Oil and Gas Terms Beginning with “L”

A linear alpha-olefin (LAO) is a synthetic hydrocarbon liquid produced by the catalytic polymerization (oligomerization) of ethylene (H2C=CH2) — typically through ethylene oligomerization processes that produce a range… Read more →

LC50 (lethal concentration 50) is the standardized toxicological measurement reporting the concentration of a substance, typically expressed in parts per million (ppm), that causes mortality in 50 percent of a test… Read more →

Lost circulation material (LCM) refers to any solid, fibrous, or flaky additive incorporated into drilling fluid or spotting pills specifically to prevent or stop the loss of drilling fluid into formation fractures,… Read more →

Low-gravity solids (LGS) are a category of drilling fluid solids that have lower density than the barite or hematite weighting materials used to weight up drilling fluid systems — the LGS category includes drill solids… Read more →

Abbreviation for liquefied natural gas. Read more →

Abbreviation for liquefied natural gas carrier, which is a sea vessel used to transport liquefied petroleum gas (LPG). Read more →

A leak-off test (LOT) is a wellbore integrity test performed after drilling out a casing shoe cement plug and drilling a short distance into new formation, in which the well is pressure-tested by pumping fluid at a… Read more →

(noun) Abbreviation for Liquefied Petroleum Gas. A mixture of light hydrocarbon gases, primarily propane (C₃H₈) and butane (C₄H₁₀), that are compressed and stored as liquids at moderate pressure for use as fuel,… Read more →

LS is a common abbreviation for lignosulfonate, the class of sulfonated lignin-based polymers used as deflocculants (thinners) in water-based drilling fluids to reduce viscosity and yield point by adsorbing on clay… Read more →

What Is Logging While Drilling (LWD)? Logging while drilling (LWD) describes the suite of formation evaluation sensors integrated into the bottom hole assembly that measures petrophysical rock and fluid properties,… Read more →

The Lame constants are the two independent elastic parameters that fully describe a linear, isotropic, homogeneous solid in the framework of classical elasticity, named for French mathematician and engineer Gabriel Lame… Read more →

The Laplace equation in petroleum engineering is the second-order partial differential equation ∇²P = 0 (the Laplacian of pressure equals zero) that describes steady-state pressure distribution in a porous medium when… Read more →

To attach elevators to the upper section of drillpipe to pull it out of or run into the hole. Read more →

To pull drill pipe from the hole and lay it down on the catwalk. Read more →

What Is Lockout/Tagout? Lockout/tagout (LOTO) is a mandatory safety procedure used at oil and gas facilities, drilling operations, and processing plants to ensure that hazardous energy sources — electrical, hydraulic,… Read more →

What Is a Love Wave? A Love wave is a dispersive seismic surface wave in which particles oscillate horizontally and perpendicular to the propagation direction (SH-polarised motion), requires a low-velocity surface layer… Read more →

A ball valve installed at one end of the kelly that can be used to stop mud draining from the kelly during a connection. Read more →

What Is Lacustrine? Lacustrine (also called lake-derived or lake-facies) refers to sediments, rocks, and organic matter deposited in ancient lake environments. In petroleum geology, lacustrine systems are significant as… Read more →

Lag in well logging context refers to the spatial offset between the static measure point and the dynamic measure point of a logging measurement — the static measure point being the location at which the measurement… Read more →

Lag gas is the natural gas (and other formation gases including H2S, CO2, and formation vapors) that is released from cuttings, cavings, and formation fluids at the bit face during drilling, mixes with the drilling… Read more →

The time taken for cuttings to reach the surface. The term is also used in place of cycle time. Read more →

Laminar flow is a type of streamlined, ordered flow regime for single-phase fluids in which the fluid moves in parallel layers (laminae) that do not mix with each other, with each layer sliding past adjacent layers… Read more →

Laminated sand is a petrophysical model and reservoir rock type in which thin layers (laminae) of clean, hydrocarbon-bearing sand alternate with thin layers of shale at a scale too fine to be individually resolved by… Read more →

A lamination, also called a lamina (plural laminae), is the smallest visible unit of sedimentary layering, conventionally a layer less than about one centimetre and often near one millimetre thick that differs from the… Read more →

What Is a Landing Collar? Landing collar (also called a plug-landing collar or cementing collar) is a downhole completion accessory installed in a casing or liner string that receives and seats a wiper plug or cementing… Read more →

(noun) A short section of internally machined tubing with a precisely profiled bore, installed at specific locations in a completion string to provide a seating and locking surface for flow-control devices such as… Read more →

What Is a Landman? A landman negotiates the acquisition of mineral rights and surface access agreements between energy companies and landowners across oil and gas producing regions worldwide. Operating at the… Read more →

Laser diffraction (also called laser light scattering or laser particle size analysis) is an analytical technique that measures the size distribution of particles in a liquid suspension or dry powder by illuminating the… Read more →

A last reading in oil and gas operations refers to the final recorded measurement from a downhole sensor, logging tool, or surface metering instrument before the tool is retrieved from the wellbore, before a well is… Read more →

A surface detection system used to ensure that all tubing-conveyed perforating guns have fired, from the top shot to the bottom shot. Read more →