Discover the IHRDC Energy Glossary_beta

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I

I/O bus

The network that typically connects input and output smart field devices, controllers, and operator interfaces.

iadc

The International Association of Drilling Contractors, whose codes and reports standardize drilling practice.

IASB (International Accounting Standards Board)

The body that sets IFRS.

ICD

Inflow control device: a passive restriction built into a screen joint that balances inflow along a long horizontal completion.

ichnofacies

An ichnofacies is an assemblage of trace fossils that provide an indication of the conditions that their formative organisms inhabited.

icon

A small graphic, or "picture," used on graphical user interfaces such as Windows and RSLogix.

ICV

Interval control valve: a remotely operated downhole choke that opens, closes or throttles flow from one zone of a multi-zone completion.

ID

Inside diameter; the length of a straight line that passes from one side on the inside surface of a pipe, through the center of the pipe.

ideal gas

A hypothetical gas whose molecules have no volume and no attraction for one another, so that pressure, volume and temperature follow pV = nRT exactly.

identification method

How a user asserts identity before authentication tests the claim.

identity and access management (IAM)

The systems governing who exists in the directory and what they may reach.

identity law

In logic, the law that states an object is the same as itself: A = A.

idler

A wheel or pulley that guides or tensions without transmitting power.

Immediately Dangerous to Life or Health. An atmospheric concentration of any toxic, corrosive, or asphyxiant substance that poses an immediate threat to life, would interfere with an individual's ability to escape from a dangerous atmosphere, or is likely to have adverse delayed effects on health.

IFRS (International Financial Reporting Standards)

The accounting standards used across most of the world outside the United States.

IGBT

Insulated Gate Bipolar Transistor. A high-speed, solid-state switch typically used in modern PWM inverter and variable speed drives.

igneous

Igneous rocks are a category of rocks that are formed through the cooling and solidification of molten magma. These can be formed both below and above Earth's surface. Common igneous rocks include granite, gabbro, basalt, obsidian, pumice and rhyolite.

igneous rock

Rock crystallized from melt, rarely a reservoir but sometimes a seal or basement.

ignite

To heat a flammable material to a point where it catches fire.

ignition source

Anything able to ignite a flammable mixture, which hazardous area classification exists to exclude.

ignitor

The device initiating combustion at a burner.

IIBA-CBAP

The senior business analysis credential from the International Institute of Business Analysis.

IIP

Initially in place — the volume of hydrocarbon in a reservoir before any production, as in STOIIP and GIIP.

illegal bunkering

Unauthorized loading of stolen crude or product onto vessels.

illite

A non-expanding, clay-sized, micaceous mineral. Illite is a phyllosilicate or layered alumino-silicate with a structure constituted by the repetition of tetrahedron–octahedron–tetrahedron (TOT) layers.

ilmenite

Ferrous titanium oxide, a dense mineral used as an alternative weighting material to barite.

image

A representation of a surface or subsurface produced from measured data, whether photographic, satellite or geophysical.

image recognition

Machine interpretation of images to identify objects, features or patterns in them.

image table

A PLC data file in which the processor stores the current states of the inputs as it scans them or the desired states of the outputs as it determines them.

image well

A fictitious well introduced in well test analysis to reproduce the effect of a boundary, replacing the boundary with a mirrored source or sink.

imager

A logging tool producing a picture of the borehole wall rather than a curve.

imager tool

A logging tool producing a picture of the borehole wall.

imaging tool

A logging tool producing a picture of the borehole wall rather than a single curve.

imbibition

The displacement of one fluid by another immiscible fluid, absorbing a wetting phase into a porous rock.

immature

Describing a source rock that has not been buried hot enough or long enough to have generated hydrocarbons.

immediate instruction

An instruction that scans or sets I/O addresses during the perform-the-logic part of the PLC scan cycle.

immediately dangerous to life or health

An atmospheric concentration of any toxic, corrosive or asphyxiant substance that poses an immediate threat to life or would interfere with an individual's ability to escape from a dangerous atmosphere.

immediately dangerous to life or health (IDLH)

Any condition that poses an immediate or delayed threat to life or that would cause irreversible adverse health effects or that would interfere with an individual's ability to escape unaided from a permit space.NOTE: Some materials -- hydrogen fluoride gas and cadmium vapor, for example -- may produce immediate transient effects that, even if severe, may pass without medical attention, but are followed by sudden, possibly fatal collapse 12-72 hours after exposure. The victim "feels normal" from recovery from transient effects until collapse. Such materials in hazardous quantities are considered to be "immediately" dangerous to life or health.

immiscibility

The inability of two substances to dissolve together to form a solution.

immiscible

Immiscible liquids do not form a homogeneous mixture when added together.

immiscible fluid

A fluid that will not mix with another, so an interface remains between them.

immiscible gas injection

Injecting gas that does not mix with the oil, displacing it by pressure rather than dissolution.

immiscible liquids

Liquids that do not mix with each other.

immobile

Held in place by capillary force and not displaceable by flow.

immune system

A diffuse, complex network of interacting cells, cell products and cell-forming tissues that includes the thymus, spleen, lymph nodes and lymph tissue, stem cells, white blood cells, antibodies, and the chemicals produced by lymphocytes. The immune system recognizes and attacks pathogens.

impairment

Reduced capacity to perform safely, whatever the cause.

impasse

The point at which negotiation stops making progress.

impedance

In seismic acoustics, the product of velocity times density, also called acoustic impedance and symbolized by Z. The reflection coefficient of an interface depends on the acoustic impedance contrast of rock on either side of the interface.

impediment

Anything blocking the team, which it is the scrum master's job to remove.

impeller

A device used to move fluid in a centrifugal pump, typically consisting of a series of curved vanes extending from the center of a circular component that mounts onto the shaft and rotates.

impeller-type reactor

A reactor that uses a motor or turbine driven impeller to mix the reactants with the catalyst.

imperfection

A flaw in material or weld, which inspection grades rather than simply finds.

impermeable

Having no significant permeability over the life of a field.

impermeable barrier

A rock layer that fluids cannot pass through, sealing what lies beneath it.

impermeable cap rock

The sealing layer above a reservoir that prevents upward escape.

impermeable shale

Shale that will not transmit fluid, and so acts as a seal.

impingement

Contact between the flame from a burner and a tube in a furnace.

implicit bias

The same phenomenon, measured through response patterns rather than stated belief.

importing country

A country consuming more petroleum than it produces.

impressed current

A method of cathodic protection.

impressed current anodes

Anodes fed by an external DC supply, driving protective current onto a buried or submerged structure.

improper fraction

A fraction with a numerator larger than the denominator.

improved oil recovery (IOR)

Term used to describe methods employed to improve the flow of hydrocarbons from the reservoir to the wellbore or to recover more oil or natural gas. Enhanced oil recovery (EOR) would be one form of IOR.

improvement team

The cross-functional group assembled to work one process problem.

impulse

A type of turbine wheel blade that causes the wheel to rotate when high pressure steam strikes the blades.

impulse response

The output a system gives to a sharp input, the earth's version of which seismic processing tries to recover.

impulsive seismic data

Data from a source that releases its energy in a single short burst, such as dynamite or an air gun.

impurity

A component that must be removed to meet specification, such as sulfur or mercury.

in line

Aligned with the direction of flow or of the axis in question.

in phase

A situation in which the voltages at the top or bottom of the primary and secondary windings on a transformer are of the same polarity.

in situ

In the original place — describing a property, process or measurement as it exists in the reservoir rather than in the laboratory.

in situ combustion

A thermal recovery process in which part of the oil in the reservoir is ignited and air injection sustains a combustion front that drives the rest toward the producers.

in situ fluid analysis

Measuring a reservoir fluid's composition and properties downhole, in the tool, rather than sending a sample to a laboratory.

in situ viscosity evaluation

Measurement of fluid viscosity downhole, at reservoir pressure and temperature.

in-line blending systems

Blending systems in which the blend components from rundown tanks or directly from process units are metered into a blend header and mixed together.

in-situ recovery

Techniques used to extract hydrocarbons from deposits of extra-heavy crude oil, bitumen or oil shale without removing the soil and other overburden materials.

in-situ stress

The stress state in the undisturbed rock, which decides fracture orientation and hole stability.

inboard

The end of a pump that is closest to the pump's driver.

inboard feet

The reading taken at the coupling end during alignment.

inbound logistics

Bringing materials in from suppliers.

inbox management

Handling incoming mail so it does not displace the actual work.

inch mercury

Pressure expressed as the height of a mercury column, used for vacuum.

inch of water

A very small unit of pressure. An inch of water is equal to 0.036 psig.

inches of water

Very small units of pressure used to measure differential pressure. An inch of water is equal to 0.036 psig or 0.248 kPa.

inchnospecies

An ichnospecies is a species-level classification within ichnology, the study of fossilized traces, analogous to a species classification in biological taxonomy. It is essentially a name given to a specific type of trace fossil, such as a footprint, burrow, or trail.

incident angle

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

incident investigation

Establishing what happened and why, to prevent recurrence rather than to assign blame.

incident management and response

The organized process for detecting, containing and recovering from a security incident.

incineration

The process of converting gaseous organic vapor emissions into relatively harmless substances through combustion.

incinerator

A device that destroys gas stream contaminants by burning them.

incised valley

A valley cut during low sea level and later filled, forming a stratigraphic trap.

inclination

The angle of a wellbore from vertical, in degrees, regardless of compass direction.

inclined manometer

A type of manometer used to measure pressures that are too low to be measured easily on a U-tube manometer.

inclinometer

An instrument measuring angle from the horizontal or the vertical — in a logging tool, the tool's own deviation.

inclusion

Whether those differences are actually able to contribute, which diversity alone does not ensure.

inclusive culture

A workplace where difference is used rather than merely tolerated.

inclusive decision-making

Deciding in a way that surfaces and uses the full range of views available.

inclusive engagement

Involving people so that participation is real rather than nominal.

inclusive leader

A leader who actively ensures every member can contribute.

inclusive leadership

Leading so every member can contribute fully regardless of background.

incoherence function

The incoherence function expresses the lack of coherence between logs, results, response equations and constraints.

income statement

The statement of revenue, cost and profit over a period.

incoming air

Air entering a machine or furnace.

incoming emulsion

Emulsion arriving at a treater, before heat or chemical is applied.

incoming gas

Gas arriving at a unit, before treatment.

incoming gas stream

Gas arriving at the plant, whose composition and pressure the whole train is designed around.

incoming stream

Fluid arriving at a unit, before any treatment has been applied.

incompetent

Describing strata ductile enough to flow under stress rather than fracture, so their thickness changes through a fold.

incorporated joint venture (IJV)

A venture held through a jointly owned company rather than by contract alone.

incoterms

The standard trade terms fixing where risk, cost and delivery responsibility pass between buyer and seller.

increment

The working output produced by a sprint, usable whether or not it is released.

incremental sample

A sample taken in predetermined quantities at predetermined time intervals.

incursion

The advance of water or another fluid into a zone.

indemnity

A promise to bear another party's loss, shifting risk regardless of who was at fault.

indempotent law

A Boolean algebra law stating that when a Boolean proposition X is OR'ed with itself, the result is the proposition X itself.

independent

An oil company active only in exploration and production, without refining or marketing arms.

independent contractor

Someone engaged to deliver a result, controlling how the work is done.

independent inspector

The neutral surveyor who measures and samples cargo so both parties accept the quantity and quality.

independent standards

External benchmarks both sides can accept, so the outcome does not turn on who pushed harder.

independent variable

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

index

A detailed alphabetical listing of the items covered in the NEC.

indicating light

A lamp showing a device's state.

indicating silica gel

An adsorbent that removes moisture from substances and indicates adsorption by changing colors.

indicator

A substance used to change the color of a liquid to give a visual sign that a chemical reaction is complete.

indicator light

A lamp showing a state.

indicator methods

Non-parametric geostatistical methods that recode data into zeros and ones at a threshold, and simulate the resulting binary field.

indicator models

Reservoir models built by simulating a binary indicator — above or below a cutoff — rather than the property value itself.

indicator of compromise

Evidence suggesting a system has already been breached.

indicator reading

The value shown on an indicator.

indicator stem

The moving stem of a dial indicator that contacts the surface being measured.

indirect level measurement device

A device that measures a physical aspect of a fluid that varies in proportion to level and uses that information to provide a level measurement.

individual contributor

Someone who delivers work personally rather than through others.

Individual Development Plan (IDP)

The agreed plan closing one person's gaps, with actions, dates and accountability.

individual X chart

A control chart that is plotted using single samples taken from a process; often used to monitor processes in which single samples are taken some time apart.

induced draft

Draft created by a fan drawing gas out, holding the furnace below atmospheric pressure.

induced draft draft fan

A fan that draws combustion gases out of a boiler.

induced draft fan

A type of fan that creates a pressure that is less than atmospheric pressure inside a system.

induced fracture

A fracture created by operations rather than present naturally.

induced fractures

Induced fractures are those fractures caused by operational activities such as drilling and hydraulic fracturing.

induced gamma ray spectroscopy

Measuring the energy spectrum of gamma rays emitted after formation nuclei are activated by a neutron source, to identify the elements present.

induced particle plugging

Near-wellbore damage caused by particles carried in with injected or circulated fluid.

induced polarization

An electrical method measuring how long a formation holds a charge after the applied current is switched off, abbreviated IP.

induced voltage

An EMF created by electromagnetic induction.

induced-draft cooling tower

A mechanical-draft tower in which air is pulled through the tower by fans.

inductance

A physical property of all conductors and circuits that opposes a change in current flow, measured in henrys. In electrical formulas, inductance is typically represented as a capital L.

inductance filter

A filter circuit that smooths out a pulsating DC voltage by opposing changes in current.

induction

The process that produces a voltage as a result of the interaction of a conductor, a magnetic field, and relative motion between them.

induction cup

The rotating cup element in an electromechanical relay.

induction cup element

A relay element that uses magnetic fields, created at the pole face of several electromagnets, to create a torque on a cup to close contacts.

induction disc

The rotating disc in an electromechanical relay whose travel sets the time delay.

induction disc element

A relay element that has an electromagnet that is intersected by a metallic disc.

induction electrical survey

A combined log pairing a deep induction measurement with a shallow electrode curve such as the 16-inch short normal.

induction logging

Resistivity logging by electromagnetic induction, needed in non-conductive mud.

induction resistivity, induction resistivity log

A wireline log of formation resistivity based on the principle of inducing alternating current loops in the formation and measuring the resultant signal in a receiver. An alternating current of medium frequency (tens of kHz) is passed through a transmitter coil, inducing an alternating magnetic field in the formation.

induction tool

A resistivity tool inducing currents in the formation, usable where the mud will not conduct.

induction, induction log, induction resistivity

A wireline log of formation resistivity based on inducing alternating current loops in the formation and measuring the resultant signal in a receiver. An alternating current of medium frequency (tens of kHz) is passed through a transmitter coil, inducing an alternating magnetic field in the formation.

inductive

Working through a magnetic field rather than by contact, as in a proximity sensor.

inductive loads

Any devices that have coils of wire in there manufacture can be classed as an inductive load.

inductive power

Non-working power that is a result of magnetizing current such as the current required to create a magnetic field in a motor.

inductive reactance

The opposition to AC current flow provided by an inductance, measured in ohms. Typically represented as XL in electrical formulas.

inductor

A component specifically designed to increase the amount of inductance in a circuit. In inverter controllers, the part of the DC bus that helps smooth out pulses of DC produced by the converter.

inductors

An inductor is a passive electrical component that can store energy in a magnetic field created by the electric current passing through it. Typically an inductor is a wire shaped as a coil to create a magnetic field.

indurated

A condition of a rock or soil hardened or consolidated by pressure, cementation, or heat.

industrial control system

The hardware and software directing industrial processes, including SCADA and distributed control.

industrial grade asphalts

Asphalts that are thinner, or less viscous, than road grade asphalts and are used in applications such as roofing or waterproofing.

inelastic

Deforming permanently rather than returning to shape, and the neutron scattering used in logging.

inelastic neutron scattering

Inelastic neutron scattering is a neutron interaction in which part of the kinetic energy lost by a neutron in a nuclear collision excites the nucleus. The excited nucleus will usually emit characteristic gamma rays upon de-excitation.

inelastic scattering

Inelastic scattering is a fundamental scattering process in which the kinetic energy of an incident particle is not conserved, in contrast to elastic scattering.

inequality

Unequal distribution of income, wealth or opportunity, and its consequences.

inert gas

A gas used as a displacement fluid which does react with the prod¬uct being sampled.

inert sulfide

Sulfide already bound into an insoluble precipitate, and so no longer chemically available in the fluid.

inertia

A property of matter that resists changes in motion.

inertial systems

A frame of reference in which a body remains at rest or moves with constant linear velocity unless acted upon by forces.

inertinite

An oxidized maceral group, inert and generating little hydrocarbon.

inferential

Derived from another measurement rather than measured directly, as flow inferred from differential pressure.

inferential meter

A metering device that does not measure volume directly, but as a function of some action related to volume.

infill

Additional wells drilled between existing ones to recover bypassed oil.

infill drilling

Drilling additional wells within an existing field to reduce well spacing and access reserves the original pattern missed.

infill wells

Wells drilled into the same reservoir as known producing wells so that oil or natural gas does not have to travel as far through the formation, thereby helping to improve or accelerate recovery.

infinite acting radial flow

The period in a well test when pressure transients are propagating radially outward and no boundary has yet been felt.

infinite positioning

The characteristic that allows the spool in a directional control valve to be moved anywhere within its range of movement, so that specific ports are completely blocked, partially blocked, or completely open.

infinite-acting reservoir

A reservoir that behaves during a test as though it had no outer boundary, because no boundary effect has reached the well.

infinite-conductivity fracture

An idealized hydraulic fracture along which there is no pressure drop, so the whole fracture acts as an extension of the wellbore.

inflatable packer

A packer whose element is an inflatable bladder, expanded by pumped fluid to seal against casing or an irregular openhole wall.

inflection

The point at which a curve changes its direction of bending.

inflow

Flow from the formation into the wellbore.

inflow control device

A passive restriction built into a completion to even out inflow along a long horizontal section.

inflow control valve

A remotely adjustable downhole valve that chokes or shuts off flow from one zone of a completion.

inflow performance

The relationship between how hard a well is drawn down and how much it delivers.

inflow performance relationship

The curve relating a well's production rate to its flowing bottomhole pressure at a given reservoir pressure.

influence without authority

Getting outcomes from people who do not report to you.

influx

Influx into the wellbore occurs when the hydrostatic pressure is low enough to allow formation fluids to enter the wellbore; flushing away from the open wellbore occurs under reciprocal pressure conditions.

information life cycle

The stages from creation through use and storage to destruction.

information radiator

A display kept visible so the team sees status without asking.

information security

Protecting information from unauthorized access, alteration or loss.

information technology (IT)

The corporate systems handling business data and communication.

information theory

The mathematical treatment of how much information a signal carries and how much can be transmitted through a channel.

infrared spectroscopy

A form of spectroscopy that uses radiation in the infrared bandwidth of the electromagnetic spectrum. Abbreviated as IR spectroscopy.

ingestion

Taking a substance in by mouth, one of the exposure routes a safety data sheet addresses.

inhibit

To prevent, arrest or slow a reaction or process.

inhibited acid

An acid blended with a corrosion inhibitor so that it attacks the formation without destroying the tubulars and pumping equipment it passes through.

inhibition

The prevention or slowing of an unwanted process — corrosion, scale, hydrate formation or clay swelling.

inhibitive

Formulated to prevent clay from swelling and destabilizing the borehole.

inhibitive mud

A mud formulated to slow or stop shale from hydrating, swelling and disintegrating.

inhibitor

A chemical added to a fluid to retard or prevent an unwanted reaction within it.

inhomogeneity

Variation of properties from place to place within a body.

initial boiling point (IBP)

The temperature at which a fraction starts to boil.

initial flow period

A short flow at the start of a drillstem test, taken to bleed off pressure trapped while setting the packer.

initial pressure limiter

A device that is installed on most turbines to regulate inlet steam pressure.

initial public offering (IPO)

First sale of shares to the public, which brings capital and external accountability together.

initial reservoir pressure

The undisturbed reservoir pressure before production begins, usually measured in the discovery well.

initial shut-in period

The short buildup following the initial flow of a drillstem test, from which initial reservoir pressure is obtained.

initiating

Defining the project and authorizing it to begin.

injected fluid

Fluid pumped into the formation for pressure support, disposal or stimulation.

injected gas

Gas pumped in for pressure support, lift or miscible displacement.

injected water

Water pumped in for pressure support or disposal.

injection gas

Gas injected into a well or reservoir, whether to maintain pressure or to lift fluid in a gas lift system.

injection line

A small-diameter conduit run alongside the production tubulars to deliver chemical inhibitors downhole during production.

injection mandrel

A tubing component with a port and valve through which chemical can be injected into the produced stream downhole.

injection nozzle

The fitting delivering an injected chemical into the stream, sized to atomize rather than dribble.

injection pattern

The geometric arrangement of injection and production wells in a flood.

injection point

Where a chemical enters the process, chosen so it mixes before the equipment it protects.

injection pressure

The surface or bottomhole pressure at which fluid is pumped into a formation or, in gas lift, into the tubing.

injection pulsed neutron log

A log-inject-log survey in which a high-capture-cross-section brine is injected and the pulsed neutron response before and after is compared.

injection pump

A pump that delivers fluid into a reservoir or into a production system, at the pressure the destination requires.

injection rate

The amount of gas that can be injected into a storage facility on a daily basis.

injection test

A test establishing the rate and pressure at which fluid can be pumped into a formation without fracturing it.

injection torch

A type of torch that uses a restriction called a venturi to increase the velocity of oxygen, enabling it to draw acetylene into its stream. The gases then flow into the tip, where they are mixed.

injection water

Water injected into a reservoir to maintain pressure and displace hydrocarbons toward the producers.

injection well

An injection well is used to place fluid underground into porous geologic formations.

injection wells

Wells used to inject fluids, such as water, steam, or gas, into underground reservoirs to enhance oil and gas recovery or to dispose of waste fluids produced during extraction. Development and Injection wells may be vertical, high angle, horizontal, multilateral or directed to enter the reservoir at favorable locations.

injection-well testing

Pressure transient testing carried out on a well taking fluid rather than producing it.

injectite

Injectites are structures formed by sediment injection.

injectivity

How readily a formation accepts injected fluid.

injectivity test

A test in which fluid is injected at constant rate and the pressure response recorded, to establish how readily the formation takes fluid.

injector

A well used to put water or gas into the reservoir.

injector head

The component of a coiled tubing unit that grips the tubing between opposed chain-driven blocks and pushes or pulls it against wellhead pressure.

inlet box

A component in a fan system that provides enough space for air to move evenly into a fan's inlet from around the inlet. Also called a plenum.

inlet compressor

Compressor raising incoming gas to the pressure the plant needs, ahead of treatment.

inlet damper

A damper that is located on the inlet side of a fan and used to control air flow into the fan.

inlet diverter

The internal baffle turning incoming flow in a separator to begin phase separation.

inlet gas

The raw gas stream entering a processing plant.

inlet gas pressure

The pressure gas arrives at, which sets what compression is needed and what liquid has already dropped out.

inlet gas separator

Separator at a plant inlet removing free liquid before treatment.

inlet gas stream

The gas feed to a unit, with its liquid, water and acid gas content as received.

inlet gas temperature

Temperature of gas entering a unit, which decides how much liquid is already condensed.

inlet header

The manifold collecting several feed lines into one, upstream of the first vessel.

inlet line

The line feeding a unit.

inlet port

The opening fluid enters by.

inlet pressure

Pressure at a unit's entry, the variable most upstream controls are holding steady.

inlet pressure control

The loop holding plant inlet pressure steady as well and pipeline conditions move.

inlet separator

The separator removing liquid at a unit's inlet.

inlet steam

Steam entering a turbine or unit.

inlet stream

Fluid entering a unit as received.

inlet temperature

The temperature of the stream entering a unit.

inlet valve

The valve on an inlet.

inlet water

Water entering a unit, before any treatment or heating.

innage

A measurement of liquid level from the bottom of a container to the surface of the liquid.

inner seat ring

The inboard component of a two-piece valve seat, carrying the sealing surface against the closure member.

inorganic chemistry

The branch of chemistry dealing with compounds that do not contain carbon.

inorganic solids

Solids composed of non-living matter such as rocks, sand, and clay.

input

Data entered into the EFC or instrument system.

input bias current

The average of the currents into the two input terminals with the output at a specified level.

input capacitance

The capacitance between the input terminals with either input grounded.

input common-mode voltage range

The range of common-mode input voltage that, if exceeded, may cause the operational amplifier to cease functioning properly. This is sometimes is taken as the voltage range over which the input offset voltage remains within a set limit.

input current

The amount of current that can be sourced or sinked by the op-amp input. Usually specified as an absolute maximum rating.

input device

A real device that is wired to an input module and provides an input to a PLC.

input image table

Input Image Table The part of data memory in which the current states of the real inputs are stored.

input instruction

The programmable controller instruction examining an input.

input noise current

The internal noise current reflected back to an ideal current source in parallel with the input pins.

input noise voltage

The internal noise voltage reflected back to an ideal voltage source in parallel with the input pins.

input offset current

The difference between the currents into the two input terminals with the output at the specified level.

input offset voltage

The dc voltage that must be applied between the input terminals to cancel dc offsets within the op-amp.

input parameter

A value supplied to a model, whose uncertainty propagates into every result.

input resistance

The dc resistance between the input terminals with either input grounded.

input resistor

The resistor setting the current into an amplifier input.

input voltage

The voltage supplied to a device.

input voltage range

The range of input voltages that may be applied to either the IN+ or IN. inputs.

input waveform

The wavelet assumed to have entered the ground, needed to interpret amplitude.

input/output testing

A process of elimination method in which the condition of the process entering a component and the condition of the process leaving the component are checked.

insert

A hard cutting element pressed into a machined socket in a bit cone, rather than milled from the cone itself.

inside blowout preventer

A check valve installed in the drillstring to stop flow coming up the pipe, abbreviated IBOP.

inside casing

The interior of a machine casing.

inside diameter

The internal bore dimension of a pipe or vessel.

inside micrometer

A micrometer used to measure inside diameters and distances between parallel surfaces composed of a micrometer head and attachable rods and collars.

inside-out air seat test

A low-pressure air test of a trunnion-mounted ball valve's seats, applied outward from the body cavity. Only double-piston-effect seats can be tested this way.

insider threat

Harm caused by someone with legitimate access, against whom perimeter controls do not help.

insoluble

Not dissolving in a given fluid, and so remaining as solids to be removed.

instability

In process control, a loop response characterized by continuing oscillations. In quality control, a condition where abnormal variations exist in a process even though values remain within control limits.

installed ground

An intentional electrical connection between electrical equipment and the earth, or ground.

instantaneous contacts

The contacts on a timer that become energized as soon as the timer becomes enabled.

instruction

A command to a PLC, usually a single item or graphic on a PLC ladder program rung, corresponding to a command or series of commands to the PLC microprocessor.

instruction manual

The maker's document describing operation and maintenance.

instructional design

Designing learning so that it produces a defined change in capability.

instructional format

How a program is taught — the mix of lecture, case, workshop and simulation.

instructional scaffolding

Support given early and withdrawn as the learner becomes able to work unaided.

instructor-led training (ILT)

Usually refers to traditional classroom training, in which an instructor teaches a course to a room of learners. Skills and knowledge are taught through lectures, demonstrations, discussions, and presentations. ILT can be extremely beneficial when the material is new or complex.

instrument

Any device used to measure, indicate, control, or transmit information about a process or system.

instrument hanger

A downhole tool that supports gauges or instruments left temporarily in the well.

instrument technician

The tradesperson maintaining and calibrating instruments.

instrumentation amplifier

A precision amplifier that is typically a combination of a differential amplifier and two voltage followers.

instrumentation diagram

The drawing showing instruments, control loops and their connections.

instrumented pig

An inline inspection tool that records wall thickness, geometry or position as it travels through a pipeline.

insulate

Cover to prevent the passage of heat or current.

insulated gate field effect transistor (IGFET)

A type of FET. The gate of an IGFET is insulated from the transistor body.

insulated ship

A vessel whose tanks are insulated to carry refrigerated cargo such as LNG.

insulated wire

A wire that's covered with an insulating material.

insulating material

Material resisting the passage of heat or current.

insulation

A material that is a poor conductor of electrical current.

insulative material

A material that prevents or limits the flow of electrons across its surface or through its volume is called an insulator.

insulator

A material that offers a great deal of resistance to electron flow, through which current cannot flow easily.

insurance policies

Are obtained by the operator to cover a number of potential areas of liability including environmental damage, accidents, well blowouts and subsurface damage, damage to property and equipment, and general liability.

integral compressor

A compressor with the compression and drive units on the same frame.

integral control

A process control algorithm (sometimes called reset control) that relates the control output to the time integral of the error, often combined with proportional control to eliminate offset by essentially repeating the proportional action until the process returns to steady state.

integrated circuit

An electronic circuit containing many interconnected active and passive circuit elements formed on a single chip of semiconductor material. These components are particularly vulnerable to voltage spikes and static discharges.

integrated oil company

A company operating across upstream, midstream and downstream rather than in one segment.

integrated reservoir management

Coordinating subsurface, wells and facilities as one system rather than optimizing each alone.

integrated risk management plan

A single plan covering HSE and security risk for an asset, rather than separate documents.

integrated travel time, integrated transit time

Integrated travel/transit time is the amount of time for a wave to travel a certain distance, proportional to the reciprocal of velocity, typically measured in microseconds per foot by a sonic/acoustic log.

integration framework

A structure for combining agile delivery with existing governance and reporting.

integrator

A control device or circuit whose output is a total, summed over time, of the input; also called a totalizer.

intellectual property

Legally protected creations: inventions, works, marks and confidential information.

intelligent (smart) module

A type of I/O module that contains a microprocessor to perform sophisticated data manipulation.

intelligent well

A well fitted with downhole monitoring and remotely adjustable flow control, so production can be changed without intervention.

intensifier

A downhole tool run with a jar that stores energy and releases it as the jar fires, raising the impact delivered.

intensity

The loudness of sound, measured in decibels.

interactive petrophysics

Interactive Petrophysics is a petrophysics package used as a tool by Petrophysicists, Geologists and Reservoir Engineers.

interbedded

Occurring as alternating layers of different rock types.

intercalated

Interlayered with beds of another rock type.

intercept valve

The valve isolating steam to a turbine stage on overspeed.

intercept valves

Hydraulic cylinder actuated valves in a reheat steam system that stop the flow of steam to the IP section of the turbine in case of turbine overspeed.

interconnection diagram

A drawing that shows the connection points between two or more units.

intercooler

A cooling device for cooling gas between stages on multi-stage compressors.

intercrystalline

Between crystals, the location of much carbonate porosity.

interdune

Interdune refers to the relatively flat area of land situated between sand dunes, essentially the low-lying space between individual dune ridges where sediments may accumulate or be eroded by wind, depending on the local conditions. This can also describe the sedimentary deposits found within these areas between dunes.

interface

The point of interaction between persons, groups, systems, etc. In process engineering, the contact surface or point where two liquid phases or two fluids (such as oil and water) separate or meet.

interface level

The boundary between two liquid layers in a vessel, controlled separately from the total level.

interface module

In PLC systems, a module that plugs into a PC used as a programming terminal to allow the PC to communicate with a PLC network.

interface panel

A device used to convert trip signals to other types of signals and back again during a transfer trip.

interfacial

Of the boundary between two immiscible phases, where tension and wettability act.

interfacial tension

The force that holds the surface of a particular phase together when two phases are present (gas/oil, oil/water, or gas/water), normally measured in dynes/cm. Surface tension applies to a single liquid surface, whereas interfacial tension applies to the interface of two immiscible liquids.

interference testing

A test in which rate is changed at one well and the resulting pressure response is recorded at another, establishing whether the two are connected.

intergranular

Intergranular is situated or occurring between grains or granules.

intergranular porosity

Pore space between grains, the primary porosity of a clastic rock.

interim assessment results (IAR)

Prior to Assessor Assessment, the lower of the Employee Assessment and the Supervisor Assessment scores.

interior basin

A basin within a continent rather than at its margin.

interlayer

The space between clay mineral sheets, where water and ions are held.

interlock

A discrete control function or mechanical/electrical connection that prevents or enables an action depending on the state of another variable, ensuring equipment operations occur only in a specific sequence.

interlocked contactors

Contactors whose control circuits have been wired together either to prevent their being closed at the same time or to make certain that one does not close before the other has already closed.

intermediaries

The agents, brokers and distributors standing between exporter and end buyer.

intermediate

In the strict API sense, a particle in the 250 to 2,000 micron size range.

intermediate bulk storage

Tankage between the producing or refining point and final distribution.

intermediate casing

A casing string set between the surface casing and the production casing, isolating troublesome intervals so drilling can continue.

intermediate casing string

The pipe run below the surface casing and before the production casing, to case off zones that would otherwise prevent deeper drilling.

intermediate pressure

A pressure level between high and low in a staged system.

intermittent gas lift

Gas lift in which slugs of liquid are accumulated and then pushed to surface by periodic injections of gas, rather than by continuous aeration.

intermittent monitoring

A method of source sampling in which samples are collected periodically and taken to a laboratory for analysis; also called wet chemistry.

intermitter

A regulation device used in production of a flowing well. The well flows for several short periods each day and then closed in.

internal audit

An audit of a plant's quality system performed by employees of the plant.

internal auxiliary relay

A relay that responds to the operation of multiphase or ground elements to close contacts; also called a telephone relay.

internal combustion

Combustion inside the engine's own cylinders.

internal combustion engine

Engine burning fuel in its own cylinders, the usual prime mover where grid power is absent.

internal controls

The procedures preventing and detecting error and fraud.

internal diameter

The bore of pipe or tubing, which sets flow area and tool passage.

internal flash

The weld bead left on the inside of coiled tubing by the longitudinal seam weld during manufacture.

internal heat

The heat produced when current flows through a conductor.

internal phase

The dispersed phase of an emulsion — the droplets suspended within the continuous phase.

internal pulling tool

A pulling tool that latches inside a device's fishing neck to retrieve it.

internal rate of return (IRR)

The discount rate at which a project's net present value falls to zero.

internal reflux

Liquid in a distillation tower that comes from condensed vapours; used to help separate a mixture into components.

internal safety valve

A relief valve fitted inside the vessel it protects.

internal vs. external recruitment

Promoting from within against hiring from outside, each with different cost and risk.

international affiliate of an NOC

The subsidiary through which a state oil company invests outside its home country.

international nautical mile

A distance of exactly 1,852 meters, used in marine and aerial navigation.

Internet of Things (IoT)

Networks of instrumented devices reporting condition and performance continuously.

interpersonal skills

The abilities that determine how well someone works with other people.

interpolate

To estimate values between measured points.

interpolated

Estimated between measured points.

interpolation

Estimating values at points between existing data points.

interpretation

The analysis of processed data to produce a model of the subsurface — its structure, stratigraphy, lithology and fluids.

interrupted customer

A gas customer whose supply may be curtailed when firm demand is high.

interrupter

The element breaking current in a switching device.

interruptible customer

A customer receiving service under rate schedules or contracts which permit interruption of service on short notice due to insufficient gas supply or capacity to deliver that supply.

interruptible service

Low-priority service offered to customers under schedules or contracts which anticipate and permit interruption on short notice, generally in peak-load seasons.

interruptible supply

Service a pipeline may curtail when firm customers need the capacity, sold at a discount.

interruption management

Controlling the flow of demands so sustained work is possible.

interstage

Between two compression stages, where cooling and liquid knockout are done.

interstitial

Occupying the spaces between grains.

interstitial gas

Gas held in the pore space of a rock, as distinct from gas dissolved in the oil or water.

interstitial water

Water occupying the pore space of a rock, particularly the fraction adsorbed onto grain surfaces rather than free to move.

intertidal

Between high and low tide, alternately exposed and flooded.

interval method

Time-to-depth conversion that works layer by layer, using each interval's own velocity and thickness rather than an average.

interval time

The traveltime through a single layer, obtained from the interval velocity and the layer's thickness.

interval transit

The time sound takes to cross a set distance in the formation, the sonic log's raw measurement.

interval transit time

The time an acoustic wave takes to travel one foot of formation, in microseconds — the quantity a sonic log records.

interval transit time, interval travel time

The interval transit time is the amount of time for a wave to travel a certain distance, proportional to the reciprocal of velocity, typically measured in microseconds per foot by an acoustic log.

interval velocity

The velocity of a specific layer of rock, as distinct from the average velocity to that depth.

intervertebral disc

A fibrous, fluid-filled sac that separates two vertebrae in the spine. The discs act as a cushion between the vertebrae and allow the spine to flex and bend.

interview question types

Behavioral, situational, technical and competency questions, each testing something different.

interwell

Between wells, the region where properties must be inferred rather than measured.

interwell tomography

Imaging the rock between two wells from signals sent from a source in one and recorded by an array in the other.

intraclasts

Intraclasts are irregularly shaped grains that form by syndepositional erosion-erosion simultaneous with deposition-of partially-lithified sediment.

intranet and extranet

A private internal network, and one extended to selected outside parties.

intrastate versus interstate

Whether activity crosses a state line, which in the United States decides who regulates it.

invaded

The invaded, or flushed, zone is the volume close to the borehole wall in which some, or all, of the moveable fluids have been displaced by mud filtrate. It consists of the flushed zone and the transition zone.

invaded zone

The annulus of formation around the borehole in which mud filtrate has displaced some of the original pore fluid.

invaded zone water saturation

The water saturation (Sxo) in the formation zone adjacent to the borehole that has been invaded by drilling mud filtrate.

invaded zone, flushed zone

The invaded or flushed zone is the volume close to the borehole wall in which some or all of the moveable fluids have been displaced by drilling mud filtrate. It consists of the flushed zone and the transition zone.

invaded, or flushed, zone

The volume close to the borehole wall in which some or all of the moveable fluids have been displaced by mud filtrate, consisting of the flushed zone and the transition zone.

invaded, or flushed, zone, invasion

invasion

The displacement of formation fluid near the wellbore by mud filtrate driven in by the overbalance.

inventory management

Deciding how much stock to hold, where, and when to reorder.

inventory optimization

Reducing stock holdings without exposing operations to shortage.

inverse

Reversed in effect — an operation that undoes another.

inverse filter

A filter designed to undo the effect of another filter, restoring the signal that entered it.

inverse modeling

Deducing model parameters from observed data, rather than predicting data from a model.

inverse problem

Determining the properties of a system from its observed response, rather than predicting the response from known properties.

inversion

Inversion is the mathematical process of calculating the cause from a set of observations.

invert

To reverse positions of two items; used with fractions to reverse the positions of the numerator and the denominator.

invert emulsion

An emulsion with oil as the continuous phase and water dispersed within it — the basis of oil-base mud.

invert-emulsion oil mud

An oil mud carrying an appreciable water phase emulsified into the oil, as against a true oil mud with almost none.

inverted bucket trap

A steam trap using a buoyant inverted bucket to discharge condensate and hold steam back.

inverted five-spot

A flood pattern with one injector at the center of a square of four producers — the reverse of a five-spot.

inverter

See NOT gate.

inverter drive

A drive synthesizing variable frequency from a direct current link to change motor speed.

inverter section

The part of an inverter controller that contains the high-speed switches typically IGBTs that apply voltage to a motor.

inverting amplifier

An op amp circuit in which a signal is applied to the inverting input terminal; the output signal is opposite in polarity to the input signal.

inverting input terminal

The input terminal of an op amp represented by a negative (-) sign. An inverting input terminal will invert (reverse) the polarity of any signal applied to it.

inverting summing amplifier

See Summing amplifier.

investment decision fid

The board approval committing capital and starting construction.

investment options

The available places to put savings, differing in risk, return and access.

Invincible and Tiger (purchase-and-sale briefs)

The paired buyer and seller briefs in the purchase-and-sale negotiation exercise.

IO

Isomerized olefin — a synthetic base fluid made by polymerizing ethylene, used for synthetic-base muds.

IOC (International Oil Company)

A privately owned, shareholder-accountable oil company operating internationally.

IOGP (International Association of Oil and Gas Producers)

The global association whose reports and recommended practices set much industry safety benchmarking.

ion

An atom or molecule that has lost or gained one or more electrons, giving it a net positive or negative electrical charge. Positive ions (cations) have lost electrons; negative ions (anions) have gained electrons.

ion exchange

The substitution of one ion for another on a charged solid substrate such as a clay, zeolite or resin.

ion exchange resin

Plastic beads containing numerous charged areas; used to exchange ions.

ion exchanger

A device used to accomplish ion exchange; a demineralizer.

ion-selective electrodes

Electrodes that are designed to sense only specific ions in a fluid. Also called ion-specific electrodes. Abbreviated as ISE's.

ionization

A chemical change by which ions are formed from a neutral molecule of an inorganic substance.

ions

An atom or group of atoms that carries a positive or negative charge as a result of having lost or gained one or more electrons.

IP

Induced polarization — an electrical method measuring how the ground stores and releases charge after a current is switched.

IPA

Isopropyl alcohol: a simple alcohol used as a mutual solvent and water-removal stage in acid treatments, and as a solvent in mud analysis.

IPCC (Intergovernmental Panel on Climate Change)

The United Nations body that assesses and summarizes the state of climate science.

IPIECA

The oil and gas industry association that publishes environmental and social good-practice guidance.

IPR

Inflow performance relationship: the curve of a well's production rate against flowing bottomhole pressure at a given average reservoir pressure.

ipr curve

The inflow performance relationship, plotting production rate against flowing pressure.

iron carbonate

Siderite, FeCO3, formed as a corrosion product where carbon dioxide attacks steel in the presence of water.

iron oxide

A compound of iron and oxygen — rust being the familiar product of iron oxidizing in air and water.

iron sponge

A batch process that uses a chemical reaction to sweeten sour gas. Wood chips soaked with iron oxide are mixed with hydrogen sulfide to form ferrous sulfide (Fe₂S₃), which must then be disposed of carefully because it will spontaneously combust when exposed to air.

iron stabilizer

An acid additive that keeps dissolved iron in solution so it cannot precipitate as ferric hydroxide when the acid spends.

iron sulfide

A compound of iron and sulfur formed where hydrogen sulfide attacks steel in processing equipment.

iron-oxidizing bacteria

Aerobic bacteria that oxidize ferrous iron to ferric, precipitating insoluble ferric hydroxide.

irreducible

The saturation below which a fluid will not be displaced, being held by capillary force.

irreducible water

The lowest water saturation a rock can be brought to by displacement with oil or gas, held in place by capillary forces.

irreducible water saturation

The minimum fraction of the pore space occupied by water when the hydrocarbon content is at maximum (Swirr), representing the minimum water saturation that can be established using mechanically forced fluid displacement.

irreducible water saturation, critical water saturation

The fraction of the pore space occupied by water when the hydrocarbon content is at maximum (Swirr), sometimes termed the critical water saturation.

irrevocable

Incapable of being withdrawn once given.

irritant

A chemical that is not corrosive, but causes a reversible inflammatory effect on living tissue by chemical action at the site of contact.

ISC2

The body awarding the CISSP and other information security credentials.

isip

Instantaneous shut-in pressure, read at the moment pumping stops to infer fracture pressure.

ISO

The International Organization for Standardization.

ISO 9000

A series of international quality system standards and guidelines intended to adopt a consistent quality approach for all companies.

ISO accessibility standards

The international standards covering accessible products, services and information.

iso-butane

Gaseous hydrocarbon (C₄H₁₀) found in natural gas. Used as an additive to gasoline to add volatility during cold weather...

iso-octane

The product of a reaction between butylene and isobutane; consists of eight carbon atoms and 18 hydrogen atoms.

ISO/IEC 17024

The international standard for bodies certifying persons, which credible credentials meet.

isobutane

A chemical compound (also known as 2-methylpropane or methylpropane) with molecular formula C4H10, consisting of four carbon atoms and 10 hydrogen atoms. A colorless, odorless gas that is reacted with olefins in the alkylation process.

isobutane-to-olefin ratio

The amount of isobutane that is fed to the reactor in an alkylation unit, divided by the amount of olefins.

isochore

A contour of equal true vertical thickness between two surfaces.

isochron

A line joining points of equal time — in seismic, of equal traveltime difference between two reflections.

isochron map

A contour map of the traveltime difference between two seismic reflections — a time thickness map.

isochronal

A well test using equal flow periods, used to establish gas well deliverability.

isochronal test

A gas well test of several flow periods of equal duration, each followed by a shut-in long enough for pressure to return to its initial value.

isochronous stratal surfaces

Isochronous stratal surfaces are geological layers that have the same age or time value across a given area, indicating that they were formed simultaneously. This concept is important in stratigraphy for understanding the temporal relationships between different rock layers.

isoclinally

Inclining or dipping in the same direction.

isoheptane

The product of a reaction between propylene and isobutane; consists of seven carbon atoms and 16 hydrogen atoms.

isolated porosity

Pore volume with no connection to the rest of the pore network, so nothing it contains can be produced.

isolating

See Blocking in.

isolation

The process by which a permit space is removed from service and completely protected against the release of energy and material into the space by such means as: blanking or blinding; misaligning or removing sections of lines, pipes, or ducts; a double block and bleed system; lockout or tagout of all sources of energy; or blocking or disconnecting all mechanical linkages.

isolation valve

A valve that can be used to shut down or isolate a section of pipe or equipment, such as a gauge glass from the container to which it is attached.

isomer

A compound with the same formula but a different structure, and different properties.

isomerization

A reforming reaction in which a paraffin is converted to an isoparaffin.

isomerization unit

A unit that changes straight-chain paraffins into branched-chain paraffins that are used as a feed for an alkylation unit.

isomerized olefin

A synthetic base fluid made by rearranging the double bond and branching of linear alpha olefins, abbreviated IO.

isometric view

A method of presenting three-dimensional objects in two dimensions that eliminates the distortion of shape created by true perspective, where all lines on each axis are parallel and do not converge.

isopach

A contour of equal thickness between two surfaces, measured perpendicular to bedding.

isopach map

An isopach map shows thickness variations within a rock unit. Isopachs are contour lines of equal thickness over a mapped area.

isoparaffin

A hydrocarbon with a branched-chain, single-bonded arrangement of carbon atoms; the product of a reaction between an olefin and isobutane.

isopropanol

Isopropyl alcohol, a simple alcohol used as a mutual solvent in acid treatments and as a solvent in mud analysis.

isopropyl alcohol

A simple alcohol, C3H7OH, used as a mutual solvent and water-removal stage in acid treatments and as a laboratory solvent.

isosceles triangle

A triangle that has two equal sides and two equal angles.

isostasy

The gravitational equilibrium in which lithospheric blocks float on the asthenosphere at a level set by their thickness and density.

isostatic

Pertaining to isostasy — the balance between lithospheric loads and the buoyant support of the asthenosphere.

isostatic correction

A gravity correction removing the effect of the crustal root that compensates topography at depth.

isostatic subsidence

The crust floats buoyantly on the asthenosphere, with a ratio of mass below the "surface" in proportion to the crust's density and the density of the asthenosphere. If additional mass is added to a local area of the crust through deposition, the crust subsides to compensate and maintain isostatic balance.