Page 517 - Practical Well Planning and Drilling Manual

Appendix NEW! revised 11/00/bc 1/30/01 3:30 PM Page 493

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Glossary

and chemistry; water would be a gas at normal temperatures if the
polarity of the molecules didn’t tend to hold the molecules together.
Polarity also effects attractions with other, different polar molecules,
including clays (which have different electrostatic charges on the
faces and edges of the crystals) and polymers. Water also dissolves
some ionic compounds by attraction due to its polarity.

Polished bore receptacle. A close tolerance bore at the top of a liner;
may be used to stab in with a seal assembly, e.g., as part of a mono-
bore completion.

Porosity. The amount of void space in a formation rock usually
expressed as percent voids per bulk volume. Absolute porosity refers
to the total amount of pore space in a rock, regardless of whether or
not that space is accessible to fluid penetration. Effective porosity
refers to the amount of connected pore spaces, i.e., the space avail-
able to fluid penetration. See also Permeability.

Precipitate. Material that separates out of solution or slurry as a
solid. Precipitation of solids in a drilling fluid may follow flocculation
or coagulation, such as the dispersed red bed clays upon addition of a
flocculation agent to the fluid.

Pressure Surge. A sudden, usually short duration increase in pres-
sure. When pipe or casing is run into a hole too rapidly, an increase
in the hydrostatic pressure results, which may be great enough to cre-
ate lost circulation.

Pressure-Drop Loss. The pressure lost in a pipeline or annulus due
to the velocity of the liquid in the pipeline, the properties of the fluid,
the condition of the pipe wall, and the alignment of the pipe. In cer-
tain mud-mixing systems, the loss of head can be substantial.

Prime Mover. As applied to oil well drilling, this is the diesel drive,
electric motor, or internal combustion engine which is the source of
power for the drilling rig.

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