PROPERTIES OF BLACK OILS - Petroleum Reservoir Fluid Property Correlations - page 37

where

(3.2b)

and

(3.2c)

n VAR n C0 n C1 n C2 n

1 lnp SP -8.005 2.7 -0.161

2 lnT SP 1.224 -0.5 0

3 API -1.587 0.0441 -2.29x10 -5

Equation (3.2) requires values of separator pressure and separator
temperature. Often this information is not available. If so, an option is
to use equation (3.3). 3

(3.3)

Evaluation of proposed correlation equations for solution gas-oil
ratios at bubblepoint pressures from field data
The available correlation equations for stock-tank gas-oil ratio have
been evaluated using the data set described in table 3-1. Most of the
data of table 3-1 were used in the preparation of both equation (3.2)
and equation (3.3).

Table 3-1. Separator/stock-tank data set for use in evaluating solution gas-oil ratio and weighted-
average surface-gas specific gravity correlation equations has a wide range of values of the
independent variables (881 lines of data from 881 reservoir fluid studies with worldwide origins).
Laboratory measurement Minimum Median Mean Maximum

Separator pressure, p SP , psig 12 80 130 950

Separator temperature, T SP , ºF 35 80 92 194

Stock-tank oil gravity, API , ºAPI 6.0 38.8 36.2 56.8

Separator gas-oil ratio, R SP , scf/STB 8 520 559 1,817

Stock-tank gas-oil ratio, R ST , scf/STB 2 54 70 527

Surface gas specific gravity, γ g 0.566 0.881 0.879 1.292

Separator gas specific gravity, γ gSP 0.561 0.815 0.837 1.237

0.581 1.285 1.256 1.598

Stock-tank gas specific gravity, γ gST

Evaluations of the published correlations for this property are given
in table 3-2.