Page 366 - Geology and Geochemistry of Oil and Gas

GLOSSARY 327
Pay zone The zone of production where commercially
recoverable oil and/or gas are present, i.e., productive
or producing formation. Syn: Pay sand.
Pelagic Pertaining to open ocean water as an environment;
deep-sea sediments without terrigenous material
(either inorganic red clays or organic oozes).
Pellet A particle composed of fecal material. Partial syn:
Pelletoid, Peloid.
Peloid A cryptocrystalline carbonate particle of
unrecognizable origin, most likely a completely
micritized grain, less likely a fecal pellet. Partial syn:
Pellet.
Penecontemporaneous Contemporaneous with deposition. Syn:
Syndepositional.
Perforating Making holes in the casing (or liner), cement and
formation so that formation fluids can enter the
wellbore. There are three basic types of perforation:
mechanical, gun, and jet.
Periplatform Said of sediments or environments in deeper water
immediately seaward of carbonate platforms, atolls,
or banks.
Peritidal Inclusive term for supratidal and intertidal
environments, or in some definitions, supratidal,
intertidal, and upper subtidal environments.
Permeability The ability of a porous medium to transmit fluids.
3
Permeability is equal to one Darcy if 1 cm of fluid
2
flows through 1 cm of cross-section of rock per
second under a pressure gradient of 1 atm/cm, the
fluid viscosity being 1 cP. See also: Absolute
permeability, Effective permeability, and Relative
permeability.
Petroleum A naturally occurring complex of liquid
hydrocarbons that may contain varying amounts of
impurities (sulfur, nitrogen), which after distillation
yields a range of combustible fuels, petrochemicals,
and lubricants. Syn: Crude oil.
Petrophysics The physical properties of reservoir rocks and the
methods of their study.
pH The negative logarithm of the hydrogen ion
+
concentration in a solution, pH ¼ log 10 1/[H ].
The pH is measured on a scale of 0 to 14; a neutral
mediums (such as pure water) has pH of 7; pH47
indicate relative alkalinity; pHo7 indicates relative
acidity. Most pH values in natural systems lie in the
range of 4–9.