Discover the IHRDC Energy Glossary_beta

a

The tortuosity factor in Archie's equation, F = a/φ^m, often taken as 1.0 in carbonates and about 0.62 to 0.81 in sandstone.

A.G.A.

American Gas Association.

A.N.S.I.

American National Standards Institute.

A.P.I.

American Petroleum Institute.

A.P.I. gravity

The American Petroleum Institute gravity, a measure of how heavy or light a petroleum liquid is compared to water. If its API gravity is greater than 10, it is lighter and floats on water; if less than 10, it is heavier and sinks.

A.S.M.E.

American Society of Mechanical Engineers.

A/B testing

Comparing two versions with live traffic to see which performs better.

abandonment

Permanently plugging a well or retiring a facility.

abandonment cost

The provision a company must carry for plugging wells and removing installations.

abatement

Any action that avoids or removes emissions, ranked by cost per tonne.

ABC analysis

Classifying inventory by value so control effort is concentrated where it matters.

abnormal condition

A state outside the normal operating envelope, requiring action rather than observation.

abnormal operating condition

A departure from normal running that is not yet an emergency but has left the safe envelope.

abnormal pressure

Pressure differing from the expected gradient, high or low, and a hazard either way.

abnormal temperature

Temperature outside the expected range.

abnormal trend

A measurement moving steadily in a direction it should not, which signals a developing fault.

abnormal variation

Variation outside the range the process normally shows, which signals a cause rather than noise.

aboveground storage tank

A tank at grade holding liquid, regulated for containment and vapor loss.

abrasion

Wear by mechanical rubbing, which limits bit and pump life.

absolute open flow potential

Absolute open flow potential (AOF) is the maximum flow rate a well could theoretically deliver with zero pressure at the middle of the perforations.

absolute permeability

The measurement of a rock's ability to flow or transmit fluids when only a single fluid, or phase, is present in the rock pore spaces.

absolute permeability, specific permeability

Sometimes referred to as specific permeability, the permeability when a single fluid, or phase, is present in the rock.

absolute pressure

Pressure measured against a perfect vacuum — the gauge reading plus atmospheric pressure.

absorbance

The light a sample absorbs, from which concentration is calculated.

absorbent

A type of chemical used in absorption refrigeration systems to control the pressure and temperature inside the system.

absorber

The section of an absorption refrigeration system in which the refrigerant is absorbed by the absorbent. Also, an auxiliary vessel that separates specified components from a feed stream and produces one or more valuable products as a result.

absorptance

The fraction of incident radiant energy a surface absorbs rather than reflecting or transmitting.

absorption

A chemical process in which one substance penetrates and is drawn into the bulk of another substance. In gas processing, a method of removing one or more components of a gas mixture by contacting the gas with a liquid, such as the removal of water vapor from natural gas by contact with a liquid desiccant (e.g., glycol) or the removal of acid gases (H2S, CO2) by contact with an amine solution.

absorption band

The range of wavelengths absorbed by a given substance, giving it a diagnostic signature in a reflectance or transmission spectrum.

absorption oil

A light hydrocarbon liquid circulated through an absorber to strip heavier liquids from a wet gas stream; also called wash oil.

absorption process

The attraction and retention of water vapor by glycol from gas, or of acid gases by amine from natural gas.

absorption tower

The column in which a liquid absorbs a component from a gas stream.

abuse of official position

Using authority for personal benefit.

abyss

The deepest part of an ocean basin, where depositional energy is low and fine sediment settles slowly from suspension or from waning turbidity currents.

abyssal

Pertaining to the abyss — the depositional environment of the deepest ocean floor, beyond the continental rise.

AC motor controller

A device, or group of devices, that controls and protects the operation of an AC motor.

acceleration

The rate of change of velocity per unit of time.

acceleration ramp

The time it takes for a variable speed drive to speed up to a preset speed.

accelerator source

A downhole neutron source that produces high-energy neutrons electronically by accelerating charged particles, instead of relying on a chemical source.

accelerometer

A sensor measuring acceleration, used in survey tools and in seismic recording.

acceptable entry conditions

The conditions that must exist in a permit space to allow entry and to ensure that employees involved with a permit-required confined space entry can safely enter into and work within the space.

access

The ability to place information into and retrieve information from a storage device.

access control

Restricting who may reach which resources and do what with them.

access control model

The scheme by which those rules are expressed, such as role-based or discretionary.

accessible fonts and colours

Type and color choices readable by people with impaired vision or color perception.

accessory grains

An accessory grain is a non-essential grain found in rocks, typically rich in trace elements and present in small quantities.

accident

An unplanned and unexpected even. However virtually all accidents are preventable.

accommodation space

The space available for the deposition of sediments.

account titling

How an account is legally named, which determines who owns and controls it.

accounting cycle

The recurring sequence from transaction through recording to financial statements.

accreditation of prior achievement (APA) [evidence]

A prior achievement, learning or experience that can be either performance or knowledge, e.g., certificates, qualifications, company awards, which must:

• Be specific enough to meet the standard
• Belong to the employee and be authenticated
• Be current enough to work now
• Actually prove either performance or knowledge
• Be presented in a way that allows it to be judged.

accretion

The process of growth or increase, typically by the gradual accumulation of additional layers or matter. In geology, accretion is the process where material such as sediment, volcanic arcs, seamounts, oceanic crust, or other igneous features is added to a tectonic plate, causing it to grow larger, frequently on the edge of existing continental landmasses.

accretionary

Built by material added at a margin, as at a subduction complex.

accumulator

A PLC memory word in which a timer or a counter stores the current time or count.

acetic

Relating to acetic acid, a weaker acid used where hydrochloric would corrode too aggressively.

acetic acid

A weak organic acid used in stimulation where hydrochloric acid would be too corrosive, typically as a 10% solution in water.

acetylene

A carbon and hydrogen compound that, when combined with oxygen, creates the extremely hot flame needed for welding and cutting.

acicular

Acicular describes a mineral habit where crystals are slender and needle-like, tapering to a point. These crystals are typically much longer than they are wide, often forming radiating or fan-shaped aggregates.

acid

A substance that releases hydrogen ions when added to water.

acid effect

The change in a pulsed neutron capture log after an acid treatment, caused by chloride from the spent acid remaining in the formation.

acid frac

A fracture treatment in carbonate where acid etches the fracture faces unevenly, so they prop themselves open when the pressure is released.

acid gas

A gas that, when combined with water, produces acids or acidic solutions. The most common acid gases are hydrogen sulfide (H2S) and carbon dioxide (CO2).

acid hydraulic fracturing

In acid hydraulic fracturing, the acid is injected into the formation above the fracture pressure of the adjacent formation rock.

acid inhibitor

An additive that adsorbs onto steel and slows acid attack on tubulars and pumping equipment during a treatment.

acid job

A treatment pumping reactive acid into a formation to dissolve damage or rock, so the well produces closer to its natural potential.

acid number

A measure of the acidic components in a crude oil, reported as the total acid number in milligrams of potassium hydroxide per gram.

acid regenerator

A piece of equipment used to remove contaminants such as tar or constant boiling mixtures from hydrofluoric acid.

acid settler

A component in the reaction section of an alkylation unit in which separation of the reactor effluent occurs; the heavier acid settles to the bottom, while the lighter hydrocarbons rise to the top.

acid stimulation

Treating a formation with reactive acid to remove damage or create conductive channels, so the well produces closer to its potential.

acid strength

The concentration of the acid catalyst in an alkylation process.

acid tank

The rubber-lined tank used to transport and blend acid at the wellsite.

acid wash

A wellbore acid treatment that removes scale and debris from the wellbore and perforations without penetrating the formation.

acidity

The condition of an aqueous system holding more hydrogen ions than hydroxide ions, or the potential to release them, measured as pH.

acidize

To pump acid into a well to dissolve near-wellbore damage and other flow-restricting material.

acidized

Treated with acid to dissolve rock or damage and restore permeability.

acidizing

Pumping acid to dissolve rock or damage near the wellbore and restore permeability.

acoustic

Acoustic, alternatively termed sonic, is the branch of physics concerned with the properties of sound.

acoustic basement

The level below which seismic data show no coherent reflections, taken in practice as the deepest continuous reflector.

acoustic coupler

An obsolete device that converted digital data to audio tones for transmission over a telephone handset and back.

acoustic emission

A high-frequency elastic wave released as a material deforms or cracks — the sound a structure makes while it is failing.

acoustic energy

Sound energy, the form seismic and sonic measurements use.

acoustic image log

Acoustic image logs are generated by bouncing an ultrasonic acoustic pulse from an acoustic imaging logging tool to, and then from, the borehole wall. The tool uses a transducer that both emits and records the acoustic pulse.

acoustic impedance

The product of density and velocity; a measure of the opposition that a system presents to acoustic flow resulting from an acoustic pressure applied to the system.

acoustic impedance section

A seismic section inverted from reflectivity to acoustic impedance, so each sample represents a rock property rather than an interface.

acoustic log, sonic log

A display of the travel time of acoustic waves versus depth in a well.

acoustic logging

Logging with sound to obtain travel time and waveform character.

acoustic mode

Acoustic energy guided along an interface or a borehole, confined in the directions across its path.

acoustic positioning

Locating marine seismic equipment by timing acoustic signals between transponders on the vessel, the sources and the streamers.

acoustic propagation

Acoustic propagation is the propagation of acoustic, or sonic, waves in a medium.

acoustic pulse

An acoustic pulse is produced by the alternate expansions and contractions of a transducer.

acoustic signal

The sound wave a sonic tool emits and records.

acoustic slowness

Acoustic slowness is the inverse of the acoustic velocity.

acoustic source

The device generating the sound pulse in a sonic or seismic measurement.

acoustic transmission

Acoustic transmission is the transmission of sounds through and between materials.

acoustic transparency

The property of a body whose acoustic impedance is uniform, so it returns no internal reflections.

acoustic traveltime

The time an acoustic pulse takes to travel a known distance through the formation, the basis of the sonic log.

acoustic velocity log

A log of formation acoustic velocity or its reciprocal slowness against depth, usually meaning the sonic log.

acoustic velocity, sonic velocity

Acoustic, or sonic velocity, is the velocity of an acoustic, or sonic, wave in a medium.

acoustic wave

A body wave in which particles oscillate along the direction of travel — the compressional or P-wave that conventional seismic records.

acoustic, sonic

Acoustic relates to sound or vibrational events.

acquisition

The generation and recording of seismic data in the field, covering the source, the receiver layout and the geometry that ties them together.

acquisition geometry

The layout of sources and receivers, which determines fold, offset and azimuth coverage.

acquisition integration

The work of combining an acquired business into the acquirer's operations and systems.

acquisition log

The log as recorded at the time of measurement, as distinct from a playback generated later from the stored digital data.

acquisition parameter

A survey design choice such as spacing, fold or record length, fixed before shooting and hard to change after.

acreage

Land leased for oil and gas exploration and/or land for which a company owns the mineral rights.

acres

A measurement of area. 1 acre equals 43,560 square feet. 1 mile x 1 mile in area equals 640 acres, which is equal to 259 hectares, the common measurement of area in many countries of the world. 1 square kilometer is equal to 100 hectares.

acrylamide acrylate polymer

A copolymer of nonionic acrylamide and anionic acrylate units, also called partially hydrolysed polyacrylamide, abbreviated PHPA.

acrylamide polymer

A nonionic linear polymer of acrylamide, used at high molecular weight as a selective flocculant.

acrylamido-methyl-propane sulfonate polymer

An AMPS copolymer — a strongly anionic, highly water-soluble additive for high-salinity and high-temperature muds.

acrylate polymer

A linear anionic polymer of acrylic acid, used for filtration control and as a deflocculant.

acrylonitrile

A petrochemical monomer used in synthetic fibers and plastics.

action level

A concentration designated in OSHA Regulations (29 CFR part 1910) for a specific substance, calculated as an eight-hour time-weighted average, which initiates certain required activities such as exposure monitoring, medical surveillance, and hearing protection. The current action level for noise is 85 decibels.

action plan vs. task list

A sequenced plan toward an outcome against an undifferentiated list of things to do.

activated alumina

An adsorbent used to remove moisture from gases and liquids.

activated carbon

An adsorbent created by treating coal or carbon with steam in a process called activation, producing a honeycomb structure that can trap individual ions and molecules of dissolved substances.

activated carbon filter

A type of specialty filter that is designed to control odors.

activated sludge

Sludge that contains micro-organisms; used for biological treatment of wastewater.

activation log

A log of elemental concentrations derived from the gamma rays emitted by nuclei that neutron bombardment has made radioactive.

activation, neutron

Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus often decays immediately by emitting gamma rays, or particles such as beta particles and alpha particles.

activator

A chemical that initiates or accelerates a reaction, as in setting a cement or breaking a gel.

active device

A device that has the ability to change its internal resistance.

active energy

Hazardous energy that is present in equipment as a source of power for the equipment.

active learning

Learning through doing and discussing rather than through listening.

active light

The light on a network device that blinks whenever data is being transmitted or received.

active listening

Demonstrating understanding of the other side's position before responding to it.

active margin

A continental margin sitting on a colliding or sliding plate boundary, marked by earthquakes, volcanism and a narrow shelf.

active shooter and hostage situation

Emergency scenarios requiring rehearsed, specific response rather than general evacuation.

active sites

Acidic areas on the surface of a catalyst particle where the cat cracking reaction occurs.

active sulfide

Sulfide ion present and chemically available in the mud, as opposed to sulfide already locked into an insoluble precipitate.

activity

The ability of a catalyst to crack hydrocarbons; determined by the number or strength of the catalyst's active sites.

activity of aqueous solutions

The vapor pressure of water in a solution relative to that of pure water, abbreviated aw.

actuarial assumption

The estimate of longevity, discount rate or salary growth underlying a pension obligation.

actuator

A device used to operate valves or other equipment in process systems. In limit switches, it is the part that something moves to operate the switch mechanism. Common types include pneumatic, hydraulic, motor, and solenoid actuators.

acute

Having a rapid onset and relatively short but severe course. The time scale depends on the particular disease but is generally measured in days or weeks.

acute angle

Any angle between 0 degree and 90 degree.

acute effects

Effects that develop immediately after brief exposure to a hazardous chemical.

acute health effect

An adverse health effect that occurs rapidly as a result of a single or short-duration exposure to a health hazard and is typically short in duration.

acute health effects

Health effects that occur as a result of a single or short-duration exposure to a chemical.

acyclic compound

An organic compound whose carbon atoms form open chains, straight or branched, with no ring.

ad targeting

Selecting who sees an advertisement, by attribute, behavior or context.

adaptability

The capacity to change approach as conditions change.

adapter spool

A short spool piece fitted between two wellhead or valve components to match their connections or dimensions.

adaptive control

A controller enhancement in which an automatic means is used to adjust the controller's response to its inputs based on previous experience.

adaptive scoreboard

A display adjusting to the learner's performance and showing progress against required mastery.

adaptor

A fitting connecting components of different size or thread.

ADC

Analog-to-digital converter; a digital electronic component that converts an electrical signal into discrete binary values.

addendum

A formal issue amending tender documents while bidding is still open.

additives

Additional components that are added to a gasoline blend to produce a product that meets customer requirements.

additivity

The property that permissible variogram models can be summed to build a more complex one that is still valid.

address

A unique alphanumeric identifier for an input terminal, an output terminal, or a memory location.

adequacy of disclosure

Whether the notes tell a reader enough to understand the numbers.

adhesion tension

The difference between the two fluid-solid surface tensions where two immiscible fluids meet a solid, deciding which of them wets the surface.

adhesive force

A molecular force that exists between unlike molecules.

adiabatic

Adiabatic process is a conversion that occur without input or release of heat within a system.

adjacent bed

The formation layer above or below the bed a logging tool is measuring, whose properties leak into the reading.

adjacent shale

The shale beside the interval of interest, used as a log reference and often the seal.

adjustable choke

A variable-orifice valve used to drop pressure in a controlled way, from full wellbore pressure toward atmospheric during well control.

adjustable nozzle

A nozzle for a fire hose that can be adjusted to provide a straight stream or a fog pattern.

adjusted flow time

An equivalent constant-rate flow duration used in analyzing a test whose rate actually varied.

adjusting ring

The part of a spring-loaded safety valve used to adjust blowdown.

adjusting screw

The part of a spring-loaded safety valve or relief valve used to adjust the tension of the spring which controls the set point.

adjustment screw

A screw setting a position or a spring load.

ADKAR

The individual change model: awareness, desire, knowledge, ability, reinforcement.

administering

Keeping established processes running correctly, as distinct from improving or redirecting them.

administrative control

A control implemented through policy, procedure or training rather than technology.

administrator

A user role in CMS Online. Administrators can manage user accounts, edit users' information, add and delete users, assign and manage assessments, assign supervisors, set system-wide settings, work with competency models and a variety of other tasks related to the set-up and management of CMS Online.

adsorbed

Held on a surface rather than dissolved within, as methane on coal.

adsorbed gas

Gas held on the surface of a solid — reservoir rock grains, or the organic particles in a shale — rather than as free gas in the pore space.

adsorbent

A natural or synthetic drying substance that dries material by removing gas or liquid molecules.

adsorber

An auxiliary vessel that uses a porous solid to remove impurities, such as dissolved solids and gases from liquids.

adsorption

A chemical process in which a thin layer of molecules adheres to the surface of a porous solid material. Used as a method for removing liquids and gases from mixtures, such as the removal of water from a gas stream by contact with a solid desiccant (e.g., silica gel) or the adhesion of liquid hydrocarbons to activated carbon.

adult learner

A learner who brings experience, wants relevance and expects to direct their own learning.

advanced analytics

Statistical and machine-learning methods that go beyond reporting to prediction and optimization.

advective transport modeling

Modeling the movement of fluid and dissolved substances carried along with it, through a geostatistically described subsurface.

adversarial attack

Feeding a model deliberately crafted input designed to make it produce a wrong answer.

adverse impact

A neutral practice that disadvantages a protected group disproportionately.

aeolian

Aeolian, or eolian, refers to structures that are created by the wind.

aeolian depositional environments

Aeolian depositional environments are those in which sediment deposition is primarily governed by wind.

aeolian deposits

Sediments that are transported by wind and then deposited.

aeolian environments

An aeolian environment is a depositional environment in which sediment deposition is primarily governed by wind.

aeolianite

Aeolianites are rocks formed by the lithification of sediments that are deposited by wind processes.

aeolotropy

Anisotropy — the variation of a property with the direction in which it is measured.

aerated

Containing entrained air or gas, used to lighten drilling fluid.

aerated layer

The near-surface weathered layer whose pores hold air rather than water, and whose seismic velocity is correspondingly low.

aerated mud

Drilling fluid lightened with injected air or nitrogen.

aeration

A process that supplies oxygen for an activated sludge process.

aeration basin

The tank where air is blown through wastewater so bacteria can break down the load.

aerator

A device for mixing air into a liquid such as wastewater.

aerial cooler

Air-cooled exchanger with forced-draft fans, rejecting heat where cooling water is unavailable.

aerobic

Describing a condition in which free oxygen is present, and the organisms that require it.

aerobic process

A biological treatment process that requires the presence of oxygen.

aeromagnetic

Magnetic measurement made from an aircraft, used to map basement depth cheaply over wide areas.

aeromagnetic survey

A survey measuring the Earth's magnetic field from an aircraft, mapping basement depth and structure over a wide area quickly.

aerosol

A stream of product containing both gases and liquids.

AFCI

Arc Fault Circuit Interrupter. Similar to a GFCI, an AFCI shuts down power to a circuit when it detects an arcing situation. AFCIS help to prevent fires.

affirmative action program

A structured plan to correct historic under-representation.

aframax

A mid-size crude tanker of roughly 750,000 barrels, favored on shorter regional routes.

afterburning

The igniting of fuel in the convection section of a furnace, which can be caused by an air leak in the convection section combined with insufficient air at the burners. Also, a condition in which excessive amounts of carbon monoxide are allowed to burn to carbon dioxide in the dilute phase of a regenerator.

aftercooler

An exchanger cooling gas after compression so liquid drops out before the next stage.

afterflow

Afterflow is the flow associated with wellbore storage following a surface shut-in. When a well is first shut in at the surface, flow from the formation into the bottom of the wellbore continues unabated until compression of the fluids in the wellbore causes the downhole pressure to rise. If the wellbore fluid is highly compressible and the well rate is low, the afterflow period can be long. Conversely, high-rate wells producing little gas have negligible afterflow periods.

agbami field

The deepwater Nigerian field widely cited as an industry safety and performance benchmark.

AGC

Automatic gain control: processing that scales each part of a seismic trace toward a common amplitude, so weak late arrivals show alongside strong early ones.

AGC time constant

The time over which an automatic gain control adjusts to a change in signal level.

age diversity

The spread of ages present, and the range of experience it brings.

age-inclusive compensation

Reward designed to suit employees at different life stages.

ageism

Discrimination on the basis of age, in either direction.

agent-to-agent (a2a)

A pattern in which autonomous software agents communicate and coordinate with each other directly, without a person in the loop.

agentic ai

An AI system that plans and carries out multi-step tasks on its own initiative rather than answering one query at a time.

agglutinated

Agglutinated refers to the tests being formed from foreign particles that are "glued" together with a variety of cements.

aggradation

Vertical stacking of beds during a period when sediment supply and accommodation are roughly in balance, so the shoreline neither advances nor retreats.

aggradational

Describing a succession built by vertical stacking, where beds accumulate one atop another without the shoreline moving landward or seaward.

aggregate

A cluster of particles bound together — in water-base mud, clay platelets in a dehydrated face-to-face arrangement; in carbonates, grains joined into a composite particle.

aggregation

The process by which particles cluster into aggregates in a fluid — for clay in mud, face-to-face association following dehydration.

agile

Delivering in short increments with continuous feedback, rather than to a fixed long plan.

agile coach

Someone who helps teams and organizations adopt agile ways of working.

agile development cycle

The repeating loop of plan, build, review and adapt.

agile methodologies

The family of frameworks — Scrum, Kanban, XP — sharing agile principles.

agile practitioner

Someone working within an agile framework day to day.

agile transformation

An organization-wide shift to agile, which usually founders on structure rather than method.

agitation

Mixing or otherwise causing rapid and close contact between a solute and a solvent.

agitator

A propeller-like mixing device located inside a reactor's shell.

ai accelerator

In the reference glossary's usage, a program intended to speed the adoption of AI within an organization.

ai agent

A software component that carries out a defined task using a model, calling tools and acting on the result.

ai ethics

The principles governing responsible design, deployment and use of AI systems.

AI-powered scam

Fraud using generated voice, video or text to impersonate convincingly.

AIDA

Attention, interest, desire, action — the classic sequence a persuasive message follows.

AIDS

A disease of the immune system characterized by increased susceptibility to opportunistic infections, to certain cancers and to neurological disorders. AIDS is caused by the human immunodeficiency virus and is transmitted chiefly through blood or blood products that enter the body's bloodstream, especially by sexual contact or contaminated hypodermic needles.

aim

The desired value of a monitored variable. Ideal process centerline in a CUSUM system. Also called "target".

aipn

The Association of International Petroleum Negotiators, whose model contracts are widely used.

air bag

An inflatable bag mounted in the steering column, under the dashboard or on the doors of a car that cushions the driver and/or passengers by inflating automatically in the event of collision.

air bag (air cell)

A flexible bag inside some conservator tanks that separates the air in the tank from the oil in the tank.

air binding

A condition in which air is trapped in a heat exchanger, feedwater heater, or condenser, either blanketing the tubes or blocking the flow of fluid, typically as a result of improper venting.

air compressor

A machine raising air pressure for plant and instrument use.

air conditioning

Controlling air temperature and humidity in an enclosure.

air conditioning system

The equipment controlling temperature and humidity in an enclosure.

air cooler

Exchanger rejecting heat to ambient air with fans, used where cooling water is unavailable.

air cooling

Rejecting heat to ambient air rather than to water.

air core inductor

An inductor that uses air as the only core material.

air drill

To drill using compressed air or nitrogen instead of liquid mud, cooling the bit and carrying cuttings to surface.

air drilling

Drilling with compressed air or nitrogen as the circulating fluid, cooling the bit and lifting cuttings without any liquid mud.

air dryer

Equipment removing moisture from compressed air, without which instruments freeze and corrode.

air duct

Ducting carrying air to or from equipment.

air ejector

A device, sometimes called a jet pump or a steam jet air ejector (SJAE), that uses high-velocity fluid flow to create a vacuum that removes air and non-condensable gases from a condenser.

air eliminator

Device venting air from a liquid stream before metering, since air measures as though it were product.

air gun

A marine seismic source that releases a volume of high-pressure air into the water, the collapsing bubble generating the acoustic pulse.

air hose

Flexible hose carrying compressed air.

air inlet

The connection air enters by.

air intake

An opening that allows air to enter a duct or go directly to a fan.

air leak

Air entering where it should not, which on vacuum service destroys the vacuum and adds oxygen.

air permeability

The permeability measurement resulting from the use of the compressible fluid equation is known as the air permeability.

air pollution

Emissions that can cause harm to people, animals, or plants and are present in the environment in large enough amounts to actually be harmful.

air preheater

An exchanger warming combustion air with flue gas, the largest single efficiency gain on a boiler.

air purifying

Removing contaminant from air rather than supplying clean air, the limit of a filter respirator.

air purifying respirator

A mask or device that cleans or purifies air by filtering out airborne particulates such as dust, or chemically adsorbing relatively small amounts of toxic vapors and gases.

air receiver

Vessel storing compressed air, smoothing demand so the compressor does not cycle.

air registers

Adjustable openings that admit air into a furnace.

air removal system

A system that removes air and non-condensable gases from a condenser and helps establish and maintain the vacuum in the condenser on startup.

air rich

An operating condition in which more air than is necessary for complete combustion is supplied to the boiler.

air shooting

A seismic source fired above ground level, on poles or suspended, instead of in a drilled shothole. Also known as the Poulter method.

air supplied respirator

A respirator that supplies users with breathable air from a clean air source, such as a compressed air cylinder.

air wave

The sound wave travelling through air at about 330 m/s that a seismic spread records alongside the ground signal.

air-core shunt reactor

A shunt reactor without an iron core, giving linear reactance at high current.

air-cut mud

Mud carrying entrained air or gas bubbles, so its measured surface density is below its true density.

air-operated drum pump

A small pump commonly used to transfer thick liquids, such as grease, from large drums to smaller containers.

air-purifying respirator

A device used to filter out particulates, vapors, or gases that could be hazardous if inhaled, either by filtering out particulates or chemically adsorbing relatively small amounts of toxic vapors and gases.

air-supplied respirator

A respirator that supplies the user with breathable air from a clean air source, such as a compressed air cylinder or a self-contained air supply; used in work areas with large concentrations of hazardous gas or insufficient oxygen to support life.

airfoil fan

A type of centrifugal fan that has blades shaped like the cross-section of an airplane wing.

airgun array

The group of airguns fired together to produce a stronger, cleaner marine seismic source.

alarm

Any condition that represents a departure from the desired condition and that someone needs to acknowledge. For example, a hot motor, missed production goal, empty hopper, absence of flow, excess absenteeism, etc.

Alford rotation

A processing rotation that projects two orthogonal shear-wave recordings onto the fast and slow polarization directions where shear-wave splitting is present.

algal

Derived from algae, the origin of most oil-prone source material.

algorithm

An algorithm is a specific procedure for solving a well-defined computational problem.

algorithmic bias

Systematic error in a model's output arising from unrepresentative training data or from choices made in its design.

alias

The name given to a device to identify it in a ladder diagram; synonym for label, tag, or symbol.

alias filter

A low-pass filter applied before sampling, cutting frequencies above the Nyquist limit so they cannot fold back into the recorded band.

aliased

Distorted because the signal was sampled too coarsely.

aliasing

The ambiguity introduced by sampling a signal less than twice per cycle, so a high frequency is recorded as a lower one.

alidade

A telescopic sighting instrument used with a plane table to map topography and geology in the field.

alignment

A coherent event on a seismic display — samples lining up across traces at a consistent time or dip.

alignment procedure

The ordered method for bringing shafts onto a common axis.

aliphatic

Of hydrocarbons with chain rather than ring structure.

aliphatic compound

An organic compound whose carbons form chains or non-aromatic rings, rather than a benzene ring.

alkali

A base added to raise pH, used in mud chemistry and in chemical flooding.

alkaline

Describing an aqueous system holding more hydroxyl ions than hydrogen ions, with a pH above 7.

alkaline flooding

An enhanced oil recovery method injecting alkali — caustic soda, sodium carbonate or orthosilicate — to generate surfactant in place from an acidic crude.

alkaline-surfactant-polymer flooding

A chemical flood combining alkali, surfactant and polymer, abbreviated ASP.

alkalinity

The capacity of an aqueous system to neutralize acid, from hydroxyl ions present or generated, measured by titration.

alkalinity test

A titration with standardized acid measuring how much alkali a mud or water sample contains.

alkane

A saturated hydrocarbon of single bonds only, chemically stable and unreactive.

alkanes

Saturated straight or branched hydrocarbons, also called paraffins.

alkanolamine

The chemical family the sweetening amines belong to, combining an amine group with an alcohol group.

alkene

An unsaturated hydrocarbon with a carbon double bond, reactive and therefore a chemical feedstock.

alkyl

A saturated hydrocarbon group attached to a larger molecule.

alkylate

A high-quality gasoline blending component produced in an alkylation unit, typically used for motor fuel or aviation fuel.

alkylation

A chemical reaction in which an olefin reacts with isobutane to produce an isoparaffin (alkylate).

alkylation unit

A reactor system that uses a catalyst in a chemical reaction to combine olefins and isobutane to make alkylate.

alkyne

A hydrocarbon with a carbon triple bond, the most reactive of the series.

all-welded construction

Construction in which every joint is welded rather than threaded or bolted, leaving no mechanical seal to leak.

allochthon

A rock mass now resting far from where it formed, carried there by thrust faulting or large-scale gravity sliding.

allochthonous

Describing rock or material that formed elsewhere and was transported to its present position by faulting or gravity sliding.

allogenic

Describing minerals or rock fragments that formed in one place, were transported, and were deposited in another — the opposite of authigenic.

allowable

The maximum production rate a regulator permits from a well or field.

allowable ampacity

The maximum amount of current that an insulated conductor can carry without overheating.

alluvial

Pertaining to a stream or river acting on land — its subaerial environment, processes and deposits.

alluvial fan

A cone of sediment where a stream leaves confinement, coarse at the apex and fine at the edge.

alluvium

Sediment deposited by running water on land, typically detrital and poorly sorted.

alpha processing

A pulsed-neutron technique that combines a high-accuracy, low-precision measurement with a high-precision, low-accuracy one to obtain both qualities.

altered zone

The few inches of formation immediately around the borehole whose acoustic velocity has been changed by mud invasion, stress relief, or both.

alternate mode control

A vertical control that allows an oscilloscope to display two high-frequency signals at the same time. This done by alternately tracing each signal at a speed quick enough so that the eye perceives both signals at the same time.

alternating current

Current that flows in one direction and then reverses and flows in the opposite direction.

alternating current (AC)

Current that periodically reverses direction as it flows.

alum

A double sulfate salt of aluminum and an alkali metal, used in the oilfield as a crosslinker and as a coagulant.

alumina

Aluminum oxide, used as a solid desiccant and as a catalyst support.

aluminum activation log

A log of formation aluminum content, from the gamma rays emitted by aluminum activated by neutron bombardment.

aluminum stearate

The aluminum salt of stearic acid, used as a defoamer in drilling and completion fluids.

AMA (American Marketing Association)

The American Marketing Association, which awards the Professional Certified Marketer credentials.

ambient air

Surrounding air at its prevailing temperature, the heat sink every air cooler depends on.

ambient noise

Background energy unrelated to the source, which limits what a survey can resolve.

ambient temperature

The temperature of the air, fluid, or environment surrounding a vessel, device, or area.

American petroleum institute (API)

The American Petroleum Institute is the oil and gas industry's trade organization. API's research and engineering work provides a basis for establishing operating and safety standard issues and specifications for the manufacturing of oil field equipment and furnishes statistical and other information to related agencies. Visit API at www.api.org.

American wire gauge (AWG)

Wire sizing standard that is a measure of the thickness of copper, aluminum, and other wiring.

amides

Organic compounds of the form RCO-NH2, formed by reacting a carboxylic acid with ammonia or an amine.

amine

A chemical compound derived from ammonia by replacement of hydrogen by one or more hydrocarbon radicals. Mixed with water, it absorbs acid gases (hydrogen sulfide and carbon dioxide) from liquid and gas fractions. Common name for alkanolamines.

amine (lean)

Amine solution that is free of acid gases.

amine (rich)

Amine solution that has absorbed acid gases.

amine circulation

Pumping amine between contactor and regenerator, the loop the whole sweetening duty depends on.

amine flow

The amine circulation rate, matched to the acid gas load rather than to gas rate.

amine loss

Amine leaving the loop by carryover, degradation or vaporization, and a running cost as well as a fault.

amine seal

A level of amine solution between the tray and downcomer weir which forces gas/vapor to pass through bubble caps.

amine stream

The circulating amine flow, rich or lean depending on where it is taken.

amine sweetening

Removing hydrogen sulfide and carbon dioxide by absorbing them into an amine solution.

amine sweetening unit

The contactor, regenerator and heat exchange that strip acid gas with amine.

amine system

The circulating solvent loop that strips hydrogen sulfide and carbon dioxide from sour gas.

amine temperature

The amine's temperature, which sets both how much acid gas it absorbs and how fast it degrades.

amine treater

A piece of equipment that uses amine to remove hydrogen sulfide from an alkylation unit feed stream.

amines

Organic analogues of ammonia in which one, two or three hydrogens are replaced by organic groups, used to sweeten gas and to inhibit clays.

ammeter

A device used to measure and indicate current flow.

ammonia

A nitrogen compound made from gas, the basis of fertilizer and a candidate hydrogen carrier.

ammonia production

Combining hydrogen and nitrogen under pressure, the largest existing use of hydrogen and a way to ship it.

amorphous

Without crystalline structure, as silica gel and some scale deposits.

amortized cost

The carrying value of a financial instrument after systematic write-down over its life.

ampacity

The amount of current that a wire can carry without overheating.

amperage

Current expressed in amperes, the quantity a conductor is sized on.

ampere

The unit of measurement of electrical current. In the meter-kilogram-second system, it is the steady current that, when flowing in straight parallel wires of infinite length and negligible cross section separated by one meter in free space, produces a force of 2 × 10⁻⁷ newtons per meter of length. It is also the current produced in a circuit by 1 volt acting through a resistance of 1 ohm.

ampere (amp)

A unit of electrical current.

ampere rating

The current a device is rated to carry continuously.

amperes

The ampere is a measure of the amount of electric charge passing a point per unit time. It is often shortened to amp.

amplifier

A device that receives a signal at its input and delivers a larger, undistorted version at its output.

amplifier circuit

A circuit that produces an output signal that is a larger version of the input signal.

amplifier output

The signal an amplifier delivers.

amplify

To produce a larger, undistorted version of an input signal.

amplitude

The maximum extent of a vibration or oscillation, measured from the position of equilibrium (null point). Also, the magnitude of a quantity or the strength of a signal.

amplitude anomaly

A local increase in seismic reflection amplitude that may indicate hydrocarbons, and that has to be tested against the geology before it is believed.

amplitude distortion

Any failure of a recording or processing system to preserve the true relative amplitudes of its input.

amplitude spectra

The distribution of amplitude across frequency, which shows what the data can resolve.

amplitude spectrum

The distribution of energy across frequencies in a seismic signal.

amplitude variation with offset

The change in seismic reflection amplitude with source-receiver distance, read as an indicator of lithology and pore fluid.

amplitude variation with offset and azimuth

The variation of AVO response with the direction as well as the distance between source and receiver, abbreviated AVAZ.

amplitude versus offset (AVO)

Amplitude versus offset is the variation in seismic reflection amplitude with a change in distance between shot point and receiver that indicates differences in lithology and/or fluid content in rocks above and below the reflector.

amplitude-frequency response

How a system's gain varies with frequency, which decides what the data can and cannot show.

anaerobic

Describing a condition in which free oxygen is absent, and the organisms that live without it.

anaerobic process

A biological treatment process that occurs in the absence of oxygen.

analog

A measurement that varies continuously in relationship to an actual physical condition. Also refers to the one-way communication from a transmitter to a controller or DCS in 4-to-20 milliamps, 3-to-15 psi, or other analog scale.

analog data

Data that is represented in a physical way, stored as voltages and represented as lengths.

analog device

A device working on continuously variable signals.

analog display

A display that indicates values by converting current flow into the motion of a pointer across a scale.

analog field

A producing field of similar geology, used to forecast how an undeveloped one will behave.

analog input

A continuously variable signal brought into a control system.

analog module

A type of I/O module that converts a varying voltage or current signal into a digital signal, or vice versa.

analog output

A continuously variable signal a control system sends out.

analog signal

A continuous signal similar to a sine wave signal, such as the kind of signal that electro-mechanical relays receive from current transformers or voltage transformers.

analyte

The substance an analysis is measuring.

analytical instrument

An instrument determining composition rather than a physical condition.

analytical procedure

The written method for performing an analysis.

analytical system

The sampling, conditioning and analyzer equipment measuring composition on line.

analytical variable

A process variable that is based on the physical or chemical composition of materials.

analyzer

An instrument or device that measures and indicates physical or chemical characteristics based on the composition of a material or conditions in a process.

analyzer transmitter

A device that senses an analytical process variable, such as pH, and produces a signal that can be used to monitor or control the operation of a process system.

anchor pin

A pin fixed to a valve body that locates a seat or a trunnion and stops it rotating with the closure member.

anchorage

A secure point of attachment for lifelines, lanyards, and similar devices that are connected to a body harness.

anchorage connector

A connector, such as an eyebolt, that is installed at an anchorage; the connector enables other parts of a fall arrest system to be easily connected and disconnected at the anchorage.

AND gate

A digital logic gate that produces a HIGH output (1) only when all of its inputs are HIGH (1).

ane

A suffix for the name of a hydrocarbon that has a straight chain of carbon atoms linked together by single bonds.

angle

The shape that is made when two straight lines come together.

angle grinder

A large, portable power grinder that has a handle mounted on the side of the casing and a grinding wheel mounted at a right angle to the tool's motor. Also called a side grinder.

angle of approach

The angle at which a wavefront meets an interface, measured from the normal.

angle of incidence

The angle between an arriving ray and the normal to the interface it strikes.

angle valve

A type of globe valve in which the outlet is at a right angle to the inlet.

angular dispersion

The variation of seismic velocity with the direction of propagation.

angular misalignment

Shaft axes at an angle to each other.

angular momentum

The rotational momentum a spinning mass carries, which is what a centrifugal separator uses to throw droplets out.

angular unconformity

An angular unconformity is an unconformity in which horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers.

angularity

The angle between shaft axes.

anhydrite

Anhydrite is a mineral, anhydrous calcium sulfate, CaSO4.

aniline

The aromatic amine used in the aniline point test of a distillate.

aniline point

The temperature at which oil and aniline become miscible, indicating how paraffinic a stream is.

anion

A negatively charged ion.

anionic

Carrying a negative charge — of clay surfaces, groups on polymer chains, colloids, and the active part of certain surfactants.

anions

Negatively charged ions.

anisotropic

Anisotropic is having a physical property that has a different value when measured in different directions.

anisotropic formation

A formation whose properties differ with direction — permeability, resistivity or elastic stiffness measured along bedding against across it.

anisotropic media

Rock whose properties differ with direction, which laminated and fractured rock always is.

anisotropy

The property of being directionally dependent. Geological formations can have directionally dependent properties, and in seismics it refers to the difference between horizontal and vertical velocities.

anisotropy, anisotropic

Anisotropy is the property of being directionally dependent.

annihilation

Annihilation is the process whereby the positron and electron disappear immediately after pair production takes place.

annual campaign

The recurring yearly appeal that funds a nonprofit's operating costs.

annual report

The yearly publication combining financial statements with management's account of the business.

Annual Work Program and Budget

The yearly plan and spending the partners approve, and the main lever a non-operator has.

annubar

An averaging Pitot device spanning a pipe, sensing total pressure at several points and static pressure separately to give a mean flow rate.

annuity

A series of equal payments at regular intervals.

annular

Relating to the annulus, the ring-shaped space between two concentric strings.

annular BOP

A blowout preventer whose doughnut-shaped elastomer element is squeezed inward to seal on pipe of any size, or on open hole.

annular flow

A multiphase flow regime in which gas travels up the center of the pipe while liquid moves as a film on the wall.

annular gas flow

Formation gas migrating up the annulus between casing and borehole wall, generally through cement that has failed to seal.

annular pressure

Pressure carried by the fluid in an annulus, whether between tubing and casing or between two casing strings.

annular production

Producing formation fluid up the casing-tubing annulus rather than through the tubing.

annular space

The space between one cylindrical object and another surrounding it — most often between pipe and the wellbore, or between two casing strings.

annular velocity

The speed at which drilling fluid or cement travels up the annulus.

annuli

The plural of annulus.

annulment

Act of reducing to the lowest possible level by cancelling or nullifying terms.

annulus

The space between two concentric objects, such as between drill pipe and casing or between a core barrel and the borehole wall, where fluid can flow. Also, the area between the casing and the production tubing.

anode

The part of a corrosion cell at which electrons are released and positive metal ions are formed.

anomalous

Differing from what is typical, from what is expected, or from what a theoretical model predicts.

anomaly

A value or feature differing from what a model, or the surrounding data, would lead you to expect.

anoxic

Describing an environment without free oxygen, in which organic matter escapes aerobic degradation and can be preserved.

ANSI

The American National Standards Institute.

ANSI/ASQC Q90

Quality regulations developed by ANSI and ASQC that are the equivalent of ISO 9000.

anthracite coal

A hard variety of coal that is used to filter organic materials out of wastewater.

anthropogenic CO2

Carbon dioxide from human activity, as distinct from CO2 produced naturally underground.

anti-discrimination law

The statutes prohibiting employment decisions based on protected characteristics.

antialias filter

The low-pass filter applied before digitizing, removing energy above the Nyquist frequency so it cannot alias into the recorded band.

anticlinal

Pertaining to an anticline — an upwardly convex fold in rock layers.

anticlinal trap

A structural trap whose closure comes from an anticline, with hydrocarbons gathering in the crest beneath a seal.

anticline

A convex-upward formation of rock layers, which may form a trap for hydrocarbons.

antifoam

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

antifoam agent

An additive that lowers the surface tension of bubble films so entrained gas can break out of a fluid.

antilock braking system (ABS)

A braking system that when pressed hard (like in a panic stop or accident) the ABS pumps the brakes up to 30 times/sec. This occurs in an alternating pattern, left front/right rear and right front/left rear. This system helps the driver maintain control and stop the car in a straight line rather than spinning out of control.

antisqueeze

The defocusing of laterolog current beyond a certain distance into the formation, the opposite of current squeeze.

antithetic

A minor fault dipping opposite to the main fault it accompanies.

antithetic fault

A minor fault dipping opposite to the major fault it accompanies, with the opposite sense of displacement.

antithetic faults

Antithetic faults are usually smaller faults which dip in the opposite direction of the major fault.

antiwhirl bit

A PDC bit whose cutters are laid out to produce a deliberate net side force, pressing a smooth pad against the wall.

anvil

An iron or steel block on which metal objects are hammered into shape.

AOF

Absolute open flow: the rate a gas well would deliver at zero sandface pressure, read by extrapolating the back-pressure plot to that point.

AOFP

Absolute open flow potential — the rate a gas well would produce against zero flowing bottomhole pressure.

aperture

The extent of data brought into a calculation — in migration, the lateral range of traces summed into each output point.

aPHRi

The entry-level international HR credential from HRCI, requiring no prior HR experience.

API cement

A well cement manufactured to API Specification 10A, which classifies cements by class according to the depth, temperature and pressure they must serve.

api filtrate

The volume of filtrate a mud loses in the standard low-pressure test.

API fluid-loss test

The standard filtration test for water-base mud, run at room temperature and 100 psi differential for 30 minutes.

API Recommended Practice 10B: Recommended Practice for Testing Well Cements

The API document setting out the standard laboratory procedures for testing well cements and slurry designs.

API Spec 10A: Specification for Cements and Materials for Well Cementing

The API specification defining the classes of well cement and the requirements each must meet.

API Spec 6D: Specification for Pipeline Valves

The API standard for pipeline valves, covering how ball, check, gate and plug valves are designed, built, tested and documented.

API unit

The calibration unit for natural gamma ray logs, defined by the artificial formation in the API test pit at Houston.

apparent anisotropy

The ratio of the velocity measured from normal moveout, which is largely horizontal, to the vertical velocity from a borehole survey.

apparent dip

Apparent dip is the angle that a plane makes with the horizontal measured in any randomly oriented section rather than perpendicular to strike.

apparent matrix

The matrix density or transit time back-calculated from a pair of logs, used to identify lithology where the true matrix is unknown.

apparent power

The total power that a utility must produce to meet the demands for both working power and non-working power (power stored and returned by inductance and capacitance); equal to voltage times current in any circuit.

apparent velocity

The velocity a wavefront appears to have along a line of receivers, always greater than the true velocity unless the front travels along that line.

apparent viscosity

The viscosity a non-Newtonian fluid appears to have at one particular shear rate and temperature.

apparent wavelength

The wavelength a line of receivers measures when a wave arrives at an angle — always longer than the true wavelength.

applicant tracking system (ATS)

The system managing applications through the hiring process, and screening many of them out.

application programming interface (API)

The defined set of calls through which one piece of software uses another.

application security control

A control built into software to prevent misuse or exploitation.

applied voltage

The voltage impressed across a component.

applied-potential method

An electrical survey in which current is driven between fixed electrodes and the resulting potential field is mapped with a roving electrode.

appraisal

The phase following a discovery, in which wells are drilled to establish the extent and character of the accumulation before development is committed.

appraisal of an exploration discovery

A process for evaluating an exploration discovery by steadily reducing subsurface uncertainties sufficiently to allow decision-makers to proceed with confidence in an economically viable, optimized field development with a good understanding and full description of the remaining uncertainties.

appraisal strategy

The plan for how many appraisal wells and tests are needed to reduce uncertainty enough to sanction.

appraisal well

A well drilled after a discovery to size the accumulation and test how well it flows.

approved solvent

A solvent permitted for the task, others being excluded on flammability or toxicity.

aqueous depositional environment

An aqueous depositional environment entails the deposition of sediments in oceans, seas, rivers, deltas and lakes.

aquifer

A body of rock or underground layer of water-bearing permeable rock or unconsolidated materials (gravel, sand, silt, or clay) whose fluid saturation, porosity, and permeability permit the production of groundwater, which can be extracted using a water well.

aquifer storage

Gas stored in a water-bearing formation rather than a depleted field.

aquifer storage field

The underground storage of natural gas in a porous and permeable rock formation topped by an impermeable cap rock, the pore space of which was originally filled with water.

aragonite

A calcium carbonate form that recrystallizes to calcite, altering carbonate porosity.

arbitrary line

A section extracted along any chosen path through a seismic volume.

arbitration

Binding private determination by a chosen tribunal instead of a national court.

arc chute

The structure confining and cooling the arc as a breaker opens.

arc fault

A fault that occurs when current jumps through the air between two terminals that have different potential.

arc welding

Welding using an electric arc as the heat source.

Archie equation

Archie's relation linking formation resistivity to porosity and water saturation through the formation factor, cementation exponent and saturation exponent.

Archie rock

A clean rock whose resistivity follows Archie's equation with constant cementation and saturation exponents.

Archie's law

In petrophysics, Archie's law relates the in-situ electrical conductivity (C) of a porous rock to its porosity and fluid saturation of the pores.

Archimedes' principle

Archimedes' principle states that the upward buoyant force that is exerted on a body immersed in a fluid, whether fully or partially submerged, is equal to the weight of the fluid that the body displaces.

architect

A person who designs buildings and supervises their construction.

arcing

Current flow through air, as can occur across an open switch.

arcuate

Arcuate refers to something that is curved or bent like a bow or arc.

arcuate to cuspate-shaped

Arcuate refers to something that is curved or bent like a bow or arc. Cuspate-shaped refers to something that is triangular or pointed, resembling a cusp or tooth.

area

The two-dimensional measurement of a defined region, generally obtained by multiplying width times length and expressed in square units such as square inches, square feet, or square miles.

areal

Relating to plan-view extent, as in areal sweep across a reservoir.

areal array

The pattern in which injectors and producers are laid out across a field.

areal displacement efficiency

The fraction of a pattern's area swept by the injected fluid at the moment it breaks through at the producer.

areal extent

The plan-view area a reservoir or feature covers.

areal sweep efficiency

The fraction of a flood pattern's area that the injected fluid has contacted at a given time.

arenes

Aromatic hydrocarbons.

arenite

Arenite, or sandstone, is a clastic sedimentary rock composed of sand-sized minerals and rock grains. Most sandstone is composed of quartz and/or feldspar.

argillaceous

Describing rock or sediment containing an appreciable proportion of clay- and silt-sized particles.

argillaceous beds

Argillaceous beds refer to sedimentary rock layers that are primarily composed of clay and silt-sized particles, which often contain a high proportion of clay minerals. These beds are commonly found in shales, mudstones, and argillites.

argon

An inert gas used for shielding welds and as a carrier in analysis.

argus assessment

A published price from Argus Media, the main alternative reference to Platts.

arithmetic mean

The sum of a set of values divided by how many there are — the ordinary average.

arkosic

Arkosic sandstone is a detrital sedimentary rock that contains at least 25% feldspar.

armature

The movable part of a magnetic contactor that allows contacts to close. In a DC motor, it refers to the entire rotating assembly including the shaft, armature core, armature windings, and commutator.

armor

The steel strands wound around the outside of a wireline logging cable, carrying its tensile strength.

Armstrong oscillator

An LC oscillator that produces a sinusoidal wave. A transformer arrangement is used for the feedback circuit.

arm’s length basis

Dealing on terms unrelated parties would accept, which tax authorities test transactions against.

aromatic

A cyclic hydrocarbon whose carbon atoms are connected by both double bonds and single bonds, typically a high-octane compound produced by applying heat and pressure to naphtha and reforming the hydrocarbon molecules.

aromatic content test

The API procedure measuring how much aromatic hydrocarbon a base oil contains before it is used in an oil mud.

aromatic hydrocarbon

A hydrocarbon built on a benzene ring, with single and double bonds alternating around a six-carbon ring.

aromatics

Ring hydrocarbons with alternating double bonds, high in octane but restricted on health grounds.

array

An array is generally a group of source or receiver points along a seismic line (known as an inline array), respectively.

array design

The chosen arrangement of sources or receivers, which fixes what wavenumbers the survey can record.

array dielectric logging tool

Array dielectric logs acquire dielectric data at a number of different frequencies, giving a resistivity profile at those different depths of investigation. They also measure the signal phase shift, from which can be derived the water-filled porosity.

array induction

An induction tool carrying several mutually balanced coil arrays, recorded separately and combined in software to give the depth of investigation wanted.

array induction tool, log

An array induction tool is a tool that consists of several mutually balanced arrays whose signals are recorded separately and combined in software to produce the response desired. Typically, there is one transmitter and five to ten pairs of receivers.

array laterolog

An electrode device with multiple current electrodes configured in several different ways to produce several different responses. A typical array consists of a central electrode emitting survey current with multiple guard electrodes above and below it. Current is sent between different guard electrodes to achieve greater or less focusing, with greater focusing providing greater depth of investigation. About five basic measurements are obtained, which may be further improved by software focusing to ensure proper response in a wide range of conditions.

array length

The array length is the distance from the first receiver in an array to the last receiver in the array.

array propagation resistivity

An LWD resistivity from several transmitter-receiver spacings, giving a set of curves at different depths of investigation.

array sonic

An acoustic logging tool with a row of receivers, typically four to twelve, so the whole wavetrain can be processed rather than merely timed.

array sonic tool, log

An array sonic is a type of acoustic logging tool that uses a large number of receivers, typically 4 to 12.

arrays

A geometric arrangement of seismic receivers (geophones) with signals recorded by one channel, which can contain numerous closely spaced geophones. An areal array involves the placement of receivers around the source (often in a circular or oval shape) as opposed to in a straight line radial to the shot.

arrester

A device diverting a voltage surge safely to earth.

arrestor

A device stopping the passage of flame or of a surge.

arrival

An event appearing in seismic data — a reflection, refraction, diffraction or direct wave — or the time at which it appears.

arrival time

The elapsed time between a source releasing energy and that energy reaching a receiver.

article

A subdivision of the chapters in the NEC. Beginning with Article 90 "Introduction" and ending with Article 820 "Community Antenna and Radio Distribution Systems," the NEC articles are the main topics of the code.

artificial general intelligence (AGI)

A hypothetical AI matching human cognitive ability across arbitrary tasks rather than one narrow domain.

artificial intelligence

The ability of some controllers to "learn" from normal process operation and thus improve their response. Also referred to as "fuzzy logic."

artificial lift

A method of bringing well fluids to the surface when the downhole pressure is not great enough to force the fluids up naturally.

artificial lin

A method of bringing well fluids to the surface when the downhole pressure is not great enough to force the fluids up naturally.

artificial neural networks (ANN)

Artificial Neural Networks, usually just termed neural networks or neural nets, are computing systems inspired by the biological neural networks that constitute animal brains. An ANN is based on a collection of connected units or nodes called artificial neurons, which loosely model the neurons in a biological brain.

artificial superintelligence (ASI)

A hypothetical AI exceeding human ability across all domains.

as-delivered BTU

The heating value of gas actually delivered, in BTU per standard cubic foot at the point of sale.

ASCII

American Standard Code for Information Interchange standard set of 256 codes that express many of the common digits and characters used by most people throughout the world.

ash gate

An internal gate that separates the bottom of the boiler from the rest of the bottom ash handling system.

ash hopper

A bin that is used to collect the ash that is left over from combustion.

ASIC

ASIC is an application-specific integrated circuit chip customized for a particular use. Modern ASICs often have microprocessors and memory blocks, including ROM, RAM, EEPROM and flash memory.

ASP flooding

Alkaline-surfactant-polymer flooding, combining alkali, surfactant and polymer in one chemical flood.

asphalt

A solid or near-solid bitumen that melts on heating, carrying nitrogen, oxygen and sulfur impurities.

asphaltene

The heaviest, most polar fraction of crude, which drops out and plugs when conditions change.

asphaltene onset concentration

The amount of injected solvent that first causes asphaltene to drop out of a reservoir oil at given conditions.

asphaltene onset pressure

The pressure at which asphaltene first precipitates from a reservoir fluid as pressure falls, abbreviated AOP.

asphaltene precipitation

The flocculation of asphaltenes out of a crude oil when pressure, temperature or composition change and they can no longer stay in colloidal suspension.

asphaltenes

The heaviest fraction of a crude oil: fused aromatic and naphthenic ring networks carrying nitrogen, sulfur, oxygen and metals, so not true hydrocarbons.

asphaltic

Rich in asphaltenes and bitumen, and so heavy and difficult to process.

asphaltic crude

A crude oil low in paraffin wax and high in naphthenic and asphaltic components.

asphaltic crude oil

Crude oil that contains a high proportion of asphalt.

asphaltic mud additive

Naturally occurring or refinery-residue asphaltic material used for filtration control and shale stabilization.

asphalts

Heavy products made from the bottom of the crude oil barrel and used for applications such as paving, roofing, and waterproofing.

ASQC

The American Society for Quality Control.

assemblage

The set of minerals or fossils occurring together, diagnostic of conditions or age.

assemblages

The associated set of minerals or fossils that characterize a rock unit.

assembly bha

The bottomhole assembly, the collars, stabilizers and tools above the bit.

assessment

A process to determine gaps between an individual's current skills and those required of a particular position. It begins with an Employee Assessment and a Supervisor Assessment and ends with an Assessor Assessment of the results by an independent third party, after which a Competency Development Plan can be built.

assessor

A person (usually a supervisor) who assesses an employee's performance and/or related knowledge in a range of tasks to determine if the competence demonstrated meets the requirements of the specified standards.

assessor assessment [formerly verification]

An objective assessment by a third-party SME to resolve differences between employee and supervisor ratings by providing an opportunity for the employee to demonstrate or document skill. The process ensures the system remains objective and fair across the organization.

asset development process

The asset development process is a sequential process, often with stage gates, which progresses an oil and gas property through the following stages: a) Identify and assess exploration opportunities. b) Analyze alternative development options. c) Optimize preferred development plan. d) Execute development plan. e) Manage production life cycle.

asset sale versus stock sale

Selling the license interest itself, or selling the company that holds it, with different tax and liability outcomes.

asset security

Protecting information assets across their whole life.

assets

Assets are items that have earning power, or some other value, to their owner.

assistant secretary

The Assistant Secretary of Labor for Occupational Safety and Health, U.S. Department of Labor, or designee.

associated gas

Gas produced along with oil, whose disposal shapes the development plan.

astable multivibrator

A multivibrator that has no stable state.

asthenosphere

The mechanically weak, plastic layer of the upper mantle on which the rigid lithospheric plates move.

ASTM

A standard published by ASTM International, the body whose material and sieve specifications the oil industry uses alongside API, ASME and ISO.

ASTM specification

A published test method or product standard from ASTM International, cited in sales contracts.

asymmetry

A characteristic of many process loops in which the process response differs in either amount or speed depending on the direction of change.

asynchronous

These inputs; set and reset, regardless of the status of the clock signal can set or reset the flip-flop because they can override the synchronous (normal data) inputs.

ATC

Automatic Temperature Compensator.

ATG

Automatic Temperature Gravity Selector.

athabasca oil sands

The Alberta deposit of bitumen-saturated sand, recovered by mining or in-situ methods.

Atlantica (West Africa offshore E&P simulation)

The E&P project development simulation, taking a deepwater West African prospect through the stage gates.

atmospheric condition

Ambient temperature and pressure, the reference state for surface measurement.

atmospheric corrosion

Oxidation of a susceptible metal exposed to air and moisture at surface.

atmospheric distillation

The first separation of crude into fractions by boiling point at near-ambient pressure.

atmospheric pressure

The atmospheric pressure exerted at a certain location. At sea level, it is about 14.73.

atmospheric pressure base

The atmospheric pressure exerted at a certain location. At sea level, it is approximately 14.73.

atmospheric residue

What remains at the bottom of the crude tower, feeding the vacuum unit.

atmospheric tank

A tank designed to store liquids at or near atmospheric pressure, ranging from 0 psig to 0.5 psig.

atmospheric testing

Measuring oxygen, flammable gas and toxics before entry or hot work is permitted.

atmospheric tower

A tower whose interior is kept at or near atmospheric pressure; used in a crude oil distillation unit to separate basic fractions from incoming crude.

atom

The smallest particle to which an element can be reduced while still retaining the properties of that element; an elemental particle that makes up all forms of matter.

atomic mass

The atomic mass is the quantity of matter contained in an atom of an element.

atomic number

Atomic number is the number of protons in the nucleus of an atom, which is characteristic of a chemical element and determines its place in the periodic table.

atomic particles

Protons, electrons, and neutrons. Protons are positively charged, and electrons are negatively charged. Neutrons are not charged, so they are not considered when looking at an atom's electrical characteristics.

atomic weight

The mass of an atom relative to carbon twelve.

atomizer

The part of an oil burner that uses pressure, steam, or air to change oil into a mist.

attapulgite

A needle-shaped magnesium-aluminum silicate clay used to build viscosity in salt water, where bentonite will not hydrate.

attemperator

A device that sprays water into the steam flowing through a superheater or reheater to prevent the final outlet steam temperature from exceeding established limits. Also called a desuperheater.

attendant

An individual stationed outside one or more permit spaces who monitors the authorized entrants and who performs all attendant's duties assigned in the employer's permit space program.

attention mechanism

The component of a neural network that weights which parts of its input matter most for each part of its output.

attenuate

To reduce the amplitude of unwanted energy — multiples, ground roll or random noise — relative to the signal.

attenuation

The reduction of the amplitude of a signal, electric current, or other oscillation; a decrease in signal voltage during its transmission from one point to another.

attenuation resistivity

Formation resistivity derived from the loss of amplitude in an electromagnetic wave travelling between the receivers of a propagation tool.

attitude

The orientation of a planar or linear feature in space, given as strike and dip, or as trend and plunge.

attribute

A measurable property extracted from seismic data — amplitude, dip, frequency, phase or polarity — displayed to reveal geology the raw section does not show.

attributes

Items that can be counted.

attrition

The natural loss of employees over time, whether or not they are replaced.

attrition prediction

Modeling who is likely to leave, so retention effort can be directed.

auctioneering control

A system of control in which the controlled variable is measured in two or more places, and the highest measured value is selected as the loop input.

audience analysis

Establishing who will be present, what they know and what they want, before preparing.

audience targeting

Directing a message to a defined group rather than broadcasting it.

audio measurement

Recording the sound at successive depths in a well to produce a noise log.

audiometric test

A hearing test that measures the ear's ability to detect sound at specific frequencies or tones.

audit

An evaluation performed to make sure that the individual components of a quality system are operating effectively and that procedures are being followed properly.

audit and assurance framework

The planned program of checks giving management confidence that controls work as claimed.

auditing, monitoring and detection

The continuous observation that reveals whether controls are working and whether an attack is underway.

auger

A device that bores down into large quantities of solid materials to obtain samples.

aulacogen

A failed rift arm: the third arm of a three-way rift junction that stopped extending, left as a trough reaching into the continent.

authentication

Establishing that someone is who they claim to be.

authigenesis

Authigenesis is the process whereby a mineral or sedimentary rock deposit is generated where it is found or observed.

authigenic

An authigenic mineral or sedimentary rock is one that was generated where it is found. Authigenic sedimentary minerals form during sedimentation by precipitation or recrystallization instead of being transported from elsewhere by water or wind.

authigenic clay

Clay formed in place within the pore space, which reduces permeability disproportionately.

authority for expenditure

The operator's budget document estimating the cost of drilling a well to a stated depth or objective and of completing it.

authorization

Determining what an authenticated party is permitted to do.

authorization for expenditure (AFE)

The operator's budget document estimating the cost of drilling and completing a well, issued to partners for approval before work begins.

authorized entrant

An employee who is authorized by the employer to enter a permit space.

auto vs. manual scheduling

Letting the tool calculate dates from dependencies against fixing them by hand.

auto-assess

In cases where an assessor assessment is not required, an Administrator can select assessments to auto-assess, which records the lower of the employee and supervisor assessment scores for each competency unit as the Final Assessment Result (FAR).

auto-correlation function

A signal correlated with itself, used to find repeating structure such as multiples.

auto-tune

A feature of some single-Loop and multiple-loop controllers that automatically sets optimized loop parameters.

auto-tuning

A controller enhancement that imposes a process upset to test the system response automatically and then resets the controller's parameters based on that response.

autochthon

A rock mass still in the place it formed, as opposed to an allochthon that has been transported over it.

autochthonous

Describing rock that formed in the position where it now sits and has not been transported.

autocorrelation

The comparison of a waveform with a shifted copy of itself, measuring similarity as a function of lag.

automatic control

A basic form of process control in which input devices, controllers, and output devices control a process with minimal input from operating personnel.

automatic gain control

Processing that scales each part of a trace toward a common amplitude, computed over a window that slides in both time and space.

automatic gauge

A gauge reading and reporting without an operator.

automatic temperature compensator

Mechanism correcting a meter's volume to reference temperature without operator action.

automation

Having machines perform work previously done by people.

automotive gas oil (AGO)

Diesel fuel, under the name used across West African markets.

autoranging

A feature on most digital test instruments that allows the instrument to control the measurement range automatically.

autotrack

To let software follow a seismic reflection through a volume automatically from a few seeded picks.

autotransformer

A transformer with one winding tapped, cheaper than two windings but with no isolation.

auxiliary contacts

Contacts used in a magnetic contactor for auxiliary control functions such as completing current flow to an indicating light used to indicate a motor is on.

auxiliary device

A supporting device serving a main item of equipment.

auxiliary drawings

Supplemental drawings that are often included with the working drawings in a set of blueprints.

auxiliary equipment

Supporting equipment whose failure stops the main machine.

auxiliary relay

A type of relay that only operates when it receives a signal from a protective relay.

auxiliary steam

Steam used for purposes other than driving a main turbine or heating feedwater.

auxiliary system

A supporting system such as lube oil, cooling or instrument air, whose failure stops the main machine.

auxiliary vessel

A secondary vessel associated with a process system.

AV

Apparent viscosity — the viscosity a mud appears to have at one particular shear rate, taken as half the 600 rpm viscometer reading.

AVAZ

Amplitude variation with azimuth — the change in reflection amplitude with the direction between source and receiver.

average reservoir pressure

The pressure a reservoir volume would settle to if all fluid motion ceased — the pressure a shut-in well eventually builds back to.

average velocity

Depth divided by the traveltime to that depth — total distance over total time.

averaging

A processing technique used by digital oscilloscopes to eliminate noise in a signal.

AVO

Amplitude variation with offset: the change in seismic reflection amplitude with source-receiver distance, read as an indicator of lithology and pore fluid.

AVO analysis

AVO analysis is a technique by which geophysicists attempt to determine thickness, porosity, density, velocity, lithology and fluid content of rocks.

AVOAZ

Amplitude variation with offset and azimuth — AVO analyzed separately in each azimuth sector.

awareness (competency level 1)

Has general, limited comprehension of a particular topic / Able to identify and define key elements of the topic / Understands basic concepts and principles / Able to provide basic assistance / Able to carry out assigned tasks with guidance and monitoring.

AWG system

A system used to indicate the size of wires used in routine electrical work; sizes range from 40 (smallest) through 0000 or 4/0 (largest).

awkward postures

An ergonomic risk factor involving postures that differ significantly from neutral positions. Awkward postures include repeated or prolonged reaching, twisting, bending, kneeling, squatting, and working overhead with your hands or arms.

axial

Relating to a line or direction parallel to the axis of a shaft.

axial air flow

Air flow that is parallel to the shaft of a fan.

axial clearance

The distance that a thrust bearing allows a pump shaft to move in an axial direction.

axial clearance check

A measurement taken with a dial indicator to determine the amount of thrust bearing wear.

axial compressor

A compressor moving gas along its axis through rows of blades, high flow at modest ratio.

axial fan

A fan that produces axial air flow; typically moves large quantities of air or gas at relatively low pressure.

axial impeller

An impeller that produces flow that is basically parallel to the shaft of a mixer.

axial load

Load acting along the shaft axis.

axial loading

Force acting along the axis of an object — for casing, the tension or compression carried along the string.

axial movement

Movement along the shaft axis, which thrust bearings exist to restrain.

axial surface

The imaginary surface through a fold that bisects the angle between its limbs.

axial thrust

A force that is exerted parallel to the centerline, or axis, of a shaft.

axially split pump

A pump with a casing that is split parallel to, or along, the axis of the pump's shaft.

axis of rotational symmetry

The axis about which a material's properties are unchanged by rotation — for a layered rock, the axis perpendicular to bedding.

axis rotation

The line a body turns about.

azeotrope

A mixture of components that behaves as if it were a single component with a constant boiling point.

azeotropic

Of a mixture that boils at constant composition, and so cannot be separated by simple distillation.

azeotropic column

A column using an added component to break an azeotrope.

azeotropic distillation

A type of distillation that uses a solvent or two distillation towers in a special arrangement to separate mixtures whose components form azeotropes and are difficult to separate.

azeotropic distillation system

A distillation system using an added component to break an azeotrope.

azimuth

The horizontal angle or direction of a compass bearing.

azimuthal

Referring to direction around a vertical axis — the compass-bearing component of an orientation or a measurement.

azimuthal density

An LWD density log recorded separately in sectors around the collar, giving a density image as the tool rotates.

azimuthal laterolog

An azimuthal laterolog is a type of electrode device that is able to measure resistivity in different directions around the sonde. In most laterologs, the electrodes are cylinders that average the resistivity azimuthally around the sonde. In azimuthal laterologs, the electrode is segmented radially in several portions, each of which responds to the resistivity in the direction it is facing.

azimuthal resolution

The angular detail an azimuthal logging measurement can resolve around the tool, set by the number and spacing of its sensors.