Page 333 - Shale Shakers Drilling Fluid Systems

GLOSSARY 315

Particle A discrete unit of solid material that may consist of a single grain or of
any number of grains stuck- together.

Particle Size Particle diameter expressed in microns. See: ESD, Equivalent Spherical
Diameter.

Particle Size Distribution The volume classification of solid particles into each of the various size
ranges as a percentage of the total solids of all sizes in a fluid sample.

Parts Per Million The unit weight of solute per million unit weights of solution (solute plus
solvent), corresponding to weight percent. For example, the results of
standard API titration of chloride hardness are correctly expressed in
milligrams (mg) per liter, not in ppm. At low concentrations, mg/l is about
numerically equal to ppm. A correction for the solution specific gravity
or density in g/ml must be made as follows:

Ppm = [milligrams/liter] / Solution Density (grams/liter)

Weight % = [milligrams/liter] / [10,000 x Solution Density (grams/liter)!

Weight % = [Ppm] / [10,000]

Thus, 316,000 mg/l salt is commonly called 316,000 ppm or 31.6%, which
corrected should be 264,000 ppm and 26.4%, respectively. See: Ppm.

Pay Zone A formation that contains oil and/or gas in commercial quantities.

Penetration Rate The rate at which the drill bit penetrates the formation, usually expressed
in feet per hour or meters per hour. See: Rate of Penetration, ROP.

Peptization An increased flocculation of clays caused by the addition of electrolytes or
other chemical substances. See: Deflocculation Dispersion, High-Yield Clay.

Peptized Clay A clay to which an agent has been added to increase its initial yield. For
example, soda ash is frequently added to calcium montmorillonite clay
to increase the yield. See: High-Yield Clay.

Percent Open Area Ratio of the area of the screen openings to the total area of the screen
surface.

Percent Separated Curve A plot of mass distributions of solid sizes discarded from a solids sepa-
ration device divided by the mass distributions of each size of solids fed
to the device.

Perforated Cylinder A mechanical centrifugal separator in which the rotating element is a per-
Centrifuge forated cylinder (the rotor) inside of and concentric with an outer sta-
tionary cylindrical case.

Perforated Panel Screen A screen in which the backing plate used to provide support to the screen
cloths is a metal sheet with openings.

Perforated Plate Screen Shale shaker screens mounted on metal plates that have holes punched
through them.

Perforated Rotor The rotating inner cylinder of the perforated cylinder centrifuge. See:
Perforated Cylinder Centrifuge.