Oil and Gas Terms Beginning with “A” — Page 3

An acoustic emission (AE) is a transient elastic wave generated when material undergoes rapid internal deformation, crack initiation, crack propagation, or localised brittle failure. The energy stored in a stressed… Read more →

What Is Acoustic Impedance? Acoustic impedance quantifies a rock's resistance to the propagation of seismic energy by multiplying its bulk density (rho) by the compressional wave velocity (Vp), yielding the property Z =… Read more →

An acoustic impedance section is a two-dimensional or three-dimensional seismic data volume that has been mathematically transformed, through a process called seismic inversion, from its native form as a record of… Read more →

What Is an Acoustic Log? An acoustic log records the acoustic properties of subsurface formations and the borehole by measuring traveltimes, amplitudes, and waveforms of compressional, shear, and Stoneley waves… Read more →

An acoustic mode is a pattern of elastic wave propagation in which acoustic energy travels freely in one direction while being constrained or guided in the remaining two directions by the impedance contrasts at the… Read more →

What Is Acoustic Positioning? Acoustic positioning calculates the three-dimensional location of underwater equipment by measuring the two-way traveltime of acoustic signals between transponders and transceivers, then… Read more →

An acoustic transducer is a device that converts electrical energy into sound (acoustic energy) or, conversely, converts received sound waves back into electrical signals. In oilfield applications, acoustic transducers… Read more →

Acoustic transparency describes the condition of a geological medium whose acoustic impedance remains effectively constant throughout its interior, so that seismic energy passes through the medium without generating… Read more →

(noun) A mechanical pressure disturbance that propagates through a medium as a compressional (P-wave) or shear (S-wave) oscillation. In petroleum geoscience, acoustic waves are generated by seismic sources and logging… Read more →

What Is Seismic Acquisition? Seismic acquisition describes the field phase of seismic exploration in which controlled acoustic or elastic energy is generated at the surface or in a borehole, propagated through… Read more →

An acquisition log is the raw log record produced at the wellsite at the moment the logging tool moves through the wellbore and captures measurements. Also called a field log or raw log , it represents the unedited,… Read more →

An acrylamide-acrylate polymer is a linear copolymer built from two repeating monomer units: acrylamide (a nonionic, water-soluble monomer) and acrylate (the anionic, carboxylate-bearing monomer produced by partial… Read more →

An acrylamide polymer is a linear, water-soluble synthetic polymer built from acrylamide monomers (CH 2 =CHCONH 2 ), the simplest member of the acrylamide monomer family. Unlike the anionic polyacrylates derived from… Read more →

A linear copolymer of acrylate (anionic) and acrylamide (nonionic) monomers, also called partially-hydrolyzed polyacrylamide (PHPA). The ratio of acrylic acid to acrylamide groups on the polymer chain can be varied in… Read more →

An AMPS polymer is a copolymer or terpolymer built from the monomer 2-acrylamido-2-methylpropane sulfonic acid (AMPS, CAS 15214-89-8), an acrylamide derivative in which a methylpropane sulfonic acid group replaces the… Read more →

A copolymer of 2-acrylamido-2methyl propane sulfonate and acrylamide. AMPS polymers are highly water-soluble anionic additives designed for high-salinity and high-temperature water-mud applications. (Alkyl-substituted… Read more →

What Is Acrylate Polymer? Acrylate polymer designates a family of linear, water-soluble anionic polymers derived from acrylic acid (CH 2 =CHCOOH) or its salts, used throughout the petroleum industry as clay… Read more →

What Is an Activation Log? An activation log is a nuclear well log that derives elemental concentrations from the characteristic gamma-ray energies emitted by atomic nuclei that have been irradiated by a neutron source.… Read more →

An active margin is a tectonic boundary where two lithospheric plates are converging, resulting in ongoing compressional deformation, seismic activity, and volcanism along the continental edge. The term contrasts… Read more →

The activity of an aqueous solution (symbol a w ) is the thermodynamic measure of how readily water molecules escape from a solution compared with their tendency to escape from pure water under identical temperature and… Read more →

In petroleum geostatistics, additivity is the mathematical property that allows two or more valid (admissible) semivariogram models to be summed with positive coefficients to produce a new model that is itself valid.… Read more →

What Is Adhesion Tension? Adhesion tension is the net interfacial force acting on a solid surface when two immiscible fluids compete to wet that surface. Mathematically it equals the product of the interfacial tension… Read more →

What Is an Adjustable Choke? An adjustable choke is a surface wellhead valve with a variable-diameter orifice or needle assembly that the operator adjusts to control the flow rate and wellbore pressure of produced… Read more →

Adjusted flow time is the approximated equivalent producing time used in pressure transient analysis (PTA) when a well's flow rate has varied before or during the test period. Rather than using the actual elapsed… Read more →

What Is Adsorbed Gas? Adsorbed gas describes natural gas molecules held on the surface of solid organic material or mineral grains within a reservoir rock by Van der Waals forces rather than occupying open pore space.… Read more →

What Is Adsorption? Adsorption is the process by which molecules of a gas, liquid, or dissolved substance accumulate and bind onto the surface of a solid or liquid material, forming a concentrated layer at the… Read more →

Advective transport modeling is the application of mathematical and computational methods to quantify the movement of solutes, contaminants, or tracers through porous media by bulk fluid flow. The term derives from… Read more →

The aerated layer is the surface or near-surface zone of unconsolidated sediment whose pore space is occupied by air rather than water or hydrocarbon liquids. Because seismic P-wave velocity depends heavily on the bulk… Read more →

In the oil and gas industry, aerobic refers to any condition, process, or living organism that requires or uses free molecular oxygen (O 2 ) to sustain metabolic activity. The term is derived from the Greek aer (air)… Read more →

What Is an Aeromagnetic Survey? An aeromagnetic survey deploys a magnetometer aboard or towed beneath an aircraft to map spatial variations in the intensity of Earth's total magnetic field across a study area. The… Read more →