Oil and Gas Terms Beginning with “D” — Page 6

The procedure in seismic processing that compensates for the effects of a dipping reflector. DMO processing was developed in the early 1980s. Read more →

A small antenna used in electromagnetic surveying that can be represented mathematically as a dipole. Read more →

A layer of rock or sediment that is not horizontal. Read more →

What Is Direct Hydrocarbon Typing? Direct hydrocarbon typing (also called DHI analysis or direct hydrocarbon indication) is a seismic interpretation technique that uses amplitude anomalies and other seismic attributes —… Read more →

A direct-indicating viscometer is a rotational instrument (most commonly the Fann Model 35 VG meter or equivalent) used in drilling fluid engineering to measure mud rheological properties by rotating a cylindrical rotor… Read more →

Note: this entry covers the alternate unhyphenated spelling of the same instrument described at direct-indicating viscometer . A direct indicating viscometer is a rotational oilfield instrument, standardized in the Fann… Read more →

What Is a Directional Driller? Directional driller (also called a directional drilling specialist or DD) is a highly skilled drilling professional responsible for steering a wellbore along a planned three-dimensional… Read more →

Directional drilling is the intentional deviation of a wellbore from a vertical path, following a planned trajectory that curves away from vertical to reach a subsurface target that cannot be accessed by a straight… Read more →

Directional permeability is the variation in permeability of a reservoir rock with direction of fluid flow — arising from preferred grain alignment, sedimentary fabric, natural fractures, or stress-induced anisotropy —… Read more →

Directional variograms (and the related semivariograms) are geostatistical functions that quantify the spatial correlation structure of a regionalized variable (such as porosity, permeability, or hydrocarbon saturation… Read more →

What Is a Directional Well? Directional well (also called a deviated well) is a wellbore intentionally drilled at an angle from vertical to reach a subsurface target that cannot be accessed directly from the surface… Read more →

What Is Directivity in Oil and Gas Geophysics? Directivity in oil and gas geophysics refers to the angular dependence of seismic source energy radiation — the variation in amplitude, frequency content, and wavelet shape… Read more →

In petroleum geology and petrophysics, "dirty" is an informal but widely used descriptor for a sedimentary rock (most commonly a sandstone, limestone, or dolomite reservoir rock) that contains a significant proportion… Read more →

What Is Disbonding? Disbonding (also called cement disbond or casing disbond) is the separation or loss of adhesion between casing cement and either the outer wall of the casing string (pipe-to-cement disbond) or the… Read more →

A disconformity is a type of stratigraphic unconformity in which younger strata overlie older strata along a surface that represents a significant gap in the geologic record (a period of nondeposition, erosion, or both)… Read more →

A discontinuity in geophysics and petroleum geology is a subsurface boundary or interface at which a physical quantity, most commonly the velocity of seismic wave propagation, changes abruptly or over a very short depth… Read more →

Disharmonic in structural geology describes folded rock sequences in which adjacent mechanically contrasting layers develop different fold geometries that do not conform to one another across the mechanical boundary… Read more →

A dispersant in oil and gas is a chemical agent — typically an anionic, cationic, or amphoteric surfactant or polymer — that adsorbs onto the surface of suspended solid or liquid particles and imparts a surface charge… Read more →

(noun) A multiphase flow regime in a pipe or wellbore characterised by small gas bubbles distributed uniformly throughout a continuous liquid phase at relatively high liquid velocities, where the buoyancy forces are… Read more →

Clay that is scattered throughout the pore space. There are three general types: pore lining, pore filling and pore bridging. The terms dispersed clay and dispersed shale tend to be used synonymously. Read more →

Dispersion in the oilfield context refers to the spatial separation and mixing of fluid components as they flow through porous rock — a process by which an initially sharp boundary between two fluids (such as the flood… Read more →

Displacement in cementing operations is the act of forcing a cement slurry that has been pumped into a casing string or drillstring to exit the bottom of the casing or drillstring by pumping another fluid (the… Read more →

What Is Displacement Efficiency? Displacement efficiency (also called microscopic displacement efficiency or Ed ) is the fraction of movable hydrocarbons that are actually displaced from a swept pore volume when an… Read more →

The fluid, usually drilling mud, used to force a cementslurry out of the casing string and into the annulus. Read more →

The interface between an injectant and the fluid it is displacing. Read more →

What Is a Disposal Well? Disposal well (also called a saltwater disposal well or SWD well ) is a well drilled or converted for the sole purpose of injecting produced water, brine, or other oilfield waste fluids into a… Read more →

Dissolved solids in petroleum production and water management contexts refers to the ionic and molecular species that are dissolved in produced water, injection water, or process water and remain in solution after… Read more →

Distillation extraction is a core analysis method used to quantify the oil and water content of a freshly recovered core sample by extracting the pore fluids through a combination of solvent washing and steam… Read more →

A change in a waveform that is generally undesirable, such as in seismic waves. Read more →

A distributed temperature log (DTS) is a continuous, full-wellbore temperature profile acquired by deploying a single-mode or multimode optical fiber cable in the wellbore and interrogating it with pulsed laser light,… Read more →