Alkenes (olefins) – unsaturated hydrocarbons consisting only of carbon and hydrogen and containing one or more double bonds. General formula is CnH2n. They rarely occur in «normal» petroleums (oils); higher concentrations of these compounds are integral components of petroleums (oils) generated by pyrolysis of petroleum (oil) shales.
Alkylation – a chemical reaction in which propylene and butylenes are reacted with isobutylene resulting in isoheptane and isooctane (alkylates) with a high octane number.
API standards - (API – American Petroleum Institute), generally accepted standards in the petroleum industry for drilling tools, casing pipes, tubing, extraction pumps etc. The measuring units in use are foot (ft) and inch (in) for length, pound (lb) for weight, pound per square inch (psi) for pressure etc. For example, a standard 12Ľ" bit has a diameter of 311, 2 mm, standard 9⅝" casing has a calibre of 244,5 mm, standard 4˝" drilling pipe has a calibre of 139,7 mm and so on.
API-weight – American Petroleum Institute expresses density of petroleum (oil) in API degrees. API-weight = 141, 5/spec. mass – 131, 5. Oil density expressed in 0API is generally accepted and is used for determining the price of oil in the world market. Light crude oil> 31, 1 0API, medium-gravity crude oil 22,3 to 31,1 0API, heavy crude oil 10 to 22,3 0API, extra heavy crude oil < 10 0API.
Asphalt - natural: mixture of degassed oil (bitumen) and solid particles of rocks; artificial: mixture of bitumen produced by refining oil/petroleum and stone mixtures for cementing roads surfaces (asphalting).
Asphalt/pitch/bitumen – old name for oil/petroleum which freely seeps to the surface.
Asphaltenes – complex mixture of big organic molecules, mostly of aromatic structure enriched with heteroatoms. Asphaltenes are an integral part of oil/petroleum and bitumen. They are the result of diagenesis and metagenesis, but in oil/petroleum reservoirs they are the by-product of cracking. An asphaltene molecule is very similar to a kerogen molecule in structure and size and has low melting properties.
Associated-dissolved gas/petroleum gas – natural gas dissolved in well conditions in petroleum or separated in a well above petroelum in a gas cap.
Atmospheric distillation - distillation of crude oil in a plant which operates approximately under atmospheric pressure (pressure of the environment). It is also called primary distillation.