three before taking your foot off the brake and then looking left, right and left again before moving.

delegated authority

The decision rights passed down with a task, without which delegation is only instruction.

delegation

Assigning work and the authority to do it, while retaining accountability for the outcome.

delimiter

A punctuation mark that separates parts of an address.

delineation

Establishing the extent of a discovery through appraisal.

delineation drilling

Appraisal drilling aimed specifically at mapping the extent of a discovery.

deliverability

The rate at which a well or storage facility can deliver, as distinct from how much it holds.

deliverability test

A test flowing a well at several rates to establish what it will deliver against a given wellhead or reservoir pressure.

deliverable

A defined output the project must hand over.

delivering value

Judging progress by benefit released rather than by tasks completed.

delta

The body of sediment built where a sediment-laden river enters standing water and drops its load.

delta connection

A connection in a three-phase AC system in which three coils or windings are connected end to end, with the load attached to each of the three junctions between the windings.

Delta Energy Corridor (stakeholder simulation)

The stakeholder simulation set on a Nigerian pipeline project with competing community and government blocs.

delta plain

The low-relief surface of a delta above the shoreline, with channels and marsh.

delta rho

The correction curve on a density log, showing how much the long-spacing reading was adjusted using the short-spacing detector.

delta t

Interval transit time: the time a sonic wave takes to cross one foot of formation, in microseconds, and the reciprocal of velocity.

delta t stretch

A sonic log error in which a weak arrival triggers the far receiver late, biasing the interval transit time longer than it should be.

delta-connected stator

A stator in which the coils are connected end to end.

deltaic

Pertaining to a delta — its environment, processes and deposits.

deltas

River-mouth deposits, among the most productive reservoir settings.

deluge system

A type of fire protection system that automatically dumps large amounts of water in an area in response to a fire, with valves opening due to the heat from the fire.

demand

The amount of power needed by a power system's customers.

demand chain

The chain viewed from the customer backward rather than from supply forward.

demand forecasting

Estimating future demand as the basis for production and inventory planning.

demand-type respirator

A type of air-supplied respirator in which air is supplied to the wearer on demand as the wearer inhales.

demethanizer

A type of fractionating tower used to remove entrained methane from the liquid product of a cryogenic plant.

demineralizer

The ion exchange plant removing dissolved salts from water.

demister

A pad or vane bank removing entrained droplets from gas.

demister pad

A device in a distillation column that prevents entrained liquid from carrying over with the overhead product vapors.

demulsification

The process of breaking an emulsion.

demulsifier

A chemical that is added to crude to help speed up the breakdown of the water/oil emulsion in the desalter.

demurrage

Compensation owed to the shipowner when loading or discharge exceeds the agreed laytime.

denitrification

A hydrotreating reaction in which hydrogen is used to remove nitrogen.

denominator

In a fraction, the number below the fraction bar, indicating how many parts a whole unit has been divided into.

dense phase

The area at the bottom of a regenerator where the greatest concentration of catalyst is located and where most of the combustion takes place.

denser

Of greater mass per unit volume, which determines where a fluid sits in the reservoir.

densimeter

An instrument measuring the density or specific gravity of a fluid stream, including mixtures of gas, liquid and solids.

densitometer

A device which measures the mass or weight per unit of volume.

density

The mass per unit volume of a substance (volumetric mass density).

density bubbler system

A system that measures the density of a liquid by using differential pressure.

density contrast

The difference in density between adjacent rock bodies, which is what a gravity survey actually senses.

density correction curve

The density correction curve shows how much correction has been applied to the bulk density data to compensate for borehole irregularities, rugosity and mud cake.

density current

A current that flows beneath surrounding water because it is denser, driven downslope by gravity.

density logging

Logging formation bulk density from gamma ray scattering, the most direct porosity measurement.

density measurement

A log of formation bulk density, derived from the attenuation of gamma rays between a source and detector by Compton scattering.

density porosity, density log, density logging tool

Density porosity is a formation's porosity calculated only using a density log.

density profile

A set of gravity measurements taken across a topographic feature to determine the near-surface density that best flattens the anomaly.

density-neutron crossplot

The paired log display from which porosity and lithology are read together.

department of transportation (DOT)

The U.S. government agency charged with regulating the transportation of hazardous materials.

departure curve

A chart showing how borehole size, mud, temperature or bed thickness shifts a log reading away from its ideal response.

dependent variable

In a ratio control system, the variable that is tied to a percentage of the independent variable.

dependent vs. independent demand

Demand derived from producing something else against demand arising directly from customers.

depleted gas

A produced-out gas reservoir, often reused for storage.

depleted reservoir storage field

A depleted gas or oil field, used for storing and cycling of natural gas.

depleted zone

An isolated part of a reservoir whose pressure has fallen below that of the surrounding rock through production.

depletion

The decline in reservoir pressure, and in remaining recoverable volume, caused by producing fluids out of the reservoir.

depletion region

The area along a P-N junction that is nearly depleted of electrons and holes, where electrons from the N-type material and holes from the P-type material have drifted across the junction and recombined.

depletion type MOSFET

A MOSFET that has a channel across it. Current flow through the channel is controlled by the capacitance effect between the gate and the substrate. When the gate potential is negative with respect to the source, the MOSFET is in the depletion mode. When the gate potential is positive with respect to the source, the MOSFET is in the enhancement mode.

deployment system

A stack of lubricator sections and rams that lets a tool string longer than the lubricator be run into a live well in stages.

depocenter

A basin's depocenter is an area of maximum deposition, or the geographic location of the thickest part of any specific geographic unit in a depositional basin.

deposit

Sediment that has accumulated after transport by wind, water or ice.

depositional

Relating to how sediment was laid down, which controls reservoir quality and continuity.

depositional energy

The kinetic energy of the environment in which sediment is laid down.

depositional environment

The combination of physical, chemical, and biological processes associated with the deposition of a particular type of sediment, describing the conditions under which sediments are deposited.

depositional environment, environment of deposition

Depositional environment, or sedimentary environment, describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment.

depositional fabric

Depositional fabric, also known as primary fabric, is a type of “fabric” in sedimentary rocks that develops while sediment is accumulating. It results from the orientation of the crystals or grains that make up a sedimentary rock.

depositional facies

The rock character produced by a particular depositional environment.

depositional history

The sequence of environments that built the succession.

depositional model

A conceptual picture of how and where the sediment was laid down, used to predict away from wells.

depositional sequence

A package of strata bounded by unconformities, deposited during one cycle of sea level.

depositional sequence boundary

The surface bounding a depositional sequence, usually an unconformity.

depositional setting

The environment in which sediment accumulated, which predicts reservoir geometry.

depositional surface

The surface on which sediment was accumulating at a given time.

depositional system

A three-dimensional assemblage of genetically related facies deposited by one set of processes — a delta, a fan, a shelf.

depreciation, depletion and amortization (DD&A)

The accounting charge spreading the cost of assets and reserves over the periods they earn in.

depropanizer

A tower that removes propane from isobutane through fractionation.

depth control

The measurements and equipment that fix where a tool or treatment actually sits in a well, tied back to a reference log.

depth controller

A device clamped to a marine streamer that holds it at a set depth in the water.

depth conversion

The transformation of seismic data from the traveltime domain in which it is recorded into depth, using a velocity model.

depth correlation

Matching measured depths against known features on a reference log, so that later operations are placed on the same depth scale.

depth datum

The fixed point in a well from which all depths are measured — the rotary table, kelly bushing or another agreed reference.

depth interval

The depth range a measurement or unit covers.

depth map

A contour map of a subsurface horizon in depth, converted from seismic traveltimes with a velocity model.

depth mark

A magnetic mark placed at intervals along a logging cable and read at surface as the depth reference.

depth matched

Describing two or more log curves that have been shifted so their features line up on the same depth scale.

depth matching

The practice of shifting one dataset's depths onto another that is known to be on depth.

depth micrometer

A micrometer used to measure the depths of holes and recesses; accurate to the nearest .001 inch, or , 01 mm. Also called a depth gauge.

depth migration

Migration that moves reflections to their correct positions and outputs directly in depth, using an interval velocity model.

depth of invasion

How far mud filtrate has displaced formation fluid radially into the rock around the borehole.

depth of investigation

How far into the formation a logging measurement effectively senses, from the tool face or borehole wall.

depth point

The subsurface point beneath a surface location for which a horizon depth has been computed.

depth reference

The fixed point in a well from which depth is measured, set at the start of an operation.

depth reference point

The fixed surface point from which all well depths are measured, usually the rotary table or kelly bushing.

depth section

A seismic display whose vertical axis is depth rather than traveltime.

depth wheel

The calibrated measuring wheel that drives the depth recording system of a wireline unit.

depth-derived

A borehole compensation scheme for sonic logs that combines readings taken with the tool at two different depths rather than from paired transmitters.

derailer

A device that fits over rails and prevents oncoming tank cars from running into a tank car spotted at a loading rack.

derivative control

A process control algorithm (sometimes called rate control) in which the control output is proportional to the rate of change of either the process variable or the error between the process variable and the set point, producing faster corrective action than proportional control alone.

derivative instrument

A contract whose value is derived from an underlying price rather than from any physical holding.

derivative logs

Curves computed from other logs to show how fast a measurement is changing with depth.

derrick

The structure used to support the crown blocks and drill string of a drilling rig, usually pyramidal in shape offering a good strength-to-weight ratio. Also, any of several types of stationary cranes used primarily for lifting loads.

derrick floor

The working platform of the rig where the crew handles pipe and operates the drilling equipment.

derrickman

The crew member who works on the platform up the derrick, handling the top of the pipe stand while tripping.

DES (Delivered Ex Ship)

The seller delivers on board at the discharge port, bearing the voyage risk throughout.

desalination

Removing salt from water, relevant because electrolysis needs water far purer than seawater.

desalter

A component of a crude unit in which water containing salt separates from the crude and is removed.

desalting

Washing salt out of crude before distillation to prevent corrosion and fouling.

desander

A hydrocyclone that removes the coarser drilled solids from whole mud, downstream of the shale shakers.

desanders

Hydrocyclones removing sand-sized solids from drilling fluid.

descriptive analytics

Analysis describing what has happened, without projecting forward.

descriptive statistics

Summary measures describing a data set without inferring beyond it.

desiccant

A drying agent or substance used to remove water, such as activated alumina, silica gel, or glycol.

design injection rate

The rate a facility or well is engineered to accept.

design parameter

A value fixed in design, which the built equipment then has to be operated within.

design specification

The conditions equipment was built for, and the boundary beyond which its ratings no longer hold.

design winter

The potential gas demand for the coldest winter in 50 years and the coldest historical peak 10-day period in January (Northern Hemisphere), or July (Southern Hemisphere).

designated area

An area that may be used for work with “select carcinogens,” reproductive toxins, or substances that have a high degree of acute toxicity.

desilter

A hydrocyclone like a desander but built from a larger number of smaller cones, so it removes finer solids.

desilters

Hydrocyclones removing fine solids from drilling fluid.

desired setpoint

The value a controller is asked to hold, as distinct from the value it currently reads.

desorption

The process of regenerating an activated carbon bed by removing contaminants.

destination clause

A restriction on where the buyer may deliver the cargo, limiting resale.

desulfurization

Removing sulfur from a stream to meet product specification.

desulfurize

To strip sulfur compounds out of a hydrocarbon stream, usually to meet a product or emissions specification.

desuperheater

A device that sprays water into steam flowing through a superheater, reheater, or line to control steam temperature; also called a spray attemperator.

desuperheating section

A baffled section inside the shell of a closed heater through which superheated extraction steam flows.

detail (A point)

Detail (A Point) To display on-screen all the information contained in a DCS relating to a specific point in a loop or process, such as configuration or alarm settings, process variable, related output devices, etc.

detail drawing

An enlarged-view drawing that shows special features of a structure more clearly.

detail log

A log printed at an expanded depth scale, typically 1:200 or 1:40, to show bed-scale detail.

detectable limit

The thinnest bed that produces a recognisable amplitude response on seismic, well below the thickness that can be resolved.

detection system

The instruments and logic sensing a hazardous condition and raising alarm.

detector

In a level measurement system that uses radiation, the part of the system that absorbs the directed beam of radiation and converts the radioactive energy into a proportional electrical current.

detector switch

A switch operating on a sensed condition, giving an alarm or a trip rather than a reading.

detergency

A chemical's ability to lift a contaminant off a solid surface and keep it suspended.

determinant

The scalar computed from a matrix, used in solving simultaneous equations.

determinism

An approach giving one definite answer from the input data, rather than a distribution of possible answers.

deterministic

If something is deterministic, you have all of the data necessary to predict (determine) the outcome with 100% certainty.

deterministic deconvolution

Deconvolution in which the filter to be removed is measured or otherwise known, rather than estimated statistically from the data.

deterministic methods

Methods that produce a single answer from fixed equations or algorithms, with no explicit representation of uncertainty.

deterministic model

A deterministic model does not include elements of randomness. Every time you run the model with the same initial conditions you will get the same results.

deterministic versus probabilistic analysis

Working with single best estimates against working with full distributions.

detonate

To initiate an explosive so that it decomposes in a supersonic shock wave rather than merely burning.

detonating cord

Flexible cord filled with high explosive, used to carry detonation from the detonator to each charge in a perforating gun.

detonator

A small, electrically fired charge that initiates a larger and less sensitive explosive.

detraining tank

A tank in a seal oil system that allows oil to stand so that trapped air or hydrogen can bubble off before the oil is reused.

detrital

Pertaining to particles derived from the mechanical breakdown of pre-existing rock by weathering and erosion.

detritus

The particles produced by mechanical breakdown of pre-existing rock, before or after transport.

developed acreage

The number of acres that are allocated or assignable to productive wells or wells capable of production.

developed reserves

Reserves that can be expected to be recovered through existing wells with existing equipment and operating methods or in which the cost of the required equipment is relatively minor compared to the cost of a new well and, if extraction is by means other than a well, through installed equipment and infrastructure operational at the time of the reserves estimate.

development

The phase after a successful exploration and appraisal program, in which wells and facilities are built to bring a field on production.

development phase

The phase of petroleum operations in which a proven oil or gas field is brought into production by drilling development wells and constructing surface processing and field pipeline facilities.

development well

A well drilled within the proved area of an oil or gas reservoir to the depth of a stratigraphic horizon known to be productive.

development wells

Development wells are drilled to economically drain the reservoir. Some of these wells are drilled at the outset, while others are added later in the life of the field as production begins to decline. To enhance recovery, fluids such as water, gas, carbon dioxide (CO₂), chemicals, or steam may be injected into the reservoir at a later stage.

deviated

Drilled at an angle from vertical rather than straight down.

deviated hole

A wellbore that is not vertical, usually because it was intentionally drilled away from vertical.

deviated wellbore

A hole drilled at an angle from vertical.

deviation

The difference between the set point and the value of a process variable; also called error.

deviation amplifier

The amplifier producing an output proportional to the difference between measurement and setpoint.

deviation survey

A measurement of the inclination and azimuth of the wellbore at a given depth, from which its position in space is computed.

device function numbers table

A table that identifies the general functions of many electrical devices in terms of number designations.

DeviceNet

Allen-Bradley's proprietary network for connecting individual input and/or output devices and their power sources to a PLC system.

DeviceNet protocol

A standard communications protocol that governs the transmission of data through networks.

dew point

The temperature at which vapor condenses into a liquid. Used as a measure of water vapor or hydrocarbon content in natural gas.

dew point depression

The amount which the dew point is lowered.

Dewar flask

A Dewar flask is a glass or metal container made like a vacuum bottle.

dewatering

The removal of water from a water-base mud, so solids can be discarded and the liquid phase reused.

dextral

Describing a strike-slip fault on which the block across the fault has moved to the right as seen by an observer facing it.

DH+

Data Highway Plus. An Allen-Bradley peer network for connecting members of the PLC-5 family, some newer members of the SLC-500 family, PCs, and high-end HMIs together.

DH-485

Data Highway 485. An Allen-Bradley peer network for connecting members of the SLC-500 family, PCs, and low-end HMIs together.

diagenesis

The process by which sediments are lithified into sedimentary rocks through physical, chemical, and biological changes that occur during and after burial, including water-rock interactions, microbial activity, and compaction. Diagenesis transforms sediments into sedimentary rocks, altering their mineralogy, texture, and other properties.

diagenesis, diagenetic

Diagenesis is the term for the physical and chemical changes occurring during the conversion of sediment to sedimentary rock.

diagenetic

Diagenesis is the physical and chemical changes that occur when sediment is transformed into sedimentary rock, which involves processes such as mineral dissolution, precipitation, and microbial reactions.

diagenetic porosity

Secondary porosity created after deposition, typically by dissolution or dolomitization.

diagnostic output

The report an assessment produces, useful only if it leads to a development action.

diagnostic test

An assessment taken beforehand to establish what the learner already knows.

diagram abbreviations table

A table that lists abbreviations commonly used to identify components in an electrical system.

diagrammatic

Presented as a simplified diagram rather than to scale.

diagrams and figures

Illustrations that appear in the NFC.

dial indicator

A precision measurement instrument that indicates values using a pointer and a scale, often in 1 mil increments, used to determine variance in the dimensions of a rotating surface and to measure very small movements, usually to the nearest 0.001 inch.

dial indicator reading

The displacement a dial indicator shows during alignment.

dial indicator stem

The contacting plunger of a dial indicator.

diameter

The length of a straight line passing through the center of a circle from one side to the other.

diameter of invasion

The diameter of the zone around the borehole into which mud filtrate has displaced the original formation fluid.

diameter of investigation

How far out from the borehole axis a logging measurement effectively senses.

diamond bit

A drilling bit that cuts by dragging industrial diamonds across the rock face rather than by crushing it with rolling cones.

diaphragm

In a turbine, a stationary part that contains blades or nozzles to direct steam between rotating blade sets. In a valve, a flexible material that serves as the flow control component.

diaphragm actuator

An actuator using air pressure on a flexible diaphragm against a spring.

diaphragm pressure element

A type of pressure element that has a plate, or diaphragm, that flexes in response to changes in pressure and moves a pointer through a mechanical linkage.

diaphragm pump

A reciprocating pump that uses a flexible diaphragm to move fluid.

diaphragm valve

A valve that uses a flexible diaphragm instead of a disc to control fluid flow.

diapir

A mobile mass of low-density material — usually salt or overpressured shale — that has risen and intruded into the rock above it.

diapirism

Diapirism is the process in which buoyant and deformable material, such as salt, rises through the surrounding rocks, forming a bulbous-like structure.

diapirs

Bodies of salt or mud that have risen through overlying rock, forming traps around their flanks.

diatom

A microscopic single-celled alga with a silica cell wall, or frustule, living in fresh and salt water.

diatomaceous

Consisting of, or containing, the siliceous remains of diatoms.

diatomaceous earth

A siliceous sediment used as a filter medium and forming some unusual reservoirs.

diatomite

A soft, silica-rich rock made of diatom remains — the indurated equivalent of diatomaceous earth.

dichromate salt

A salt containing the dichromate ion, in which chromium is in the plus-6 state, such as potassium dichromate.

dielectric

An insulating material that stores energy in an applied electric field by polarizing rather than conducting.

dielectric constant

The ratio of the permittivity of a substance to the permittivity of free space, measuring the ability of a substance to store electrical energy in an electric field. It is the electrical equivalent of relative magnetic permeability.

dielectric log, dielectric propagation log

A dielectric log measures the high frequency (on the order of 25 MHz) dielectric properties of the formation. The log usually includes two curves: the relative dielectric permittivity, symbolized by epsilon which is unit less, and the resistivity in ohm-m.

dielectric log, dielectric propagation log, dielectric

A dielectric log measures the high frequency (on the order of 25 MHz) dielectric properties of the formation. The log usually includes two curves: the relative dielectric permittivity, symbolized by epsilon which is unit less, and the resistivity in ohm-m.

dielectric permitivity

A physical property which characterizes the degree of electrical polarization a material experiences under the influence of an external electric field.

dielectric permittivity

The degree to which a medium resists the flow of electric charge, defined as the ratio of electric displacement to electric field strength. It characterizes the degree of electrical polarization a material experiences under an external electric field.

dielectric propagation log

A log measuring the formation's dielectric permittivity at high frequency, around 25 MHz and above.

dielectric resistivity

Formation resistivity computed from the attenuation and phase shift of a high-frequency electromagnetic measurement.

diesel engine

The compression-ignition engine driving rigs, pumps and marine propulsion.

diesel fuel

The middle distillate fuel used in compression-ignition engines.

diesel index

An older calculated measure of diesel ignition quality, derived from gravity and aniline point.

diesel-oil mud

An oil-base mud whose continuous phase is diesel.

diesel-oil plug

A slurry of bentonite or cement mixed in diesel, pumped as a pill that thickens on contact with water downhole.

dietary guidelines

Published nutrition standards used in workplace catering and wellness advice.

diethanolamine (DEA)

A type of amine that consists of one nitrogen atom, one hydrogen atom, and two ethanol molecules.

dietz

The shape factor accounting for drainage area geometry in well test analysis.

difference map

A map of the change between two other maps — two survey vintages, or an observed field minus a modeled regional trend.

differential

A method of transmitting signal data in which the data always includes opposite states.

differential amplifier

An op amp circuit that is a combination of an inverting amplifier and a non-inverting amplifier; the output depends on the difference between the signals applied to the input terminals.

differential compaction

The development of different compaction, and so different geometry, between adjacent sediment bodies that started at similar levels.

differential encoder

A type of encoder in which the transmitted signal data always includes opposite states.

differential expansion

An uneven response to temperature change that is experienced by components such as the rotor and shell of a turbine.

differential gain error

The change in ac gain with change in dc level.

differential input resistance

The small-signal resistance between two ungrounded input terminals.

differential input voltage

The voltage at the non-inverting input with respect to the inverting input.

differential pay

Additional pay for conditions such as shift, hazard or location.

differential pen

The recorder pen tracing differential pressure on a circular chart.

differential phase error

The change in AC phase with change in DC level.

differential pressure

The difference between two related pressures, such as inlet and outlet pressures in a heat exchanger, or upstream and downstream static pressures in a pipe. Often measured in inches of water. In reciprocating compressors, it operates the suction and discharge valves.

differential pressure (D/P) cell

A device used to measure the difference between two related pressures, such as an indirect level measurement device that measures the pressure difference from the bottom to the top of a tank.

differential pressure flowmeter

A meter inferring flow from the pressure drop across a restriction.

differential pressure indicator

Gauge showing the pressure drop across a filter or exchanger, the usual sign it is fouling.

differential pressure sticking

Sticking that occurs when pipe rests against filter cake opposite a permeable formation whose pressure is below that of the mud column.

differential pressure transmitter

The instrument transmitting the pressure difference between two points, the commonest flow and level device.

differential range

The span of differential pressure a device is calibrated over, outside which its reading is not valid.

differential relay

A relay that compares current going to a device with current leaving the device and trips circuit breakers to isolate a fault under undesirable conditions.

differential SP

The SP measured between two closely spaced electrodes rather than against a surface reference, giving the rate of change of potential with depth.

differential spectrum

An NMR technique that subtracts T2 distributions acquired at different polarization times, isolating the fluids that respond differently between them.

differential spectrum method

The differential spectrum method (DSM) in NMR logging is a commonly-used commonly used fluid identification method.

differential sticking

Sticking caused by the pressure difference between the mud column and a permeable formation pressing the pipe into the filter cake.

differential stress

Differential stress is the difference between the greatest and the least compressive stress experienced by an object.

differential temperature log

A log of the difference in temperature between two closely spaced sensors, rather than absolute temperature against depth.

differential weathering correction

The part of the static correction that removes the varying delay between one receiver station and the next.

differentiator

A circuit that develops a constant output voltage, given a changing input voltage over a period of time.

difficult behaviour types

The recurring patterns — aggressive, passive, negative, unreliable — each needing a different response.

difficult conversation

A discussion avoided because it risks a strong reaction, and which grows worse for waiting.

difficult employee

Someone whose behavior, not capability, is the problem.

difficult to disperse

Said of a cement whose rheology changes little as dispersant is added.

difficult to disperse in salt

Said of a cement that resists dispersion when mixed on salt water.

diffraction

The radial scattering of seismic energy from a point discontinuity such as a fault edge or a pinchout, recorded as a hyperbolic event.

diffraction hyperbola

The hyperbolic pattern a point scatterer produces before migration collapses it.

diffraction hyperbolas

The curved patterns point scatterers produce before migration collapses them.

diffraction stack

Migration by summing amplitudes along the diffraction traveltime curve for each output point — Kirchhoff migration.

diffuser

A set of stationary vanes that surround an impeller in a centrifugal pump, directing fluid away from the impeller and converting fluid speed into pressure while minimizing radial thrust.

diffusion

The movement of ions or molecules from higher to lower concentration by random molecular motion.

diffusion equation

The partial differential equation describing how a quantity governed by diffusion spreads in space and time.

diffusion models

Generative models that produce data by starting from noise and removing it step by step until structured output remains.

diffusion of responsibility

Nobody acting because everyone assumes someone else will.

diffusion relaxation

NMR signal decay caused by protons diffusing through magnetic field gradients while the measurement is being made.

diffusivity

Diffusivity (D) in NMR logging is a measure of the extent to which molecules move at random in the fluid.

digital

An electronic signal that uses two discrete states (such as 1 and 0) to represent analog or varying measurements. Also refers to two-way communication between a smart field device and a controller or DCS, and to data in the form of digits or numbers.

digital circuit

A circuit that functions like a switch, in that it is either "on" or "off'; more correctly called a binary circuit.

digital data

Digital data is information represented as a string of discrete symbols each of which can take on one of only a finite number of values from some alphabet, such as letters or digits.

digital display

A display that shows numeric values; used in test instruments that employ solid-state integrated circuits.

digital forensics

Recovering and analyzing evidence from systems in a way that stands up to scrutiny.

digital instrumentation and controls

Electronic sensing and control replacing pneumatic and analog equipment.

digital leadership

Leadership capable of setting direction and building capability for digital change.

digital logic circuit

See Logic circuit.

digital logic element

See Logic gate.

digital maturity model

A scale placing an organization's digital capability, used to set realistic next steps.

digital meter

An instrument that expresses a variable value as a series of numbers, which can either be electronically lighted or displayed on a mechanically rotated set of wheels.

digital multimeter

A handheld instrument displaying voltage, current and resistance digitally.

digital signals

On/off signals that can be considered as a series of electrical pulses or information bits.

digital transformation

Changing how a business operates using digital technology, not merely digitizing existing steps.

digital twin

A model of a physical system kept continuously updated from its live sensor data, so it tracks the real asset.

digitalization

Converting processes and information into digital form so they can be automated and analyzed.

digitization

Digitization is the conversion of text, pictures, or well log curves into a digital form that can be processed by a computer.

digitizing

Converting an analog record or a paper log into numerical form.

digits

Figures that are used to represent numbers in a number system; the base ten number system has ten digits.

dike

A walled containment area or barrier that surrounds one or more above ground storage tanks, used to confine liquids in an enclosed space.

dilatancy

The increase in bulk volume of a rock as it deforms, typically as microfractures open before failure.

dilatancy theory

The proposal that rock under stress opens microcracks and increases in volume before it fails, changing its P to S velocity ratio.

dilatation

The fractional change in volume of a body under applied stress.

dilatational wave

A compressional wave, in which particles move along the direction of travel and the medium alternately compresses and expands.

diluent

A light hydrocarbon blended into heavy oil or bitumen to cut its viscosity enough for pipeline transport.

dilute phase

The area at the top of a regenerator where there is less concentration of catalyst and very little combustion takes place.

dilute solution

A solution that contains a relatively small amount of dissolved solute per unit volume of solution.

dilution

Adding fresh liquid phase to the active mud system to reduce solids content and hold properties in specification.

dilution water

The water added to a fluid stream to dilute it — in desalting, the wash water mixed into the crude to dissolve salt.

dim spot

A local reduction in seismic amplitude that can indicate hydrocarbons, where the fluid change lowers rather than raises the reflection coefficient.

dimensionless

Expressed as a pure ratio, so the result holds regardless of the units used.

dimensionless fracture conductivity

The ratio comparing a fracture's flow capacity to the formation's, which sets treatment design.

dimensionless pressure

Pressure expressed as a ratio, so type curves apply regardless of the units or scale.

dimensions of wellness

The distinct aspects — physical, emotional, social, financial, occupational — that make up well-being.

diode

An electrical device that allows the passage of current in one direction only; typically used to convert AC into DC.

dip

The magnitude of the inclination of a plane from the horizontal.

dip angle

The angle a bed makes with horizontal.

dip azimuth

The compass direction of dip.

dip direction

The compass direction of steepest descent of a bed.

dip fault

A fault whose displacement is along the dip of the fault plane, and whose trace runs parallel to the regional dip direction.

dip leg

A pipe dipping below a liquid level so gas cannot pass, or returning solids from a cyclone.

dip line

A seismic line shot along structural dip, giving the truest cross-section.

dip moveout

A processing correction removing the effect of reflector dip from a gather, so that dipping and flat events can be stacked together correctly.

dip pattern

The way dip changes with depth, read to identify faults, unconformities and sedimentary features.

dipmeter

A dipmeter, sometimes termed a diplog depending on the logging service company, is a well logging instrument designed to determine the direction and angle of dip of geological formations.

dipmeter data

Borehole measurements of bed orientation, from which structure and depositional features are read.

dipmeter log

The recorded bed orientations against depth.

dipmeter tool

The wireline tool measuring bed orientation from multiple pad contacts.

dipmeter, dip

A dipmeter is a tool for measuring the formation dips in a wellbore.

dipmeter/diplog

A dipmeter (sometimes termed a diplog depending on the logging service company) is a well logging instrument designed for determining the direction and angle of dip of geological formations.

dipole

A pair of equal and opposite charges, poles or forces separated by a distance.

dipole field

The field of a dipole source, symmetric about its axis — and, for the Earth, the dominant part of the main magnetic field.

dipole sonic logging tool

A diploe sonic logging tool is a sonic array tool in which sources are dipoles, as opposed to radially symmetric monopoles, so that it generates both P- and S-waves in formations.

dipping bed

A layer of rock inclined from horizontal.

dipstick

A calibrated rod specifically designed to read liquid levels on a particular engine or piece of machinery. When a dipstick is inserted into and withdrawn from a liquid, the level is the point at which the liquid no longer coats the rod.

dipswitches

Small on/off switches that are frequently used for configuring PLCs.

direct acting

A controller setup in which an increase in the value of the input causes an increase in the value of the output.

direct current

Current that flows in only one direction.

direct current (DC)

Current that flows in only one direction.

direct emulsifier

The surfactant that disperses oil as droplets through the water phase of an emulsion mud.

direct hydrocarbon indicator (DHI)

A direct hydrocarbon indicator (DHI), is any seismic attribute that indicates the presence of hydrocarbons. DHIs are particularly useful in hydrocarbon exploration for reducing the risk of exploration wells. DHIs most commonly occur as bright spots, a local high amplitude anomaly which are displayed with bright colors so as to stand out from background amplitude variation, or as flat spots, which are horizontal reflectors that cross existing stratigraphy and indicate a hydrocarbon fluid level within an oil or gas reservoir.

direct hydrocarbon typing

Identifying the hydrocarbon type — gas, light, medium or heavy oil — from NMR data alone, without other logs.

direct level measurement device

A device that indicates level based on the distance between the surface of the substance being measured and some reference point.

direct measurement

A quantity measured rather than inferred from something else.

direct report

An employee who reports to a given manager without an intervening level.

direct-fired heater

Heater whose burner heats the process fluid through a firetube, with no intermediate medium.

direct-indicating viscometer

The rotational instrument that reads drilling mud viscosity and gel strength directly from a dial at standard speeds.

directional control valve

A hydraulic valve routing flow to select the direction an actuator moves.

directional driller

The specialist responsible for steering a well along its planned three-dimensional path.

directional drilling

The application of special tools and techniques to drill a wellbore at a predetermined angle. Horizontal drilling is a form of directional drilling where the wellbore is ultimately drilled at +/- 90 degrees to the vertical direction.

directional overcurrent

Overcurrent protection responding only to fault current flowing in one direction.

directional overcurrent relay

An overcurrent relay unit and a directional relay unit combined in a single case.

directional permeability

Permeability that differs with the direction of flow through the rock.

directional relay

A relay responding to the direction of power or current flow.

directional survey

A measurement of the inclination and azimuth of a wellbore at a given depth, used to compute its position in space.

directional unit

Part of a directional overcurrent relay that operates when current flow is in an undesirable direction.

directional variograms

Variograms computed along specified azimuths, so spatial continuity can be compared direction by direction.

directional well

A well deliberately steered along a non-vertical path to reach a target offset from the surface location.

directivity

The variation of a source's output — amplitude, frequency or waveform — with the direction in which the energy leaves it.

dirty

Describing a sedimentary rock that contains an appreciable proportion of clay minerals.

dirty tanker

A tanker carrying crude or fuel oil.

disaggregated sample

A disaggregated sample is one that is no longer held together by cement.

disaster recovery plan (DRP)

The plan for restoring systems and data after a major failure.

disbonding

Detachment of a protective coating from the pipe surface it was applied to.

disbonding of coating

The failure of a coating to adhere to the substrate to which it was applied. It is a loss of adhesion between a cathodic coating and its metal substrate due to a cathodic reduction reaction (corrosion reaction) taking place.

disc

A movable part of a valve that presses against a seat to stop fluid flow. In safety valves, it is the part that blocks the path between the inlet and outlet.

disc burst

A rupture disc opening, which relieves pressure but does not reseat.

discharge air

Air leaving a compressor or fan.

discharge gas

Gas leaving a compressor, at raised pressure and temperature.

discharge line

The line carrying flow away from a machine.

discharge nozzle

The connection fluid leaves a machine or vessel through.

discharge pipe

The pipe carrying flow away from a machine.

discharge piping

The pipework carrying flow from a machine.

discharge port

Where the cargo is delivered and unloaded.

discharge pressure

The pressure at the discharge port of a compressor.

discharge ring

A component of a multistage centrifugal pump that mounts onto the shaft and prevents leakage between two stages; may also be called a stage piece.

discharge side

The outlet side of a machine.

discharge stroke

The part of a reciprocating cycle that delivers fluid.

discharge valve

The valve on a machine's outlet.

discharge valves

Valves which open to discharge compressed gas.

discoloration

A change of color, often the first visible sign of overheating.

disconformity

A disconformity is an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition.

disconnect device

A device capable of breaking the electrical connection between a motor branch circuit and a power source.

discontinuity

A boundary at which a physical property, such as seismic velocity, changes abruptly.

discount rate

The rate used to bring future money to present value, reflecting cost of capital and risk.

discounted cash flow (DCF)

Valuing a project by restating all future cash flows at today's worth.

discovery

A petroleum accumulation for which one or more exploration wells have established the existence of a significant quantity of potentially moveable hydrocarbons.

discovery stage

The earliest phase, where an opportunity is identified and tested before commitment.

discrete

Discrete In process control, generally a reference to output devices, such as valves or pumps, that are used in only two possible states: on or off, open or closed, etc.

discrete (bit) module

A type of I/O module that handles an individual input or output device on each of its terminals.

discrete component

A component that functions individually in a circuit.

discrete device

A device that switches between only two states: on and off, closed and open, etc.

discrete fracture network (DFN)

A discrete fracture network (DFN) refers to a computational model that explicitly represents the geometrical properties of each individual fracture (e.g., orientation, size, position, shape and aperture), and the topological relationships between individual fractures and fracture sets.

discrete input

An on-off signal brought into a control system.

discrete output

An on-off signal a control system sends out.

discrimination

Acting on prejudice or bias so that someone is treated less favorably.

discrimination complaint

A formal allegation that a decision rested on a protected characteristic.

discussion [evidence]

Discussion enables a holistic approach to assessment that can test the validity and reliability of other evidence. In order to be successful, it must be well planned. Considerations during the planning for this type of method include:

• What is purpose?
• What is required outcome?
• Does it meet evidence requirement, or fill gaps?

discussion forum

An asynchronous space where learners debate and extend the material.

disengage

Release a mechanical connection so the driven part is free.

dish structures

Dishes are a type of sedimentary structure formed by liquefaction and fluidization of water-charged soft sediment either during or immediately following deposition. These structures are most commonly found in turbidites and other types of clastic deposits that result from subaqueous sediment gravity flows.

disharmonic

Describing folds whose shape changes from layer to layer, because the layers have different mechanical properties.

dislocation

A defect in crystal structure, and a displacement along a fault.

dispersant

A chemical that keeps fine particles or droplets separated in a medium, preventing them from aggregating.

dispersants

Chemicals that separate aggregated particles, used in mud and in oil spill response.

dispersed bubble flow

A multiphase regime in which gas is carried as fine bubbles distributed through a continuous liquid, without coalescing into slugs.

dispersed clay

Clay distributed through the pore space of a sand rather than laminated or structural, so it occupies porosity and lines pore throats.

dispersed contact leaching

A type of leaching system that removes a soluble component from solid particles that are suspended in the solvent; both the particles and the sol vent are in motion during the time of contact.

dispersed shale

Shale distributed through the pore space rather than as beds.

dispersion

In physics, dispersion describes the effect on the properties of a wave traveling through a medium. In statistics, a term describing the size of the distribution of values expected for a particular variable, measurable by range, variance, and standard deviation.

dispersive

Varying with frequency, which spreads a wave as it travels.

displace

To push one fluid out of the pore space or the wellbore with another.

displacement

The offset between points or segments that were once continuous — across a fault, or between an original and a final position.

displacement efficiency

The fraction of oil removed from the pore volume that a displacing fluid has actually contacted.

displacement fluid

The fluid pumped behind a cement slurry to push it out of the casing and up into the annulus.

displacement front

The moving interface between an injected fluid and the reservoir fluid it is pushing.

displacement pump

A pump delivering a fixed volume per cycle.

displacer

A level measurement device that operates on the principle of buoyancy—a cylinder or sphere suspended in a liquid whose apparent weight changes are proportional to changes in level. Also, a piston or sphere that displaces a fixed volume of fluid in a pipe prover.

display advertising

Visual advertising placed on websites and apps rather than in search results.

disposal well

A well used to inject waste fluid, usually produced water, into a subsurface formation for permanent disposal.

dispute resolution

The agreed route — negotiation, expert, mediation, arbitration — for settling disagreements.

Dispute Settlement Negotiation (DSN)

Negotiating to resolve an existing disagreement.

dissimilarity

The seismic attribute measuring how unlike neighboring traces are, which highlights faults.

dissipate

Dissipation embodies the concept of a dynamical system where important mechanical models, such as waves or oscillations, lose energy over time, typically from friction or turbulence. The lost energy converts into heat, which raises the temperature of the system. Such systems are called dissipative systems.

dissolved contaminant

A contaminant in solution rather than suspension, which filtration cannot remove.

dissolved gas

Gas in solution in a liquid, which breaks out when pressure falls.

dissolved gases

Gases in solution in cooling water that can produce or speed up corrosion, which deteriorates metal in pipes and equipment.

dissolved oxygen

Oxygen in solution in water, which corrodes boiler steel and must be removed.

dissolved solid

Solid in solution, which concentrates and scales as water evaporates.

dissolved solids

Contaminants, such as calcium and magnesium, in water that can cause scale buildup.

dissolved water

Water in solution in a hydrocarbon, which drops out as free water when conditions change.

distance piece

The housing which connects the compression unit to the drive unit.

distance relay

A relay that operates in response to a specific ratio of voltage to current on a protected transmission line.

distillate

The liquid that is condensed from process vapours other than steam.

distillate fuel

Fuel from the middle of the boiling range, chiefly diesel and heating oil.

distillate fuels

Fuels, such as jet fuel, diesel fuel, and furnace oil, that are produced by blending components from the middle of the crude oil barrel.

distillate gasoil

The gasoil cut used as diesel and heating oil.

distillation

The regeneration process of removing water from glycol, or acid gases from amine solution, by heating.

distillation column

The tower in which a mixture is separated into fractions by boiling point.

distillation curve

The plot of temperature against fraction boiled off, defining what a crude yields.

distillation extraction

A core cleaning and saturation method in which water is distilled out of the sample and the oil is then removed with solvent.

distillation process

The process of removing water from glycol by raising the temperature above the boiling point of water, or removing acid gases from amine by generating steam to strip the acid gases.

distillation system

A group of equipment designed to separate materials.

distillation tower

The column separating a mixture into fractions by boiling point.

distillation unit

The tower and its associated equipment separating crude into fractions.

distillation yield

The proportion of each product fraction a crude gives on distillation.

distilled water

Water purified by distillation, used where dissolved solids would foul or interfere.

distortion

Any failure of a system to reproduce its input faithfully at the output.

distributary

A branching channel across a delta, whose sands form reservoir bodies.

distributary channel

A branching delta channel whose sand fill forms reservoir bodies.

distributary mouth

Where a delta channel enters standing water and drops its load, building a sand bar.

distributary mouth bar

When sediment-laden river water flows into the standing water at the mouth of a distributary, the river water slows and deposits its load. This forms a sediment body called a distributary mouth bar, or bar finger sand.

distributed temperature log

A continuous temperature profile along the whole well, measured by laser backscatter in a permanently installed fiber-optic cable, abbreviated DTS.

distributed workforce

A workforce spread across locations by design rather than by exception.

distribution

An operation in which the quantity that is outside of a grouping symbol is multiplied by each term that is inside the grouping symbol.

distribution centre

A facility for receiving, holding and dispatching goods, oriented to flow rather than storage.

distribution channel

The chain of intermediaries through which a product reaches the end customer.

distributive justice

The question of how benefits and burdens should be shared across a society.

disulfide

A compound with two linked sulfur atoms, formed when mercaptans are oxidized in sweetening.

disulfides (RSSR)

Sulfur compounds that do not have an offensive odor.

ditch cuttings

Small pieces of rock that break away due to the action of the drill bit's teeth, which are screened out of the liquid mud system at the shale shakers.

ditch cuttings, drill cuttings

Ditch, or drill, cuttings are small pieces of rock that break away due to the action of the drill bit's teeth, which are screened out of the liquid mud system at the shale shakers.

diurnal

Varying over a day, as gas demand does between morning and night.

diurnal variation

The daily change in the Earth's magnetic field caused by solar-driven currents in the ionosphere.

divergence

The loss of amplitude as a wavefront spreads geometrically over an ever larger surface.

divergent margin

A plate boundary where crust is being created and pulled apart.

diverse interview panel

Assembling interviewers of varied background to reduce single-perspective bias.

diversifiable risk

Risk specific to one asset, which spreading removes.

diversification

Spreading investment so that no single outcome dominates the result.

diversion

The technique of forcing treatment fluid away from the zones taking it most easily, so the whole interval is treated.

diversity

The range of differences present among the people in an organization.

diversity and inclusion

Building a workforce of varied backgrounds and an environment where that variety is actually used.

diversity and inclusion initiative

A structured program to improve representation and inclusion.

diversity scorecard

The set of measures by which diversity progress is tracked and reported.

diversity, equity & inclusion (DEI)

The combined agenda of representation, fair treatment and genuine participation.

diverter

A chemical agent or mechanical device that redirects treatment fluid from a thief zone to the rest of the interval.

diverter flowmeter

A production logging tool that forces the whole flow through a spinner using a basket or inflatable packer.

diverter valve

A three-way valve on the LACT unit which automatically directs bad oilto the treating system or directs good oil to the meter for sales.

diverting agent

A chemical added to a treatment to temporarily block the most permeable zones, so fluid goes into the tighter rock instead.

divestment

Selling an asset, whether to raise cash, exit a country or sharpen the portfolio.

dividend

The number that is to be divided in a division problem.

divider bar

The line that separates the numerator and the denominator in a fraction.

divider blocks

A device used to divide oil evenly to each injection point.

division

A subcategory of a hazardous materials class.

division order

The document by which every owner confirms their decimal share of the proceeds, authorizing the purchaser to pay on that basis.

divisions

Measurement markings on an oscilloscope graticule.

divisor

The number that does the dividing in a division problem.

Dix formula

The relation converting stacking velocities and their traveltimes into the interval velocity of each flat, parallel layer between them.

DMAIC

The Six Sigma improvement cycle applied to an existing process.

DMO

DMO, or dip moveout, is a processing correction for the effect of dip on stacking velocities, which preserve reflections that have differing dips during stacking.

DN

The mnemonic for the "Done" bit in many common functions. The rung becomes true when the instruction has finished.

dockman

An operator who works on a dock during a barge transfer.

document repository

The area in CMS Online where users can access procedure-related as well as other useful documents. Depending on the access privileges, users may be able to view all documents across the organization and upload new ones. Dashboard > 9-dot icon (upper right) > Resources > Documentation.

DoD directive 8140 / 8570.01-M

The United States defense requirements specifying which certifications each cyber role demands.

dog collar

A clamp fitted around a smooth tubular so that slips or elevators have a shoulder to hold, preventing it dropping through the rotary.

dog leg

A dog leg is a particularly crooked place in a wellbore where the trajectory of the wellbore in three-dimensional space changes rapidly.

doghouse

The steel-sided room on the rig floor beside the driller's position, used for records, tools and shelter.

dogleg, dog leg

A dog leg is a particularly crooked place in a wellbore where the trajectory of the wellbore in three-dimensional space changes rapidly.

dolomite

An anhydrous carbonate mineral composed of calcium magnesium carbonate.

dolomitization

A geological process by which the carbonate mineral dolomite is formed when magnesium ions replace calcium ions in calcite. This commonly occurs in sabkha areas.

dolostone

A rock composed chiefly of the mineral dolomite, the magnesium-bearing counterpart of limestone.

domain

The variable a dataset is expressed against — time, depth, frequency or wavenumber.

domainal fabric

A rock fabric divided into distinct domains of differing composition or orientation, as in a cleavage with alternating mica-rich and quartz-rich bands.

domainal structure

A structure built of superposed domains of different size or wavelength.

dome

An anticline that is roughly circular or elliptical in plan rather than elongate.

Domestic Crude Supply Obligation (DCSO)

The requirement to offer a share of production to Nigerian refineries before exporting.

domestic market obligation

A requirement to sell part of production into the home market, often below export price.

doodlebugger

Slang for a member of a seismic field crew.

dope

Pipe dope: a grease loaded with fine metallic particles, applied to threads to prevent galling and to seal the thread roots.

dosing pump

A small positive displacement pump metering chemical into a fluid stream at a controlled rate.

double

Two joints of drill pipe (each approximately 30 ft / 9.1 m in length) screwed together.

double block and bleed

A type of fuel gas valve arrangement that automatically shuts off fuel flow and diverts trapped fuel to collection or disposal equipment.

double descent

The pattern in which a model's error falls, rises, and then falls again as its capacity is increased past the point of fitting the training data exactly.

double hull

A tanker design with a second hull inside the first, mandated to reduce spill risk.

double hull tanker

A tanker with a second hull inside the first, mandated to reduce spill risk.

double insulated tool

An electrical tool that has a plastic casing designed to insulate the user from any fault inside the tool.

double refraction

The splitting of a wave into two components of different velocity and orthogonal polarization on entering an anisotropic medium.

double-acting compressor

A compressor which compresses gas on both the forward and backstrokes.

double-acting hydraulic

A hydraulic cylinder driven under pressure in both directions.

double-acting piston pump

A piston pump that both admits and discharges liquid on each part of the reciprocating movement.

double-acting pump

A reciprocating pump that admits and discharges fluid on each part of the reciprocating movement.

double-action lock

A lock that requires at least two separate, consecutive actions to open it.

double-arm mixer

A mixer that has two mix blades, each of which is mounted on a shaft.

double-cone dryer

A type of rotary dryer that is shaped like two cones that are connected.

double-duct ventilation system

A system characterized by a supply air duct that branches into two supply air ducts (one for heating and one for cooling), and a return air duct.

double-entry accounting

Recording every transaction twice, so the accounts must balance.

double-suction impeller

An impeller that has a suction eye on each side.

doublet

A pair of closely spaced arrivals or features that behave as one.

dowel

A pin locating two parts so they reassemble in the same relative position.

dowel pins

Pins that are used to help align parts of a pump, such as a bearing housing or the two halves of the casing.

down dip

Located in the direction of the downward slope of a dipping surface.

down lap

The termination of inclined strata downward against a lower-dipping surface beneath them.

down time

The time during which a machine or process has been idle, or otherwise not producing.

downcomer

The tube or pipe carrying liquid downward, in a boiler returning water to the drum.

downcomers

In drum-type boilers, the large pipes that recirculate water from the steam drum back to the waterwalls. In separators, vertical piping that allows liquids to flow from the top tube to the bottom tube of a two-tube horizontal separator.

downgoing

Traveling downward, as the direct wavefield before reflection.

downhole

Located in the wellbore rather than at surface.

downhole condition

The pressure, temperature and fluid environment tools and materials must withstand.

downhole equipment

The tools and completion hardware installed in the well.

downhole gauge

A pressure or temperature gauge run into the well, on slickline or installed permanently, to record conditions at depth.

downhole motor

A mud-driven motor turning the bit without rotating the whole string.

downhole pressure

The pressure measured in the wellbore rather than at surface.

downhole pump

The pump installed in the well to lift fluid to surface.

downhole receiver

A seismic receiver placed in a wellbore rather than at surface, as in a VSP or a crosswell survey.

downhole safety valve (DSV)

A valve set in the tubing that closes to isolate the well if surface control or surface equipment is lost.

downhole sensors

Devices placed in the well to measure pressure, temperature, flow or composition at depth, in real time.

downhole source

A seismic source placed in a wellbore rather than at surface.

downhole tool

Any device run into the well to measure, actuate or intervene.

downhole video

A camera run into the well to see what logs and pressure data cannot show.

download

Allen-Bradley's term for copying a PLC project from a PC to a PLC.

downloading

The process of electronically transferring data or files from one device to another, such as from a programming terminal (PC) to a PLC, or from an EFC to a handheld device or central control station.

downslope

Toward deeper water, the direction sediment is transported.

downstream

A term used for anything located past the orifice plate or metering device in a meter tube in the direction of flow.

downstream dependency

Work that cannot start until an upstream deliverable is complete.

downstream equipment

Equipment after the point in question, and what a protective device is installed to shield.

downstream line pressure

Pressure in the line after the device, and what the device must deliver against.

downstream market

The market for refined products.

downstream oil

The refining, distribution and marketing end of the oil business.

downstream pipeline

The pipeline receiving fluid at a delivery point from another line or facility.

downstream pressure

Pressure after the element in question.

downstream sector

Refining, distribution and marketing of petroleum products.

downstream side

The side after the element, whose pressure the device is not controlling.

downstream static pressure

Line pressure measured after the element, needed with the differential to compute flow.

downstroke

The downward movement of the sucker rod string.

downthrown

On the side of a fault that has moved down.

downthrown block

The fault block that has moved down.

downthrown fault block

In a downthrown fault block, the hanging wall has moved downwards relative to the footwall. This usually occurs with normal faulting, which occurs when the crust is extended. Alternatively, such a fault can be called an extensional fault.

downthrown side

The side of a normal fault that has moved down, where the younger rock sits.

downward continuation

Computing what a measured field would have looked like on a surface below the one it was recorded on.

downward force

Force acting toward the ground, which in a rod string is what the weight of the rods contributes.

downwarp

A region bent downward, forming a basin without faulting.

downwarp basin

A basin formed by downward flexure without significant faulting.

Draeger tube

A glass tube of reagent through which a measured volume of air is drawn, the length of the color stain giving the gas concentration.

draft

The flow of air and other gases through a boiler or furnace, typically indicated by pressure instruments.

draft furnace

A furnace whose combustion gas movement is created by draft rather than by forced air.

drag bag

A production logging technique in which a packer flowmeter is inflated only partly and dragged up the hole, giving a continuous rather than stationary reading.

drag bit

A bit with no moving parts that cuts by shearing rock with fixed cutters dragged across the face.

drag with faulting

Fault drag refers to the deflection of curved markers adjacent to a fault.

drain cooler

A section inside the shell of a closed heater that surrounds the tube bundle near the heater's inlet water box. Drips collect there and are subcooled to keep them from flashing to steam in the drain line.

drain cooler approach (DCA)

The difference between the temperature of the drips leaving the drain cooler of a closed heater and the temperature of the condensate or feedwater entering the tubes from the inlet water box.

drain hole

A hole or short passage that lets fluid drain out of a component or housing.

drain line

The line removing liquid from a low point.

drain pad

An area at a loading site through which spills drain to a collection point for recovery and treatment or disposal.

drain valve

A valve at a low point for removing liquid.

drainage

Drainage is the process of forcing a non-wetting phase into a porous rock.

drainage area

The surface area of reservoir from which a single well produces.

drainage area of a well

Drainage area of a well is the reservoir area or volume drained by the well. When several wells drain the same reservoir, each drains its own drainage area, a subset of the reservoir area.

drainage radius

The distance from a well over which it is actually drawing fluid.

drainage volume

The reservoir volume that a single well drains.

drained test

A rock mechanics test run slowly enough, with the pore fluid free to escape, that no excess pore pressure builds up in the sample.

drape

A fold-like configuration formed by sediment settling over a pre-existing high, or by differential compaction around it, without tectonic folding.

draw

A product that flows out of a multidraw tower.

draw temperature

The temperature at which a side-stream is drawn from a distillation tower.

draw works

The machinery on a drilling rig consisting of a large diameter steel spool, brakes, a power source, and various auxiliary devices. Its primary function is to reel out and reel in the drilling line (a large-diameter wire rope) in a controlled manner.

drawdown

The difference between average reservoir pressure and the flowing bottomhole pressure — the pressure drop driving inflow.

drawdown test

A test recording bottomhole pressure as a well is produced at a constant rate after a period of shut-in.

drawdown well test

A drawdown well test is one in which the flow rate is held approximately constant while the well pressure is measured.

drawdown, pressure drawdown

Pressure drawdown is the difference between the reservoir pressure and the flowing wellbore pressure, which drives fluids from the reservoir into the wellbore.

drift

The inclination of a wellbore from vertical, and by extension the gauge run to prove a tubular's minimum internal diameter.

drift pin

A metal tool with a pointed end used to align adjoining components, i.e., bolt holes of valves and flanges or a pair of mating flanges.

drill bit

A piece of equipment that cuts or crushes formation rock, attached to a drill string where forces are applied to rotate it. Also, the replaceable cutting attachment used in a power drill.

drill collar

A component of a drill string that provides weight on bit for drilling. Drill collars are thick-walled tubular pieces machined from solid bars of steel, usually plain carbon steel but sometimes nonmagnetic nickel-copper alloy or other nonmagnetic premium alloys.

drill cutting

Rock chipped by the bit and returned in the mud, the cheapest sample of the formation there is.

drill cuttings

Small pieces of rock chipped away by a drill bit while drilling a well, which are transported to the surface by drilling mud and screened out of the liquid mud system at the shale shakers. Also called rock cuttings or simply cuttings.

drill cuttings, ditch cuttings

Drill, or ditch, cuttings are small pieces of rock that break away due to the action of the drill bit's teeth, which are screened out of the liquid mud system at the shale shakers.

drill noise vertical seismic profile

A VSP using the drill bit itself as the seismic source, with receivers on the surface or seabed, also called seismic while drilling.

drill pipe

A tubular steel conduit fitted with special threaded ends called tool joints. The drill pipe connects the rig surface equipment with the bottom hole assembly and the bit.

drill solids

Formation solids that have entered the mud system from the hole being drilled.

drill stem test

A procedure for isolating and testing the pressure, permeability, and productive capacity of a geological formation in situ within a reservoir during the drilling of a well. The zone is sealed off from the rest of the wellbore by packers, and the formation's pressure and fluids are measured.

drill string

The drill string, also called the drillstem, is the combination of the drill pipe, the bottomhole assembly (BHA), and any other tools used to make the drill bit turn at the bottom of the borehole.

drill to earn

Earning an interest by paying for a well rather than by paying cash for the share.

drill-in fluid

A fluid formulated specifically for drilling the reservoir section, chosen to minimize damage rather than to optimize drilling.

drill-off trend

Drill-off trend is a gradual and uniform increase in the ROP, typically associated with increasing formation pressure.

drillable

Made of material a bit can drill through, so the tool need not be retrieved.

drillable packer

A packer built of cast iron or composite so it can be drilled or milled out rather than retrieved.

drilled solids

Formation solids incorporated into the mud during drilling — salt, carbonate and clay among them.

driller

The crew member who operates the rig's drilling systems and is responsible for the crew's safety and the rig's efficient operation.

driller's depth

Depth measured from the length of pipe run into the well, as recorded while drilling.

drilling break

A drilling break is a sudden increase in the rate of penetration during drilling.

drilling contract

The agreement hiring a rig and crew, fixing day rate, standby terms and liability allocation.

drilling contractor

The company that owns and operates the rig and supplies its crew, working for the operator under a drilling contract.

drilling cost

The cost of making the hole, usually the largest single item in a well.

drilling crew

The team that operates the rig — driller, derrickman, floor hands, motorman and assistant driller, under the toolpusher.

drilling detergent

A surfactant added to keep shale and clay from adhering to the bit and bottomhole assembly.

drilling engineer

The engineer designing the well and its execution.

drilling fluid

Drilling fluid, also called drilling mud, is a specially formulated mixture of solids, liquids, and/or gases used when drilling an oil well. The formulation of the mud depends on several factors, for example, the type of formation being drilled. The main purposes of drilling fluid include cooling the drill bit, removing the cuttings from under the bit and circulating them to the surface, and well control during drilling.

drilling foreman

The drilling contractor's supervisor at the rig, another term for toolpusher.

drilling line

A drilling line is a wire rope hoisting line, reeved on the sheeves of the crown block.

drilling lwd

Logging while drilling, taking formation measurements as the hole is made.

drilling mud

Mixtures of fluids and solids (as solid suspensions, mixtures, and emulsions of liquids, gases, and solids) used in well operations to drill boreholes.

drilling mud filtrate

Drilling mud filtrate is the liquid that passes through a filter cake from a slurry held against the filter medium, driven by differential pressure. Dynamic, or static, filtration can produce a filtrate.

drilling mud pulse telemetry

The most common method used for data transmission in MWD and LWD systems. The three main systems are positive pulse, negative pulse, and continuous wave, named for the ways their pulses are propagated in the mud volume.

drilling mud slowness

Drilling mud slowness is the travel time per foot, termed DTmud, traveled by the acoustic wave in the drilling mud.

drilling mud, mud

Mixtures of fluids and solids (as solid suspensions, mixtures, and emulsions of liquids, gases, and solids) used in well operations to drill boreholes.

drilling mud, mud, drilling fluid

Drilling muds are mixtures of fluids and solids (as solid suspensions, mixtures and emulsions of liquids, gases and solids) used in well operations to drill boreholes.

drilling operation

The whole activity of making hole, from spudding in to reaching total depth.

drilling overbalanced

Drilling overbalance conditions occur when the hydrostatic pressure in the wellbore is greater than the reservoir pressure.

drilling parameter

A controllable drilling variable such as weight on bit, rotary speed or flow rate.

drilling procedure

The step-by-step guide the wellsite supervisor follows to execute the drilling engineer's design.

drilling program

The engineering plan for constructing a well, covering objectives, hole sections, casing, fluids and procedures.

drilling project

A campaign of wells managed as one investment.

drilling rate

The speed at which the bit deepens the hole, usually quoted in feet or meters per hour.

drilling rig

The machine used to drill a wellbore.

drilling rig day rate

The daily charge for hiring a rig, the largest single variable in well cost.

drilling riser

The large-diameter pipe joining a subsea BOP stack to a floating rig, carrying mud returns and giving the string a guided path to the seabed.

drilling system

The rig, fluid and downhole assembly considered as one system.

drilling-fluid engineer

The specialist who tests the mud at the rig and prescribes the treatments that keep its properties within the program.

drillpipe conveyed

Said of sensors or tools carried into the well on drillpipe rather than on wireline.

drillship

A ship-shaped vessel fitted with a drilling rig and station-keeping equipment, able to drill in deep water without touching the seabed.

drillstem

The whole assembly turned from surface — drillpipe, bottomhole assembly and the tools between them — that drives the bit.

drip accumulator

A vessel at a low point in a gas line that collects the water and heavy hydrocarbons dropping out of the stream.

drips

Condensate that forms on the shell side in a closed heater as steam transfers its heat to the condensate or feedwater.

drive

Generally, a combination of a motor, its controller, and other associated control or field devices.

drive reservoir

A reservoir producing by a defined natural mechanism, such as water or gas cap drive.

drive shaft

The shaft transmitting power from driver to driven machine.

drive sleeve

A component of a motor operator that transmits the motion of the worm gear to the valve stem.

drive unit

The power source for a compressor which is either an electric motor or engine.

driven shaft

The shaft receiving power, as distinct from the driving shaft.

driver

A computer program that allows a non-standard hardware device or network to communicate with a PC system. Also, a source of power such as an electric motor, engine, or steam turbine.

driving potentials

The difference in potential between the anode and the cathode. The output current of the anodic material depends on the driving potential and the resistance between the anode and the structure to be protected (cathode).

droop

The fall in a regulator's outlet pressure as flow through it increases toward maximum.

drop ball

A ball dropped or pumped down the tubulars to seat in a tool and actuate it.

drop bar

A heavy steel bar dropped down the string to strike a percussion detonator and fire a tubing-conveyed perforating gun.

drop sub

A sub that releases the perforating guns after firing so they fall into the rathole or sump, clearing the tubing for production.

drop-out voltage

The amount of voltage needed to reposition a relay element.

droplet

A small drop of liquid dispersed in another phase.

droplet size

The size of dispersed drops, which sets how fast they will coalesce and settle.

dropoff gun

A perforating gun designed to release from the string after firing and fall into the rathole.

dropout

The loss of recorded data, originally from tape damage and now more generally from any channel or trace that fails to record.

drug testing

Screening for prohibited substances, subject to legal limits on when it may be required.

drum

A round switch that opens or closes electrical contacts by rotating. Also called a rotor.

drum dryer

A dryer that uses one or more heated drums to dry a wet cake that is very dilute, in a slurry-like form.

drum filter

A device that uses a rotating screen and a vacuum to remove solid particles from water.

drum level

The water level in a boiler drum, the most critical single measurement on a boiler.

drum, logging drum

A drum is used for spooling the wireline cable when it is not down the borehole.

drum-type boiler

A type of boiler that has a large steam drum located on top to collect the steam produced by the boiler.

dry bed

A bed of solid desiccant — silica gel, molecular sieve, activated alumina or calcium chloride — used to adsorb water from a gas stream.

dry combustion

In-situ combustion with air alone injected, no water added.

dry formation test

A dry formation test is one that does not acquire a valid formation pressure.

dry forward combustion

In-situ combustion in which the burning front advances in the same direction as the injected air, with no water injected alongside.

dry gas

Dry gas is almost pure methane and occurs in the absence of liquid hydrocarbons or by processing natural gas to remove liquid hydrocarbons and impurities.

dry gas / lean gas

A gas made up of primarily light hydrocarbon vapors.

dry glycol

Regenerated glycol with water removed, ready to absorb again.

dry glycol (or lean glycol)

Glycol that is free of water.

dry hole

A well found to be incapable of producing either oil or gas in sufficient quantities to justify commercial exploitation or completion.

dry ice

The solid form of carbon dioxide.

dry oil

Treated oil whose water and sediment content is low enough to meet the pipeline specification, also called clean oil.

dry rock

Rock isolated from aquifers and meteoric water, so its pore space holds no mobile water.

dry trays

An abnormal condition that occurs in a distillation tower when there is not enough liquid on the trays.

dry-bed dehydrator

A gas dryer using beds of solid desiccant, with one bed adsorbing while another is regenerated.

dry-desiccant dehydration

Drying gas by adsorption onto a solid bed, reaching dew points glycol cannot.

dry-type filter

A filter made of a dry filter material that is held in a frame; may be stationary or movable.

drying

The process of removing liquid from a solid or a gas, by either heat transfer or the use of an adsorbent.

Dräger tube

A calibrated glass tube of reagent, drawn through with a hand pump, whose stain length gives the concentration of a specific gas.

DSM

differential spectrum method.

DSS

Deep seismic sounding — a long-offset seismic profile recorded to image the lower crust, the Moho and the upper mantle.

DST

Drillstem test: a temporary completion made on the drillstring to flow and shut in a formation, measuring pressure and recovering fluid samples.

DST pressure chart

The pressure-against-time record from a drillstem test gauge, read as a sequence of flow and shut-in periods.

dual completion

A single wellbore completed so that two zones can be produced separately, each through its own conduit.

dual induction

An induction tool carrying deep and medium arrays on the same sonde, so invasion can be assessed from the difference between them.

dual porosity

Rock with two connected pore systems, typically fractures that flow and matrix that stores.

dual porosity reservoir

A reservoir characterized by having primary porosity from original deposition and secondary porosity from diagenesis or other mechanisms, in which all flow to the well effectively occurs in one porosity system and most of the fluid is stored in the other. Examples include naturally fractured reservoirs, vugular carbonates, and layered reservoirs with extreme permeability contrasts.

dual purpose kerosene (DPK)

Kerosene meeting both aviation and domestic lighting specifications.

dual water

A shaly-sand model treating pore water as two components: far water, the ordinary formation water, and clay-bound water held near the clay surface.

dual water interpretation model

The dual water interpretation model is a petrophysical interpretation model of shaly formations that considers there to be two different waters in the pore spaces: far water, which is the normal formation water; and near water, or clay-bound water, in the electrical double layer near the clay surface.

dual water model

The dual water model is a model of shaly formations that considers there to be two waters within the pore spaces: far water, which is the normal formation water; and near water, or clay bound water, in the electrical double layer near the clay surface. The clay bound water consists of clay counterions and the associated water of hydration.

dual-element fuse

A fuse that has two elements in series—a short circuit element and a time delay element—providing both overload and short circuit protection.

dual-permeability reservoir

A dual-porosity reservoir in which the matrix as well as the fractures delivers fluid directly to the well.

dual-rated connector

A connector that is designed for use with both aluminum and copper conductors.

DUALDIP

The DUALDIP presentation for the 8-curve dipmeter tool allows results from more than one computation to be combined.

dubai crude

The medium sour Gulf crude that benchmarks Asian pricing.

dubai partials

Small standardized Dubai cargo lots whose trades set the Asian sour crude benchmark.

duct

A fabricated enclosure, usually rectangular or round, that provides a path to carry and distribute air to where it is needed in a ventilation system.

ductile

Deforming by flow rather than fracture, the behavior of salt and some shales.

ductility

The capacity to deform without breaking.

ductwork

The ducting distributing air or flue gas.

due diligence

The examination of an asset's technical, legal and financial records before a purchase is committed to.

dummy valve

A solid blank set in a gas lift mandrel in place of a valve, isolating the tubing from the annulus at that station.

dump bailer

A wireline tool carrying a small volume of cement or other slurry, which opens on contact to place it at a chosen depth.

dump valve

Another name for liquid-level control valve.

Dunning-Kruger effect

The tendency of the least competent to overestimate their ability, relevant to self-assessment.

duplex

Optical cable containing two fibers.

duplex pump

A reciprocating pump that uses two pistons, plungers, or similar devices to move fluid.

duration of short-circuit current

Amount of time that the output can be shorted to network ground. Usually specified as an absolute maximum.

duster

Slang for a dry hole — a well that finds nothing worth completing.

dusts

Solid particles generated by handling, crushing, grinding, rapid impact, or detonation of materials such as rock, ore, metal, coal, wood, or grain.

duty cycle

The percentage of ten minutes that a welding machine can continuously produce its rated amperage without overheating.

dye penetrant inspection

A non-destructive test in which dye drawn into surface-breaking cracks is revealed by a developer applied afterwards.

dynamic content

Material that varies by viewer, based on what is known about them.

dynamic correction

A time-variant shift applied to seismic traces, whose size changes down the trace — normal moveout being the standard case.

dynamic filter press

A filtration cell in which the fluid is circulated across the filter medium while filtration is measured.

dynamic filtration

Filtration with the fluid flowing across the cake, so deposition and erosion reach a balance and the cake stops thickening.

dynamic fluid level

The level the fluid column settles to in the annulus while a well is being pumped, below the static level.

dynamic miscibility

Miscibility developed as injected gas and reservoir oil exchange components during flow, rather than on first contact.

dynamic operation

The period of operation between one set of steady-state conditions and another.

dynamic positioning

Holding a vessel on station with computer-controlled thrusters responding to position references, without anchors.

dynamic range

Dynamic range is the ratio between the largest and smallest values that a certain quantity can assume.

dynamic response curve

A curve on a graph that represents a process variable's response to changes in a system.

dynamic seal

A seal working between parts that move relative to one another, such as a valve stem seal.

dynamic underbalance

Momentarily lowering wellbore pressure at the instant of perforating to clean the tunnels.

dynamic-aging test

Heating a mud sample while rolling it, so it ages under motion rather than at rest.

dynamite

A nitroglycerin-based explosive used as an impulsive seismic source, fired in a shothole.

dynamometer

A device to show the variation in load on the polished rod as the rod string moves through the pumping cycle.

dynamometer card

A plot of load against position through a sucker-rod pump stroke, at surface or computed downhole.