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

The pressure of the weight of overburden, or overlying rock, on a formation; also called geostatic pressure. Read more →

A seismic inversion technique that attempts to describe lithology of individual rock layers and evaluate properties and distribution of pore fluids through analysis of variation of reflected seismic amplitude with… Read more →

The study and correlation of strata to elucidate Earth history on the basis of their lithology, or the nature of the well log response, mineral content, grain size, texture and color of rocks. Read more →

Pertaining to an environment of deposition affected by tides, the area between high tide and low tide. Given the variation of tides and land forms from place to place, geologists describe littoral zones locally… Read more →

A term used to describe a cementslurry that remains liquid but is still capable of thickening or setting to become an unmovable solid mass. Some remedial operations treat the excess live cement slurry with a contaminant… Read more →

Oil containing dissolved gas in solution that may be released from solution at surface conditions. Live oil must be handled and pumped under closely controlled conditions to avoid the risk of explosion or fire. Read more →

The sensor component in a weight-indicator system that detects the tensional or compressional forces being imparted to the running string at surface. Load cells are hydraulically or electronically operated and are… Read more →

Oil pumped into a wellbore in preparation for, or as part of, a treatment. Some treatments, such as hydraulic fracturing, involve pumping large volumes of fluid. Using load oil, often produced and processed from… Read more →

The amount of local personnel, material and services that working interest owners are required to employ when drilling and operating a well, as specified under the terms of a concession agreement. Read more →

The fraction of a particular fluid measured in the vicinity of a small probe in a production well. The small, or local, probes respond digitally to the type of fluid in front of them, indicating gas, oil or water… Read more →

A small sensor, part of a productionlogging tool, which determines the type of fluid in its vicinity as it moves up and down a production well. Typically there are four or more sensors, or probes, held on arms to… Read more →

A downhole device, run and retrieved on slickline, that is placed and anchored within the tubing string to provide a setting point for flow-control equipment such as valves, chokes and plugs. The three main types of… 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 →

A condition that may occur when a coiled tubing string is run into a horizontal or highly deviated wellbore. Lock-up occurs when the frictional force encountered by the string running on the wellbore tubular reaches a… 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 average value of a set of measurements, calculated by taking the logarithms of the measurements, finding the arithmetic average of the logarithms and then taking the antilogarithm of the average. 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 →

An operation in which a logging tool is lowered into a borehole and then retrieved from the hole while recording measurements. The term is used in three different ways. First, the term refers to logging operations… Read more →

The downhole hardware needed to make a log. The term is often shortened to simply "tool." Measurements-while-drilling (MWD) logging tools, in some cases known as logging while drilling (LWD) tools, are drill collars… Read more →

The cabin that contains the surface hardware needed to make wirelinelogging measurements. The logging unit contains at the minimum the surface instrumentation, a winch, a depth recording system and a data recorder. The… Read more →

The measurement of formation properties during the excavation of the hole, or shortly thereafter, through the use of tools integrated into the bottomhole assembly. LWD, while sometimes risky and expensive, has the… Read more →

A type of multiply-reflected seismic energy that appears as an event. Long-path multiples generate distinct events because their travel path is much longer than primary reflections giving rise to them. They typically… Read more →

A sonic tool with a longer transmitter-to-receiverspacing (generally 10 to 15 ft) than a standard sonic tool. The rock near the borehole is sometimes altered by drilling fluids, stress relief, or both, causing a thin… Read more →

A plot of the longitudinal component of the dip vector computed from a dipmeter. Longitudinal plots are used in the SCAT (Statistical Curvature Analysis Technique) method of interpreting dipmeter data for… Read more →

During a nuclear magnetic resonance measurement, the loss of energy by hydrogen atoms in a rock as they align themselves with the static magnetic field. The atoms behave like spinning bar magnets so that when a static… 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 →

Solid material intentionally introduced into a mud system to reduce and eventually prevent the flow of drilling fluid into a weak, fractured or vugularformation. This material is generally fibrous or plate-like in… Read more →

The collective term for substances added to drilling fluids when drilling fluids are being lost to the formations downhole. Commonly used lost-circulation materials include are fibrous (cedar bark, shredded cane stalks,… Read more →

An oil mud designed and maintained with a minimum of colloid-sized solids, typically by omitting fatty-acid soap and lime, and minimizing organophilic clays and fluid-loss additives. Low-colloid oil mud, also called a… Read more →