BAKER HUGHES - Drilling Fluids Reference Manual

GLOSSARY OF TERMS
hole-cleaning capacity and cuttings lifting. Carrying capacity is determined principally by the
annular velocity, hole angle and flow profile of the drilling, but is also affected by mud density,
cuttings size and pipe position and movement.
Cation - The positively charged particle in the solution of an electrolyte. Which under the influence
of an electrical potential, moves toward the anode (negative electrode). Examples are: Na + , H + , NH 4 + ,
Ca ++ , Mg ++ , Al +++ .
Cation-Exchange Capacity (CEC) - The quantity of positively charged ions (cations) that a clay
mineral or similar material can accommodate on its negatively charged surface, expressed as million
equivalent per 100 g, or more commonly as milliequivalent (meq) per 100 g. Clays are
aluminosilicates in which some of the aluminum and silicon ions have been replaced by elements
with different valence, or charge. For example, aluminum (Al +++ ) may be replaced by iron (Fe ++ ) or
magnesium (Mg ++ ), leading to a net negative charge. This charge attracts cations when the clay is
immersed in an electrolyte such as salty water and causes an electrical double layer. The
cation-exchange capacity (CEC) is often expressed in terms of its contribution per unit pore volume,
Q v See Methylene Blue Capacity.
Caustic or Caustic Soda - See Sodium Hydroxide.
Cave-In - See Sloughing. Cave-in is a severe form of wellbore instability where as the formation
falls into the annulus from the wellbore wall.
Cavernous Formation - A formation having voluminous voids, usually the result of dissolution by
formation waters which or may not be still present.
cc or Cubic Centimeter - A metric-system unit for the measure of volume. It is essentially equal to
the milliliter and commonly used interchangeably. One cubic centimeter of water at room
temperature weighs approximately 1 g.
Cement - A mixture of calcium aluminates and silicates made by combining lime and clay while
heating. Slaked cement contains about 62.5 percent calcium hydroxide, which is the major source of
trouble when cement contaminates fluid.
Centipoise (Cp) - A unit of viscosity equal to 0.01 Poise. Poise equals 1 g per meter-second. and a
centipoises is 1 g per centimeter-second. The viscosity of water at 20°C is 1.005 cp (1 cp = 0.000672
lb/ft-sec).
Centrifuge - A device for the mechanical separation of high-specific gravity solids from a drilling
fluid. Normal application is on weighted fluids to recover weight material and discard drill solids.
The centrifuge uses high-speed mechanical rotation to achieve this separation as distinguished from
BAKER HUGHES DRILLING FLUIDS
REFERENCE MANUAL
REVISION 2006 15-9