Page 350 - Shale Shakers Drilling Fluid Systems

332 SHALE SHAKERS AND DRILLING FLUID SYSTEMS

Well Logging See: Electric Logging, Mud Logging.

Wetting The adhesion of a liquid to the surface of a solid.

Wetting Agent A substance which, when added to a liquid, increases the spreading of
the liquid on a surface or the penetration of the liquid into a material.

Whipstock A device inserted in a wellbore that causes the drill bit to exit the estab-
lished path of the existing wellbore. The whipstock is the tool used for
the initiation of directional drilling.
Wildcat A well in unproved territory.

Windage Loss (1) The resisting power of air, or air friction, acting against a rapidly
rotating armature or cooling fan to create a power loss. (2) The resisting
power of air, or air friction, against the rotating bowl of a centrifuge.

Wire Cloth Screen cloth of woven wire. See.- Screen Cloth.

Working Pressure (WP) The maximum pressure to which equipment should be exposed in order
to comply with the manufacturer's warranty and to be within industry
codes and safety standards.
Workover Fluid Any type of fluid used in the work-over operation of a well.

Yield A term used to define the quality of a clay by describing the number of
barrels of a given viscosity (usually 15 cp) slurry that can be made from
a ton of the clay. Based on the yield, clays are classified as bentonite,
high-yield, low-yield, and so forth. Not related to yield point as described
below. See.- API Bulletin RP 13B.
Yield Point (1) A term derived from a direct-reading viscometer (Fann V.G. or equiva-
lent) based on subtracting the plastic viscosity from the 300 RPM read-
x
ing. (2) An extrapolated shear stress at zero shear rate created by as-
suming a linear relationship between shear stress and shear rate and
determining the intercept on the shear stress axis. The linear relation-
ship between shear stress and shear rate which results in a yield point
is called a Bingham Plastic Model. See: Viscosity, Plastic Viscosity, API
Bulletin RP-13B.

Yield Value See.- Yield Point.

Zero-Zero Gels A condition wherein the drilling fluid fails to form measurable gels dur-
ing a quiescent time interval (usually 10 minutes). The measurements of
gel are made with a direct-reading viscometer at intervals of 10 seconds
and 10 minutes. See: Progressive Gel, Flat Gel.

Zeta Potential The electro-kinetic potential of a particle as determined by its electro-
phoretic mobility. This electric potential causes colloidal particles to re-
pel each other and remain suspended.
Zinc Bromide ZnBr 2. A very soluble salt used to increase the density of water or brine
to more than double that of water. Normally added to calcium chloride/
calcium bromide mixed brines.