Oil and Gas Terms Beginning with “L” — Page 4

The lithosphere is the mechanically rigid outer layer of the Earth comprising the crust and the uppermost portion of the mantle above the asthenosphere, extending from the surface to depths of approximately 70-250 km… Read more →

What Is Lithostatic Pressure? Lithostatic pressure (also called overburden pressure or geostatic pressure) is the total compressive stress exerted on a subsurface rock formation by the weight of all overlying rock and… Read more →

Lithostratigraphic inversion is a quantitative seismic interpretation technique that uses the variation in reflected seismic amplitude as a function of source-receiver offset (amplitude-versus-offset or AVO behaviour)… Read more →

What Is Lithostratigraphy? Lithostratigraphy (also called lithologic stratigraphy or rock stratigraphy) is the branch of stratigraphy concerned with the description, classification, and correlation of rock units based… Read more →

Littoral pertains to the coastal depositional environment between the high-tide level and the low-tide level (the intertidal zone), where sediments are deposited and reworked by the alternating effects of tidal flooding… Read more →

Live cement in oilfield well construction refers to cement slurry that has been mixed and pumped into the wellbore but has not yet achieved its final compressive strength and hydraulic set, remaining in a transitional… Read more →

Live oil is crude that still contains dissolved gas in solution at reservoir conditions, gas that will come out of solution as the oil moves toward the lower pressures and temperatures found near the wellbore and at… Read more →

A load cell in oil and gas operations is an electronic force transducer that converts mechanical force or weight into an electrical signal proportional to the applied load, used throughout drilling, completion,… Read more →

Load oil in well completion and stimulation operations is crude oil or refined petroleum fluid that is pumped into the wellbore to provide hydrostatic pressure for well control, to condition the wellbore for downhole… Read more →

What Is Local Content? Local content (also called local content requirement or in-country value) is a regulatory requirement or contractual obligation in oil and gas licensing agreements and production sharing contracts… Read more →

Local holdup, in multiphase flow engineering and production engineering, is the volume fraction of a specific phase (liquid or gas) occupying a cross-sectional area of a pipe, wellbore, or flow channel at a given… Read more →

What Is a Local Probe? A local probe is a small fluid-identification sensor mounted on an extendable arm in a production logging tool string that determines the type of fluid — gas, oil, or water — present at its… Read more →

In oilfield completion and workover operations, a lock is a mechanical latching device used to secure downhole completion components — packers, plugs, mandrels, and other retrievable tools — in their set position within… Read more →

(noun) A tubing-mounted receptacle with an internal locking profile that accepts and secures a flow-control device (such as a gas lift valve, chemical injection valve, or dummy valve) delivered and retrieved by… Read more →

Lock-up in drilling engineering refers to the condition in which a drill string in a directional or horizontal well becomes unable to transmit torque from the surface rotary to the bit because the cumulative friction… Read more →

Associated with the information from a log. For example, a log print is a paper print on which log data have been recorded. Read more →

The logarithmic mean is an averaging technique in which a set of measurements is converted to logarithms, the arithmetic average of those logarithms is taken, and the antilogarithm of that average is reported as the… Read more →

(noun) The practice of acquiring continuous measurements of formation and borehole properties as a function of depth using specialised instruments conveyed on wireline, drillpipe, coiled tubing, or permanently installed… Read more →

A logging run is a single descent and ascent of a wireline logging tool string into the wellbore to acquire petrophysical measurements over a specified depth interval, encompassing tool deployment, downhole calibration,… Read more →

What Is a Logging Tool? A logging tool is a downhole instrument, either run on wireline cable after drilling or incorporated into the drill string during drilling as LWD (logging while drilling), that measures physical… Read more →

A logging unit is the cabin or self-contained equipment package containing the surface hardware required to perform wireline logging measurements at the wellsite — providing the operational interface between the logging… Read more →

What Is Logging While Drilling? Logging while drilling (also called LWD) is the acquisition of formation evaluation measurements by sensors integrated into the bottom hole assembly (BHA) of the drill string… Read more →

A long-path multiple (also called a long-period multiple or far-offset multiple) is a type of multiply-reflected seismic event generated when seismic energy undergoes two or more reflections from subsurface interfaces… Read more →

A long-spacing sonic (LSS) log is a borehole acoustic measurement in which the transmitter-to-receiver spacing is increased to 3-5 feet (versus the 2-foot standard), forcing the first-arrival compressional wave to… Read more →

A longitudinal plot (also called a longitudinal dip component plot or L-plot) is one of two complementary dipmeter log presentations that displays the component of formation dip in the direction along the borehole's… Read more →

Longitudinal relaxation (T1 relaxation) in NMR (nuclear magnetic resonance) logging is the process by which hydrogen nuclei (protons) in formation fluids return to their equilibrium alignment with the static magnetic… Read more →

An emulsion with large and widely distributed droplets. A loose emulsion can be easy to break. Read more →

What Is Lost Circulation? Lost circulation occurs when drilling fluid pumped down the drillstring flows out of the wellbore into the surrounding formation rather than returning to surface through the annulus, signaled… Read more →

What Is Lost Circulation Material? Lost circulation material (also called LCM) is any solid, fibrous, or gelling substance added to drilling fluid to seal fractures, natural vugs, or highly permeable formations that… Read more →

Lost-circulation material (LCM) is the collective term for solid additives introduced into drilling fluids when fluid is being lost to the formation through fractures, vugs, or other downhole flow paths — added as a… Read more →