Page 335 - Shale Shakers Drilling Fluid Systems

GLOSSARY 317

Plug Flow The movement of material as a unit without shearing within the mass.
Plug flow is the first type of flow exhibited by a plastic fluid after over-
coming the initial force required to produce flow. See.- Bingham Model,
Newtonian Fluid, Laminar Flow, Turbulent Flow.

Plugging The wedging or jamming of openings in a screening surface by near-size
particles, preventing passage of undersize particles and leading to blind-
ing of the screen. See: Blinding, Coating.

Pm The phenolphthalein alkalinity of drilling fluid is reported as the number
of milliliters of 0.02 normal (N/50) sulfuric acid required per milliliter of
drilling fluid for the pH to reach the phenolphthalein end point of 8.3.

Polyelectrolytes (Polymers) Long chain organic molecules possessing ionizable sites that,
when dissolved in water, become charges.

Polymer A substance formed when two or more molecules of the same kind are
linked end to end to another compound having the same elements in the
same proportion, but higher molecular weight and different physical prop-
erties (e.g., paraformaldehyde). Polymers are used in drilling fluids to
maintain viscosity and control fluid loss. See.- Co-polymer.

Polymer Drilling Fluid A drilling fluid to which polymers have been added to increase the low-
shear-rate viscosity.

Polyurethane A high-performance, elastomer polymer used in construction of hydro-
cyclones for its unique combination of physical properties, especially
abrasion, toughness, and resiliency.

Pool (1) The reservoir or pond of fluid, or slurry, formed inside the wall of
hydrocyclones and centrifuges and where classification or separation of
solids occurs due to the settling effect of centrifugal force. (2) The reser-
voir or pond of fluid which can form on the feed end of an uphill shaker
basket (a shaker basket with a positive deck angle).

Poor Boy Degasser See: Gas Buster, Mud/Gas Separator.

Porosity The volume of void space in a formation rock, usually expressed as per-
cent void volume per bulk volume.

Ports The openings in a centrifuge for entry or exit of materials. Usually applied
in connection with a descriptive term (i.e., feed ports, overflow ports, etc.).

Positive Deck Angle The angle of adjustment to a screen deck, which causes the screened
solids to travel "uphill" to reach the discharge end of the screen surface.
This "uphill" travel increases the fluid throughput of a screen but also
shortens the life of a screen. See.- Negative Deck Angle.

Possum Belly The compartment on a shale shaker into which the flow line discharges,
and from which the drilling fluid is either fed to the screens or to a suc-
ceeding tank. See: Back Tank, Mud Box.

Potassium One of the alkali metal elements with a valence of 1 and an atomic
weight of approximately 39. Potassium compounds, most commonly
potassium hydroxide (KOH), are sometimes added to drilling fluids to
impart special properties, usually inhibition.