PETROLEUM
At surface
conditions these will condense out of the gas to form natural gas condensate, often
shortened to condensate. Condensate resembles petrol in appearance and is similar in
composition to some volatile light crude oils.
The proportion of light hydrocarbons in the petroleum mixture varies greatly among
different oil fields, ranging from as much as 97 percent by weight in the lighter oils to as
little as 50 percent in the heavier oils and bitumens.
The hydrocarbons in crude oil are mostly alkanes, cycloalkanes and various aromatic
hydrocarbons while the other organic compounds contain nitrogen, oxygen and sulfur,
and trace amounts of metals such as iron, nickel, copper and vanadium. The exact
molecular composition varies widely from formation to formation but the proportion of
chemical elements vary over fairly narrow limits as follows:
Composition by weight
Element Percent range
Carbon 83 to 87%
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