Oil and Gas Terms Beginning with “D” — Page 9

What Is a Drillship? A drillship is a ship-shaped mobile offshore drilling unit (MODU) equipped with a drilling derrick and a central through-hull opening called a moonpool, through which the drill string, marine riser,… Read more →

A drillstem test (DST) is a well test conducted while the drill string is still in the hole, before the well is cased and completed. By packing off a zone of interest with inflatable packers or mechanically set packers… Read more →

The combination of the drillpipe, the bottomhole assembly and any other tools used to make the drill bit turn at the bottom of the wellbore. Read more →

The water and heavy hydrocarbons that condense from the gas stream and accumulate in the lower points of the flowlines. Read more →

A device used to collect water and heavy hydrocarbons that drop out of a gas stream in a pipeline. Read more →

A drop ball is a precisely machined spherical object that is gravity-dropped or pump-circulated through wellbore tubulars to activate a downhole tool, sleeve, plug, or pressure-actuated mechanism by seating in a… Read more →

A drop bar (also called a sinker bar, go-devil, or bar) in wireline operations is a heavy, solid cylindrical weight made of steel or a dense alloy (typically 1-3/4 to 2-1/4 inch OD, 3-6 feet long, weighing 20-80 pounds)… Read more →

A drop sub (also called a dart sub, drop-in sub, or ball-drop sub) is a downhole tool that can be activated by dropping a ball, dart, or plug from the surface into the drill string or tubing string, allowing the dropped… Read more →

A drop-off gun is a type of perforating gun assembly designed to be released and left at the bottom of the wellbore after firing — the gun string falls to the bottom of the perforated interval or the rathole below the… Read more →

The failure of a channel or geophone to record a shot or shots in a seismicsurvey, which results in a loss of data. Read more →

A hygroscopic solid such as silica gel, calcium chloride [CaCl2] or other materials used in dry-bed dehydrators to absorb water and water vapor from a gas stream. Read more →

Dry combustion is an in-situ combustion (ISC) enhanced oil recovery (EOR) technique in which only air, or oxygen-enriched air, is injected into a heavy-oil or bitumen reservoir to ignite and sustain a moving combustion… Read more →

Dry forward combustion is the fundamental variant of in-situ combustion (ISC) enhanced oil recovery in which only air or oxygen-enriched air (without water) is injected into the reservoir through an ignition well to… Read more →

Dry gas is natural gas composed predominantly of methane with little or no heavier hydrocarbons (ethane, propane, butane, and pentane-plus) that would condense into liquid at normal pipeline conditions. The distinction… Read more →

A dry hole is a wellbore that has not encountered hydrocarbons in economically producible quantities — a well that may contain traces of oil or gas shows, intervals of saline formation water, or nothing but… Read more →

A treated oil that contains small amounts of basic sediments and water (BS&W). Dry oil is also called clean oil. Read more →

A subsurface rock that lacks contact with aquifers or meteoric water within the Earth. Read more →

A dry-bed dehydrator (also called a solid desiccant dehydrator) is a gas processing device that removes water and water vapor from a natural gas stream using two or more beds of solid desiccant materials such as silica… Read more →

A dual completion (also called a dual-string completion, selective dual completion, or commingled dual completion) is a well completion configuration in which two separate reservoir zones or pay intervals are produced… Read more →

A dual induction log (DIL) is a wireline resistivity logging tool that measures the electrical resistivity of the formation surrounding the wellbore at two different radial depths of investigation simultaneously,… Read more →

What Is the Dual-Water Model? The dual-water model is a petrophysical model for shaly sandstone reservoirs that accounts for the additional electrical conductivity contributed by clay minerals by treating the pore water… Read more →

A dual-porosityreservoir in which flow to the well occurs in both primary and secondary porosity systems. Read more →

What Is a Dual-Porosity Reservoir? Dual-porosity reservoir (also called a naturally fractured reservoir or double-porosity system ) is a reservoir containing two distinct and coupled pore systems: a primary matrix… Read more →

A dummy valve is a solid, ported-but-plugged or wholly blank gas-lift valve insert that is run into a side-pocket mandrel (SPM) on the production tubing string to mechanically isolate the tubing bore from the casing… Read more →

A dump bailer is a slim cylindrical wireline or slickline tool designed to carry a small, pre-measured volume of cement slurry, sand-laden gel, or similar setting material into a wellbore and release that material at a… Read more →

A duplex pump is a positive-displacement reciprocating pump with two cylinders (two pistons or plungers), each powered by a common crankshaft through connecting rods and crosshead assemblies, with each cylinder equipped… Read more →

(noun) An informal industry term for a dry hole — a well that fails to encounter commercially producible quantities of oil or gas and is subsequently plugged and abandoned. The term reflects the disappointment of… Read more →

A time-variant operation performed on seismic data. Normal moveout (NMO) is a dynamic correction. Read more →

A dynamic filter press is a laboratory instrument used in drilling fluid evaluation that measures the filtration rate and filter cake properties of drilling mud under simulated dynamic conditions — with the mud… Read more →

Dynamic filtration in drilling fluid engineering refers to the filtration of fluid through a permeable surface (the formation face or filter cake) while the fluid is in motion parallel to the filtration surface — in… Read more →