Discover the IHRDC Energy Glossary_beta

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H

H2S

Hydrogen sulfide: a highly toxic and corrosive gas found in sour hydrocarbon streams, able to kill after seconds of exposure at relatively low concentration.

hade

The angle a fault plane makes with the vertical, measured perpendicular to strike — the complement of dip.

haematite

Iron oxide ore, Fe2O3, ground and used as a high-density weighting material for drilling mud.

half-life

Half-life is the amount of time required for half of the unstable, radioactive atoms in a sample to undergo radioactive decay.

half-splitting

A troubleshooting method in which each test performed on a circuit reduces the remaining number of possible causes of a problem by half.

half-splitting method

Aprocess of elimination method in which each test performed on a process during troubleshooting divides the part of the process being tested in half.

half-wave rectifier

A rectification device or circuit that conducts during one half of an AC cycle, thus producing one DC output pulse during each AC cycle.

half-wave voltage doubler

A circuit that develops an output pulse during one half of the AC input cycle; the output is equal to twice the input voltage.

halite

Halite, commonly known as rock salt, is the mineral form of sodium chloride, NaCl.

halliburton

One of the major oilfield service companies.

hallucination

A model output that is fluent and plausible but not grounded in fact.

halo effect

An anomaly forming a ring around a feature rather than over it, as with geochemical or resistivity halos above hydrocarbon accumulations.

halogen

A highly reactive element whose atoms need only one more electron to complete their valence shell.

halogenation

A reaction in which atoms from the halogen group are added to a double-bonded hydrocarbon to form a new compound.

hammer drill

A power drill that hammers, or pounds, as it rotates.

hammer union

A quick connection whose threaded nut is tightened by striking its lugs with a hammer.

hand lever

A manual lever operating a valve or mechanism.

hand-operated drum pump

A manually operated pump that is often used to move liquid from large drums to smaller containers.

handling difficult questions

Responding to challenge without becoming defensive or evasive.

handover

The formal transfer of a completed facility from the project team to operations.

handwheel

The wheel allowing manual operation of a valve or actuator.

hangoff

A fitting or arrangement that carries the weight of a cable, umbilical or line at a fixed point.

harassment

Unwanted conduct that creates an intimidating or hostile working environment.

hard drive

The long-term storage area for a computer, containing its operating system instructions, data files, and any application programs that have been installed.

hard stringers

Hard stringers are thin intervals of hard formation rock, for example, low porosity dolomitic rock.

hard water

Water that contains a lot of hard ions, such as calcium and magnesium ions.

hardbanding

A wear-resistant alloy applied to the tool joints of drillpipe, so the joint rather than the pipe body takes the abrasion.

hardfacing

Applying a harder material to a softer base metal to resist wear.

hardground

A seafloor surface cemented by carbonate precipitation while still at or just below the sediment-water interface.

hardness ion

A divalent cation in water — calcium, magnesium or ferrous iron — that makes the water hard.

hardware

The physical mechanical, magnetic, and electronic components of a computer, such as the monitor, hard drive, CPU, keyboard, etc.

hardwired

Directly connected by wires that determine the fixed connection functionality, as opposed to connected through programmable circuits.

harmonic

A component whose frequency is an integer multiple of a fundamental frequency.

harmonic distortion

An electrical effect created when current is drawn at more than one frequency.

harmonics

Frequency components at multiples of the fundamental, which distort a signal.

HART interface

Highway Addressable Remote Transducer. A device that is often used in PLC systems as part of a device-type network.

HART protocol

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

Hartley oscillator

An LC oscillator that produces a sinusoidal wave. An autotransformer or tapped coil is used for the feedback circuit.

Hassler holder

Hassler type core holders are defined as core holders that have radial pressure applied to the core sample.

hatch

A closable opening in a tank roof, used to gauge the level, draw a sample or look inside.

hazard assessment

Systematically identifying what could cause harm and how severely, before deciding controls.

hazard classification

Assigning a substance or area to a defined hazard category, which then sets the controls.

hazard communication

The labelling and data sheets telling people what a substance can do to them.

hazard communication standard (HAZCOM)

The OSHA standard that requires all companies to educate employees about hazardous chemicals in the workplace and the risks associated with those chemicals, including how to work safely in their presence.

hazardous atmosphere

An atmosphere that may expose employees to the risk of death, incapacitation, impairment of ability to self-rescue (that is, escape unaided from a permit space), injury, or acute illness from one or more of the following causes:1. Flammable gas, vapor, or mist in excess of 10 percent of its lower flammable limit (LFL);2. Airborne combustible dust at a concentration that meets or exceeds its LFL;3. NOTE: This concentration may be approximated as a condition in which the dust obscures vision at a distance of 5 feet (1.52 m) or less.4. Atmospheric oxygen concentration below 19.5 percent or above 23.5 percent;5. Atmospheric concentration of any substance for which a dose or a permissible exposure limit is published in Subpart G, Occupational Health and Environmental Control, or in Subpart Z, Toxic and Hazardous Substances, of this Part and which could result in employee exposure in excess of its dose or permissible exposure limit; 6. Any other atmospheric condition that is immediately dangerous to life or health.

hazardous chemical

Any chemical that is a physical hazard or a health hazard, for which there is statistically significant evidence that acute or chronic health effects may occur in exposed employees. This includes carcinogens, toxic or highly toxic agents, reproductive toxins, irritants, corrosives, sensitizers, hepatotoxins, nephrotoxins, neurotoxins, agents that act on the hematopoietic system, and agents that damage the lungs, skin, eyes, or mucous membranes.

hazardous energy

Any kind of energy that is capable of injuring or killing people or damaging equipment or property.

hazardous gas

Gas able to harm by toxicity, asphyxiation or ignition.

hazardous gas analyzer

An analyzer that is used to measure the concentration of a hazardous gas, such as sulfur dioxide, in an area.

hazardous material

Any material or substance that is capable of posing an unreasonable risk to health, safety, and property, or presents a danger to human health or the environment.

hazardous material identification system (HMIS)

A labeling system that uses color coded sections to rate the flammability, reactivity, and health risks of a hazardous chemical with regard to its use and handling in a workplace. The label also identifies personal protective equipment that should be used by individuals handling the chemical.

hazardous material identification system (HMIS®)

A hazardous material labeling system that uses color-coded sections to rate the flammability, reactivity, and health risks of a hazardous substance. The label also identifies personal protection equipment required for personnel handling the material.

hazardous materials class

Any one of nine categories of hazardous materials established by the Department of Transportation. Each class consists of hazardous materials with similar properties.

hazardous substance

A material able to harm people or environment, whose handling is regulated.

hazardous vapor

Vapor able to harm by toxicity or ignition.

hazardous waste

Waste containing substances that can harm the environment if small quantities of them escape into the air, water, or ground.

hazardous waste site

A facility or location within the scope of the HAZWOPER standard at which hazardous waste operations take place.

HBP

Held by production — a lease continuing in force past its primary term because the well is still producing.

HBV

A severe liver infection caused by the hepatitis B virus. Hepatitis B is transmitted by sexual contact and blood to blood contact from: transfusions, needlesticks, cuts, scrapes, sores and skin irritations.

HCl

Hydrochloric acid: the acid used to dissolve carbonate in matrix and fracture acidizing, most often at 15% strength.

HCV

A severe liver infection caused by the hepatitis C virus. Hepatitis C is transmitted by sexual contact and blood to blood contact from: transfusions, needlesticks, cuts scrapes, sores and skin irritations.

HE starch

Hydroxyethyl starch — a nonionic starch derivative used for filtration control in water-base and completion fluids.

head

The pressure exerted by a liquid as a result of its depth, expressed as vertical distance. For water, 1 foot of head equals 0.433 PSI. In heat exchangers, the part that directs flow into or out of the tubes.

head wave

Head waves are the sound waves refracted back into the borehole.

head, logging head

The head, or logging head, is the wireline cable and logging tool attachment mechanism.

header

A relatively large-diameter pipe that delivers collected material to a single discharge point.

header box

The box on the shale shaker that receives the flowline return and spreads it evenly across the screens through adjustable weirs.

heading

Cyclical surging of pressure and flow rate in a well that is otherwise stable.

health and wellness guidelines

The standards an employer sets or follows for workplace health provision.

health hazard

A chemical, mixture of chemicals, or pathogen for which there is statistically significant evidence that acute or chronic health effects may occur in exposed employees. Includes carcinogens, toxic agents, reproductive toxins, irritants, corrosives, sensitizers, and agents that damage various body systems. Also includes stress due to temperature extremes.

health tracking technology

Wearables and apps monitoring health measures, raising privacy questions at work.

heat

A form of energy that can be stored or transferred, related to the motion of a body's molecules. Also, energy in transit from one place to another due to a temperature difference.

heat absorption

The taking up of heat by a fluid or surface.

heat balance

The principle that the heat supplied in the charge and regenerated catalyst is balanced by the heat used in the cracking reaction and retained in the spent catalyst.

heat content (BTU content)

A measure of a fuel's heating capability.

heat exchanger

A device used to transfer heat from a hotter fluid to a cooler fluid. Examples include shell and tube exchangers, radiators with finned tubes on power transformers, and devices that allow hot and cold fluids to flow next to each other.

heat exchanger train

A group of heat exchangers in series.

heat flow

Heat flow is heat that dissipates outward from Earth's core toward the surface.

heat medium circulation

Pumping the heat medium round its loop, whose failure removes heat from every user at once.

heat medium heater

Fired or electric heater raising a circulating heat medium, used instead of direct firing on process.

heat pump system

A refrigeration system that provides both heating and cooling functions.

heat sink

An area or substance that receives and absorbs heat, whether from a refrigerant in a refrigeration system or from a component through conduction (e.g., a metal part used to dissipate heat from power transistors).

heat source

An area or substance from which heat transfers during a heat transfer process, such as the source from which a refrigerant absorbs heat in a refrigeration system.

heat tracing

Steam or electric heating applied along a line to keep its contents fluid.

heat tracing system

The steam or electric heating keeping lines above a minimum temperature.

heat transfer

The naturally occurring movement of heat from a region or substance at a higher temperature to one at a lower temperature.

heat transfer coefficient

The rate heat crosses a surface per unit area and temperature difference.

heat-shrinkable tubing

An insulating material that is heated to shrink it so that it seals and insulates a connection.

heated emulsion

Emulsion warmed to cut viscosity and weaken the interfacial film so water can settle.

heater

Equipment that adds heat to a produced stream, to prevent hydrates, break emulsions or meet a process temperature.

heater treater

A vessel that combines heating, settling and often chemical treatment to break an oil-water emulsion into saleable oil and separated water.

heating coil

A coil of pipe carrying a heating medium into a tank or vessel.

heating ventilation

The systems conditioning and moving air in occupied spaces.

heating, ventilation, and air conditioning system

A group of interrelated devices that perform specific functions, including temperature control, air movement and ventilation, air cleaning, and air moisture control.

heating-degree-days

The number of degrees that a given day's average temperature is below 65°F (15.5°C in European countries).

heavier component

A higher molecular weight constituent, which condenses first and is worth less.

heavier crude

Crude of higher density, yielding less light product.

heavier end

The higher boiling portion of a mixture.

heavier gas

The denser fraction of a gas mixture, which settles or condenses first.

heavier liquid

The denser phase in a separation, which settles and is drawn from the bottom.

heavier product

A product from the upper boiling range, generally of lower value.

heavy crude

Dense crude yielding a low proportion of light products.

heavy hydrocarbon

The least volatile hydrocarbons, which condense first and foul cold surfaces.

heavy hydrocarbons

The components of a hydrocarbon mixture with six or more carbon atoms.

heavy hydrocarbons / heavy ends

The components of a hydrocarbon mixture that have the largest number of carbon atoms, the highest boiling point and highest viscosity; the hexanes and heptanes in a natural gas stream.

heavy metal

A dense metallic element whose compounds are toxic — in US environmental usage, principally cadmium and mercury.

heavy oil

Crude oil with high viscosity and high specific gravity, typically with an API gravity less than 20°. It generally does not flow easily.

heavy pipe

A snubbing condition in which the weight of the pipe string exceeds the force the wellhead pressure exerts against it, so the string tends to fall rather than be pushed out.

heavy residual

The heaviest material left after distillation.

heavy sour

Crude that is both dense and high in sulfur, the cheapest and hardest to refine.

heavy sour crude

Dense, high-sulfur crude requiring conversion capacity to process profitably.

heavyweight drillpipe

Drillpipe with thicker walls and longer tool joints, run between the drill collars and the drillpipe as a stiffness transition.

HEC

Hydroxyethylcellulose: a nonionic cellulose polymer used to viscosify completion and treatment brines while leaving little residue.

hectorite

A lithium-magnesium smectite clay, similar in structure to bentonite but carrying more surface charge.

hedge fund

An investment fund that takes speculative positions, including in energy futures.

hedge ratio

The proportion of a physical position covered by paper.

hedging

Taking an offsetting paper position so that price movement no longer determines the outcome.

hedging the refinery margin

Buying crude futures and selling product futures together to lock in the crack.

heel

Product or residue that remains in a tank, carbon bed, or vessel after unloading or regeneration.

held by production

A lease clause that keeps the lease alive beyond its primary term for as long as the acreage produces in paying quantities.

helical

Formed as a spiral, as in a gear tooth or a screw rotor.

helium gas

Helium is a chemical element with symbol He and atomic number 2. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas, the first in the noble gas group in the periodic table. Its boiling point is the lowest among all the elements.

help portal

A collection of useful information “articles” on various aspects of CMS Online, including functionality, reporting, administration, process and methodology and technical specifications. Access at Dashboard > 9-dot icon (upper right) > Resources > Documentation.

hematite

Iron oxide, Fe2O3, used as a high-density weighting material where barite cannot reach the required mud weight.

hemispheroid

A vertical cylindrical pressure tank with a rounded (spherical) top; also called a dome-roofed tank. Generally used as a low-pressure tank.

Henry Hub

The Louisiana delivery point whose price is the United States gas benchmark.

heptacable

Heptacable is a wireline logging cable with seven insulated copper wires located in the centre of the cable.

heptane

A hydrocarbon of the paraffin series; one of the heavy ends.

hereof

Of this agreement or document.

hereto

To this agreement or document.

hereunder

Under this agreement.

herniated disc

An MSD that results when a disc that separates the vertebrae becomes weak over time and bulges out. When a herniated disc presses against a nerve it can be extremely painful.

Herschel–Bulkley fluid

A fluid needing a yield stress before it flows and then following a power law, described by three parameters.

hertz

The SI unit of frequency, equal to one cycle per second. In electrical formulas, hertz is typically abbreviated as Hz.

hesitation squeeze

A squeeze in which slurry is pumped in short bursts separated by shut-in periods, letting filtrate leak off and the cement dehydrate against the formation between them.

heterogeneity

A material that is heterogeneous is one that is distinctly non-uniform in composition or character.

heterogeneity, heterogeneous

A material that is heterogeneous is one that is distinctly non-uniform in composition or character.

heterogeneous

Distinctly non-uniform in composition or character.

heterogeneous formation

A formation whose properties change from place to place within the reservoir.

heterogeneous mixture

A mixture consisting of two or more ingredients that remain separate and distinct from each other after the ingredients have been combined.

heterogeneous mixtures

Mixtures that consist of separate and distinct parts that are easily separated by mechanical means.

heuristics

Heuristics are methods for solving problems in a quick way that delivers a result that is sufficient enough to be useful given time constraints.

hex

The commonly used, shortened form of the term 'hexadecimal".

hexadecimal

Base sixteen numbering, used to express memory and register contents.

hexadecimal numbering system

The numbering system based on powers of sixteen.

hexane

A volatile liquid paraffin hydrocarbon molecule (C6H14) found in petroleum and natural gas streams; one of the heavy ends.

HF

Hydrofluoric acid — the only common acid that dissolves silicate minerals, used in sandstone matrix treatments.

HF acid

Hydrofluoric acid, or anhydrous hydrogen fluoride; a type of catalyst commonly used in alkylation units.

HF stripper

A piece of equipment used to separate the hydrocarbons from entrained HF acid in the reactor effluent.

HGS

High gravity solids — the dense weighting material in a mud, barite at 4.2 or hematite at about 5.0 specific gravity.

HHP

Hydraulic horsepower: the rate at which energy is expended across the bit nozzles, one of the two criteria for optimizing jet hydraulics.

hiatal

Pertaining to a hiatus — an interval of time not represented by strata at a given place.

hiatus

A break in deposition during which no strata formed, or during which strata already deposited were eroded away.

hierarchical cluster analysis

Clustering that repeatedly merges the closest pairs, producing a dendrogram from which any number of clusters can be read.

high efficiency particle (HEPA) filter

A type of specialty filter that is designed to trap very fine particles contained in air.

high explosive

An explosive that detonates, decomposing in a supersonic shock wave and generating very high pressures.

high limiter

A control device in which the output tracks the input but only up to a certain input level; the input may go higher, but the output cannot.

high line pick-up

High line pick-up is a term for the accidental recording of 60 Hz powerline energy that is in the vicinity of the prospect.

high performance computing (HPC)

The use of clustered processors and accelerators to run computations far beyond what a single machine can handle.

high potential test

A go/no-go test of the condition of a generator's insulation; usually performed by applying a test voltage across the generator windings and observing whether the insulation withstands the test voltage.

high pressure side

The part of a refrigeration cycle from the discharge of the compressor to the inlet of the expansion valve.

high pressure squeeze

A squeeze in which the applied pressure exceeds the formation's fracture pressure, so cement is placed into fractures as well as into the intended channels.

high pressure tank

A tank that is capable of handling pressures in excess of 15 psig; also called a pressurized tank.

high shot density gun

A perforating gun carrying more than four shots per foot.

high speed rotor

See cylindrical rotor.

high-gravity solids

Dense solids such as barite or hematite added deliberately to raise mud density.

high-level output voltage

The highest positive op-amp output voltage for the bias conditions applied to the power pins.

high-pass filter

A high-pass filter passes high-frequency signals, but reduces the amplitude of signals with frequencies lower than the cutoff frequency.

high-performance work practices

The bundle of practices — selection, training, participation, reward — associated with better results.

high-performing team

A team consistently exceeding what its members could achieve separately.

high-permeability

Allowing fluid to flow readily, so wells produce at high rate.

high-potential employee

Someone assessed as capable of advancing well beyond their present role.

high-pressure air injection

An enhanced recovery process injecting compressed air into a light-oil reservoir, where it oxidizes in place to generate drive gas and heat.

high-pressure manifold

The steel piping and valve assembly that collects the output of all the frac pumps and delivers it to the wellhead.

high-pressure pipeline

A transmission line operating at pressure well above distribution level.

high-pressure, high-temperature

Describing wells whose undisturbed bottomhole conditions exceed the pressure and temperature ordinary equipment is rated for.

high-pressure, high-temperature filtration test

The filtration test run at downhole temperature and 500 psi differential rather than at ambient conditions.

high-pressure, high-temperature viscometer

A laboratory viscometer that measures rheology at simulated downhole pressure and temperature.

high-side toolface

Toolface measured from the high side of a deviated hole rather than from magnetic north.

high-specific-gravity solids

Dense weighting solids such as barite or hematite added to increase the density of a mud or cement slurry.

high-speed mixer

A mixer with a specialized impeller, often used to pre-mix solid ingredients before they are added to a main mixture.

high-temperature completions

Completion equipment and design for wells whose temperature exceeds the range standard components are rated for.

high-voltage conductor

A conductor that is designed to safely handle over 2,000 volts.

highstand

Strata deposited when relative sea level was high and the shoreline near its landward limit.

highstand systems tract

The systems tract deposited when sediment supply outpaces accommodation after maximum flooding, aggrading then prograding basinward.

hinged plate

A plate swinging on a hinge, as the closure of a check valve.

hip flexors

The muscles in the front of the hips.

hiring manager

The person the role reports to, who makes the decision.

histogram

A software troubleshooting tool that allows building and displaying a historical record of a specific data word.

historically underutilized business (HUB)

A supplier from a group historically excluded from procurement, recognized for targeted sourcing.

history matching

History matching is the act of adjusting a model of a reservoir until it closely reproduces the past behavior of a reservoir. The historical production and pressures are matched as closely as possible.

hitch

Any of several sling arrangements, or patterns, that can be used to attach a lifting device to a load.

HIV

Human immunodeficiency virus, a virus that breaks down the human body's natural immune system. HIV infection leads to AIDS.

HLB number

Hydrophile-lipophile balance — a number from about 1 to 40 describing where a surfactant's affinity lies between water and oil.

HMI

Human-Machine Interface. The controls that allow people to interact with a machine or process control system; a broader term than operator interface.

hodogram

A plot of one component of particle motion against another at the same instants, showing the direction the motion is polarized in.

hodogram analysis

A hodogram analysis is a technique by which signals from more than one source are plotted on orthogonal axes. If the signals are from the same source, a straight line will be created. The direction of this line indicates the direction from which the event originated.

hoist

A lifting device that uses wire rope or chain and a set of gears to provide a mechanical advantage.

hoisting

Raising and lowering the drillstring, the rig's primary mechanical function.

hold down

An anchoring device for retaining a rod pump in its working position.

holding coil

The coil keeping a contactor closed after it has pulled in.

holding current

The minimum amount of current flow required to keep an SCR in a highly conductive state.

holding, ordering and setup costs

The three costs that inventory policy trades off against each other.

holdup

The fraction of a pipe's volume occupied by one phase at a given point in multiphase flow.

holdup depth

The depth at which a tool or drift of a given size can go no deeper because the wellbore has narrowed.

holdup image

A color or greyscale display of local phase holdup around the borehole plotted against depth.

holdup log

A record of what fraction of the pipe cross section each phase occupies at every depth.

holdup map

A color or grey-scale display of holdup around the borehole circumference against depth.

holdup meter

A production logging sensor that determines water holdup from the capacitance or impedance of the fluid around it.

holdup tool

A production logging sensor measuring the fraction of each phase in the flow.

holdup, hold-up

Holdup is the volume fraction of pipe occupied by a particular fluid in multi-phase flow.

hole cleaning

The removal of drilled cuttings from the wellbore by the circulating fluid.

hole diameter

The borehole's diameter, which the log response and the cement volume both depend on.

hole washout

An enlarged section of borehole where the wall has eroded.

holiday check

An inspection method used to detect discontinuities in painted/coated surfaces using specialized tools and equipment. These tools, called holiday detectors, are portable devices that are swept across the coated surface.

hollow carrier

A perforating gun whose charges sit inside a sealed tube, so debris stays contained.

hollow carrier gun

A perforating gun whose charges sit inside a sealed steel tube, which contains the debris and the pressure of the detonation.

home networking

The domestic network arrangements on which remote work depends, and their security.

homogeneity

The quality of being uniform throughout, so that properties do not change from place to place.

homogeneous

Uniform throughout, with the same properties and composition at every point.

homogeneous formation

A formation whose rock properties do not change with location within the reservoir.

homogeneous isotropic

Having the same properties everywhere and in every direction, the simplifying assumption.

homogeneous mixture

A mixture consisting of two or more ingredients that do not remain separate and distinct, once they are evenly dispersed within one another.

homogeneous mixtures

Mixtures that consist of one or more substances dispersed uniformly in another substance.

homogenous

Uniform in composition or character.

hook

A J-shaped rigging component or fitting used to connect rope or chain to other rigging equipment for lifting and moving loads.

hook load

The total force pulling down on the hook, including the weight of the drill string in air, the drill collars, and any other bottom hole assembly equipment.

hookwall packer

A packer set by friction blocks and slips that grip the casing wall when the string is rotated and set down.

hoop stress

Circumferential stress in a pipe or casing wall under internal pressure.

hopper

A funnel-shaped vessel, or receptacle, with a relatively large opening at the top, through which material is loaded into the vessel, and a smaller opening at the bottom, through which material is discharged from the vessel.

horizon

A surface in the subsurface — a bedding plane or interface — that can be traced as a distinct reflection across seismic data.

horizon slice

A map extracted along a picked horizon through a 3D volume, following the reflector rather than a flat time or depth.

horizontal component

The sideways part of ground motion, recorded to capture shear waves.

horizontal distance

Distance measured horizontally, which in a deviated well differs greatly from along-hole distance.

horizontal drilling

A drilling technique whereby a well is progressively turned from vertical to horizontal so as to allow for greater exposure to an oil or natural gas reservoir. Horizontal laterals can be more than a mile long. In general, longer exposure lengths allow for more oil and natural gas to be recovered from a well and often can reduce the number of wells required to develop a field, thereby minimizing surface disturbance. Horizontal drilling technology has been extensively used since the 1980s and is appropriate for many, but not all, developments.

horizontal geophone

A sensor recording horizontal ground motion, used for shear wave measurement.

horizontal misalignment

Shaft axes offset in the horizontal plane.

horizontal permeability

The permeability along the bedding plane.

horizontal resistivity

Resistivity measured with current flowing parallel to bedding.

horizontal separator

A separator vessel mounted with its cylindrical axis parallel to the ground.

horizontal severance

Splitting mineral ownership by depth, so different parties hold the rights above and below a stated horizon.

horizontal stress

Stress acting sideways in the rock, whose magnitude and direction decide which way a fracture grows.

horizontal transverse isotropy

Transverse isotropy whose symmetry axis is horizontal, produced by one set of aligned vertical fractures, abbreviated HTI.

horizontal tree

A subsea Christmas tree with the master valves and flow controls arranged on a horizontal axis alongside the bore rather than stacked above it.

horizontal vessel

A vessel lying on its side, giving long residence time and a large liquid surface.

horizontal well

A well turned to run along the reservoir, exposing far more pay than a vertical hole.

horizontal wellbore

The section of a well drilled along the reservoir.

Horner slope

The slope of the straight-line portion of a Horner plot of shut-in pressure against the Horner time function.

horsehead

The curved component of the beam assembly located over the wellhead.

horst

A block of crust standing high between two normal faults that dip away from each other.

hose

The component of an oxy-fuel gas welding rig that transports oxygen and acetylene from the regulators to the torch.

hose-line

A breathing apparatus where air is supplied by means of a hose connected to a fresh air manifold.

Host Communities Development Trust (HCDT)

The fund each settlor must establish, taking a share of operating expenditure for community projects.

host country

The country in which an operator holds acreage and conducts petroleum operations.

host government

The state granting rights over petroleum resources within its territory.

Host Government Agreement (HGA)

The overarching contract between a state and an investor governing petroleum operations.

host government contract

Any of the agreement forms — concession, production sharing or service — a state uses to grant rights.

hostile environment

A set of well conditions severe enough to attack steel, elastomers, mud additives or electronics — high temperature, high pressure, sour gas or all three.

hot button issue

The point that reliably provokes a strong reaction and derails the discussion.

hot combustion gas

The hot products of combustion, the heat source in a fired heater or gas turbine.

hot discharge gas

Compressed gas leaving a compressor before cooling, at its highest temperature in the circuit.

hot lime

Calcium oxide, CaO, also called quicklime — lime before it has been slaked with water.

hot oiler

A truck- or skid-mounted heater used to pump heated oil or treatment fluid into a well.

hot oiling

Circulating heated oil down a well to melt and carry away paraffin deposited on the tubing wall.

hot spot

An overheated part of a furnace tube; may be cause by insufficient process fluid flow or by flame impingement.

hot surge tank

A storage tank that holds de-aerated feedwater to supply the demands of the feedwater system, if needed; also referred to as a de-aerator storage tank or a feedwater storage tank.

hot tapping

Drilling into a pressurized line or vessel through equipment that contains the pressure, so a connection can be made without shutting down.

hot vapor

Vapor above ambient temperature, which must be cooled before it can be stored or measured.

hot waterflooding

Thermal recovery by injecting hot water, reducing oil viscosity ahead of the flood front.

hot work

Any work that produces enough heat to be a potential ignition source for a flammable or combustible material.

hot work permit

The employer's written authorization to perform operations (for example, riveting, welding, cutting, burning, and heating) capable of providing a source of ignition.

hotwell

The bottom section of the main condenser.

Hough transform

A pattern detection method that maps points into a parameter space, so points lying on a common line or curve accumulate at one location.

housing

The pressure-bearing outer case of a downhole tool, protecting its internals from well fluid and pressure.

HP starch

Hydroxypropyl starch — a starch derivative used for filtration control in drilling, drill-in and completion fluids.

HPHT

High-pressure, high-temperature: wells whose pressure and temperature exceed the range that standard equipment, elastomers and electronics are rated for.

HPHT filtration test

The filtration test run at downhole temperature and 500 psi differential, to about 380°F or 450°F in a special cell.

HPHT viscometer

A pressurized, heated rotational viscometer that measures mud rheology at simulated downhole conditions.

HPU

Hydraulic power unit: the topside skid that generates, stores and supplies pressurized hydraulic fluid for actuating subsea valves and chokes.

HR analytics

Using workforce data to answer business questions rather than to report headcount.

HR metrics

The standard measures of workforce cost, movement and capability.

HRCI

The HR Certification Institute, which awards the PHR and SPHR credentials.

HRM planning

Aligning people capability and cost with what the business plan will require.

HSE

Health, safety and environment: the discipline covering the identification and control of hazards across an operation.

HSE management system

The documented structure of policy, procedure, competence and audit through which HSE is managed.

HSFO (High Sulphur Fuel Oil)

High sulfur fuel oil, usable only by ships fitted with exhaust scrubbers.

HSSE (Health, Safety, Security and Environment)

The same, with security added, reflecting that a security event often becomes a safety one.

HTI

Horizontal transverse isotropy — anisotropy with a horizontal symmetry axis, typically from one set of aligned vertical fractures.

hub website

A central site to which other channels and campaigns direct traffic.

HUD

Hold-up depth: the depth at which a tool or drift of a given size can no longer pass, usually because fill or debris has bridged the wellbore.

huddling chamber

The chamber in a spring-loaded safety valve to give additional lift which results in a popping action and prevents the disc from slamming into the seat.

huff and puff

A cyclic single-well process in which fluid is injected, left to soak, and then produced back from the same well.

human factors

How people's capabilities and limitations shape whether systems fail.

human oversight

Keeping a person accountable for consequential decisions rather than deferring to the model.

human performance feedback loop

The cycle in which measurement informs action, which changes performance, which is measured again.

human resource management (HRM)

The function responsible for how an organization acquires, develops and manages its people.

human-in-the-loop (HITL)

A workflow in which a person reviews, approves or corrects a model's output before it is acted on.

Humble formula

The Archie relation with a = 0.62 and m = 2.15, proposed by Humble Oil for unconsolidated sandstone.

humic

Derived from land plant material, and so gas-prone on maturation.

humic acid

A complex mixture of aromatic and phenolic carboxylic acids that makes up much of lignite, used in muds as a thinner and filtration control agent.

humidifier

A device that adds moisture to air.

humidistat

A device used to control the amount of moisture contained in conditioned air.

humidity

The amount of moisture or water vapor contained in a given volume of air.

humidity meter

An instrument that measures the water vapor content of air, as relative humidity or dewpoint.

humping

A hump in a pressure buildup curve caused by phases redistributing in the wellbore after shut-in.

hurdle rate

The minimum return a company requires before it will commit capital.

HWDP

Heavy-weight drillpipe: drillpipe with thicker walls and longer tool joints, run between the collars and the drillpipe to ease the stiffness transition.

hybrid cloud

A computing arrangement combining private infrastructure with public cloud services, with data and applications able to move between them.

hybrid fiscal regime

A system combining features of production sharing, royalty and service arrangements.

hybrid NOC strategy

A state oil company adopting commercial disciplines and partial listing while remaining state controlled.

hybrid scale

An early log presentation combining a linear resistivity scale at low values with a logarithmic one above.

hybrid work

Splitting time between remote and on-site working.

hydrate

Ice-like accumulations formed by the combination of water and hydrocarbon molecules.

hydrate formation

Ice-like solids of water and light hydrocarbons forming under pressure and cold, which plug lines rather than freeze them.

hydrates

Solids (ice) formed by a mixture of water vapor and hydrocarbons at the proper temperature and pressure.

hydration

The chemical incorporation of water into a substance's structure.

hydraulic actuator

A cylinder or motor converting hydraulic pressure into motion.

hydraulic bypass

Flow ports built into a packer or large downhole tool so fluid can pass it as it is run and pulled.

hydraulic cement

Cement that sets by chemical reaction with water, and continues to harden under water.

hydraulic centralizer

A toolstring centraliser whose arms or bows are pushed out by hydraulic force rather than by spring tension.

hydraulic circuit

The connected pump, valves and actuators of a hydraulic system.

hydraulic cylinder

A cylinder converting hydraulic pressure into linear force.

hydraulic disconnect

A downhole release that parts the tool string on command, so the upper section and the running string can be recovered.

hydraulic flow unit

Hydraulic flow units represent the zones of the reservoir rock that can be mapped and correlated and have constant petrophysical and geological properties affecting the fluid flow.

hydraulic fluid

The liquid transmitting power in a hydraulic system, chosen for viscosity and fire resistance.

hydraulic fracture

A fracture created by pumping fluid above formation breakdown pressure.

hydraulic fracture monitoring

Tracking where and how a hydraulic fracture grows, most often by locating the microseismic events it generates.

hydraulic fracturing

The fracturing of rock by a pressurized liquid. A completion technique (commonly known as fracking) in which typically water is mixed with sand (proppant) and chemicals, and the mixture is injected at high pressure into a wellbore to create small fractures (typically less than 1mm) through which oil and gas may migrate to the well. In use since the 1940s.

hydraulic fracturing fluids

Mixture of water and proppant along with minor amounts of chemical additives used to hydraulically fracture low permeability formations. Water and sand typically comprise up to 99.5 percent of the mixture.

hydraulic fracturing, fraccing

Hydraulic fracturing, or fraccing, is the fracturing of rock by a pressurized liquid. Induced hydraulic fracturing or hydro fracturing, commonly known as fracking, is a technique in which typically water is mixed with sand and chemicals, and the mixture is injected at high pressure into a wellbore to create small fractures (typically less than 1mm), along which fluids such as gas and oil may migrate to the well.

hydraulic head

The pressure a column of liquid exerts at depth, expressed as the height of that column.

hydraulic horsepower

The rate at which hydraulic energy is delivered across the bit nozzles.

hydraulic jack

A portable jack in which the lifting or pushing force is supplied by pressurized hydraulic fluid.

hydraulic motor

A motor converting hydraulic flow into rotation.

hydraulic packer

A packer set by applied tubing pressure rather than by mechanical manipulation of the string.

hydraulic power pack

The self-contained engine, pump and reservoir unit that supplies hydraulic power to a coiled tubing or workover spread.

hydraulic power unit

The topside skid that generates, stores and supplies pressurized hydraulic fluid to operate subsea valves and chokes.

hydraulic pressure

Pressure in a hydraulic circuit.

hydraulic pump

The pump generating flow in a hydraulic system.

hydraulic pumping

An artificial lift method in which pressurized power fluid from surface drives a downhole pump.

hydraulic release tool

A connector that parts on applied pressure, tension or both, letting the running string be recovered if the assembly below is stuck.

hydraulic set

A setting method in which pressure applied inside the running string, against a plug or ball, drives the tool's setting mechanism.

hydraulic system

The pump, valves and actuators transmitting force through pressurized liquid.

hydraulically fractured

Stimulated by pumping above fracture pressure to create conductive paths.

hydraulically operated

Actuated by fluid pressure rather than mechanically or electrically.

hydraulics

The calculation of pressures and flow rates through the circulating system.

hydro testing

See Water testing.

hydrocarbon

A chemical compound made up of hydrogen and carbon, generally used to identify oil and natural gas products. Examples include methane, propane, etc.

hydrocarbon accumulation

Hydrocarbons collected and held in a trap.

hydrocarbon component

An individual compound in the mixture, whose proportion determines phase behavior.

hydrocarbon compound

An individual molecule of hydrogen and carbon.

hydrocarbon condensate

Liquid hydrocarbon condensed from a gas stream.

hydrocarbon condensation

Hydrocarbon liquid dropping out of gas as it cools or is compressed.

hydrocarbon dew point

The temperature at which hydrocarbon liquid begins to condense from gas, controlled to keep pipelines dry.

hydrocarbon exploration

The search for undiscovered accumulations, from basin screening to the first well.

hydrocarbon gas

Gaseous hydrocarbons, as distinct from the inert and acid gases produced with them.

hydrocarbon generation

The conversion of kerogen to oil and gas as burial temperature rises.

hydrocarbon indicator

A seismic amplitude anomaly or characteristic that suggests hydrocarbons are present in a reservoir.

hydrocarbon kitchen

The part of a basin where source rock has been buried deep enough and hot enough to be generating hydrocarbons.

hydrocarbon level

The depth of hydrocarbon liquid in a vessel, controlled separately from any water layer beneath it.

hydrocarbon liquid

Oil, condensate or natural gas liquids, as distinct from gas.

hydrocarbon migration

The movement of oil and gas from source rock to trap.

hydrocarbon pay

Hydrocarbon pay denotes a portion of a reservoir that contains economically recoverable hydrocarbons.

hydrocarbon pore

Pore space occupied by hydrocarbons rather than water.

hydrocarbon pore volume

The hydrocarbon pore volume (HPV) is the product of the volume of a reservoir multiplied by the porosity multiplied by the hydrocarbon saturation.

hydrocarbon potential

The likelihood and size of hydrocarbons a play or prospect could hold.

hydrocarbon production

Bringing hydrocarbons to surface and to sale.

hydrocarbon province

A region whose geology has proved capable of generating and trapping petroleum.

hydrocarbon recovery

The proportion of hydrocarbons in place that is produced.

hydrocarbon reserve

The portion of an accumulation that is both technically recoverable and commercial.

hydrocarbon reservoir

Rock holding hydrocarbons in connected pore space at recoverable rates.

hydrocarbon saturation

Hydrocarbon saturation refers to the proportion of pore space in a rock formation that contains hydrocarbons (oil and gas). It's a key parameter in reservoir characterization, and it directly influences estimates of oil and gas reserves and reservoir performance.

hydrocarbon source

The rock that generated the oil or gas.

hydrocarbon source rock, petroleum source rock

Hydrocarbon, or petroleum, source rock is defined as the fine-grained sediment with sufficient amount of organic matter, which can generate and release enough hydrocarbons to form a commercial accumulation of oil or gas.

hydrocarbon stream

A process flow of hydrocarbons, as distinct from utility or treatment streams.

hydrocarbon vapor

Hydrocarbons in gas phase, the fraction that must be recovered rather than vented.

hydrocarbon vapour

Hydrocarbons in gas phase, the fraction that must be recovered rather than vented.

hydrocarbons

Organic chemical compounds consisting wholly of hydrogen and carbon, whose densities, boiling points, and freezing points increase as their molecular weights increase. They often occur in nature as petroleum, natural gas, coal, and bitumens.

hydrochloric

Of hydrochloric acid, the standard treatment for dissolving carbonate near the wellbore.

hydrochloric acid

The strong mineral acid used for most carbonate stimulation, dissolving limestone and dolomite to water and carbon dioxide.

hydrocracker

A unit that uses hydrogen and a catalyst to crack hydrocarbons into lighter, more valuable products.

hydrocracking

Reforming reactions in which naphthenes are converted to paraffins, and larger paraffins are converted to smaller paraffins.

hydrocyclone

A cone-shaped solids separator into which fluid is fed tangentially, so that spinning throws the heavier particles to the wall and out of the apex.

hydrocycloning

Separating solids from mud in a cone-shaped vessel fed tangentially, so the spin throws heavier particles to the wall and out the apex.

hydrodesulphurization

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

hydrodynamic

Involving fluid in motion, as in a tilted contact caused by regional water flow.

hydrodynamics

Hydrodynamics is the scientific study of fluids in motion.

hydroelectric plant

A power plant that uses energy from water stored behind a dam to produce electric power.

hydrofluoric (HF) acid

A common catalyst that is used in an alkylation unit.

hydrofluoric acid

The only common inexpensive acid that dissolves silica and silicates, used in sandstone acidizing and always in a mixture with HCl.

hydrofluoric-hydrochloric acid

The mixture of HF and HCl, commonly 12 percent HCl with 3 percent HF, used to dissolve clay and silica in a sandstone matrix treatment.

hydrogen

Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element.

hydrogen blistering

A hydrogen-induced failure in which atomic hydrogen collects at internal defects in low-strength steel and forces blisters open as it recombines into gas.

hydrogen combustion

Burning hydrogen for heat or shaft power, producing water and, at flame temperature, nitrogen oxides.

hydrogen commercialization

Turning hydrogen from a technically proven fuel into one with markets, infrastructure and buyers.

hydrogen content

The proportion of hydrogen in a stream, which sets how much a pipeline or burner can accept unmodified.

hydrogen derivative

A hydrogen-bearing product such as ammonia or methanol, easier to ship than hydrogen itself.

hydrogen dryer

A device that removes moisture from the hydrogen circulating inside a hydrogen-cooled generator.

hydrogen economy

An energy system where hydrogen carries energy between sectors, long proposed and repeatedly deferred.

hydrogen embrittlement

The loss of ductility and strength in steel as atomic hydrogen diffuses in and recombines internally, leading to sudden brittle failure.

hydrogen fuel

Hydrogen burned or reacted for energy, emitting water rather than carbon dioxide at the point of use.

hydrogen fuel cell

A device converting hydrogen and oxygen directly to electricity, avoiding the efficiency limit of combustion.

hydrogen gas

Hydrogen in gas phase, the lightest and most leak-prone of the industrial gases.

hydrogen generation

Producing hydrogen at the point of use, avoiding transport and storage entirely.

hydrogen index

The ratio of the concentration of hydrogen atoms per cm³ in a material to that of pure water at 75°F (surface conditions). The hydrogen index is thus the density of hydrogen relative to that of water.

hydrogen industry

The producers, users and suppliers trading hydrogen, historically industrial rather than energy-facing.

hydrogen infrastructure

The pipelines, storage and refueling assets hydrogen needs, and the reason supply outruns demand.

hydrogen ion

A positively charged hydrogen particle.

hydrogen leak

An escape of hydrogen, hard to detect because the gas is colorless, odorless and ignites over a very wide range.

hydrogen leak detection

Sensing escaped hydrogen, required because the gas gives no smell, color or visible flame.

hydrogen make

The hydrogen that is not recycled by the recycle compressor in a catalytic reforming unit; also called export hydrogen.

hydrogen market

The trade in hydrogen as a commodity, currently thin because most is made where it is consumed.

hydrogen network

Connected pipelines and storage moving hydrogen between producers and users.

hydrogen pipeline

Pipe carrying hydrogen, needing steel selected against embrittlement and seals tighter than for methane.

hydrogen probe

A corrosion monitor that measures hydrogen permeating through a steel wall, indicating the rate of sour attack.

hydrogen production

Making hydrogen from a feedstock, which is where nearly all of its cost and its emissions sit.

hydrogen purity

The percentage of pure hydrogen in the recycle gas.

hydrogen safety

Managing hydrogen's wide flammability range, invisible flame and tendency to embrittle metal and escape through small gaps.

hydrogen seal oil system

A system of seals used at both ends of an AC generator to prevent hydrogen and air from mixing.

hydrogen storage

Holding hydrogen as compressed gas, cryogenic liquid or a chemical carrier, each trading density against energy cost.

hydrogen sulfide

Hydrogen sulfide is a chemical compound with the formula H2S. It is a colorless chalcogen-hydride gas, and is poisonous, corrosive, and flammable, with trace amounts in ambient atmosphere having a characteristic foul odor of rotten eggs.

hydrogen sulfide (H2S)

(H₂S) A highly toxic gas that has an offensive odor.

hydrogen sulfide gas

A toxic, corrosive, flammable gas produced with many hydrocarbons, deadly at very low concentration.

hydrogen transportation

Moving hydrogen by pipeline, tube trailer or ship as a carrier, the step that decides delivered cost.

hydrogen-induced failures

Cracking or blistering that occurs when atomic hydrogen enters steel and recombines within it.

hydrogen/ hydrocarbon ratio

A ratio of the amount of hydrogen in the recycle gas to the amount of hydrocarbon feed.

hydrogenation

A reaction in which a hydrogen molecule is added to a double-bonded hydrocarbon to form a new compound.

hydrography

Hydrography is the science that measures, describes, and maps the physical features of bodies of water, including oceans, seas, lakes, and rivers, primarily for the purpose of navigation and understanding the water environment.

hydrolysis

A chemical reaction in which water splits a compound, breaking it into new products.

hydrometer

An instrument used for measuring the specific gravity or weight of a material, such as oil samples.

hydrophile-lipophile balance number

A one-to-forty scale rating how strongly a surfactant favours water over oil, abbreviated HLB.

hydrophilic

Water-attracting — describing a surface or a molecular group that associates readily with water.

hydrophobic

Water-repelling — describing a surface or a molecular group that avoids association with water.

hydrophone

A hydrophone is an underwater device that detects and records ocean sounds from all directions.

hydropower

Electricity from falling or flowing water, the oldest large-scale renewable and the most site-constrained.

hydroscopic clays

Hydroscopic clays readily take up, and retain, moisture.

hydroskimming

The simplest refinery configuration, distilling and treating without conversion units.

hydroskimming refinery

A simple refinery that distills and treats but cannot convert heavy fractions.

hydrostatic

Relating to the pressure exerted by a static fluid column.

hydrostatic bailer

A slickline bailer that uses the pressure difference between the wellbore and an evacuated chamber to suck sand and debris in when a disc is broken.

hydrostatic gradient

The rate at which pressure increases with depth in a static fluid column.

hydrostatic head

The pressure exerted at depth by the weight of the fluid column above, expressed as an equivalent height of fresh water.

hydrostatic pressure

The normal, predicted pressure for a given depth, or the pressure exerted per unit area by a column of freshwater from sea level to a given depth. Pressure related to the height of a column of liquid.

hydrostatic stress

A hydrostatic stress is an isotropic stress that is given by the weight of rock above a certain point.

hydrostatics

Hydrostatics is a branch of physics that deals with the characteristics of fluids at rest, particularly with the pressure in a fluid or exerted by a fluid (gas or liquid).

hydrothermal

Pertaining to hot water circulating in the subsurface, its activity, and the minerals it precipitates.

hydrothermal alteration

Mineralogical change in a rock produced by hot circulating fluids, typically magma-related.

hydrotreater

A unit that uses hydrogen to remove sulfur from various fractions.

hydrotreating

A process that pretreats feed material by removing contaminants, especially sulfur.

hydrotreating unit

The refinery unit reacting streams with hydrogen over catalyst to remove sulfur and nitrogen.

hydroxide

A base used in drilling fluids and treating to raise pH and neutralize acid gas.

hydroxyethyl starch

A nonionic starch derivative used for fluid-loss control in drilling, drill-in, completion and workover fluids.

hydroxyethylcellulose

A nonionic cellulose polymer used to viscosify brines and treatment fluids while leaving little residue.

hydroxyl

The oxygen-hydrogen group that makes alcohols and glycols able to hydrogen bond.

hydroxyl ion

A negatively charged particle consisting of oxygen and hydrogen.

hydroxyls

The chemical group, ion, or radical OH consisting of one atom of hydrogen and one of oxygen, which are neutral or negatively charged.

hydroxypropyl starch

A propylene oxide derivative of starch used mainly for fluid-loss control in drilling and completion fluids.

hygiene plan

The written scheme controlling exposure to hazardous substances.

hygrometer

A device that uses the expansion and contraction of a material, such as hair, to measure humidity.

hygroscopic

Describing a substance that takes up water from the surrounding air.

hyperbaric welding

Hyperbaric welding, also known as underwater welding, is a process that involves welding at high pressures, usually underwater.

hyperbola

The curve a diffraction traces on an unmigrated seismic section.

hyperbolas

The curved patterns diffractions produce on unmigrated seismic sections.

hyperbolic

A convex hyperbolic reflector has two foci and will reflect all light rays directed at one of its two foci towards its other focus.

hyperparameters

The settings chosen before training that govern how a model learns, as distinct from the parameters it learns.

hyperscaler

A cloud provider operating at global scale — AWS, Microsoft Azure or Google Cloud.

hypocenters

A hypocenter is the point of origin of an earthquake at depth.

hypotenuse

The side of a right triangle that is opposite the 90 angle.

hysteresis

A condition in which the output action of an instrument or process depends not only on the value of the input but also on whether the input is increasing or decreasing, resulting in the failure of a process variable to respond fully when the control output direction changes.

H

H2S

hacksaw