BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
Whole Mud Dilution - A dilution process which involves selective dumping of the active system
(such as sand traps and “bottoms up” mud) and replacement of the lost volume with fresh mud. This
process has proved economical with inhibitive water-base systems and is the only method that
actually removes colloidal size particles. Water dilution of the mud recovered from the
aforementioned circumstances to reduce low gravity solids concentration, does not remove the
undesirable solids which remain in the mud and require additional chemical treatment.
Wildcat - A well in unproved territory,
Workover Fluid - Any type of fluid used in the workover operation of a well.
Yield - A term used to define the quality of a clay by describing the number of barrels of a given
centipoise slurry that can be made from a ton of the clay. Based on the yield, clays are classified as
high-, medium-, low-yield bentonite, etc. types of clays.
Yield Point - In drilling-fluid technology, yield point means yield value. Of the two terms, yield
point is by far the most commonly used expression. See Yield Value.
Yield Value - The yield value (commonly called "yield point") is the resistance to initial flow, or
represents the stress required to start fluid movement. This resistance is due to electrical charges
located on or near the surfaces of the particles. The values of the yield point and thixotropy,
respectively, are measurements of the same fluid properties under dynamic and static states. The
Bingham yield value, reported in Ib/l00 sq ft, is determined by the direct-indicating viscometer by
subtracting the plastic viscosity from the 300-rpm reading.
Zero-Zero Gel - A condition wherein the drilling fluid fails to form measurable gels during a
quiescent time interval (usually 10 minutes).
Zeta Potential - Electrokinetic potential of a particle as determined by its electrophoretic mobility.
This electrical potential causes colloidal particles to repel each other and stay in suspension.
Zinc Chloride - ZnCI 2 . A very soluble salt used to increase the density of water to points more than
double that of water. Normally added to a system first saturated with calcium chloride.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-50