Page 354 - Geology and Geochemistry of Oil and Gas

GLOSSARY 315
Frasch process Process to remove sulfur from a sulfur-bearing crude
oil, by using cupric acid developed by Herman
Frasch.
Free gas Gas present in a vapor state.
Frequency distribution A systematic arrangement of statistical data (such as
graphic or tabular display of the number of
observations of a variable) that exhibits the division
of the values of the variable into mutually exclusive
(but closely related), usually ranked, and exhaustive
discrete categories or classes. It indicates the
frequencies or relative frequencies that correspond to
each of the categories or classes.
Funnel viscosity Viscosity as measured by the Marsh funnel, based on
3
the number of seconds it takes for 1,000 cm of
drilling fluid to flow through the funnel.
Fuzzy set theory A form of informal set theory in which belonging
is replaced by an index of membership between
0 and 1.
G
Gamma-ray log Measurement of the natural formation radioactivity
to determine lithology.
Gas cap Free natural gas above the crude oil sometimes
present in the reservoir.
Gas cap expansion Expansion of the gas cap upon reduction of reservoir
pressure; it forces reservoir fluids toward the wellbore.
Gas drive The use of the energy that arises from the expansion
of compressed gas in a reservoir to move crude oil to a
wellbore.
Gas drilling Use of compressed natural gas instead of liquid as the
circulation medium in rotary drilling. See also: Air
drilling.
Gas lift Injection of gas into the well to lift fluids out of the
wellbore.
Gas-oil ratio (GOR) A measure of the volume of gas produced with oil,
3
3
expressed in ft /barrel or m /ton.
Gel strength A measure of the ability of colloidal dispersion to
develop and retain a gel form, based on it resistance
to shear.
Geochemistry (a) The study of the distribution and amounts of the
chemical elements in minerals, ores, rocks, soils,
water, and the atmosphere. (b) The study of the
circulation of the elements in nature, on the basis of
the properties of their atoms and ions. (c) The study