Page 335 - Geology and Geochemistry of Oil and Gas

296 APPENDIX C

Aerobic Said of an organism that can live only in the presence
of free oxygen; also said of its activities. Cf:
Anaerobic, Anoxic.
Aggradation Vertical accumulation of deposits as a consequence of
sedimentation or biotic activities. Cf: Degradation.
Air drilling Use of compressed air instead of liquid as the
circulation medium in rotary drilling. See also: Gas
drilling.
Algorithm A set of rules which specify a sequence of actions to
be taken to solve a mathematical problem. It
frequently involves repetition of an action.
Alkali Any strongly basic substance, such as a hydroxide or
carbonate of an alkali metal (e.g., sodium,
potassium). Plural: Alkalis. Adj: Alkaline.
Alkaline (soft) water Water containing not more than 60 ppm (60 mg/l) of
hardness-forming constituents (calcium and
magnesium) expressed as CaCO 3 equivalent. Cf: Hard
water.
Alkanes (or paraffins) Methane series derived from petroleum, with carbon
atoms arranged in a straight chain. It includes
methane, ethane, propane, butane, pentane, hexane,
and octane (C n H 2n+2 ).
Alkenes See: Olefins.
Alkylation The reaction of alkenes or olefins with branched-
chain alkane to form a branched, paraffinic
hydrocarbon with high anti-knock qualities.
Allochem Carbonate particle of either skeletal or non-skeletal
origin.
Allochthonous Sediments or rocks formed elsewhere than where they
are ultimately deposited; of foreign or introduced
origin. Syn: Allogenous.
Alluvial Pertaining to or composed of alluvium, or deposited
by a stream or running water.
Alluvial fan An outspread, gently slopping mass of alluvium
deposited by a stream, especially in an arid or
semiarid region where a stream issues from a narrow
canyon onto a plain or valley floor.
Alluvium A general term for detrital deposits made by streams
on river beds, flood plains, and alluvial fans;
especially a deposit of silt or silty clay laid down
during the time of flood.
Anaerobic Said of an organism that can live in the absence
of free oxygen; also said of its activities. Cf:
Aerobic.
Analogy Likeness in form of function but not in origin.