Oil and gas terminology · MLC-0103

Oil and gas terms: L (140)

• LacustrineRelating to or formed in a lake, describing a depositional environment and the resulting sediments...
• LagA delay or time difference between two related events or signals in seismic data. It can refer to the time...
• Lag gasHydrocarbon gas that reaches the surface after the drilling fluid that carried it from the bit. This delay...
• Lamé constantOne of two elastic moduli, denoted by lambda (λ) and mu (μ), that describe the elastic properties of an...
• Laminar flowA fluid flow regime characterized by smooth, parallel layers of fluid moving without lateral mixing. In this...
• Laminated sandA sedimentary rock formation characterized by alternating thin layers of sand and shale or other fine-grained...
• LaminationA small-scale sequence of thin layers, or laminae, occurring in sedimentary rocks, where each layer is less...
• Landing collarA short section of casing with an internal shoulder, installed near the bottom of a casing string. This...
• Landing nippleA short, heavy-walled tubular component with an internal profile machined to accept and seal with specific...
• LAOAn abbreviation for linear alpha olefin, a type of synthetic base oil used in non-aqueous drilling fluids...
• Laplace equationA second-order partial differential equation that describes potential fields, such as gravitational...
• Large language model (LLM)A type of artificial intelligence model trained on vast amounts of text data to understand, generate, and...
• Laser diffractionA laboratory technique used to determine the particle size distribution of sediments or drilling fluid solids...
• Last readingThe final measurement recorded by a logging tool at the deepest point reached in the wellbore, or at the end...
• Last-shot detectionA system or method used to confirm that the final perforating charge in a gun string has successfully...
• LateralA type of resistivity logging tool that measures the resistivity of the formation by inducing current into...
• Late-time transient dataPressure and flow rate data collected during the later stages of a well test, after the wellbore storage...
• LatexA synthetic polymer emulsion used as an additive in drilling fluids to control fluid loss and improve filter...
• LayerA distinct stratigraphic unit within a reservoir that exhibits relatively uniform petrophysical properties...
• Layer cake geometryA simplified geological model of a reservoir where rock layers are assumed to be horizontally continuous...
• Layer strippingA seismic data processing technique that sequentially removes the effects of shallow, near-surface layers to...
• Layered reservoir testingWell testing techniques applied to reservoirs composed of multiple distinct layers with varying properties...
• Lb/bblA unit of concentration used in drilling fluid formulations, representing pounds of additive per barrel of...
• Lbm/bblAn abbreviation for pounds mass per barrel, a unit of concentration used to specify the amount of a solid...
• LC50The lethal concentration 50, a measure of the toxicity of a substance, representing the concentration that...
• LCMLost Circulation Material, a drilling fluid additive used to seal off permeable formations or fractures that...
• Lead acetate testA qualitative test used to detect the presence of hydrogen sulfide (H2S) in natural gas or other hydrocarbon...
• Lead cementThe lower-density cement slurry pumped into the annulus first during a cementing operation, preceding the...
• Leak detectionThe process of identifying and locating unintended releases of hydrocarbons or other fluids from pipelines...
• Leak offTo intentionally increase the pressure in a wellbore to determine the fracture pressure of the open-hole...
• LeakoffThe penetration of drilling fluid into a permeable formation or a fracture within the wellbore, leading to a...
• Leakoff testA pressure test conducted after cementing a casing string to determine the fracture pressure of the formation...
• Leaky modeA phenomenon in acoustic logging where acoustic energy propagates along the borehole wall but continuously...
• Lean gasNatural gas that contains a low concentration of heavier hydrocarbon components, such as propane, butane, and...
• Lean gas condensateA natural gas stream that contains a small amount of liquid hydrocarbons, or condensate, which drops out of...
• Lean glycolGlycol that has been regenerated to remove absorbed water, making it suitable for reuse in dehydration...
• Lean oilA hydrocarbon liquid, typically a light oil, used in absorption processes to remove heavier hydrocarbon...
• LeaseA legal agreement granting the right to explore for and produce oil and gas from a specific tract of land for...
• Least-time pathThe trajectory taken by a seismic wave traveling between two points in a medium, following Fermat's...
• LeonarditeA naturally oxidized lignite coal, used as a drilling fluid additive to control rheology and fluid loss. It...
• Lessor royaltyA share of the gross production of oil and gas, or the proceeds from its sale, reserved by the landowner...
• LevelwindA mechanical device on a winch or hoist that guides the wireline or cable evenly onto the drum, preventing...
• LGSAn abbreviation for low gravity solids, which are fine, suspended particles in drilling fluid that have a...
• Licensing roundA formal process conducted by a government or national oil company to invite bids from oil and gas companies...
• Life of the wellThe entire operational period of a well, from its initial drilling and completion through its production...
• Lifting frameA structural assembly used to hoist and position heavy equipment or components, such as blowout preventers...
• Lifting subA short, threaded adapter used to connect a downhole tool or tubular to the hoisting equipment on the rig...
• Light crude oilCrude oil with a low density and low viscosity, making it easier to produce and refine into high-value...
• Light hydrocarbonsA class of organic compounds consisting of hydrogen and carbon atoms with a low molecular weight, existing as...
• Light pipeTubular goods with a thinner wall or smaller diameter than standard pipe used in a particular wellbore...
• LigninA complex polymer found in the cell walls of plants, used as a deflocculant and fluid-loss control agent in...
• LigniteA low-rank coal, finely ground and added to drilling fluids as a deflocculant and fluid-loss control agent...
• LignosulfonateA chemical compound derived from lignin, widely used as a deflocculant and dispersant in water-based drilling...
• Lime mudA water-based drilling fluid containing calcium hydroxide (lime) as a primary additive, used to inhibit...
• LimestoneA sedimentary rock composed primarily of calcium carbonate, mainly in the form of the mineral calcite. It...
• Limestone compatible scaleA type of scale inhibitor designed to prevent the precipitation of mineral scales, such as calcium carbonate...
• Limestone porosity unitA standard unit of measurement for porosity, where the porosity value is calibrated to a limestone matrix...
• Limited entryA condition in a wellbore where the producing interval is restricted, either by a partial completion or by...
• Line driveAn injection pattern used in waterflooding or other fluid injection projects where injection wells are...
• Line source solutionA mathematical model used in well test analysis that describes the pressure transient behavior in an...
• LineamentA large-scale linear feature on the Earth's surface, such as a fault line, fracture zone, or straight stream...
• Linear alphaolefinA synthetic hydrocarbon compound used as a base fluid in non-aqueous drilling fluids, particularly in...
• Linear flowA flow regime where reservoir fluids move in parallel paths toward a planar source, such as a hydraulic...
• LinerA string of casing that does not extend back to the surface, but instead is suspended from the bottom of a...
• Liner hangerA mechanical device that suspends a liner from the bottom of the previous casing string in a wellbore. It...
• Liner patchA remedial technique used to repair a damaged section of casing or liner by installing a shorter...
• Lip sealA type of dynamic seal characterized by a flexible sealing element that presses against a mating surface to...
• LipophilicRelating to a substance's tendency to dissolve in or combine with fats, oils, and other nonpolar solvents...
• Liquefied natural gasNatural gas that has been cooled to approximately -162 degrees Celsius (-260 degrees Fahrenheit) at...
• Liquefied natural gas carrierA purpose-built marine vessel designed for transporting liquefied natural gas (LNG) in bulk. The natural gas...
• Liquefied petroleum gasA mixture of hydrocarbon gases, primarily propane and butane, that is stored and transported in liquid form...
• Liquid additiveA chemical substance in liquid form that is mixed into drilling fluid to modify its properties or address...
• Liquid blockingA phenomenon in heavy oil reservoirs where accumulated liquids, such as water or condensed steam, impede the...
• Liquid desiccantA hygroscopic liquid, such as glycol, used to absorb water vapor from natural gas or other gas streams. This...
• Liquid hydrocarbonsHydrocarbon compounds that exist in a liquid state at ambient temperature and pressure, ranging from light...
• Liquid levelThe depth from the surface to the interface between gas and liquid in the annulus or tubing of a wellbore...
• Liquid saturation methodA laboratory technique used to determine the porosity of core samples by saturating them with a liquid of...
• Liquid-junction potentialAn electrical potential difference that develops at the interface between two electrolyte solutions of...
• Listric faultA type of normal fault with a curved fault plane that flattens with depth, becoming nearly horizontal in its...
• LithificationThe set of processes that convert loose sediments into solid sedimentary rock. Compaction from the weight of...
• LithofaciesA body of rock characterized by specific lithological attributes, such as rock type, sedimentary structures...
• LithologicRelating to the physical characteristics of a rock or rock formation, including its composition, texture...
• Lithologic contactA boundary surface separating two distinct rock units that differ in their physical characteristics, such as...
• LithologyThe study and description of the physical characteristics of rocks, including their mineral composition...
• LithosphereThe rigid, outermost shell of a terrestrial planet, composed of the crust and the uppermost part of the...
• Lithostatic pressureThe pressure exerted on a rock at a specific depth due to the weight of all the overlying rock and any fluids...
• LithostratigraphicRelating to the classification and correlation of rock units based on their lithological characteristics...
• Lithostratigraphic inversionA geophysical technique that uses seismic data to infer the lithology and stratigraphic layering of...
• LithostratigraphyThe branch of stratigraphy that deals with the classification, description, and correlation of rock units...
• LittoralRelating to the depositional environment of a lake or sea shore, extending from the high water line to the...
• Live cementA cement slurry that has not yet set and is still in a fluid state, capable of being pumped and placed. It...
• Live oilCrude oil that contains dissolved natural gas, which will separate from the oil as pressure decreases. This...
• LNGLiquefied natural gas, which is natural gas cooled to approximately -162 degrees Celsius (-260 degrees...
• LNGCA liquefied natural gas carrier is a specialized vessel designed for transporting natural gas that has been...
• Load cellA transducer that converts a force into an electrical signal, used to measure weight or tension in drilling...
• Load oilHydrocarbon liquid injected into a well during stimulation treatments, such as fracturing or acidizing, to...
• Local contentA government policy or contractual requirement for oil and gas companies to use a specified proportion of...
• Local holdupThe fraction of the cross-sectional area of a wellbore occupied by a specific fluid phase at a particular...
• Local magnetic interferenceAn anomaly in the Earth's magnetic field caused by nearby man-made objects or small-scale geological...
• Local probeA small, intrusive sensor designed to measure fluid properties at a specific point within the wellbore. These...
• LockA downhole device designed to securely anchor a tool or component within a landing nipple or other profile in...
• Lock mandrelA downhole tool that provides a secure, retrievable seal and anchor point within a wellbore. It is run on...
• Lock-upThe condition where a downhole tool or component becomes jammed or seized within the wellbore, preventing its...
• LogA continuous record of physical properties of subsurface formations, measured by instruments lowered into a...
• Logarithmic meanA type of average used to represent the effective average of a quantity that changes exponentially over a...
• LoggingThe process of recording physical properties of rock formations versus depth, either as a well is being...
• Logging runA single descent and ascent of a logging tool or a suite of tools into a wellbore to acquire a continuous set...
• Logging toolAn instrument designed to be lowered into a wellbore to measure and record physical properties of the...
• Logging unitA specialized vehicle or skid-mounted system that houses the equipment necessary to conduct wireline logging...
• Logging-while-drillingThe technique of embedding formation evaluation sensors into the bottomhole assembly to acquire petrophysical...
• Long path multipleA type of multiple reflection in seismic data where the seismic energy travels a significantly longer path...
• Long spacing sonic logA type of acoustic logging tool characterized by a relatively long distance between its transmitter and...
• Longitudinal relaxationThe process by which the nuclear magnetization of protons, aligned with an external magnetic field, returns...
• Loose emulsionA mixture of oil and water where the two phases are not tightly bound, allowing for relatively easy...
• Lost circulationThe uncontrolled flow of drilling fluid from the wellbore into a subsurface formation, resulting in a...
• Lost returnsThe condition where drilling fluid pumped down the wellbore does not return to the surface through the...
• Lost-circulation materialA substance added to drilling fluid to seal off permeable formations or fractures that are causing fluid loss...
• LOTA leak-off test, a procedure conducted to determine the maximum pressure a formation can withstand before...
• Love waveA type of surface seismic wave that propagates by horizontal shear motion, perpendicular to the direction of...
• Low colloid oil mudAn oil-based drilling fluid formulated with a minimal amount of colloidal solids, primarily designed for...
• Low gravity solidsFine, suspended particles in drilling fluid that have a specific gravity less than 2.6, primarily consisting...
• Low velocity layerA zone of unconsolidated material near the Earth's surface, such as soil and weathered rock, characterized by...
• Low yield clayA type of clay, such as kaolinite or illite, that produces a relatively small amount of viscosity and gel...
• Low-pressure, low-temperature filtration testA standard laboratory procedure to measure the static fluid loss and filter cake thickness of a drilling...
• Low-salinity waterfloodingAn enhanced oil recovery technique that involves injecting water with a reduced salt concentration into a...
• Low-solids mudA drilling fluid formulated to contain a minimal concentration of drilled solids and commercial clays...
• Low-solids, nondispersed mudA water-based drilling fluid characterized by a low concentration of suspended solids and the absence of...
• Low-specific-gravity solidsSolid particles present in drilling fluid that possess a specific gravity less than 2.6, primarily consisting...
• Lowstand systems tractThe package of sediments deposited during a period of falling and low sea level, from the onset of a relative...
• LPGLiquefied petroleum gas, a mixture of hydrocarbon gases, primarily propane and butane, that are liquefied...
• LSAn abbreviation for low solids, referring to a type of drilling fluid formulated to contain a minimal...
• LubricantA drilling fluid additive that reduces friction between the drill string and the wellbore, as well as between...
• LubricatorA pressure-containing device installed on top of a wellhead to allow tools or equipment to be run into or...
• Lubricator valveA specialized valve installed at the top of a wellhead, above the blowout preventer, to allow the safe...
• LubricityThe measure of a drilling fluid's ability to reduce friction between contacting surfaces, such as the drill...
• LWDThe acquisition of formation and drilling data using sensors housed in the bottomhole assembly during the...
• LyophilicDescribing a substance that has a strong affinity for the dispersion medium in a colloidal system, meaning it...
• Lyophilic colloidA type of colloid in which the dispersed particles have a strong affinity for the continuous phase, or...
• LyophobicDescribing a substance that has a weak affinity for the dispersion medium in a colloidal system, meaning it...
• Lyophobic colloidA colloidal particle that has a weak affinity for the dispersion medium, tending to repel the solvent and...

140 of 4,499 terms in Oil and gas terminology (MLC-0103). Request the full dataset.