Page 343 - Shale Shakers Drilling Fluid Systems

GLOSSARY 325

Squeeze A procedure whereby slurries of cement, drilling fluid, gunk plug, and so
forth, are forced into the formation by pumping into the hole while main-
taining a backpressure. This is usually achieved by closing the blowout
preventers or by using a retrievable downhole packer.

Squirrel Cage Motor An induction motor that gets its name from the rotor assembly that re-
sembles a squirrel cage. The cage consists of rotor bars secured at each
end to the shorting rings. An induction motor is one in which there is
no physical electrical connection to the rotor. Current in the rotor is in-
duced by the magnetic field of the stator.

Stability Meter An instrument to measure the breakdown voltage of oil-based drilling
fluids. This gives an indication of the emulsion stability.

Stacking a Rig Storing a drilling rig once a job is completed and the rig is to be with-
drawn from service for a period of time.

Starch A group of carbohydrates occurring in plant cells. Starch is specially pro-
cessed (pre-gelatinized) for use in drilling fluids to reduce the filtration
rate and, occasionally, to increase the viscosity. Without the proper pre-
servative, starch can ferment.

Static Not moving, or at rest. Opposite of dynamic. See.- Quiescence.

Stearate Salt of stearic acid, which is a saturated, 18-carbon fatty acid. Certain
compounds, such as aluminum stearate, calcium stearate, and zinc stear-
ate, have been used in drilling fluids for one or more purposes such as
a defoamer, lubrication, air drilling in which a small amount of water is
encountered, and so forth.

Stirrer See: Agitator, Mechanical Agitator.

Stokes Law Stokes Law states that the terminal settling velocity of a spherical par-
ticle is proportional to the square of the particle diameter, the accel-
eration of gravity, and the density difference between the density of
the particle and the density of the liquid medium; and the terminal
settling velocity is inversely proportional to the viscosity of the liquid
medium.

2 6
V T = [gD p (p s -p L )(10- )] / 116p

where V T = Terminal settling velocity, in inches/second
D p = Particle diameter, in microns
3
p s = Density of the solids, in grams/cm
3
P L = Density of the liquid, in grams/cm
u = Viscosity of the feed slurry, in centipoise

Stormer Viscometer A rotational shear viscometer used for measuring the viscosity and gel
strength of drilling fluids. This instrument has been largely replaced by
the direct indicating viscometer.

Streaming Potential The electrokinetic portion of the spontaneous potential (SP) electric-log
curve, which can be significantly influenced by the characteristics of the
filtrate and filter cake of the drilling fluid.

Streamline Flow See: Laminar Flow.