Page 309 - Shale Shakers Drilling Fluid Systems

GLOSSARY 291

essentially equal to the milliliter and commonly used interchangeably. One
cubic centimeter of water at room temperature weighs approximately 1 gram.

Cut Point Cut point curves are developed by dividing the mass of solids in a cer-
tain size range removed by the total mass of solids in that size range
that enters the separation device. A cut point usually refers to the size
particle that has a 50% chance of being discarded. See.- Median Cut.

Cutt Points Pronounced "Koot." The equivalent spherical diameters corresponding to
the ellipsoidal volume distribution of a screen's opening sizes, as deter-
mined by image analysis. See.- API Bulletin RP 13E.

Cuttings The pieces of formation dislodged by the bit and brought to the surface
in the drilling fluid. Field practice is to refer to all solids removed by the
shaker screen as "cuttings," although some can be sloughed material from
the wall of the borehole. See: Drilled Solids, Low-Gravity Solids, Samples.

Cyclone A device for the separation of solid particles from a drilling fluid. The
most common cyclones used for solids separation are a desander or
desilter. In a cyclone, fluid is pumped tangentially into a cone, and the
fluid rotation provides enough centrifugal force to separate particles by
mass weight. See: Desander, Desilter, Hydrocyclone, Hydroclone.

Cyclone Bottom See.- Apex, Apex Valve, Underflow Opening.
Darcy A unit of permeability. A porous medium has a permeability of 1 darcy
when a pressure of 1 atm on a sample 1 cm long and 1 sq cm in cross-
section will force a liquid of 1 cp viscosity through the sample at the rate
of 1 cc per sec. See.- Millidarcy, Permeability.

Decanter See.- Decanting Centrifuge.

Decanting Centrifuge A centrifuge that removes solids from the feed slurry and discharges them
as damp underflow. Ultrafine colloidal solids are discharged with the liq-
uid overflow. The decanting centrifuge has an internal auger that moves
the solids, which have settled to the bowl walls, out of a pool of liquid
and to the underflow. See: Centrifuge.

Deck The screening surface in a shale shaker basket.
Deflocculant Chemical that promotes deflocculation. See: Thinner.

Deflocculation (1) The process of thinning the drilling fluid by bonding with (neutraliz-
ing or covering) the positive electrical charges on drilling fluid additives
to prevent one particle of drilling fluid to be attracted to another par-
ticle. (2) Breakup of floes of gel structures by use of a thinner.

Defoamer Any substance used to reduce or eliminate foam by reducing the surface
tension of a liquid. See.- Antifoam.
Degasser A device that removes entrained gas from a drilling fluid, especially the
very small bubbles that do not float readily in viscous drilling fluid.

Dehydration Removal of free or combined water from a compound.

Deliquescence The liquification of a solid substance due to the solution of the solid by
absorption of moisture from the air (e.g., calcium chloride deliquesces in
humid air).