BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
Viscosity, Funnel - See Funnel Viscosity.
Viscous Flow - See Laminar Flow.
Volatile Matter - Normally gaseous products, except moisture, given off by a substance, such as gas
breaking out of live crude oil that has been added to a fluid. In distillation of drilling fluids, the
volatile matter is the water, oil, gas, etc. that is vaporized, leaving behind the total solids which can
consist of both dissolved and suspended solids
Wall Cake – Mud solids deposited on the wall of the wellbore opposite permeable formations in the
form of filter cake resulting from filtration of the liquid fraction of the fluid.
Wall Sticking - See Differential-Pressure Sticking.
Water-Base Fluid - Common conventional drilling fluids. Water is the suspending medium for
solids and is the continuous phase, whether or not oil is present.
Water Block - Reduction of the permeability of a formation caused by the invasion of water into the
pores (capillaries). The decrease in permeability can be caused by swelling of clays, thereby shutting
off the pores, or in some cases by a capillary block of the pores due to surface tension phenomena.
Water-In-Oil Emulsion - See Invert Oil-Emulsion Fluid.
Water Loss - See Fluid Loss.
Weight - In fluid terminology, this refers to the density of a drilling fluid. This is normally expressed
in lb m /gal, lb m /ft 3 , or kg/m 3 .
Weight Material - Any of the high specific gravity materials used to increase the density of drilling
fluids. This material is most commonly barite but can be galena, etc. In special applications,
limestone (CaCO 3 ) also called a weight material.
Well Logging - See Electric Logging and Fluid Logging.
Wetting - The adhesion of a liquid to the surface of a solid.
Wetting Agent - A substance or composition 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 well bore used for deflecting or for directional drilling.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-49