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 →

The application of nuclear magnetic resonance (NMR) logging to the determination of hydrocarbon type (gas, light oil, medium oil, heavy oil), using only NMR data. Three techniques are most commonly used: differential… Read more →

The instrument used to measure viscosity and gel strength of drilling mud. The direct-indicating viscometer is a rotational cylinder and bob instrument, also known as a V-G meter. Two speeds of rotation, 300 and 600… Read more →

The instrument used to measure viscosity and gel strength of drilling mud. The direct-indicating viscometer is a rotational cylinder and bob instrument, also known as a V-G meter. Two speeds of rotation, 300 and 600… Read more →

An individual trained in the science and art of intentionally drilling a well along a predetermined path in three-dimensional space, usually involving deviating the well from vertical and directing it in a specific… Read more →

What Is Directional Drilling? Directional drilling steers a wellbore along a planned non-vertical path using a combination of mud motors, rotary steerable systems, and measurement-while-drilling tools. Operators apply… Read more →

Permeability that varies with direction of flow through the porous medium. Lateral permeability contrast can be particularly important in fractured formations, where effective permeability in the direction of the… Read more →

Variograms and semivariograms that have a directional component in addition to the normal distance component. Directional variograms and semivariograms are commonly used where geological features are heterogeneous. For… Read more →

A wellbore that requires the use of special tools or techniques to ensure that the wellbore path hits a particular subsurface target, typically located away from (as opposed to directly under) the surface location of… Read more →

The property of some seismic sources whereby the amplitude, frequency, velocity or other property of the resulting seismic waves varies with direction. A directional charge, such as a length of primer cord or a linear… Read more →

Describing sedimentaryrock that contains clay minerals. Even small amounts of clay minerals in pores can drastically reduce porosity and permeability. Dirty and clean are qualitative, descriptive terms to describe the… Read more →

A common coating problem in which the protective coating detaches from the pipeline. Read more →

A geologic surface that separates younger strata from older strata and represents a time of nondeposition, possibly combined with erosion. Some disconformities are highly irregular whereas others have no relief and can… Read more →

A subsurface boundary or interface at which a physical quantity, such as the velocity of transmission of seismic waves, changes abruptly. The velocity of P-waves increases dramatically (from about 6.5 to 8.0 km/s) at… Read more →

Pertaining to structures in which the shapes of adjacent layers differ or do not conform to one another. Folds of rock layers that have different mechanical properties or competence tend to be disharmonic, with a change… Read more →

A chemical that aids in breaking up solids or liquids as fine particles or droplets into another medium. This term is often applied incorrectly to clay deflocculants. Clay dispersants are various sodium phosphates and… 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 →

Spatial separation of components within a fluid. This separation is often driven by diffusion, mixing or differential flow. In an oil field components might be separated because of heterogeneity of permeability, or… Read more →

The act of forcing a cementslurry that has been pumped into a casing string or drillstring to exit the bottom of the casing or drillstring by pumping another fluid behind it. Cement displacement is similar to definition… Read more →

The fraction of oil that has been recovered from a zone swept by a waterflood or other displacement process. Displacement efficiency equation: 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 →

A well, often a depleted oil or gas well, into which waste fluids can be injected for safe disposal. Disposal wells typically are subject to regulatory requirements to avoid the contamination of freshwater aquifers. Read more →

In water analysis, the soluble components in a sample or the residue left after evaporation of a sample. Dissolved solids are reported as ppm or mg/L. Dissolved solids are included in retort solids and can be calculated… Read more →

A technique for cleaning core samples in which the water fraction is removed by distillation and the oil fraction is extracted using solvents. Cleaning is done with either the Soxhlet or, when fluid saturation… Read more →

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

A record of the change in temperature along a well, normally recorded by a fiber-optic cable. The distributed temperature is measured by sending a pulse of laser light down the optical fiber. Molecular vibration, which… Read more →