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

A derrick is the tall structural framework erected above a wellbore to support the hoisting equipment (traveling block, hook, and swivel) that raises and lowers the drill string, casing strings, and completion equipment… Read more →

What Is a Derrickman? Derrickman (also called derrick hand or monkey board operator) is a drilling rig crew member who works on the monkey board, a narrow platform located 80 to 90 feet above the rig floor in the… Read more →

What Is a Desander? A desander is a solids control device that removes coarse drilled solids — primarily sand-sized particles in the range of 45 to 75 microns — from drilling mud using hydrocyclone centrifugal… Read more →

What Is a Desiccant? A desiccant is a solid or liquid absorbent material used in natural gas processing and dehydration to remove water vapour from gas streams to prevent hydrate formation, corrosion, and pipeline… Read more →

A desilter is a solids-control device in the drilling fluid processing train that uses hydrocyclone technology to separate fine silt-sized particles (generally 15-44 micrometers in diameter) from the drilling fluid by… 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 detectable limit in seismic exploration is the minimum thickness of a subsurface rock layer that can be identified as a discrete reflection event in processed seismic data, distinct from the surrounding rock, even… Read more →

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

Detergency in petroleum engineering and drilling fluid chemistry refers to the ability of a surfactant or detergent molecule to remove oily, waxy, or particulate contaminants from solid surfaces — particularly the… 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 →

Deterministic methods in petroleum engineering and geoscience refer to analytical or numerical approaches that produce a single, definite answer for a given set of input parameters, without explicitly quantifying the… Read more →

Detonating cord (also called det cord, detonating fuse, or primacord) is a flexible, rope-like explosive device consisting of a core of high-explosive material (typically PETN, pentaerythritol tetranitrate, at loading… Read more →

A perforating detonator is the initiating explosive device at the top or base of a perforating gun assembly that converts an electrical, optical, or electronic firing signal into a detonation wave strong enough to… Read more →

Detrital refers to rock fragments, mineral grains, and organic particles that have been physically transported from their source area by water, wind, or ice and deposited in a sedimentary environment — as distinguished… Read more →

Development in the oil and gas industry refers to the phase of a petroleum project that follows discovery and appraisal, during which the commercially confirmed hydrocarbon accumulation is prepared for production by… Read more →

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

Deviation in drilling refers to the angular departure of a wellbore from true vertical — measured as the inclination angle between the wellbore axis and a plumb line at any given depth — arising either unintentionally… Read more →

Dewatering is the process of removing excess water from spent drilling fluid or drilling waste to reduce the volume that must be disposed of and to separate recyclable solids from the liquid. In drilling operations,… Read more →

In gas condensate production, the dewpoint is the critical pressure threshold at which a gas reservoir transitions from a single-phase gas into something far more complicated — a gas-liquid mixture where liquid… Read more →

Dextral describes a strike-slip fault on which the block on the opposite side of the fault from the observer moves to the right. The term comes from the Latin dexter, meaning right. Another name for the same geometry is… Read more →

What Is Diagenesis? Diagenesis (also called burial diagenesis or post-depositional alteration) is the suite of physical, chemical, and biological changes that affect sediment after deposition and throughout its burial… 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 →

What Is the Diameter of Invasion? The diameter of invasion (di) is the radial extent of drilling fluid filtrate penetration into a permeable formation around the borehole, measured from the centre of the borehole to the… Read more →

The diameter of investigation is the distance from the centre of a logging tool out to the point in the formation where the tool stops being able to "see." Different log tools see different distances: a shallow tool… Read more →

What Is a Diamond Bit? Diamond bit (also called a fixed-cutter bit or PDC bit in its modern form) is a rotary drilling bit that uses industrial diamonds as the primary cutting element rather than the rolling steel teeth… Read more →

A diapir is a relatively mobile, low-density geological mass that intrudes into and through preexisting rocks by buoyancy-driven flow, piercing or doming the overlying strata as it rises through the sedimentary section… Read more →

A diatom is a microscopic, single-celled algae whose cell wall (called a frustule) is composed of amorphous hydrated silica (opaline silica or biogenic silica), making diatoms significant in petroleum geology both as… Read more →

Diatomite is a fine-grained, siliceous sedimentary rock composed predominantly of the amorphous silica (opal-A) skeletal remains of diatoms, which are microscopic single-celled algae (class Bacillariophyceae) that… Read more →