Collective term for oil, condensate and natural gas and their mixtures, normally encountered in subsurface reservoirs.
Its composition is dominated by pure hydrocarbons (usually Alkanes, Naphthenes, Aromatics, Asphaltics) and may also include the other organic and inorganic chemical substances (like carbon dioxide, nitrogen, hydrogen sulfide, helium etc.)
See Also
Petroleum Industry / Upstream / Subsurface E&P Disciplines / Petroleum Geology / Petroleum Reservoir Fluids