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D, Darcy
A non-SI unit of permeability, abbreviated D, and approximately = 1μm2.

Dawsonite
A mineral: dihydroxide sodium aluminium carbonate.

Deep saline aquifer
A deep underground rock formation composed of permeable materials and containing highly saline fluids.

Deep sea
The sea below 1,000m depth.

Default emissions factor
An approximate emission factor that may be used in the absence of precise or measured values of an Emissions Factor.

Demonstration phase
Demonstration phase means that the technology is implemented in a pilot project or on a small scale, but not yet economically feasible at full scale.

Dense phase
A gas compressed to a density approaching that of the liquid.

Dense fluid
A gas compressed to a density approaching that of the liquid.

Depleted
Of a reservoir: one where production is significantly reduced.

Diagenesis
Processes that cause changes in sediment after it has been deposited and buried under another layer.

DIC
Dissolved Inorganic Carbon.

Dip
In geology, the angle below the horizontal taken by rock strata.

Discharge
The amount of water issuing from a spring or in a stream that passes a specific point in a given period of time.

Discordant sequence
In geology, sequence of rock strata that is markedly different from strata above or below.

Dolomite
A magnesium-rich carbonate sedimentary rock. Also, a magnesium-rich carbonate mineral (CaMgCO3).

Double-grip packer
A device used to seal a drill string equipped with two gripping mechanisms.

Down-hole log
Record of conditions in a borehole.

Drill cuttings
The solid particles recovered during the drilling of a well.

Drill string
The assembly of drilling rods that leads from the surface to the drilling tool.

Drive
Fluid flow created in formations by pressure differences arising from borehole operations.

Dry ice
Solid carbon dioxide.

Dynamic miscibility
The attainment of mixing following the prolonged injection of gas into an oilfield.