Page 348 - Geology and Geochemistry of Oil and Gas

GLOSSARY 309
Drilling mud Fluid composed of water or oil, clays, chemicals,
and weighting materials used to lubricate the bit
and to move cuttings out of the hole. Syn:
Drilling fluid.
Drilling program Plan for assembling all the personnel, equipment, and
supplies for drilling and completing a well.
Drill pipe Heavy seamless tubing used to rotate the bit and
circulate the drilling mud.
Drill ship Vessel especially designed for offshore drilling
operations.
Drillstem test (DST) Drillstem test employs equipment, which allows a well
to flow for a short period of time, gathering.
information on reservoir fluids and pressure and the
ability of the reservoir to produce fluids.
Drillstring A long continuous string of tubular goods of
tubing, drill collars, bit, and subsurface tool. Syn:
Drillstem.
Drive mechanism The natural force present in a reservoir which causes
the fluid to move toward the wellbore; the action of
one fluid pushing another. Drive mechanism includes
water drive, gas cap expansion, solution gas drive,
gravity drainage, and combination drive.
Dry gas Natural gas consisting principally of methane and
devoid of readily condensable constituents such as
gasoline. Cf: Wet gas.
Dry hole A well that fails to produce oil or gas.
Duricrust General term for a hard crust (carbonate, silica,
ferruginous, or aluminous) on the surface of land or
as a replacive layer in the upper horizons of soils.

E
Economic geology The study and analysis of geologic bodies and
materials (systems) that can be utilized profitably by
man, including fuels, metals, nonmetallic minerals,
and water; the application of geologic knowledge and
theory to the search for and the understanding of
mineral deposits.
Edgewater Water around the edge of a reservoir — water presses
inward.
Effective permeability A measure of the ability of the porous medium to
transmit a particular fluid at the existing saturation,
which is normally less than 100%.
Effective porosity The percentage of interconnected pores in the rock
bulk volume that allow the passage of fluids through
the rock. See: Porosity.