Page 340 - Shale Shakers Drilling Fluid Systems

322 SHALE SHAKERS AND DRILLING FLUID SYSTEMS

Self-Lubricating Units that provide their own means of lubrication.

Separation Potential The size distribution of equivalent spherical volumes calculated by de-
termining the equivalent ellipsoidal volumes of at least 1,500 openings
in a screen as determined by image analysis. Also called the "cutt" point
distribution. See: Cutt Point.

Settling Velocity The velocity a particle achieves in a given fluid when gravity forces equal
friction forces of the moving particle (i.e., when the particle achieves its
maximum velocity).

Shale Stone of widely varying hardness, color, and compaction that is formed
of clay-sized grains (less than two microns). See.- Natural Clay.

Shale Shaker Any of several mechanical devices for removing cuttings and other large
solids from drilling fluid. Common examples are the vibrating screen, ro-
tating cylindrical screen, and the like.

Sharpness Of Cut or The slope of a straight line drawn between the solids separated at the
"Separation" 84% point and the 16% point on a graph of the percent solids separated
versus particle size. The more vertical the slope, the sharper the cut.

Shear Rate The change of velocity with respect to the distance perpendicular to the
velocity changes. See: Rate of Shear.

Shear Stress The force per unit of an area parallel to the force that tends to slide one
surface past another. See: Viscosity, Bingham Model, Plastic Viscosity,
Yield Point, Gel Strength.

Shear Thinning Opposite of dilatant. The apparent viscosity decreases instantaneously
with increasing shear rate. See.- Apparent Viscosity, Viscosity, Bingham
Model, Plastic Viscosity, Yield Point, Gel Strength.

Short-Circuiting A hydraulic condition existing in parts of the tank basin, reservoir, or
hydrocyclone where the time of travel of liquid/solids is less than the
normal flow-through time. For instance, if the surface tanks contain very
viscous fluid but the returns from the flow line have a very low viscos-
ity; the flow line returns might tend to channel across the top of the sur-
face system toward the pump suction. In this case, the flow line returns
would be "short-circuiting" or bypassing the solids separation equipment.
In hydroclones, separable solids that pass directly from the feed inlet to
the vortex finder, without passing through the cone section, have "short-
circuited" the hydrocyclone processing system.

Shute In a woven cloth, the direction of the wires running perpendicular to the
loom or running across the roll of cloth. In wire cloth production, these
are the short or transverse wires. See: Weft.

Sieve See.- Testing Sieve.

Sieve Analysis The mass classification of solid particles passing through, or retained on,
a sequence of screens of increasing mesh count. Analysis may be by wet
or dry methods. See.- Partical Size Distribution.

Silt Materials whose particle size generally falls between 2 and 74 microns.
A certain portion of dispersed clays and barite falls into this particle size
range, as well as drilled solids.