Page 381 - Geology and Geochemistry of Oil and Gas

342 APPENDIX C

known reflection. The reflectance of vitrinite is
a
o
determined in immersion oil (R ) and also in air (R ).
Vug A small cavern in a rock, larger than a pore.
W
Wackestone A mud-supported carbonate rock with greater than
10% particles.
Water and sediment Sample of oil taken for obtaining the water and
sample sediment content, usually by centrifuging.
Water-base mud A drilling mud in which the continuous phase is
water.
Water block A reduction in the permeability of a formation caused
by the invasion of water into the pores.
Water cut Percentage (by volume) of water associated with the
produced oil.
Water drive The reservoir-drive mechanism in which oil is
produced by the expansion of the underlying or edge
water (as a part of aquifer), which forces the oil into
the wellbore.
Waterflooding A method of improved recovery in which water is
injected into the reservoir through the special
injection wells to remove additional quantities of oil
that have been left behind after primary recovery.
Weathering The destructive physical and/or chemical processes
constituting that part of erosion whereby earthy and
rocky material on exposure to atmospheric agents at
or near the Earth’s surface are changed in character
(color, texture, composition, firmness, or form), with
little or no transport of the loosened or altered
material.
Weight indicator Device that constantly measures the weight of the
drillstring on a drilling rig.
Well completion The activities and methods of preparing a well for the
production of oil and gas or for other purposes, such
as injection; the method by which one or more flow
paths for hydrocarbons are established between the
reservoir and the surface.
Wet gas A natural gas containing liquid hydrocarbons. Cf:
Dry gas.
Wettability The ability of a liquid to form a coherent film on a
solid rock surface, due to the dominance of molecular
attraction between the liquid and the solid surface
over the cohesive force of the liquid itself.
Wildcat A well drilled in an area where no oil or gas
production exists.