A hydrocarbon mixture classified as black oil is liquid at reservoir conditions, which are, by definition, far from the critical region of the phase envelope. At standard conditions, it shows relatively low initial gas-oil ratio (GOR).
Black oils have been the most commonly developed oil reservoir fluid type.
Some basic parameters of a black oil are:
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GOR < 1,000 scf/STB
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Density less than 45 API
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Reservoir Temperatures < 250 oF
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Oil FVF < 2.00 (low shrinkage oil)
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Dark green to black in color
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C7+ composition > 30%
See Also:
Reference:
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M. Barrufet, Texas A&M PETE 310 Reservoir Fluids Course Notes: Three & Multicomponent Mixtures, 2019.
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T. A. Blasingame, Texas A&M PETE 613 Natural Gas Engineering Course Notes, 2106