BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
Univalent – Monovalent - See Valence.
Valence or Valency - The valence is a number representing the combining power of an atom, i.e., the
number of electrons lost, gained, or shared by an atom in a compound. It is also a measure of the
number of hydrogen atoms with which an atom will combine or replace, e.g., an oxygen atom
combines with two hydrogens, hence has a valence of 2. Thus, there are mono-, di-, tri-, etc. valent
ions.
Valence Effect - In general, the higher the valence of an ion, the greater the loss of stability to
emulsions, colloidal suspensions, cross-linking etc. these polyvalent ions will impart.
Velocity - Time rate of motion in a given direction and sense. It is a measure of the fluid flow and
may be expressed in terms of linear velocity, mass velocity, volumetric velocity, etc. Velocity is one
of the factors which contribute to the carrying capacity of a drilling fluid.
Velocity, Critical - That velocity at the transitional point between laminar and turbulent types of
fluid flow. This point occurs in the transitional range of Reynolds numbers of approximately 2000 to
3000.
V-G Meter or Viscosity-Gravity Viscometer - The name commonly used for the direct-indicating
viscometer. See Viscometer.
Vibrating Screen - See Shale Shaker.
Viscometer - An apparatus to determine the viscosity of a fluid or suspension. Viscometers vary
considerably in design and methods of testing.
Viscometer, Direct- Indicating - Commonly called a.”V-G meter” The-instrument is a
rotational-type device powered by means of an electric motor or hand crank, and is used to determine
the apparent viscosity, plastic viscosity, yield point, and gel strengths of drilling fluids. The usual
speeds are 600 and 300 rpm. See API RP I3B for operational procedures.
Viscometer, Stormer - A rotational shear viscometer used for measuring the viscosity and gel
strength of drilling fluids. This instrument has been superseded by the direct-indicating viscometer.
Viscosimeter - See Viscometer.
Viscosity - The internal resistance offered by a fluid to flow. This phenomenon is attributable to the
attractions between molecules of a liquid, and is a measure of the combined effects of adhesion and
cohesion to the effects of suspended particles, and to the liquid environment. The greater this
resistance, the greater the viscosity. See Apparent Viscosity and Plastic Viscosity.
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-48