Oil and Gas Terms Beginning with “D” — Page 2

A fault surface parallel to a mechanically weak horizon or layer, or parallel to bedding, that detaches or separates deformed rocks above from undeformed or differently deformed rocks below. Decollements, or decollement… Read more →

A mathematical operation that uses downhole flow-rate measurements to transform bottomhole pressure measurements distorted by variable rates to an interpretable transient. Deconvolution also can use surface rates to… Read more →

A particular type of induction log that was designed to read deep into the formation while maintaining reasonable vertical resolution. The deep induction log (ID) is based on the measurement of a 6FF40array and was… Read more →

A seismic profile recorded specifically to study the lower crust, the Mohorovicic discontinuity and the mantle of the Earth, typically using refraction methods. Most standard seismic reflection profiles record only a… Read more →

A method of marineseismic acquisition in which a boat tows a receiver well below the surface of the water to get closer to features of interest or to reduce noise due to conditions of the sea. Deep tow devices are used… Read more →

A perforating charge designed to provide a long perforation tunnel, such as may be required to bypass any near-wellbore damage. Specially designed deep-penetrating charges achieve this additional length while retaining… Read more →

Exploration activity located in offshore areas where water depths exceed approximately 600 feet [200 m], the approximate water depth at the edge of the continental shelf. While deep-water reservoir targets are… Read more →

(noun) A production logging tool that uses a deflector plate or vane positioned in the flow stream within a wellbore to measure the velocity and direction of fluid flow. The force exerted on the deflector by the flowing… Read more →

A thinning agent used to reduce viscosity or prevent flocculation; incorrectly called a "dispersant." Most deflocculants are low-molecular weight anionic polymers that neutralize positive charges on clay edges. Examples… Read more →

A clay-based, water mud that has had its viscosity reduced with a chemical treatment; incorrectly, called a "dispersed" mud. The chemical used is a deflocculant, not a dispersant. A well-known and effective clay… Read more →

The act of reducing the viscosity of a suspension by adding a thinning agent, also known as a deflocculant. Read more →

A mud additive used to lower interfacial tension so that trapped gas will readily escape from mud. Mechanical degassing equipment is commonly used along with defoamer. Octyl alcohol, aluminum stearate, various glycols,… Read more →

In a separator, a series of inclined parallel plates or tubes to promote coalescence, or merging, of the foam bubbles liberated from the liquid. Read more →

A device that removes air or gases (methane, H2S, CO2 and others) from drilling liquids. There are two generic types that work by both expanding the size of the gas bubbles entrained in the mud (by pulling a vacuum on… Read more →

A unit of measurement established by the American Petroleum Institute (API) that indicates the density of a liquid. Fresh water has an API density of 10. Read more →

To remove water from a substance. The substance may be crude oil, natural gas or natural gas liquids (NGL).Fluid dehydration is needed to prevent corrosion and free-water accumulation in the low points of a pipeline. In… Read more →

The loss of water from cementslurry or drilling fluid by the process of filtration. Dehydration results in the deposition of a filter cake and loss of the slurrys internal fluid into a porousmatrix. The cement is not… Read more →

A device used to remove water and water vapors from gas. Gas dehydration can be accomplished through a glycol dehydrator or a dry-bed dehydrator, which use a liquid desiccant and a solid desiccant, respectively.Gas… Read more →

Consideration paid to the lessor by a lessee to extend the terms of an oil and gas lease in the absence of operations and/or production that is contractually required to hold the lease. This consideration is usually… Read more →

Tests in an oil or gas well to determine its flow capacity at specific conditions of reservoir and flowing pressures. The absolute open flow potential (AOFP) can be obtained from these tests, and then the inflow… Read more →

An area of deposition or the deposit formed by a flowing sediment-laden current as it enters an open or standing body of water, such as a river spilling into a gulf. As a river enters a body of water, its velocity drops… Read more →

A log that shows the magnitude of the correction applied to the long-spacingdetector of a density measurement. When delta rho is above a certain value, typically +/- 0.15 g/cm3, the correction may no longer be accurate,… Read more →

A feature on a sonic log caused by low signalamplitude that results in erroneously long traveltimes. Sonic logs that do not record waveforms measure the acoustic traveltime between transmitter and receiver by detecting… Read more →

A chemical used to break emulsions (that is, to separate the two phases). The type of demulsifier selected depends on the type of emulsion, either oil-in-water or water-in-oil. Demulsifiers are used in the chemical… Read more →

An instrument that measures the specific gravity of a mixture of gas, liquid and solids. This device is also known as a densitometer. Read more →

A device installed on a mixing or pumping system manifold to measure the density of fluids. The density of fluids pumped into a well is frequently a key operating parameter, requiring constant monitoring and control.… Read more →

Mass per unit of volume. Density is typically reported in g/cm3 (for example, rocks) or pounds per barrel (drilling mud) in the oil field. Read more →

The variation in the mass per unit volume of rocks, which affects the local gravitational field of the Earth. A density contrast also contributes to an acousticimpedance contrast, which affects the reflection… Read more →

A measurement of the bulk density of the formation based on borehole-gravity measurements. As the gravitational attraction between two bodies is dependent upon their masses and their separation, it follows that its… Read more →

A series of gravity measurements made along a line or over an area of a locally high topographic feature to remove or compensate for the effect of topography on deeper density readings. Read more →