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290 SHALE SHAKERS AND DRILLING FLUID SYSTEMS
Controlled Aggregation The condition in which the clay platelets are maintained stacked by a
polyvalent cation, such as calcium.
Conventional Drilling Fluid A drilling fluid containing essentially clay and water.
Conventional Mud See: Conventional Drilling Fluid.
Conventional Shale Shakers Usually refers to shale shakers that vibrate screens with a circular or
unbalanced elliptical motion. These shakers are usually limited to pro-
cessing drilling fluid through shale shaker screens up to 100 mesh.
Conveyance Movement of solids toward the discharge end of a shaker screen.
Conveyor A mechanical device for moving material from one place to another. In
a decanting centrifuge, this is a hollow hub fitted with flights rotating in
the same direction but at a different speed than the centrifuge bowl.
These flights are designed to move the coarse solids out of the bowl and
are part of the conveyor.
Co-polymer A substance formed when two or more substances polymerize at the
same time to yield a product, which is not a mixture of separate poly-
mers, but a complex substance having properties different from either of
the base polymers. Examples are polyvinyl acetate-maleic anyhdride co-
polymer (clay extender and selective flocculant), acrylamide-carboxylic
acid copolymer (total flocculant). See.- Polymer.
Corrosion A chemical degradation of a metal by oxygen in the presence of mois-
ture. An oxide is the by-product of corrosion.
Corrosion Inhibitor An agent which, when added to a system, slows down or prevents a
chemical reaction or corrosion. Corrosion inhibitors are widely used in
drilling and producing operations to prevent corrosion of metal equip-
ment exposed to hydrogen sulfide, carbon dioxide, oxygen, salt water, and
so forth. Common inhibitors added to drilling fluids are filming amines,
chromates, and oxygen scavengers.
Crater The formation of a large, funnel-shaped cavity at the top of a hole re-
sulting from either a blowout or from caving.
Creaming of Emulsions The settling or rising of particles from the dispersed phase of an emul-
sion as observed by a difference in color shading of the layers formed.
This separation can be either upward or downward, depending on the
relative densities of the continuous and dispersed phases.
Created Fractures Induced fractures by means of hydraulic or mechanical pressure exerted
in a formation by the drill string and/or circulating fluid.
Critical Velocity That velocity at the transitional point between laminar and turbulent types
of fluid flow. This point occurs in the transitional range of Reynolds num-
bers between approximately 2,000 to 3,000.
Crown The curvature of a screen deck or the difference in elevation between
its high and low points. See: Bow.
Cubic Centimeter (cc) A metric system unit for the measure of volume. A cube measuring 1 cm
3
on each side would have a volume of 1 cubic centimeter (cc, cm ). It is
