Page 364 - Geology and Geochemistry of Oil and Gas

GLOSSARY 325
mineralogy is constant) and inversion (crystal fabric
changes attending mineralogic conversions).
Neutron log Measurement of porosity; also valuable information
concerning rock composition and fluid content.
The logging tool bombards the formation with
neutrons.
Newtonian fluid A fluid in which the viscosity remains constant for all
rates of shear if constant conditions of temperature
and pressure are maintained. Most drilling fluids
behave as non-Newtonian fluids. Syn: Newtonian
flow.
Nuclear log Measurement of porosity, type of fluids and/or gas,
lithology, etc., by recording the nuclear properties of
the formation.

O
Occlusion In reference to porosity reduction as a typical
consequences of cementation or compaction.
Offlap Progressive offshore migration of the updip
terminations of sedimentary beds within a
comformable sequence of rocks. Cf: Onlap.
Oil See: Petroleum.
Oil and gas separator An item of production equipment used to separate
liquid components of the well stream from gaseous
elements. Separation is accomplished principally by
gravity, the heavier liquids falling to the bottom and
the gas rising to the top.
Oil-base mud A drilling or workover fluid in which oil is the
continuous phase and which contains about 2–5% of
water.
Oilfield The surface area overlaying an oil reservoir(s). The
term usually includes not only the surface area, but
also the reservoir, the wells, and the production
equipment.
Oil sample Small volume of oil drawn from a tank for testing;
includes bottom sample, composite sample, running
sample, spot sample, water, and sediment sample.
Oil sand Any porous stratum bearing oil.
Oil treater Equipment used to separate natural gas, BS&W, and
water from the oil by the use of heat. Syn: Heater-
treater.
Olefins Group of unsaturated hydrocarbons (one double
bond), such as ethylene (C 2n H 4n ).