Page 367 - Geology and Geochemistry of Oil and Gas

328 APPENDIX C

Phreatic Zone below the water table in an unconfined
groundwater lens, or in an aquifer, where all the pores
are filled with water.
Pinch-out trap A petroleum trap formed by the thinning out of a
porous and permeable rock (e.g., sandstone) between
two layers of impermeable rock (e.g., shale). Syn:
Wedge-out trap.
Pinnacle reef An isolated, long (thick), spire or column-shaped reef.
Pisolite An accretionary carbonate particle, usually larger
than sand-size, composed of a particulate nucleus
surrounded by a cortex, generally laminated, of
precipitated calcium carbonate; term commonly used
for rocks containing pisoids or pisoliths. Syn: Pisolith,
Pisoid.
Planktonic In reference to pelagic organisms that float.
Plastic fluid A complex, non-Newtonian fluid in which the shear
force is not proportional to the shear rate. Most
drilling muds are plastic fluids. Syn: Plastic flow.
Plasticity The ability of a substance to be deformed without
rupturing.
Platform [drill] Working surface or deck of a drilling rig, e.g., an
immobile offshore structure from which development
wells are drilled and produced.
Platform [sed] A linear region of variable width of shallow-water
calcium carbonate deposition.
Play The extent of a petroleum-bearing formation, e.g., a
productive structure.
Playa A desiccated, vegetation-free, flat-floored area
commonly found in deserts, which represents a
former shallow desert-lake basin. Syn: Playa lake.
Plug and abandon (P&A) To place cement plugs into a borehole and abandon
it.
Point counter analysis A statistical method involving the estimation of the
frequency of occurrence of an object in a sample
(thin-section), determined by counting the number of
times that object occurs at specified intervals
throughout the sample. The analysis is commonly
made with an automatic point counter attached to an
optical microscope.
Polycyclic Pertaining to more than one cycle of formation.
Polygenetic Pertaining to an origin involving more than one
process of formation, or superimposed processes of
formation.
Polymer Compound having many repeated linked units. In
oilfield operations, various types of polymers are used