Discover the IHRDC Energy Glossary_beta

Search or select a letter above to browse the glossary.

L

label

In PLC programming, the number indicating the destination of a jump. Also, the name given to a device to identify it in a ladder diagram (synonym for alias, tag, or symbol). In hazardous materials, a diamond-shaped tag or sticker identifying contents and associated risks.

labeling system

The scheme identifying a container's contents and hazards.

laboratory

A facility where the “laboratory use of hazardous chemicals” occurs. It is a workplace where relatively small quantities of hazardous chemicals are used on a non-production basis.

laboratory measurement

A property measured on a sample under controlled conditions rather than inferred downhole.

laboratory scale

Work with substances in which the containers used for reactions, transfers, and other handling of substances are designed to be easily and safety manipulated by one person. “Laboratory scale” excludes those workplaces whose function is to produce commercial quantities of materials.

laboratory use of hazardous chemicals

Handling or use of such chemicals in which all of the following conditions are met:1. Chemical manipulations are carried out on a “laboratory scale”;2. multiple chemical procedures or chemicals are used;3. the procedures involved are not part of a production process, nor in any way simulate a production process; and4. “protective laboratory practices and equipment” are available and in common use to minimize the potential for employee exposure to hazardous chemicals.

laboratory-type hood

A device located in a laboratory, enclosed on five sides with a movable sash or fixed partial enclosed on the remaining side; constructed and maintained to draw air from the laboratory and to prevent or minimize the escape of air contaminants into the laboratory; and allows chemical manipulations to be conducted in the enclosure without insertion of any portion of the employee's body other than hands and arms. Walk-in hoods with adjustable sashes meet the above definition provided that the sashes are adjusted during use so that the airflow and the exhaust of air contaminants are not compromised and employees do not work inside the enclosure during the release of airborne hazardous chemicals.

labour relations

The management of the relationship between employer and organized labor.

labour supply and demand

The comparison of available skills in the market against what the organization needs.

labyrinth

Type of seal on the expander-compressor which has a series of teeth machined on the impellers or seal rings to a small clearance between the teeth and shaft.

labyrinth seal

A seal made up of a set of grooves and ridges that correspond to another set of grooves and ridges on, for example, a turbine shaft.

LACT

Lease Automatic Custody Transfer.

LACTI chart

A project management tool to help identify individual responsibilities by identifying individuals who will Lead, Act, be Consulted, be Tasked and be Informed. See also, RACI Chart.

lacustrine

Pertaining to lakes — their depositional environment, processes and deposits.

lacustrine deposits

Lacustrine deposits are sedimentary rock formations that occur in the bottom of lakes.

ladder diagram

A control drawing laid out as rungs between two power rails, read left to right as logic.

ladder logic

Control logic drawn as rungs between power rails, the usual programmable controller language.

ladder program

The stored logic a programmable controller executes.

lag

In process control, the time between when a process variable begins to respond and when it has substantially re-stabilized (also called the time constant). The total delay caused by resistance, capacitance, and dead time. In geology, a deposit of coarse material left behind after finer materials have been removed by wind, water, or tidal action.

lag gas

Gas deliberately introduced into the mud so that its arrival at surface measures the circulation lag time.

lag time

Lag time is the difference between the time a cutting is produced (by the drill bit acting against the formation) and the time it reaches the surface (shale shaker), carried there by the circulating drilling mud.

lagoonal

Deposited in a lagoon, typically fine-grained and restricted.

laminar

Flowing in smooth parallel layers, as opposed to turbulent.

laminar flow

Laminar flow is a flow regime characterized by high momentum diffusion and low momentum convection.

laminar shale

Shale in discrete layers rather than dispersed, which affects vertical and horizontal properties differently.

laminated sand

A sand interbedded at fine scale with shale, so that individual laminae are thinner than most logging tools can resolve.

lamination

Lamination develops in fine grained sediment when fine grained particles settle, which can only happen in quiet water.

lamination, laminated, laminae

A small-scale sequence of fine layers (laminae) occurring in sedimentary rocks, normally smaller and less pronounced than bedding layering. Lamination is normally regarded as planar structures one centimeter or less in thickness, whereas bedding layers are greater than one centimeter.

Lamé constant

Either of the two elastic constants, lambda and mu, that fully describe an isotropic elastic solid.

LAN

Local Area Network; the main information network connecting controllers, servers, clients, and workstations in a typical plant.

LAN, WAN, MAN

Networks at local, wide and metropolitan scale.

land rights and compensation

Establishing who holds rights over the land a project needs, and what is owed for taking it.

land seismic

Seismic acquired on land, with buried or surface sources and planted receivers.

landed cost

The total cost of a good delivered, including freight, duty, insurance and handling.

landfill

A pit or area in which wastes are buried.

landing collar

A profiled collar set a joint or two above the shoe, on which the cement plugs land and seal.

landing nipple

A short, heavy-walled tubing section with a machined seal bore and locking profile, into which flow control devices are set.

landing page optimization

Improving the page an advertisement leads to, where most conversion is won or lost.

landward

Toward the shoreline, the direction of onlap in a transgressive sequence.

Lang lay

A form of wire rope construction in which the strands of the rope and the wires that make up the strands spiral in the same direction.

lantern ring

A ring located between rings of packing and designed to distribute gland sealing fluid.

lanyard

A flexible line of rope, wire rope, or webbing with connectors at each end.

LAO

Linear alpha olefin — a synthetic hydrocarbon base fluid made by polymerizing ethylene, used in synthetic muds.

lap-joint ﬂange

A four-piece ﬂange; a lipped piece of pipe that welds to existing pipe, with the ﬂange half sliding up to the lip on each pipe half. Lap-joint ﬂanges swivel around pipe, so two-holing is not required.

Laplace equation

The partial differential equation setting the sum of a potential's second derivatives to zero — the governing equation of a steady potential field.

lapouts

A lapout is a stratal discontinuity that separates sedimentary units that are conformable from those that are non-conformable. Lapouts are also known as seismic reflection terminations and are used to identify depositional sequences and system tracts.

lapping

Grinding two faces together with abrasive to make them seal.

large language model (LLM)

A model trained on very large text corpora to interpret and generate language.

last reading

The deepest depth at which a log curve gives a reliable value.

last-shot detection

A surface system that confirms every tubing-conveyed perforating gun has fired.

late-time transient data

The part of a pressure test after radial flow ends, when boundaries and other wells are controlling the response.

latent defect

This type of damage allows a device to work properly for the most part, but over time the small amount of damage might affect the life of the device or its ability to function. The issue with latent defects is that the item usually passes testing and can move to the next step of a process where it may fail.

latent heat

Energy that, when added to or taken away from a substance, causes a change in state (phase change) but not in temperature.

latent heat of condensation

The amount of heat that must be removed from a vapor to change it into a liquid at a particular temperature and pressure without producing a change in temperature.

latent heat of fusion

The amount of heat required to melt a substance without producing a change in temperature or pressure.

latent heat of vaporization

The amount of heat required to completely change the phase of a liquid to a vapor at a certain temperature and pressure.

latent heat transfer

A heat transfer process that causes a phase change rather than a temperature change.

latent heat vaporization

The heat absorbed turning liquid to vapor at constant temperature.

lateral

The horizontal or high-angle section of a well drilled through the reservoir.

lateral change

Change in a property with horizontal position.

lateral extent

How far a body reaches sideways, usually the least-known of its dimensions.

lateral resolution

The smallest horizontal separation two features can have and still be distinguished.

lateral variation

Change in a property sideways rather than with depth.

lateral velocity

Velocity variation sideways rather than with depth, the hardest kind to account for in imaging.

laterolog

A type of resistivity electrode device that measures resistivity by injecting electric current into the formation and measuring the potential drop. Most laterologs use cylindrical electrodes that average resistivity azimuthally; azimuthal laterologs use radially segmented electrodes that respond to resistivity in the direction each segment is facing.

laterolog resistivity

A focused resistivity measurement suited to conductive muds and hard formations.

latex

A colloidal suspension of polymer particles in water, added to cement to improve its flexibility and bonding.

law of agency

The rules determining when one person's acts legally bind another.

law of energy conservation

The law stating that energy can neither be created nor destroyed, only altered in form.

law versus fact question

The distinction between what the rule means and what actually happened, which decides who determines it.

lay

The manner in which the wires and the strands of a wire rope are laid, or twisted.

laycan

The window within which the ship must arrive and be ready to load, or the charterer may cancel.

layer

A slab of reservoir rock treated as a unit, bounded above and below and in vertical communication with its neighbors.

layer cake geometry

A simplified subsurface model of flat, continuous layers of uniform thickness stacked one on another.

layer stripping

An inversion approach that solves for the shallowest layer first and removes its effect before solving for the next one down.

layered reservoir testing

Testing that combines transient pressure with downhole flow profiles, so each layer's properties are resolved rather than the system average.

layers of protection

The principle that several independent defenses must fail together before harm occurs.

layover

A delay in transit, and the associated cost in shipping.

laytime

The time allowed, free of charge, for loading and discharging the cargo.

lb/bbl

Pounds per barrel, the oilfield unit for the concentration of a solid additive in a fluid.

lbm/bbl

Pounds mass per barrel — the US oilfield unit of additive concentration.

LC 50

The concentration of a substance that kills half a test population within a stated exposure period.

LC oscillator

An oscillator in which the tuned circuit has an inductor and a capacitor connected in parallel.

LCM

Lost circulation material: solids added to mud to bridge and seal a thief zone so drilling fluid stops flowing into the formation.

LDAR (Leak Detection and Repair)

The program of surveying equipment for fugitive emissions and fixing what leaks.

leaching

The process by which soluble constituents are removed from a solid, such as soil, by liquid passing through it.

lead

A lead in hydrocarbon exploration is a subsurface structural or stratigraphic feature with the potential to have entrapped oil or natural gas. When exploring a new area, or when new data becomes available in existing acreage, an explorer will carry out an initial screening to identify possible leads. Further work is then concentrated on the leads with the intention to mature at least some of them into drillable prospects.

lead acetate test

A field test for hydrogen sulfide in which paper soaked in lead acetate darkens on exposure to the gas.

lead capture

Obtaining contact details from a prospect in exchange for something of value.

lead cement

The first, lighter cement slurry pumped, providing fill across non-productive zones above the interval that matters.

lead nurturing

Maintaining contact with a prospect who is not yet ready to buy.

lead scoring

Ranking leads by likelihood to buy, so sales effort goes where it pays.

leadership

Setting direction and enabling others to pursue it, with or without formal authority.

leadership assessment

Structured measurement of leadership capability against a defined model.

leadership development

The deliberate building of leadership capability, mostly through experience rather than instruction.

leadership pitfalls

The recurring failures — favoritism, avoidance, micromanagement — that undermine otherwise capable leaders.

leadership self-assessment

Structured reflection on one's own style and its effect on others.

leadership styles

The recognized modes of leading, each suited to different conditions.

leadership theory

The body of models attempting to explain what makes leadership effective.

leadership theory and styles

The main models of leadership and the situations each suits.

leadership versus management competencies

The distinction between setting direction and delivering through existing arrangements.

leading others

The competencies of motivating, developing and directing individuals and teams.

leading self

The competencies of self-awareness, integrity and personal effectiveness that precede leading anyone else.

leading stakeholders

Extending leadership beyond the organization to parties one has no authority over.

leading the organization

The competencies of strategy, structure and culture exercised above the team level.

leak detection

The continuous monitoring and analysis that identifies whether and where a pipeline is losing containment.

leak-off in hydraulic fracturing

Leak-off in the hydraulic fracturing process is termed as the influx of fracturing fluid into the adjacent fracture path layers.

leakage current

The amount of current flow across the collector-base junction of a properly biased transistor. Each transistor has a specified amount of leakage current, as determined by the transistor manufacturer.

leakoff

Fluid that escapes from the stuffing box of a centrifugal pump.

leakoff test

A test pressuring up below a new casing shoe until the formation begins to take fluid, establishing its fracture pressure.

leaky mode

Borehole acoustic energy that is only partly trapped, leaking into the formation as it propagates along the hole.

lean

A method of removing everything from a process that does not add value for the customer.

lean amine

An amine solution that does not contain acid gases (hydrogen sulfide or CO2).

lean environment

A workplace organized so that flow is visible and interruption is obvious.

lean gas

Natural gas containing little or no recoverable liquid hydrocarbon — dry gas.

lean gas / dry gas

A gas which is made up of primarily light hydrocarbon vapors.

lean gas condensate

A gas condensate whose liquid dropout below the dewpoint is small, typically well under 100 bbl per million cubic feet.

lean glycol

Regenerated glycol from which absorbed water has been boiled off, ready to return to the top of the contactor.

lean manufacturing

The application of Lean to production, originating in the Toyota system.

lean oil

A special oil used in gas processing prior to containing NGLs.

lean oil absorption

A method of removing NGLs from a gas stream whereby lean oil is flowed in a column countercurrent to a gas stream, absorbing the NGLs. The NGLs are then distilled out of the lean oil, which is recycled.

Lean Six Sigma

The combination: Lean removes waste, Six Sigma removes variation.

Lean Six Sigma Green Belt certification

The combined Lean and Six Sigma credential at practitioner level.

lean supply chain

A chain designed to carry minimum inventory and waste, at some cost in resilience.

lean/rich heat exchanger

Exchanger warming rich solvent with hot lean solvent, recovering heat that would otherwise be added and removed twice.

learning and development (L&D)

The function responsible for building capability across the organization.

learning management system (LMS)

A software application for the administration, documentation, tracking, reporting, automation, and delivery of learning and development programs.

learning objective

A statement of what the learner will be able to do, written so it can be assessed.

learning plan

See, Competency Development Plan.

learning platform

The system delivering and tracking training, and linking it to competency records.

learning resource

Any form of training used to close a skill gap. Depending on the Job Level Required, learning resources may include self-study, e-Learning, instructor-led training, on-the-job training, attendance at an industry conference or seminar, etc.

learning simulator

Interactive software letting a learner practice a technical task without operational consequence.

Learning Tools Interoperability (LTI)

The standard letting external tools plug into a learning platform securely.

lease

A legal document executed between a mineral owner and a company or individual that conveys the right to explore for and develop hydrocarbons and/or other products for a specified period of time over a given area.

lease allowable

The volume of oil which can be produced from a lease during a given time period.

leasehold

The interest held under a mineral lease.

least-time path

The route between two points that a wave actually takes, being the one of stationary traveltime under Fermat's principle.

LED

An LED is a light-emitting diode.

LEED Green Associate v4

The entry credential for green building practice under the LEED system.

LEED rating system

The framework certifying buildings against defined sustainability criteria.

leeward side

The side that faces away from the wind.

leg

The part of a length of conduit that does not change direction when a stub bend is made.

legal and regulatory compliance (global)

Meeting the requirements of every jurisdiction in which the business operates.

legal compliance

Meeting the statutory obligations that apply to employment and the workplace.

legal counsel

Professional legal advice, and when it is cheaper to take it than to proceed without.

legal elements of a contract

Offer, acceptance, consideration, capacity and lawful purpose.

legal process

How disputes move through courts and tribunals, and what each stage decides.

legal structure of business organization

The choice of form, which fixes liability, tax treatment and how capital can be raised.

legally mandated vs. discretionary benefits

Benefits the law requires against those the employer chooses to offer.

legend

An information guide or chart that identifies and explains the symbols, abbreviations, designations, and special marks used on a drawing, diagram, or set of diagrams.

length

A single piece of conduit.

leonardite

An oxidized lignite used as a mud additive for thinning and filtration control.

lesion

An injury, hurt or wound.

lessee

The party holding rights under a lease, as against the lessor who granted them.

lessor royalty

The share of production reserved to the mineral owner in the lease, free of development and operating cost.

levee

The raised bank flanking a channel, built of sediment spilled at flood.

level

A surface or an object that is determined to be perfectly horizontal. Also, a tool used to determine if an object is level.

level control diagram

A drawing that shows the level points at which various controls are activated.

level control valve

A valve that controls the level in a system component by regulating the flow of a fluid.

level controller

The instrument holding liquid level.

level indication

The displayed liquid level, which lags the real level wherever the tapping can plug.

level indicator

The device showing liquid level locally.

level measurement

Determining how much liquid a vessel holds.

level measurement device

The instrument sensing liquid level.

level measuring

Determining liquid level, complicated wherever the fluid foams or carries two phases.

level setpoint

The liquid level a controller holds, set to leave both surge room and separation space.

level transmitter

The instrument converting a level measurement into a transmitted signal.

levelized cost

Lifetime cost divided by lifetime output, the figure that lets plants with different capital profiles be compared.

levelized cost of electricity (LCOE)

The lifetime cost per unit of electricity, used to compare generating technologies on one basis.

levelwind

The guide assembly that lays coiled tubing evenly onto the reel drum as it is spooled in.

lever action

A bar or rod pivoting on a support. The effect of any force applied to the bar or rod is directly related to the distance between the force and its distance from the pivot.

LGS

Low gravity solids — the drilled solids and clays in a mud, at about 2.6 specific gravity.

liability cap

A contractual ceiling on how much one party can be made to pay.

libertarian view

The position that liberty and voluntary exchange take precedence over distributive aims.

LIBOR (London Interbank Offered Rate)

The interbank rate that long served as the floating benchmark in loan pricing, now retired.

licence area

The area over which a petroleum license grants rights.

licensing round

A formal offering in which a government opens defined blocks for bid by exploration and production companies.

life cycle analysis (LCA)

LCA is an analytical methodology used to comprehensively quantify and interpret the environmental flows to and from the environment (including air emissions, water effluents, solid waste and the consumption/ depletion of energy and other resources) over the life cycle of a product or process. LCAs should be performed in adherence to the International Organization for Standardization (ISO) 14040 series of standards.

life of the well

The period over which a well can be expected to produce at economically sustainable rates.

lifeline

A flexible line that may be connected to an anchorage at one end to hang vertically or at both ends to hang horizontally used to allow a worker mobility while providing fall arrest protection.

lift

The distance that a valve disc moves from the fully closed position to the fully open position. Also called travel.

lift check valve

A type of check valve in which the disc is lifted to allow fluid flow through the valve.

lifter

Mechanism raising a component, in a pumping unit the assembly that carries the load on the upstroke.

lifting

Taking delivery of a cargo entitlement at the loading terminal.

lifting agreement

The contract scheduling how and when each partner takes its share of production.

lifting beam

A rigging component that is used to help balance a load by increasing the number of lifting points, or "pick' points, from one to two or more.

lifting capacity

The amount of weight that a forklift can lift and carry safely.

lifting device

Equipment used to raise a load.

lifting frame

A structural frame used to lift and position a coiled tubing or intervention package on a floating rig.

lifting lug

A type of lifting connector that is commonly attached to a piece of equipment to ensure that the equipment will be safely supported and balanced when its lifted.

lifting sub

A short sub made up temporarily to the top of a tool or string so it can be picked up safely.

light beam

A directed beam of light, used to sense position or presence.

light bulb

An incandescent lamp, whose filament resistance rises sharply once hot.

light condensate

Very light liquid hydrocarbon recovered from gas, close to naphtha in quality.

light crude

Low-density crude, yielding a higher proportion of valuable light products.

light crude oil

Crude oil of high API gravity, conventionally above about 40 degrees.

light cycle oil

A sidestream product of the fractionation process commonly used as a blending stock for No. 2 domestic heating oil and diesel fuels.

light distillate

The lightest refined fractions, chiefly naphtha and gasoline.

light emitting diode (LED)

A type of diode that gives off light when current flows through it.

light ends recovery unit

See Gas plant.

light gasoil

The lighter portion of the gasoil cut, blended into diesel.

light hydrocarbon

The more volatile hydrocarbons, which leave a separation first and set vapor pressure.

light hydrocarbons

The components of a hydrocarbon mixture with five or less carbon atoms.

light hydrocarbons / light ends

The components of a hydrocarbon stream that have the lowest boiling points and viscosities.

light output

The light output of a detector is the amount of photons produced by the detector per kiloelectron volt (keV) of energy deposited. Its unit is photons/keV. The light output of a detector is one of the most important parameters, as it affects the detector's efficiency and energy resolution.

light pipe

The snubbing condition in which well pressure and buoyancy together exceed the string's weight, so it must be forced into the well.

light sensitive diode

A type of diode doped with materials that are light sensitive, giving the diode the characteristic of being able to use light to produce a voltage.

light sour

Low-density crude with appreciable sulfur.

light sour crude

Low-density crude with appreciable sulfur content.

light sweet crude

Low-density, low-sulfur crude, the easiest and most valuable to refine.

light-off

The process of starting combustion in a boiler.

lighter component

The more volatile constituents of a mixture.

lighter end

The most volatile fraction of a mixture.

lighter hydrocarbon

A hydrocarbon of lower molecular weight, and generally higher value.

lighter hydrocarbon component

The more volatile fractions in a stream, which leave first in any separation.

lighter product

A product from the upper part of the boiling range, generally more valuable.

lignin

The rigid polymer that gives land plants their structural support, and the parent material of much terrestrial kerogen.

lignite

A low-rank brown coal, and the source of the humic acids used as mud thinners and filtration control agents.

lignosulfonate

A sulfonated lignin derivative used as a deflocculant in drilling mud and as a retarder in cement.

likeness

Likeness is a measure of the similarity of the dipmeter raw data curves.

lime mud

Fine-grained carbonate sediment of clay- and silt-sized calcium carbonate, deposited where currents are too weak to winnow it away.

limestone

A sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate.

limestone compatible scale

Density and neutron display scales chosen so the two curves overlie exactly in a water-filled limestone.

limestone matrix for neutron porosity

Limestone matrix for a neutron porosity log means that the neutron porosity tool is calibrated to read the correct porosity assuming that the pores are filled with fresh water and for a matrix of limestone.

limestone porosity unit

Neutron porosity reported on a limestone matrix calibration, correct in limestone and requiring correction in other lithologies.

limit switch

A pilot device that operates when a mechanical mechanism reaches its limit of travel, activated by physical contact with a part or material. Often used to stop a motor operator when a valve reaches its fully open or fully closed position.

limited entry

A completion in which only part of the productive interval is open to flow, whether by design or through damage.

line current

The current that flows through the wires in a three-phase system.

line current or voltage

The value of current or voltage in the generator leads that are attached to an electrical load.

line drive

A flood pattern in which injectors are arranged in a line parallel to a line of producers.

line manager

The manager in the direct chain of command over an employee.

line of action

An imaginary line starting at an object's center of gravity that represents the force from the object as a result of gravity.

line source solution

The analytical solution for pressure around a well treated as a line of zero radius in an infinite porous medium.

line spacing

The distance between adjacent survey lines, which limits what can be mapped between them.

line ties

A line tie is where two seismic lines intersect.

line trap

A filter that prevents incoming transfer trip signals from passing through a substation; also called a wave trap.

line valve

A valve in the run of a line rather than at equipment.

line voltage

The voltage that is applied to the wires in a three-phase system.

lineament

A long linear or gently curving surface feature that suggests an underlying structure or contact.

linear alphaolefin

A synthetic hydrocarbon made by oligomerizing ethylene, with a straight chain and the double bond at one end, abbreviated LAO.

linear flow

A flow regime in which the streamlines are parallel, as into a fracture or along a narrow channel.

linear programming

Optimizing an objective subject to linear constraints.

linear scale

A scale with divisions that have the same value from one end of the scale to the other.

linear system

A system whose output scales with its input, the assumption behind convolution and deconvolution.

lineations

Lineation refers to a repeated, parallel alignment of linear elements in a rock. These can be found in igneous, sedimentary, and metamorphic rocks.

liner

A casing string that does not reach surface, hung instead from inside the bottom of the previous string.

liner completion

A completion using a liner hung off the previous string rather than run to surface.

liner hanger

The device that suspends a liner from the inside wall of the casing above it, gripping with slips and often sealing as well.

liner patch

A thin expandable sleeve set across a hole, split or corroded section of liner to restore its integrity.

link layer

The network protocol level that governs how data bit frames are enclosed in message packets, how the transmitting and receiving clocks are synchronized, and how errors are detected.

link light

The light on a network device that remains illuminated continuously whenever the device is connected to the network and the network is functioning properly.

lip seal

A seal whose U-shaped section is energized by pressure acting inside the U, pressing its lips harder against the surfaces.

lipophilic

Having an affinity for oil; oil-loving.

liquefaction

The refrigeration process turning treated gas into LNG.

liquefaction facility

The plant chilling gas to LNG for export.

liquefaction plant

The facility chilling natural gas to LNG.

liquefaction technology

The particular refrigeration process a plant licenses, which fixes its efficiency and cost.

liquefaction train

One complete processing line at an LNG plant; capacity is added by building further trains.

liquefied natural gas (LNG)

Natural gas that has been converted to a liquid by refrigerating it to -260°F. Liquefying natural gas reduces the fuel's volume by 600 times, enabling it to be shipped economically from distant producing areas to markets.

liquefied natural gas carrier

A ship built to carry liquefied natural gas at about minus 162 degrees Celsius in insulated cryogenic tanks.

liquefied petroleum gas (LPG)

A product from a gas plant that typically consists of propane and butane.

liquid

A fluid which conforms to the shape of its container, but cannot be compressed.

liquid additive

A cement additive supplied and metered as a liquid rather than blended dry.

liquid asphalts

Straight-run asphalts that have been mixed with lighter distillates, oily distillates, or chemically treated water.

liquid blocking

An immobile oil bank near the producer in a dry combustion flood, which the advancing heated oil cannot displace.

liquid carryover

Liquid escaping with the gas from a separator, a sign the vessel is overloaded or flooded.

liquid condensate

Condensed hydrocarbon liquid recovered from gas.

liquid desiccant

A hygroscopic liquid, usually a glycol, circulated to absorb water vapor from a gas stream.

liquid drain

The low-point connection liquid is removed through, manual or automatic.

liquid droplet

A discrete drop entrained in gas, which separators and coalescers exist to remove.

liquid extraction

The removal of a substance that is dissolved in a liquid by transferring it to another liquid.

liquid hydrocarbon

Hydrocarbons in the liquid phase at the conditions considered.

liquid hydrocarbons

Hydrocarbons that are liquid at surface conditions — propane and heavier components separated from a gas stream.

liquid hydrogen

Hydrogen chilled below minus 253 Celsius, dense enough to ship but costly in energy to keep cold.

liquid level

The height of a liquid surface in a vessel or a well, measured or inferred from a sensor.

liquid level controller

Instrument holding liquid level by throttling or opening a dump valve.

liquid outlet

The connection liquid leaves by.

liquid particle

A droplet carried in a gas stream.

liquid pressure

Force exerted against an object, such as a tank, caused by the weight of a liquid.

liquid propane

Propane held under pressure as liquid, the form in which it is stored and shipped.

liquid refrigerant

Refrigerant in liquid phase, on its way to the expansion device.

liquid ring pump

A type of rotary vacuum pump that is often used in condenser air removal systems.

liquid sampling

Taking a representative liquid sample for analysis or custody.

liquid saturation method

Measuring a core's pore volume from the weight difference between the dry sample and the same sample fully saturated.

liquid seal

Level of glycol which forces gas to pass through the bubble caps.

liquid separation

Removing liquid from a gas stream, by gravity, impingement or coalescence.

liquid separator

Vessel removing liquid from a stream.

liquid slug

A plug of liquid arriving in a gas line, capable of wrecking a compressor on impact.

liquid-junction potential

The voltage generated where solutions of different salinity meet and ions diffuse across the boundary at different rates.

liquid-level control

A device which senses the liquid level in a separator and opens or closes the liquid-level control valve.

liquid-level control valve

The valve which opens or closes to maintain design liquid levels.

liquid-liquid sweetening system

A type of mercaptan conversion system in which the catalyst is dispersed in a caustic solution.

listric

A fault that flattens with depth, producing rollover structures that trap hydrocarbons.

listric fault

A normal fault whose dip flattens with depth, curving toward horizontal into a detachment.

lithic

Composed of rock fragments, which reduces reservoir quality relative to clean quartz sand.

lithics, lithic fragments

Pieces of other rocks that have been eroded down to sand size and now are sand grains in a sedimentary rock.

lithification

Lithification is the geological process by which unconsolidated sediments (like sand, mud, and silt) compact under pressure, expel connate fluids, and gradually become solid rock.

lithified, lithification

The process in which sediments compact under pressure, expel connate fluids, and gradually become solid rock. Essentially a process of porosity destruction through compaction and cementation, lithification includes all the processes that convert unconsolidated sediments into sedimentary rocks.

lithium-ion battery

A rechargeable cell storing charge by moving lithium between electrodes, hydrogen's main rival for mobile storage.

lithodensity log

A lithodensity log is a variation of the density log which uses the photoelectric effect to indicate the formation's lithology.

lithofacies

A lithofacies is a mappable subdivision of a designated stratigraphic unit, distinguished from adjacent subdivisions on the basis of lithology.

lithologic

Pertaining to lithology — a rock's mineral content, grain size, texture and color.

lithologic contact

The surface separating two rock units of different lithology.

lithological log

A lithological log is an annotated, graphical description of the formation rock characteristics encountered while drilling a well. The log is produced while the well is being drilled.

lithology

The study of the general physical characteristics of rocks, including color, texture, grain size, mineral content, and composition. Can refer to the characteristics of rocks in a particular area.

lithology, lithological

The macroscopic nature of the mineral content, grain size, texture, and color of rocks.

lithology-related

Depending on rock type rather than on fluid content.

lithosphere

The rigid outer shell of the Earth, comprising the crust and the uppermost mantle, which behaves as the plates of plate tectonics.

lithospheric

Relating to the rigid outer shell whose deformation creates sedimentary basins.

lithospheric compensation

The isostatic adjustment of the crust to loading or unloading.

lithostatic

Relating to the pressure exerted by the weight of overlying rock.

lithostatic pressure

The pressure exerted at depth by the weight of the overlying rock column.

lithostratigraphic

Pertaining to the correlation and division of strata on the basis of their rock type.

lithostratigraphic inversion

Seismic inversion that solves for the lithology and fluid content of individual layers rather than for an impedance volume alone.

lithostratigraphy

The study and correlation of strata according to their lithology.

littoral

Littoral refers to the placement of items related to, or situated near, the shore of a sea or lake.

live cement

A slurry still fluid but still chemically capable of setting.

live oil

Oil that still holds dissolved gas, which will come out of solution as pressure falls toward surface conditions.

LNG

Liquefied natural gas: natural gas, mostly methane, cooled until it becomes liquid and occupies a small fraction of its gas volume, for shipment by sea.

LNG bunkering

Supplying LNG as fuel to ships.

lng export

The shipment of liquefied natural gas from a producing country.

lng facility

A plant that liquefies, stores or regasifies natural gas.

lng import

Receipt of liquefied natural gas at a consuming country's terminal.

lng market

The trade in liquefied natural gas, now substantially spot as well as contracted.

lng plant

The facility liquefying natural gas for shipment.

lng price

The price of liquefied natural gas, historically oil-indexed and now increasingly hub-linked.

lng pricing

How LNG is priced, whether indexed to oil, to a gas hub, or hybrid.

lng project

An integrated development combining gas supply, liquefaction, shipping and market.

lng receiving terminal

The facility where LNG is unloaded, stored and regasified into the pipeline network.

lng ship

The insulated vessel carrying liquefied natural gas at cryogenic temperature.

lng storage

The insulated tankage holding LNG at the liquefaction or receiving terminal.

lng storage tank

The insulated tank holding LNG at atmospheric pressure.

lng tank

The insulated vessel storing LNG at atmospheric pressure and cryogenic temperature.

LNG tanker

The insulated ship carrying LNG, built to contain a cryogenic cargo for weeks.

lng train

One complete liquefaction processing line at an LNG plant.

lng value chain

The linked stages from gas field through liquefaction and shipping to regasification and market.

LNGC

Liquefied natural gas carrier — a ship built to carry LNG in insulated tanks at about −162°C.

load

A piece of equipment or circuit that uses electricity and creates a demand for electric power. Also, the demand on a system typically provided by the components that carry out the system's specific task.

load balancing

Matching gas supply to demand across a day or season using storage and line pack.

load balancing option

A contractual right to vary offtake to match demand.

load balancing resource

Storage or flexible supply used to match gas deliveries to fluctuating demand.

load balancing service

The service of absorbing swings between contracted gas supply and actual demand.

load cell

The sensor in a weight indicator that converts tension or compression in the running string into a readable signal.

load center

The point on which a load can be balanced and not tip; specifically, the horizontal distance from the vertical face of the forks on a forklift to the center of gravity of a load when placed directly against the forks.

load dispatcher

The individual who monitors the condition of a power system and coordinates the outputs of the plants in the system so that supply equals demand.

load duration curve

A plot of demand sorted from highest to lowest, used to size baseload and peaking capacity.

load leveler

A device used to make fairly large adjustments in the lengths of the sling legs in a hitch pattern.

load resistor

A resistor in a transistor circuit used to develop an output signal.

loader/terminal

A hardware device, generally a PC, used to communicate with and program a PLC.

loading arm

The articulated pipework connecting a loading rack to a truck or ship manifold.

loading hose

The flexible connection between terminal and ship, and a recognized spill risk point.

loading port

The terminal where a cargo is loaded onto the vessel.

loading rack

The facility where product is loaded into trucks or railcars.

Loan Life Cover Ratio (LLCR)

Discounted cash flow over the loan's life divided by debt outstanding, a lender's headroom test.

lobe pump

A rotary positive displacement pump that uses lobed rotors to move fluid.

local area network (LAN)

A geographically limited network that is sometimes used to replace the individual wires used in traditional, non-networked control systems.

local content

The proportion of personnel, materials and services that must be sourced locally under the terms of a license or contract.

local display module

A field communicator mounted on a field device that displays instrument data and can be used for calibration, configuration, and testing of the field device.

local holdup

The holdup of a phase measured by a single small probe at one point in the pipe cross section.

local magnetic interference

Distortion of the measured magnetic field by nearby steel — casing, the rig, or an adjacent well.

local probe

A small production logging sensor that identifies the fluid immediately around its tip.

local rack

The logical rack in a PLC system chassis that has the PLC processor in it.

local rack or chassis

The first rack of I/O modules in a PLC system. It usually contains the processor module, and it may contain one or more logical racks.

location specific competencies

Competencies that are related to country- or-site specific requirements.

location-based services

Services and offers triggered by where the user physically is.

LOCDIP

LOCDIP computations use pad-to-pad correlations made over short intervals centered on the bed boundaries, as defined by the major inflection points on the micro-resistivity curves.

lock

A slickline-set device that anchors in a tubing nipple to hold a flow control such as a plug or a valve.

lock mandrel

The device that locks into a landing nipple's profile and seals in its bore, carrying whatever flow control is being set.

locked-in margin

Profit secured by matching a purchase and a sale so remaining price movement cannot erode it.

locking mandrel

The device that latches a tool into a landing nipple in the tubing.

locking screw

A screw preventing a setting from moving.

locknut

A type of fitting used to secure threaded conduit or threaded connectors to a surface such as the wall of an electrical control box.

lockout

A procedure that uses locks or similar devices to actively prevent the passage of hazardous energy from a source to equipment that is being worked on.

lockout contacts

Contacts in a reclosing relay that turn the motor off with the relay in the "lockout" position.

lockout contracts

Contacts in a reclosing relay that turn the motor off with the relay in the "lockout" position.

lockout position

The position an isolating device is locked in.

lockout procedure

The method locking an isolation so it cannot be reversed while work continues.

lockout tag

The tag applied with an isolation, naming who applied it and why it must not be removed.

lockout/tagout

Placing a lock, or a device like a lock, and a tag on an energy isolating device in accordance with established procedures that ensure the energy isolating device and the equipment being controlled cannot be operated until the lock is removed.

lockout/tagout procedure

The formal method isolating and locking energy sources before work, and proving they are dead.

log

A general term for a measurement versus depth or time, or both, of one or more physical quantities in and around a well. Operations in oil and gas exploration and production use a variety of log types.

log analyst

The specialist who interprets wireline logs into porosity, saturation and lithology.

log curve, curve

A series of individual log measurements plotted versus depth or time, or both.

log measurement

A quantity recorded by a logging tool.

log on/log off

The process of typing in your identification, and often a password, in order to access a computer or its programs; to log off, a set sequence of keystrokes or actions is often required.

log-inject-log process

In the log-inject-log process, a pulsed neutron capture log is run over a zone of interest to establish a baseline reading. Subsequently, a brine of contrasting salinity is injected into the formation while logging successive passes with the pulsed neutron capture logging tool.

log-log plot

A plot with both axes logarithmic, on which power-law flow regimes appear as straight lines.

logarithm

The scale on which pressure transient and decline data become straight lines.

logarithmic mean

An average formed from the logarithms of two values, appropriate where the quantity varies exponentially between them.

logging

The recording of formation or wellbore measurements against depth.

logging device

Any instrument recording formation properties against depth.

logging head, head

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

logging operation

The wireline job itself, with its rig time and its risk of sticking tools.

logging program

The set of measurements planned for a well, decided before the rig is on depth.

logging run

One trip of a logging tool into and out of the hole, during which measurements are recorded.

logging run, logging survey run

Part of a service provided by a wireline logging company for a well operator client. To minimize rig time, several different logging tools are usually combined on the same tool string for each run into the borehole.

logging service

The contracted provision of wireline measurements at the wellsite.

logging service company

The contractor providing wireline measurement.

logging suite, suite

A number of wireline logging runs acquired in succession within the same activity stage, such as at a casing point.

logging survey

A logging survey is a service provided by a logging service company for a well operator client. During the course of the survey, the logger usually uses several different logging tools.

logging tool

A logging tool is the downhole hardware needed to make a log.

logging unit

The cabin and surface equipment housing the winch controls, telemetry and recording systems for a wireline job.

logging while drilling (LWD)

The measurement of formation properties during the drilling of the hole through the use of tools integrated into the bottom hole assembly.

logging, well logging

The measurement of formation properties.

logic

In digital logic circuitry, the expected outcome from a network of logic elements designed to perform a specific function. (See Logic function).

logic circuit

An electronic circuit used in computers to perform a logical operation on its two or more input signals. The six basic circuits are AND, NOT, NAND, OR, NOR, and exclusive OR, which can be combined into more complex circuits.

logic diagram

A diagram that illustrates the implementation of logic functions with logic symbols showing details of signal flow but not point-to-point wiring.

logic function

A definition of the relationships that hold together a set of input and output logic variables.

logic gate

A circuit made up of solid-state components that evaluates information and produces a logical output when certain input conditions are met.

logic state

One of two possible abstract states (logic 1 or logic 0) that may be taken on by a logic (binary) variable.

logic symbol

The pictorial representation of a logic gate.

logical AND

The Boolean equivalent of two switches in series.

logical NOT

The Boolean equivalent of a normally closed switch.

logical operation

The implementation of a logic gate's function to determine the logical output resulting from a specific set of inputs.

logical operator

The sign between elements of a logical expression that indicates what logical operation is being executed. For example, the AND operator is • and the OR operator is +.

logical OR

The Boolean equivalent of two switches in parallel.

logical rack

The addressing block a programmable controller groups its input and output points into.

logistics

The movement and storage of goods through the chain.

logistics channel

The route and means by which goods physically move.

lognormal

Distributed so that the logarithm is normal, the usual shape of permeability and field-size data.

lognormal distribution

A distribution whose logarithm is normal, the usual form of permeability and field size.

long array

A logging or receiver array with wide spacing, reading further from the borehole or resolving deeper.

long offset

A large source-receiver separation, which samples deeper and carries amplitude information.

long path multiple

A multiple whose extra travel is long enough that it arrives as a separate, identifiable event on the record.

long position

Holding more of a commodity than has been sold, so gaining when prices rise.

long spacing sonic log

A sonic log recorded with an unusually long transmitter-receiver spacing, typically 10 to 15 ft, so the signal path reaches beyond the altered zone.

longitudinal dune

A longitudinal dune is an elongated dune, typically tens of meters high and ranging up to several hundred kilometers long, lying parallel to the prevailing wind direction.

longitudinal plot

A dipmeter display of the component of dip resolved along a chosen direction, usually the structural strike or dip line.

longitudinal relaxation

In NMR, the recovery of nuclear magnetization along the static field direction after excitation — the T1 process.

longitudinal relaxation time

Longitudinal Relaxation Time (T1) in NMR logging is an indication of how fast the tipped protons in the fluids relax longitudinally, relative to the axis of the static magnetic field.

longshore

Along the shoreline, the direction currents move beach sand.

loop

A complete electrical circuit or current path.

loop controller

The controller closing one control loop, as distinct from a shared multi-loop processor.

loop gain

The combination of controller gain and process gain; the relationship between a change in a measured variable and the effect that the resulting control action has on that variable.

loops

A seismic loop is a continuous reflection pattern on a seismic profile.

loose emulsion

An emulsion which is easy to break.

loss of primary containment (LOPC)

Any unplanned release of hydrocarbon or hazardous material from the equipment holding it.

lost circulation

The total or partial loss of drilling fluids to high-permeability zones, cavernous formations, and natural or induced fractures during drilling or completion. It is the reduced or complete absence of fluid flow up the annulus when fluid is being pumped through the drill string, caused when drilling fluid exceeds the fracture pressure or invades the pore space of the formation.