Oil and Gas Terms Beginning with “D” — Page 5

A material used in a capacitor to store a charge from an applied electrical field. A pure dielectric does not conduct electricity. Read more →

The degree to which a medium resists the flow of electric charge, defined as the ratio of the electric displacement to the electric field strength. It is more common to use the relative dielectric permittivity. Read more →

A log of the high-frequency (on the order of 25 MHz) dielectric properties of the formation. The log usually includes two curves the relative dielectric permittivity, symbolized by epsilon which is unitless, and the… Read more →

The resistivity of the formation derived by combining the attenuation and phase shift of a propagation resistivity measurement. Common practice is to transform attenuation and phase shift independently to resistivity,… Read more →

An oil-base mud with diesel oil as its external phase. Diesel-oil mud is the traditional oil mud and has a history of excellent performance for drilling difficult wells. It has been used because the base oil is low-cost… Read more →

An oil-base mud with diesel oil as its external phase. Diesel-oil mud is the traditional oil mud and has a history of excellent performance for drilling difficult wells. It has been used because the base oil is low-cost… Read more →

A map that represents the change from one map to another, such as a reservoir map of an area made from two different seismic surveys separated in production history (one possible product of 4D seismic data), or an… Read more →

The spontaneous potential (SP) measured between two electrodes placed close together in the borehole, as opposed to the normal SP, which is measured with one electrode in the borehole and one at surface. Read more →

A phenomenon that occurs after the deposition of some sediments such that different parts of the sedimentary accumulation develop different degrees of porosity or settle unevenly during burial beneath successive layers… Read more →

The difference between two pressure measurements. For production wells, the differential pressure is the difference between average reservoir pressure and bottomhole pressure, and for injection wells, it is the… Read more →

A technique in nuclear magnetic resonance (NMR) logging that is based on the difference between the T2 distributions, or spectra, acquired at different polarization times. The technique often is used to detect gas or… Read more →

What Is Differential Sticking? Differential sticking occurs when a stationary drill pipe , drill collar , or bottomhole assembly (BHA) becomes embedded in the filter cake deposited on a permeable formation wall, held in… Read more →

A type of static correction that compensates for delays in seismicreflection or refraction times from one point to another, such as among geophone groups in a survey. These delays can be induced by low-velocity layers… Read more →

A record of the difference in temperature between two vertical points in a well. Most differential-temperature logs are obtained by differentiating a normal temperature log with respect to depth. Some are obtained by… Read more →

Pertaining to a cement that is not easily dispersed by a material known as a dispersant. This term is commonly abbreviated as DTD. Read more →

Pertaining to cement that is not easily dispersed by a material known as a dispersant when the slurry is mixed with water containing a high concentration of salt. The term is commonly abbreviated DTDS. Read more →

A type of event produced by the radial scattering of a wave into new wavefronts after the wave meets a discontinuity such as a fault surface, an unconformity or an abrupt change in rock type. Diffractions appear as… Read more →

The process by which particles move over time within a material due to their kinetic motion. The term is most commonly used in pulsed neutron capturelogging and in nuclear magnetic resonance (NMR) logging. In a pulsed… Read more →

A fundamental differential equation obtained by combining the continuity equation, flow law and equation of state. Most of the mathematics of well testing were derived from solutions of this equation, which was… Read more →

In a nuclear magnetic resonance (NMR) measurement, the loss of coherent energy by hydrogen atoms as they move within the pore space. Hydrogen atoms that move significantly within the pores during a NMR measurement will… Read more →

An intrusive rock that invades preexisting rocks, commonly in a tabular shape that cuts vertically or nearly vertically across preexisting layers. Dikes form from igneous and sedimentary rocks. Read more →

The increase in the volume of rocks as a result of deformation, such as when fractures develop. Read more →

A possible explanation for volume changes in rocks due to strain, such as microfracturing or cracking, and the accompanying change in the ratio of P- to S-wavevelocity. Support for dilatancy theory comes in the form of… Read more →

A rarefaction, or decrease in pressure and density of a medium as molecules are displaced by a P-wave. As P-waves pass through the Earth, the Earth undergoes compression and expansion. These changes in volume contribute… Read more →

A hydrocarbon fluid that is used to dilute heavy oil and reduce its viscosity for easier transportation. Generally a distillation tower cut such as naphtha is used as for heavy oil dilution and transportation. The added… Read more →

The process of adding fresh mud (or liquid phase) in order to reduce the solids content and maintain the properties of the drilling fluid in the active system. Read more →

A type of local seismicevent that, in contrast to a bright spot, shows weak rather than strong amplitude. The weak amplitude might correlate with hydrocarbons that reduce the contrast in acousticimpedance between the… Read more →

The angle between a planar feature, such as a sedimentarybed or a fault, and a horizontal plane. True dip is the angle a plane makes with a horizontal plane, the angle being measured in a direction perpendicular to the… Read more →

An algorithm for correcting the effects of dip or boreholedeviation on the response of a logging measurement. These effects are significant for deep-reading logs such as induction and electrode devices. The standard… Read more →

A fault whose primary movement is in the dip direction. Dip faults are also referred to as dip-slip faults. Read more →