Oil and Gas Terms Beginning with “D” — Page 4

The member of the drilling crew in charge of the mud-processing area during periods of circulation. The derrickman also measures mud density and conducts the Marsh funnel viscosity test on a regular basis when the mud… Read more →

A hydrocyclone device that removes large drill solids from the whole mud system. The desander should be located downstream of the shale shakers and degassers, but before the desilters or mud cleaners. A volume of mud is… Read more →

A substance used in a gas-dehydration unit to remove water and moisture. The desiccant can be liquid, such as methanol, glycol (ethylene, diethylene, triethylene, and tetraethylene). Dessicants also can be solid, such… Read more →

A hydrocyclone much like a desander except that its design incorporates a greater number of smaller cones. As with the desander, its purpose is to remove unwanted solids from the mud system. The smaller cones allow the… Read more →

To remove sulfur or sulfur compounds from an oil or gas stream. Read more →

A log with a depth scale chosen to show sufficient detail of the formation. The most common scales are 1/200 or 5 in./100 ft. Read more →

The minimum thickness necessary for a layer of rock to be visible or distinct in reflectionseismic data. Generally, the detectable limit is at least 1/30 of the wavelength. Acquisition of higher frequency seismic data… Read more →

A sensor or receiver, such as a geophone or hydrophone, gravimeter or magnetometer. Read more →

The ability of a chemical agent to remove a contaminant from a solid surface. For example, in enhanced oil recovery, a surfactant can be used to remove an oil phase from a mineral surface. At least two mechanisms can… Read more →

The use of deterministic methods to solve problems or find solutions to data sets. Read more →

A type of inverse filtering, or deconvolution, in which the effects of the filter are known by observation or assumed, as opposed to statistical deconvolution. Read more →

Techniques that use equations or algorithms that have been previously developed for similar situations. These methods do not involve stochastic or statistical approaches. Deterministic methods are generally easier and… Read more →

A cord containing high-explosive material sheathed in a flexible outer case, which is used to connect the detonator to the main high explosive. This provides an extremely rapid initiation sequence that can be used to… Read more →

A device containing primary high-explosive material that is used to initiate an explosive sequence. The two common types of detonators are electrical detonators (also known as blasting caps) and percussion detonators.… Read more →

Pertaining to particles of rock derived from the mechanical breakdown of preexisting rocks by weathering and erosion. Detrital fragments can be transported to recombine and, through the process of lithification, become… Read more →

The phase of petroleum operations that occurs after exploration has proven successful, and before full-scale production. The newly discovered oil or gas field is assessed during an appraisal phase, a plan to fully and… Read more →

A wellbore that is not vertical. The term usually indicates a wellbore intentionally drilled away from vertical. Read more →

The angle at which a wellbore diverges from vertical. Wells can deviate from vertical because of the dips in the beds being drilled through. Wells can also be deliberately deviated by the use of a whipstock or other… Read more →

The process of removing water from water-base drilling mud. Dewatering can involve chemical treatment for the flocculation and aggregation of solids followed by mechanical separation, such as centrifugation, or… Read more →

The pressure at which the first condensate liquid comes out of solution in a gas condensate. Many gas condensate reservoirs are saturated at initial conditions, meaning that the dewpoint is equal to the initial… Read more →

Pertaining to a strike-slip fault or right-lateral fault in which the block across the fault moves to the right. If it moves left, the relative motion is described as sinistral. Clockwise rotation or spiraling is also… Read more →

The initial stage of alteration of sediments and maturation of kerogen that occurs at temperatures less than 50°C [122°F]. The type of hydrocarbon generated depends on the type of organic matter in the kerogen, the… Read more →

A type of secondary porosity created during diagenesis, commonly through dissolution or dolomitization or both. Diagenesis usually destroys porosity, so diagenetic porosity is rare. Read more →

The distance from the borehole wall into the formation that the mudfiltrate has penetrated. The term assumes equal invasion on all sides of the borehole. It is the diameter of the circle thus formed, with the center… Read more →

A distance that characterizes how far a logging tool measures into the formation from the axis of the tool or borehole. The term is similar to depth of investigation but is appropriate only for azimuthally symmetric… Read more →

A tool for drilling rock that works by scraping industrial grade diamonds against the bottom of the hole. The diamonds are embedded into the metal structure (usually a sintered or powdered carbide base matrix) during… Read more →

A relatively mobile mass that intrudes into preexisting rocks. Diapirs commonly intrude vertically through more dense rocks because of buoyancy forces associated with relatively low-density rock types, such as salt,… Read more →

A microscopic, single-celled, freshwater or saltwater algae that has a silica-rich cell wall called a frustule. Diatoms are so abundant that they can form thick layers of sediment composed of the frustules of the… Read more →

A soft, silica-rich sedimentaryrock comprising diatom remains that forms most commonly in lakes and deep marine areas. Diatomite can form an excellent reservoir rock. The Belridge diatomite in the San Joaquin basin,… Read more →

A type of salt in which chromium atoms are in the plus-7 valence state, such as potassium dichromate, K2Cr2O7. Read more →