Discover the IHRDC Energy Glossary_beta

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G

gain

The ratio of an output signal to its input signal, whether in a controller, amplifier, or other device. In conduit installation, a value used to determine where to cut conduit that will be bent.

gain accuracy

An indication of how accurately the vertical system of an oscilloscope attenuates or amplifies a signal; usually listed as a percentage error.

gain bandwidth product

The product of the open-loop voltage gain and the frequency at which it is measured.

gal

The gal is the most commonly used unit of acceleration.

galena

Lead sulfide, PbS, and the densest of the weighting materials, used where extreme mud density is needed.

galling

The tearing and transfer of metal between two surfaces sliding under load, roughening both.

galvanic anodes

Blocks of a more active metal — zinc, aluminum or magnesium — bolted to a structure so they corrode instead of it.

gamma (γ)

Thomsen's parameter for the fractional difference between horizontal and vertical shear wave velocity in a VTI medium.

gamma radiation

A highly penetrating type of nuclear radiation that may be used to measure the density of a material.

A gamma ray, or gamma radiation, is a penetrating electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves and so imparts the highest photon energy.

gamma ray API unit

The gamma ray API unit is defined as 1/200 of the difference between the count rate recorded by a logging tool in the middle of the radioactive bed and that recorded in the middle of the nonradioactive bed.

gamma ray count

The number of gamma rays detected, converted to an API shale index.

gamma ray densitometer

A gamma ray densitometer is a device for measuring the density of fluids in a completed well, using a radioactive source of gamma rays and a detector.

gamma ray interactions

The processes by which a gamma ray transfers energy to matter — photoelectric absorption, Compton scattering and pair production.

gamma ray log

A measurement of the natural emission of gamma rays by a formation, used to identify rock types and correlate geological layers across different wells.

gamma ray log, natural gamma ray log

A gamma ray log is a measurement of the natural emission of gamma rays by a formation.

gamma ray signature, spectrum

A measure of the distribution of the intensity of gamma radiation versus the energy of each photon.

gamma ray spectroscopy, natural gamma ray spectroscopy

Gamma ray spectroscopy is the technique of measuring the spectrum, or number and energy, of gamma rays emitted as natural radioactivity by the formation.

gamma ray tool

The tool logging natural radioactivity to distinguish shale from clean formation.

gamma rays of capture

Gamma rays of capture are the prompt gamma rays emitted by an excited nucleus.

gamma-gamma log

A log using a gamma ray source and detector, whose count rate depends on the electron density of the formation.

gantry

A structural frame on some types of cranes that includes sheaves and drums around which boom hoist lines are reeved.

gantt chart

A bar chart showing tasks against time, with dependencies.

gap analysis

The difference between current capability and required capability, and what closing it takes.

gap or skill gap

The difference between an employee's current performance and the performance required of the specific job title.

Garrett Gas Train

The API apparatus for quantitative sulfide and carbonate analysis of mud filtrate.

gas

A fluid which can be compressed and completely fills any container in which it is contained.

gas accumulation

Gas gathered and held in a trap.

gas allowable

The regulated volume of gas which can be produced over a designated period of time.

gas analyzer

An instrument measuring gas composition on line.

gas anchor

A perforated or shrouded intake below a sucker-rod pump that lets free gas separate out before fluid enters the pump.

gas back-pressure valve

Valve holding pressure upstream on the gas outlet, keeping a vessel at its design pressure.

gas bearing

Describing a formation containing gas, whether free in the pore space or dissolved in the formation fluid.

gas blow-by

Gas blowing by a dump valve as the result of no liquid seal to prevent it from escaping with the oil or water.

gas bomb

A container used for sampling gas.

gas burner

The burner firing gaseous fuel.

gas buster

A mud-gas separator — a vessel that lets entrained gas break out of returning mud and vents it safely.

gas bypass

A method of controlling steam temperature in which a portion of the flue gas bypasses the superheaters.

gas cap

Free gas accumulated at the top of a reservoir, above the oil it overlies.

gas chiller

Exchanger cooling gas with a refrigerant to condense heavier hydrocarbons out of it.

gas chilling system

The refrigeration circuit and exchangers that cool gas to condense out liquids.

gas chimney

A vertical zone of gas-disturbed, poorly imaged seismic data above a leaking accumulation.

gas chromatograph

A device used to determine the concentrations of several materials in a complex mixture or solution.

gas chromatography

An analytical chemistry process for separating and analyzing compounds that can be vaporized without decomposition.

gas compressibility

The change in gas volume with pressure, which makes gas both an excellent drive and a hazard.

gas compression

Raising gas pressure so it can enter a pipeline or be recycled.

gas compressor

Machine raising gas pressure, sized by both flow and compression ratio.

gas condensate

Hydrocarbon that exists as gas in the reservoir and drops out as liquid when pressure falls below the dew point.

gas coning

The downward pull of the gas-oil contact toward a producing interval under drawdown, bringing gas into the well.

gas cooling

Removing heat from gas, usually after compression, so liquids drop out and equipment survives.

gas cylinder

A portable pressure vessel holding compressed or liquefied gas.

gas dehydration

Removing water from gas to meet dew point.

gas deviation factor

The compressibility factor z in the real gas law, correcting the ideal gas equation for the actual behavior of the gas.

gas discharge

The outlet gas from a compressor stage.

gas discharge pressure

The pressure at a compressor's outlet.

gas distribution

The low-pressure network delivering gas to homes and small commercial users.

gas drive

A primary recovery mechanism in which expanding gas, dissolved or free, provides the energy that pushes oil to the well.

gas drive reservoir

A reservoir whose production is driven by expanding gas.

gas feedstock

Natural gas used as chemical raw material rather than as fuel.

gas flare penalty

The charge levied per unit of gas flared, intended to make capture the cheaper option.

gas formation volume factor

The volume a quantity of gas occupies at reservoir conditions divided by the volume it occupies at standard conditions.

gas gathering

The act of bringing together large volumes of natural gas from different wells by pipelines for the purpose of processing them in a central processing plant or transferring them into sales transmission pipelines.

gas gravity

The density of a gas expressed as the ratio of its molecular weight to that of air.

gas holdup log

A record of the fraction of the pipe cross section occupied by gas at each depth.

gas hydrate

A crystalline solid in which gas molecules, usually methane, are caged within a lattice of water molecules.

gas in solution

Gas dissolved in a liquid phase — in a reservoir, the gas held in the oil at pressures above the bubble point.

gas initially in place (GIIP)

GIIP is the abbreviation for Gas Initially In Place.

gas initially in place, GIIP

GIIP is the abbreviation for Gas Initially in Place.

gas injection

Injecting gas into a reservoir to maintain pressure or to displace oil toward the producers.

gas inlet

The connection gas enters by.

gas interference

The loss of sucker-rod pump efficiency when free gas enters the pump and is compressed instead of liquid being lifted.

gas leak

Escaping gas, which on hydrocarbon service is both a loss and an ignition risk.

gas lift

An artificial lift method injecting gas into the production conduit to lighten the fluid column and reduce the hydrostatic pressure the reservoir must overcome.

gas loading

The gas rate a vessel or column is handling against its design, and what flooding is measured against.

gas lock

Gas locking is a condition caused by the induction of free gas into the wellbore that interferes with the operation of valves and pump components preventing the intake of fluids.

gas locking

A condition that occurs when gas fills the pump barrel. The gas pressure holds the traveling valve closed on the downstroke and holds the standing valve closed on the upstroke. With both valves held closed no well fluid can enter the pump.

gas measurement

Determining gas quantity, corrected for pressure, temperature and composition rather than volume alone.

gas metal arc welding

A method of arc welding that uses an electrode that is fed off a roll, and a gas, or mixture of gases, to provide a shield. Also called metal inert gas welding, or MIG welding.

gas methane

The principal component of natural gas.

gas migration

The movement of formation gas up through or around a cement sheath before or after the cement sets.

gas oils fraction

The crude oil fraction whose carbon atoms range from C27 to C33, and have boiling points between 450°F and 800°F.

gas outlet

The connection gas leaves by.

gas pipeline

The pipe system transporting gas between production, processing and market.

gas pipeline transmission system

The high-pressure network moving gas from processing to distribution and large users.

gas plant

A unit where the gases are sent after being separated from the straight run gasoline part of the fraction; recovers light products such as LPG.

gas processing plant

A facility that separates natural gas liquids and impurities from raw gas, delivering a sales-specification gas stream.

gas prospect

A mapped feature expected to hold gas rather than oil.

gas recirculation

A method of controlling steam temperature in which a portion of the flue gas is recirculated to either the windbox or to a point just above or below the burners in the furnace area.

gas recovery system

The part of a cat cracking unit in which overhead products are separated into non-condensed gases, unstabilized cat-cracked gasoline, and stripping steam condensate.

gas recycle

Returning part of the compressed gas to suction, holding a machine off its surge limit at low flow.

gas refill

Replenishing a storage reservoir after the withdrawal season.

gas reservoir

A reservoir whose hydrocarbons are predominantly in the gas phase.

Gas Sales Agreement (GSA)

The long-term contract fixing volume, price, quality and delivery point for pipeline gas.

gas sand

A porous, permeable sand body charged with natural gas.

gas saturation

The fraction of pore space occupied by gas.

gas scrubber

A vessel removing liquid droplets from a gas stream.

gas separation

Splitting gas from the liquid it is produced with, the first step in any surface facility.

gas separator

Equipment that removes entrained gas from a produced liquid stream.

gas shale

An organic-rich shale that is both the source and the reservoir for the gas it produces.

gas show

An increase in gas in the returning mud, indicating that a gas-bearing formation has been penetrated or disturbed.

gas specification

The contractual limits gas must meet on water, sulfur, inerts and heating value.

gas suction pressure

The pressure at a compressor's inlet, which with discharge pressure sets the ratio.

gas sweetening

Removing hydrogen sulfide and carbon dioxide from a sour gas stream.

gas transportation agreement

The contract for moving gas through a pipeline, fixing capacity, tariff and firmness of service.

gas treatment

Removing water, acid gases and contaminants so gas meets pipeline specification.

gas tungsten arc welding

A method of arc welding that uses a non-consumable tungsten electrode and a gas, or mixture of gases, to provide shield. Also called tungsten inert gas welding, or TIG welding.

gas turbine

A turbine driven by hot combustion gas, compact and quick to start.

gas turbine plant

A power plant that uses energy in exhaust gases from a combustor to turn a turbine, which drives a generator.

gas value chain

The sequence from gas well through processing and transport to power stations, industry and homes.

gas velocity

How fast gas moves through a vessel or line, and the variable that decides whether droplets fall out or carry over.

gas viscosity

Gas resistance to shear, low enough that gas flows readily but not negligibly.

gas volume

The amount of gas produced from a well or transported through a pipeline.

gas volume fraction (GVF)

The fraction of a flowing stream's volume that is gas at the local pressure and temperature, abbreviated GVF.

gas well

A well completed to produce natural gas as its principal product, rather than oil with associated gas.

gas-cap drive

A drive mechanism in which the expansion of free gas in a gas cap pushes oil toward the producing wells as pressure declines.

gas-condensate-glycol (G-C-G separator)

A vessel where gas is removed and liquid hydro-Separator carbons (condensate) are separated from glycol. Also known as a three-phase separator.

gas-condensate-glycol separator

Three-phase separator splitting gas, condensate and glycol downstream of injection.

gas-cut mud

Mud carrying entrained gas bubbles, so its density at surface is lower than the mud that went down the hole.

gas-fired power plant

A station burning gas to generate electricity, the largest single market for gas.

gas-lift mandrel

A tubing component that houses a gas lift valve, positioning it at the depth the design requires.

gas-lift valve

A downhole valve that admits injection gas from the annulus into the tubing at a set pressure.

gas-oil contact

The surface in a reservoir above which gas predominates and below which oil does.

gas-oil ratio

A measure of the volume of gas produced with oil, usually expressed in cubic feet per barrel.

gas-prone

Describing a source rock whose kerogen is more likely to yield gas than oil on maturation.

gas-sealed power transformer

A power transformer that is pressurized with gas from a gas cylinder to keep air and moisture from entering the transformer enclosure.

gas-solubility factor

The volume of gas dissolved in a unit volume of oil at reservoir conditions, both measured at standard conditions, symbol Rs.

gas-to-liquids (GTL)

Converting gas into liquid fuels, monetizing gas where no pipeline or LNG route exists.

gas-water contact

The surface in a reservoir above which gas predominates and below which water does.

gas-well deliverability

The rate a gas well will deliver against a given flowing pressure, expressed as a deliverability equation or curve.

gas/liquid ratio (GLR)

The volume of produced gas divided by the total volume of produced liquid, oil and water together.

gas/oil ratio

The gas/oil ratio in an oil field is calculated using measured natural gas and crude oil volumes at stated conditions.

gas/oil-sealed power transformer

A power transformer that uses a two-part expansion tank mounted along the side of the transformer and a layer of gas and oil to prevent air and moisture from entering the transformer enclosure.

gaseous

In the gas phase.

gases

Normally formless fluids that occupy the space of enclosure and that can be changed to the liquid or solid state only by the combined effects of increased pressure and decreased temperature.

gases and straight run gasoline fraction

The lightest fraction from crude oil.

gasification

Converting a solid or heavy liquid fuel into synthesis gas.

gasket

A piece of flat material softer than a flange that is compressed between two flanges to form a seal when the bolts are tightened.

gasket material

The material a gasket is made from, chosen for the fluid, temperature and pressure.

gasoil

The distillate cut between kerosene and residue, the basis of diesel and heating oil.

gasoil blending

Combining diesel-range streams to meet sulfur, cetane and cold-flow limits simultaneously.

gasoline additive

A component blended in small quantity to improve octane, detergency or stability.

gasoline blending

Combining streams to meet octane, volatility and sulfur specification at least cost.

gasoline demand

Consumption of motor gasoline, which drives much refinery configuration.

gasoline diesel fuel

The two principal road transport fuels.

gasoline engine

The spark-ignition engine, whose knock resistance requirement sets the octane specification.

gasoline fraction

The distillation cut in the gasoline boiling range.

gasoline market

The market for motor gasoline.

gasoline station

The retail outlet selling motor fuel to the public.

gaswell gas

The gas separated at surface from the full stream of a gas well.

gaswell liquids

The condensate and water separated at surface from a gas well's production.

gate

The point on a semiconductor device where an applied potential affects current flow through the device, such as the control terminal of an SCR.

gate mixer

A mixer containing an impeller, or gate, that is made of flat horizontal and vertical bars.

gate review

The formal assessment at a phase boundary deciding whether the project may proceed.

gate valve

A valve with a wedge-shaped disc that moves across the opening like a gate, raised and lowered to start or stop flow. Usually positioned fully open or fully closed; not designed for throttling.

gather

A set of seismic traces collected together because they share an acquisition attribute — a common midpoint, source, receiver or offset.

gathering lines

The small-diameter pipes carrying production from individual wells to a central battery or trunk line.

gathering system

The network of flowlines, manifolds and process equipment carrying production from the wells to a central facility.

gauge

To measure the volume of oil in a lease tank.

gauge glass

A transparent vertical tube mounted on the side of a liquid container that provides local indication of the liquid level, based on the principle that liquid levels equalize in connected containers.

gauge hole

A hole whose diameter matches the bit that drilled it, without washout or ledging.

gauge needle

The pointer on an analog gauge, whose steadiness tells an operator as much as its reading.

gauge pressure

Pressure measured relative to atmospheric pressure, so that a gauge reads zero at ambient conditions.

gauge protection

Gauge protection refers to the use of hard-facing materials, such as tungsten carbide, applied to selective parts of a bit (specifically, cutters on the bit) to prevent excessive wear that can decrease the diameter of the bit thereby resulting in a smaller-diameter (under-gauge) borehole than planned.

gauge ring

A precisely machined ring of known diameter, run to confirm that a tubular's bore is clear to that size.

gauge stick

A calibrated stick that is inserted directly into a container of liquid and read at the point where the liquid no longer coats the stick.

gauge tank

A small calibrated tank used to measure a volume of fluid produced or pumped, by the change in its level.

gauger

Company or buyer representative who gauges and tests lease tanks for sales.

gauging

Measuring the level or contents of a tank.

gaussian

Following the normal distribution, the assumption behind much statistical estimation.

Gaussian collocated cosimulation

A cosimulation method that conditions each simulated value on the secondary variable at that location only, ignoring secondary data further away.

Gaussian function in machine-learning

Gaussian probability distribution functions summarize the distribution of random variables, whereas Gaussian processes summarize the properties of the functions, e.g. the parameters of the functions. Gaussian processes can be used as a machine learning algorithm for classification predictive modeling.

Gaussian techniques

Stochastic simulation methods that assume the variable, after transformation, follows a normal distribution.

gear box

A set of gears used to reduce the speed and increase the torque of the prime mover.

gear mesh

Where gear teeth engage, and the source of both the noise and the load.

gear pump

A rotary positive displacement pump that uses gears to move fluid.

gear reducer

The gearbox lowering prime mover speed to pumping unit speed.

gearset

A pair or train of meshing gears.

gel

Rig shorthand for bentonite clay, and more generally for a viscous, crosslinked treatment fluid.

gel strength

The shear stress needed to start a fluid moving after it has stood still, measured at low shear rate after a set rest period.

gelation

The development of gel strength as suspended particles link into a structure at rest.

gelled

Having developed structure at rest, as a drilling fluid does when circulation stops.

gelled mud

Mud that has become excessively viscous, with high gel strength and yield point.

gelled-up mud

Mud that has become excessively viscous, with high gel strengths and yield point.

gelling

Developing gel structure, wanted in fracturing fluid and unwanted in stored mud.

gels

The pair of gel strength readings taken on a mud, conventionally at 10 seconds and 10 minutes of rest.

gender bias

Judgment shaped by gender rather than by evidence of capability.

gender stereotype

An assumption about capability or behavior based on gender rather than evidence.

general journal

The chronological record of transactions before they are posted.

general ledger

The set of accounts holding all posted transactions.

general purpose tank cars

Tank cars that have working pressures of 100 psi or less.

Generally Accepted Accounting Principles (GAAP)

The United States framework of accounting rules and conventions.

generating options

Inventing possible agreements before judging any of them.

generating unit

A plant boiler, turbine, generator, and associated systems and equipment.

generation

The formation of hydrocarbons from kerogen in a source rock as burial temperature rises.

generational stereotype

An assumption about someone's attitudes based on when they were born.

generative aI

Models that produce new text, images or code by learning the patterns of their training data.

generative pretrained transformer (GPT)

A transformer-based language model pre-trained on large text corpora and then adapted to particular uses.

generator

A device or machine that converts mechanical energy into electrical energy. In absorption refrigeration, the section where the refrigerant and the absorbent are separated.

generator output

The power a generator is delivering.

generator trip

The opening of a generator's circuit breakers, disconnecting the generator from the power system; may also trip the boiler and the turbine.

geochemical

Relating to the chemistry of rocks and fluids, used to type oils and assess source maturity.

geochemical data

Measurements of rock and fluid chemistry, used to establish source, maturity and correlation.

geochemical log

A log of formation elemental concentrations, from which mineralogy and rock type are computed.

geochemistry

The study of the chemical composition of the Earth and the processes that distribute and move its elements.

geochronology

The dating of rocks, minerals and fossils in absolute terms, in years before present.

geodetic

Relating to the precise measurement of position and the earth's shape.

geodynamic

Concerning the forces and motions that deform the lithosphere.

geodynamic model

A model of lithospheric deformation used to explain basin formation.

geohistory

The reconstructed burial, temperature and maturity history of a basin through time.

geoid

The equipotential surface approximating mean sea level, the reference elevations are measured from.

geologic

Pertaining to geology — the Earth's history, structure, composition and the processes that change it.

geologic age

The interval of geologic time a rock was formed in.

geologic feature

A recognizable structure or body in the rock.

geologic history

The sequence of events that produced the present rock arrangement.

geologic interpretation

The reasoned account of what the data means in rock terms.

geologic map

A map showing the distribution and type of rock units exposed at the Earth's surface, with their structure.

geologic model

A description of the subsurface rock framework.

geologic setting

The regional geological context a prospect or field sits in.

geologic structure

The arrangement of rock produced by deformation, which is what forms most traps.

geologic time

The timescale rock is dated on, in which a million years is a short interval.

geologic time scale

A chronostratigraphic framework of eons, eras, periods and stages, calibrated against absolute ages.

geological

Pertaining to geology and to interpretations founded on it.

geological basin

A crustal depression filled with sediment.

geological map

A surface map of rock units and structures, used to infer what lies beneath.

geological time

The scale on which strata are dated, from Precambrian to Quaternary.

geologist

A scientist who studies the Earth's rocks and history, and in the petroleum industry generates prospects and interprets subsurface data.

Geolograph

A geolograph is a device that measures depth and, if installed, is usually found in the doghouse, adjacent to the drilling rig floor.

geology

The science of the Earth: what it is made of, how it is arranged, how it has changed through time, and the life it has carried.

geomagnetic

Relating to the earth's magnetic field, used in surveying and in directional drilling.

geomagnetic polarity reversal

The switching of the Earth's magnetic north and south poles, recorded in rocks as alternating magnetization directions.

geomagnetic polarity time scale

The dated record of reversals in the Earth's magnetic field, used as a chronometer for magnetostratigraphy.

geomagnetic secular variation

The slow change of the Earth's main magnetic field over years to centuries, from motion in the outer core.

geomechanical

Geomechanics is the study of the mechanical condition of the borehole.

geomechanical model

A model of the stress state and rock strength, used to plan wells and fractures.

geomechanics

The geological specialty that involves understanding how rocks, stresses, pressures, and temperatures interact, including the study of the mechanical state of the Earth's crust and the processes occurring in it under the influence of natural physical factors.

geometrical

Relating to the geometry of the acquisition or the reservoir rather than to its properties.

geometrical factor

The fraction of a logging measurement's total signal contributed by a given region of formation, as a function of distance from the tool.

geophone

A receiver that converts ground velocity into an electrical signal, planted at surface or on the seabed.

geophone array

A group of geophones whose outputs are summed into a single recording channel.

geophone cable

The multiconductor cable connecting geophones to the recording instruments.

geophone group

Several geophones wired as one channel, summing to cancel noise.

geophone interval

The spacing between geophones, or between the centers of geophone groups, along a recording line.

geophone offset

The horizontal distance from the source to a geophone.

geophone pattern

The layout of the individual geophones making up one recording group.

geophysical data

Measurements of the earth's physical fields used to infer subsurface structure.

geophysical inversion

Geophysical inversion refers to the mathematical and statistical techniques for recovering information on subsurface physical properties from observed geophysical data.

geophysical method

A technique inferring subsurface properties from measurements of a physical field.

geophysicist

A scientist who studies the physical properties and fields of the Earth and the propagation of elastic waves through it.

geophysicists

Specialists who infer subsurface structure from physical measurements, chiefly seismic.

geophysics

The study of the Earth's physical properties and fields — electrical, gravitational, magnetic — and of elastic wave propagation within it.

geopressure

Reservoir fluid pressure that exceeds the hydrostatic pressure for a given depth.

geopressure gradient

The rate at which pore pressure changes with depth, in psi/ft or kPa/m.

geopressured

Describing a formation whose pore pressure is abnormally high for its depth.

geoscience

The earth sciences applied to finding and describing reservoirs.

geoscientist

A geologist or geophysicist working on subsurface interpretation.

geoscientists

The geologists and geophysicists interpreting the subsurface.

geostatic pressure

The pressure exerted by the weight of the overlying rock column — also called lithostatic or overburden pressure.

geostatistical

Using spatial statistics to estimate rock properties between the points actually measured.

geostatistical methods

Statistical techniques that use the spatial correlation of data to estimate a property at locations where it was not measured.

geostatistical modeling

Building a subsurface model with geostatistical methods, honouring the data at the wells and the spatial statistics between them.

geostatistics

The branch of statistics concerned with data that have spatial position, using their correlation with distance to estimate unsampled locations.

geosteer

To steer a well using downhole geological and petrophysical measurements as they arrive, rather than to a fixed spatial target.

geosteering

The intentional directional control and optimal placement of a wellbore based on the results of real-time downhole geological and geophysical logging measurements, rather than three-dimensional targets in space, usually to keep a directional wellbore within a pay zone.

geotechnical

Relating to soil and rock mechanics, as for foundations and seabed stability.

geothermal gradient

The rate at which temperature rises with depth in the Earth, typically around 1.4 degrees F per 100 ft.

Geronimo line

The escape line from the derrick monkeyboard to a ground anchor, allowing the derrickman to slide clear.

GFCI

See Ground fault circuit interrupter.

GFCI circuit breaker

A circuit breaker that also provides ground fault circuit interruption to protect people from electric shock.

GGT

Garrett gas train — the apparatus that liberates sulfide or carbonate from a mud sample as gas and measures it on a detector tube.

ghost

A short-path multiple created when energy travels upward first and reflects back down off the surface or the sea surface.

Gibbs' phenomenon

The overshoot and ringing that appears next to a sharp step when a signal is reconstructed from a limited band of frequencies.

gig work

Short-term, task-based engagements rather than continuing employment.

gigahertz

1,000,000,000 hertz; a unit of frequency.

GIIP

Gas initially in place: the whole gas volume held in a reservoir before production, computed from porosity, saturation, area, net thickness and the gas formation volume factor.

gilsonite

A naturally occurring black asphaltite resin, used as a lost-circulation material and as a low-density cement additive.

gin pole

A simple lifting mast used to raise equipment where a crane is unavailable or impractical.

giveaway

Product quality that exceeds the specs for that product.

glacial

Pertaining to glaciers — their environments, processes and deposits.

gland bushing

The bushing that compresses stem packing in a stuffing box, or retains the stem seals in a packless design.

gland follower

A device that compresses packing in a stuffing box to control leakoff.

gland nut

The nut compressing packing in a gland.

gland seal

A device that creates a seal between a shaft and a casing.

gland sealing

Sealing where a shaft passes out of a casing.

gland sealing line

A line that delivers water to the stuffing box of a centrifugal pump.

gland steam

Steam sealing a turbine shaft where it leaves the casing, keeping air out of the vacuum.

gland steam condenser

A part of a gland steam seal exhaust system that collects and condenses steam leaking past a turbine shaft.

gland steam exhauster

A blower that draws air and steam from turbine glands to a gland steam condenser.

gland steam seal exhaust system

A system that prevents steam from leaking out and air from leaking in by drawing them out of a gland.

gland steam seal system

A system that supplies low pressure steam to seal a turbine.

glass cloth electrical tape

An insulating tape that is coated with a silicone adhesive to make it stick well on a connection.

glass jar test

A pilot test shaking an oil mud sample with water in a jar to see whether the solids are water-wet.

glassware

Laboratory vessels of glass, chosen for chemical inertness and visibility.

glauconite

A green iron-potassium silicate that forms on continental shelves where sedimentation is slow and organic matter is present.

global business management

Managing a business operating across several countries and legal systems.

global distribution strategy

How product reaches customers in each market, and through whom.

global marketing

Marketing across countries, deciding what to standardize and what to adapt.

global mission statement

A statement of purpose intended to hold across markets and cultures.

global positioning

Satellite fixing of position, which made accurate survey location routine.

Global Positioning System

The satellite constellation from which a receiver derives three-dimensional position, velocity and time — the full name of GPS.

global supply chain management

Coordinating supply across borders, with the added complexity of customs, currency and distance.

global trade finance

The instruments financing international trade and bridging the trust gap between distant parties.

global venture viability

Whether an international venture can actually work given costs, risks and local conditions.

global warming

The long-run rise in mean surface temperature driven by accumulated greenhouse gases.

global-warming potential (GWP)

The relative measure of how much heat a greenhouse gas traps in the atmosphere. It compares the amount of heat trapped by a certain mass of the gas in question to the amount of heat trapped by a similar mass of carbon dioxide. GWP is calculated over a specific time interval, commonly 100 years. GWP is expressed as a multiple of that for carbon dioxide (whose GWP is standardized to 1).

globalization

The increasing integration of markets, production and culture across borders.

globe valve

A valve with a globe-shaped body designed for both on/off control and throttling. Flow is restricted by positioning the internal disc into the flow path, creating a two-90° turn flow pattern.

glowstick

A device used to test circuits to determine if they are energized.

GLR

Gas/liquid ratio: the volume of produced gas divided by the volume of produced liquid, oil and water together.

glycol

A liquid desiccant used to absorb water vapor from natural gas. Triethylene glycol is the most commonly used glycol.

glycol (lean)

Glycol that is free of water.

glycol (rich)

Glycol that has absorbed water.

glycol absorber

The trayed or packed contactor in which lean glycol flows down against rising wet gas and strips water out of it.

glycol dehydration

Drying gas by contacting it with glycol, which absorbs the water rather than condensing it.

glycol dehydration system

The complete glycol drying loop.

glycol dehydration unit

The contactor, reboiler and pumps drying gas with glycol.

glycol dehydrator

A contactor in which lean glycol absorbs water vapor from a gas stream, and is then regenerated for reuse.

glycol filter

Filter removing solids and degradation products from circulating glycol.

glycol flow

The glycol circulation through a dehydration loop, whose rate sets the water removed.

glycol foaming

Glycol foaming in the contactor, which carries solvent over and cuts drying at once.

glycol injection

Dosing glycol into a cold stream to stop water freezing into hydrate and blocking it.

glycol injection nozzle

Nozzle atomizing glycol into a gas stream so it contacts the water rather than running along the wall.

glycol injection pump

Metering pump delivering glycol at the rate needed to suppress hydrate formation.

glycol level

The glycol inventory level in a vessel, whose loss uncovers the reboiler or starves the pump.

glycol monobutyl ether

A mutual solvent used in acid treatments to help clean up and restore wettability.

glycol outlet

Where glycol leaves a vessel, and the point its water content is sampled.

glycol pump

Pump circulating glycol between contactor and regenerator.

glycol seal

A level of glycol between tray and downcomer to force the gas to pass through the bubble caps.

glycol stream

The circulating glycol flow, lean or rich according to where it is taken.

glycol system

The contactor, regenerator, pumps and exchangers that dry gas with glycol.

glycol temperature

The glycol's temperature, which sets absorption in the contactor and regeneration in the reboiler.

glycol vapor

Glycol carried off as vapor, a loss that rises sharply with reboiler temperature.

glyph

A symbol whose shape, size, color and orientation each encode a different variable, so several attributes are shown at one point.

goal setting

Agreeing what is to be achieved, in terms concrete enough to tell whether it was.

goal-setting process

The structured method of setting and pursuing objectives.

goals, empowerment, measurement

The three conditions under which delegation works: a clear target, the authority, and a way to know.

goat head

The flow cross on a frac tree where the treating iron connects and the treatment enters the well.

GOC

Gas-oil contact: the surface in a reservoir above which gas predominates and below which oil does.

goggles

Protective glasses set in a flexible frame that sits snugly against the face.

Google Analytics 4

The current version of Google's analytics platform, built on events rather than sessions.

goose neck

The inverted U of rigid high-pressure pipe at the top of the standpipe, where the rotary hose connects.

GOR

Gas/oil ratio: the volume of gas produced with each unit volume of oil, quoted at stated conditions.

governance, risk and compliance (GRC)

The combined discipline of directing the organization, managing its risks and meeting its obligations.

government affairs

The function managing a company's relationships with government and regulators.

government control of contractor operations

The approvals, audits and oversight through which a state supervises what the contractor does.

government entity

A state body holding rights, taking revenue or regulating operations.

government regulation

The rules agencies impose on how a business may operate.

government share

The state's portion of profit oil or of production under the sharing formula.

government take

The share of production revenue a host government receives, through royalty, tax, profit share and any other mechanism.

GPS

Global Positioning System: a constellation of US satellites from which a receiver derives three-dimensional position, velocity and time, anywhere and in any weather.

GPTS

Geomagnetic polarity time scale: the dated record of reversals in the Earth's magnetic field, used as a chronometer for magnetostratigraphy.

GR

Gamma ray — the log recording the formation's natural gamma radiation, used chiefly as a shale indicator.

graben

A block of crust dropped down between two opposing normal faults.

gradational

Changing gradually rather than at a sharp boundary.

grade markings

Markings that identify the strength and quality of a bolt or screw.

grade syncing

Passing scores from an external tool back into the platform's gradebook automatically.

graded bedding

A bed characterized by a systematic gradation of grain or clast size from base to top, occurring when current velocity decreases and grains are progressively dropped out.

gradiomanometer

A production logging sensor measuring the pressure difference between two points a fixed distance apart, to give the average fluid density between them.

graduations

The increments marked on a rule.

grain density

The density of a rock or mineral with no porosity.

grain density, matrix density

Grain, or matrix, density is the density of the minerals forming a rock, often referred to in core analysis as grain density.

grain packing

The distribution of grains and intergranular spaces (either empty or filled with cement or fine-grained matrix) in a sedimentary rock. Controlled by grain size, shape, and degree of compaction; in turn it determines the rock's bulk density.

grain size

The diameter or size of individual grains within a consolidated or unconsolidated rock.

grainstone

A carbonate rock of grains with no mud between them, commonly a good reservoir.

granite

A coarse-grained intrusive igneous rock of felsic composition, dominated by quartz, feldspar and mica.

granular LCM

Chunky, graded lost circulation material — nut shells, ground rock, plastics or seed grain — that bridges a loss zone.

granular lost-circulation material

Graded particulate material added to bridge and plug a loss zone, from fine to very coarse.

granule

A small solid particle of regular size.

graphical display

Presenting data visually so the pattern can be seen rather than computed.

grapple

The gripping element of a fishing tool, engaging the outside of a fish so it can be pulled.

graticule

The grid lines on an Oscilloscope's screen used for measuring traces.

gravel pack

A sand control completion in which sized gravel is placed between a screen and the formation, holding formation sand in place while fluid passes.

gravel packing

Placing sized gravel against the formation to hold sand back while letting fluid through.

gravel-pack gun

A perforating gun loaded with big-hole charges to give large casing entrance holes for gravel placement.

gravel-pack log

A log run after gravel packing to confirm the gravel is where it should be and to find voids in the pack.

gravel-pack screen

The slotted or wire-wrapped tube that holds the gravel in place against the formation face.

graveyard tour

The overnight drilling crew shift.

gravimeter

An instrument measuring the acceleration due to gravity, or more usefully the difference in it between stations.

gravimetry

The measurement of the Earth's gravity field and the study of its variations.

gravitometer

Instrument measuring gas specific gravity continuously, needed to compute mass from volume.

gravity

A scale used to compare the density of liquid petroleum products. Usually expressed as AP.I. gravity.

gravity anomaly

The difference between measured gravity and the value a reference Earth model predicts, once the standard corrections have been applied.

gravity differential

The density difference between two phases, and the whole driving force in gravity separation.

gravity drainage

A drive mechanism in which oil drains downward under its own weight as gas replaces it above, and is produced from low in the structure.

gravity drainage sagd

Steam-assisted gravity drainage, producing heavy oil through paired horizontal wells.

gravity measurement

Determining a fluid's specific gravity, needed to convert a measured volume into mass or energy.

gravity override

The tendency of a lighter injected fluid to rise and travel along the top of the reservoir, leaving the oil beneath it unswept.

gravity segregation

The separation of reservoir fluids into layers by density, gas rising and water sinking relative to oil.

gravity settling

Separation relying on density difference and time alone, with no applied field.

gravity survey

Measurement of gravitational acceleration across an area, reduced to Bouguer or free-air anomalies and mapped to infer density contrasts at depth.

gravity toolface

Toolface measured clockwise from the high side of the hole, in the plane perpendicular to the wellbore axis.

gravity-capillary equilibrium

Gravity-capillary equilibrium in a reservoir occurs when gravitational and capillary forces are in equilibrium.

gravity-stable displacement

A displacement slow enough that gravity segregation holds the front flat, rather than letting viscous fingers run ahead of it.

gray list

The OSPAR category of offshore chemicals requiring strong regulatory control, between the banned black list and the acceptable white list.

grease fitting

The nipple grease is injected through.

grease gun

A hand tool forcing grease into a fitting.

grease-injection system

A pressure-control head that pumps viscous grease into a flow tube around braided line, sealing on the line while it moves.

greasing

Applying lubricant to threads and moving parts.

greasing out

The agglomeration of mud solids into sticky masses when they become coated with oil or a similar substance.

great circle

A circle on the surface of a sphere that lies in a plane passing through the sphere's center, representing the shortest distance between any two points on a sphere. The best-fitting great circle of lines is deemed a reasonable estimation of structural dip.

greedy algorithm

An optimization method that takes the best move available at each step, without regard for where the sequence ends up.

Green Belt

The practitioner level, able to lead a defined improvement project.

green gas

Raw, untreated gas as it leaves the well, before dehydration, sweetening or liquids removal.

green hydrogen

Hydrogen made by electrolysis using renewable electricity.

green list

OSPAR's category for offshore chemicals judged to pose little risk to the marine environment.

greenfield

A development built from nothing, with no existing wells or facilities to work from.

greenfield project

A development on a new site with no existing infrastructure to build on.

greenhouse gas

Atmospheric gases that are transparent to solar (short-wave) radiation but opaque to long-wave (infrared) radiation, thus preventing long-wave radiant energy from leaving Earth's atmosphere. The net effect of these gases is a trapping of absorbed radiation and a tendency to warm the planet's surface. The greenhouse gases most relevant to the oil and gas industry are carbon dioxide, methane and nitrous oxide.

greenhouse gas (GHG) emissions

Releases of carbon dioxide, methane and other gases that trap heat in the atmosphere.

greenhouse gas emission

A release of gas that traps outgoing heat, measured as carbon dioxide equivalent so unlike gases can be compared.

grey hydrogen

Hydrogen from fossil feedstock with the carbon dioxide vented, the unabated baseline the color scale measures from.

grey list

OSPAR's category for offshore chemicals that may be used only under strong regulatory control.

GRI Standards (Global Reporting Initiative)

The most widely used framework for general sustainability reporting.

grid

A network of power stations, power lines and power users.

grid connectivity

Physical and contractual access to the transmission network, often the binding constraint on a renewable project.

grid line system

A system of letters and numbers in the border of some blueprints that can be used to locate specific areas on the drawing.

grid node

A point in a model grid where a value is held.

gridding

Interpolating scattered data onto a regular grid so that a surface can be mapped and computed on.

gridding algorithm

The computational rule that decides what value each grid node takes from the surrounding data.

grievance mechanism

The formal channel by which affected people raise complaints and get a response.

grinding wheel

An abrasive wheel used to cut or dress metal.

gripper blocks

The profiled blocks on a coiled tubing injector head's drive chains that grip the tubing and move it in and out of the well.

grooving

A condition that leaves a smooth, slotted area on the surface of a commutator.

gross generation

A reading that indicates how many megawatts a power plant is producing.

gross pay

Gross pay is the overall interval in which pay, or commercially viable, volumes occur.

gross product worth (GPW)

The value of the products a crude yields, used to judge what that crude is worth to a refiner.

gross production

The total volume of oil, gas and water a well or field produces over a period, before any deductions.

gross refining margin

Product value less crude cost, before operating expenses.

gross reservoir volume

The total rock volume within the field outline, before net-to-gross is applied.

gross-split model

A production sharing variant splitting gross output by formula, with no cost recovery step.

ground

In DC motors, a condition that leaves a smooth, slotted area on a commutator surface. In electrical circuits, a breakdown in insulation that provides an unintended current path to ground.

ground fault

A short circuit or fault that occurs when an unintended path is established between a conductor and a grounded object, such as the metal frame of a motor, allowing electricity to take an undesirable path to earth.

ground fault circuit interrupter

A Class A protective device that is built in accordance with the UL standard to protect people from electric shock when line-to-ground faults occur.

ground loop

The "antenna effect" created by grounding a wire at more than one point.

ground roll

Low-frequency, high-amplitude surface-wave noise that spreads out from a seismic source and can swamp reflections at near offsets.

ground state

The ground state of a quantum mechanical system is its lowest energy state; the energy of the ground state is known as the zero point energy of the system.

grounded

Conductive equipment connected to earth or to some conducting body that serves in place of the earth.

grounded tool

An electrical tool with a three pronged plug at the end of its power cord or some other means to ensure that fault current travels to the ground without passing through the body of the user.

groundwater

Groundwater, or ground water, is water located beneath the surface of the earth.

group

Sixteen input or output addresses that occupy one word of input or output image table memory. A group may be two, one, or one-half slots in an I/O rack.

group interval

The distance between adjacent receiver groups along a seismic line.

group lockout/tagout

A lockout/tagout procedure that is used when maintenance work involves more than one person.

group velocity

The speed at which the energy of a wave packet travels, as distinct from the phase velocity of its individual components.

groupthink

A group suppressing dissent in favor of consensus, producing decisions no member would defend alone.

GROW model

A coaching structure moving through goal, reality, options and will.

growth fault

A normal fault that moves during deposition, so the section is thicker on its downthrown side than on its upthrown side.

growth faulting

Faulting active during deposition, so beds thicken across the fault as it moves.

growth faults

Growth faults are faults that were active during the time of deposition.

guar

The plant gum used to thicken fracturing fluid so it can carry proppant.

guar gum

A polysaccharide from the guar bean, used to viscosify water-based fracturing fluids.

guard electrode

An electrode that emits current alongside the main survey electrode to force that current out into the formation instead of up the borehole.

guard log

A focused resistivity log in which long guard electrodes force the survey current out as a thin horizontal disk.

guardrails

Physical barriers along an elevated edge that prevent a person from falling — the primary fall protection control where one can be installed.

guide shoe

A tapered, bullet-nosed component on the bottom of a casing string that guides it past ledges and irregularities in the hole.

guided wave

An elastic wave trapped within a low-velocity layer, which acts as a waveguide and confines the energy.

guided waves

Guided waves occur in areas with a hard water bottom. The water layer provides a strong velocity contrast with the substratum, which causes most of the energy to be trapped within the water column and guided laterally through the water layer. Guided waves also present on the seismic record as early arrivals.