Oil & Gas Glossary

One-dimensional seismic data (1-D seismic data) is a single seismic trace recorded at one point on the surface, representing the acoustic response of the earth directly below that…

The 6FF40 is a specific induction logging tool array designation used by Schlumberger in the era of dual induction logging. The code describes the physical configuration of the too…

An A-leg is one of the two or more separate wellbore branches in a multilateral well or one of the parallel piping paths in a dual-completion or production manifold system. In mult…

What Is an AFE? An AFE, or Authority for Expenditure, is the budget approval document an oil and gas operator sends before spending joint-account money on a specific job. It turns…

AGC, or Automatic Gain Control, is a signal-processing technique in which the amplification applied to a recorded waveform is continuously and automatically adjusted so that the ou…

The AGC time constant, more precisely called the AGC gate length or AGC window length, is the duration of the sliding time window over which root-mean-square (RMS) amplitude energy…

Drilling deep used to be brutal on chemistry. Below 3,500 metres in Western Canada, the rock at the bottom of a horizontal well runs 140 to 180°C. The mud pumped down there has to…

AOF, or Absolute Open Flow, is the theoretical maximum rate at which a gas well would produce if the flowing bottomhole pressure (BHFP) were reduced to atmospheric pressure (approx…

AOFP, or Absolute Open Flow Potential, is the theoretical maximum rate at which a gas or gas-condensate well would produce if the bottomhole flowing pressure were reduced to atmosp…

API stands for the American Petroleum Institute, the principal trade association and technical standards body for the United States oil and natural gas industry, founded in 1919 an…

API Specification 10A (formally titled "Specification for Cements and Materials for Well Cementing," also referred to as API Spec 10A and harmonised internationally with ISO 10426-…

API cement is oilfield cement manufactured to the dimensional, chemical, and physical performance requirements specified in API Specification 10A (equivalent to ISO 10426-1:2009),…

API gravity is a specific gravity scale developed by the American Petroleum Institute (API) and the National Institute of Standards and Technology (NIST) that expresses the density…

The API unit (symbol: gAPI) is the internationally standardised unit of measurement for natural gamma ray radioactivity in wellbore logging, established by the American Petroleum I…

API water is the precisely defined quantity of mixing water prescribed by API Specification 10A (and its ISO equivalent ISO 10426-1) for preparing oilwell cement test slurries in l…

ASTM International (originally the American Society for Testing and Materials, founded in Philadelphia in 1898) is a globally recognised standards development organisation that pub…

Annular velocity (AV), sometimes abbreviated as AV in drilling engineering documentation and mud reports, is the linear speed at which drilling fluid flows upward through the annul…

AVO, an acronym for Amplitude Variation with Offset, describes the systematic change in the amplitude of a seismic reflection as the source-to-receiver offset (distance) increases…

An agitator in drilling operations is a mechanical, pneumatic, or jet-driven device installed in or on active mud pits, suction pits, mixing pits, or reserve pits to maintain drill…

An air compressor used in drilling operations is a mechanical device that increases the pressure of atmospheric air (or, in sensitive formations, nitrogen or natural gas) from ambi…

An air hoist, also called a pneumatic hoist, is a lifting device powered by compressed air in which the energy of pressurised air drives a rotary air motor to wind a wire rope or l…

Alford rotation is a four-component matrix processing algorithm applied to cross-dipole sonic log data that rotates the recorded shear-wave waveforms from the logging tool's physic…

Archie Equation is the foundational petrophysical relationship used to estimate water saturation (Sw) in a reservoir rock from wireline log measurements of electrical resistivity a…

Archie rock is a reservoir formation whose electrical properties are fully and accurately described by the Archie Equation without modification or correction for additional conduct…

A BBL (also written bbl, barrel, or oil barrel) is the standard unit of crude oil and petroleum product volume used throughout the international petroleum industry, defined as exac…

Background gas (abbreviated BGG or sometimes BG) is the continuous, baseline concentration of hydrocarbon gases detected in the drilling fluid returns at the surface during mud log…

A bottom hole assembly (BHA) is the lowermost section of the drill string, comprising the drill bit and all specialized tools and drill collars between the bit and the start of the…

Bottomhole circulating temperature (BHCT) is the equilibrium temperature at the bottom of a wellbore (or at any specified depth of interest) during active circulation of drilling f…

Bottomhole pressure (BHP) is the fluid pressure measured or calculated at a specified datum depth within the wellbore — typically at the mid-perforation depth, the producing format…

Bottomhole static temperature (BHST) is the true geothermal equilibrium temperature of the formation at a specified depth, measured or inferred after the wellbore has been shut in…