PROPERTIES OF BLACK OILS - Petroleum Reservoir Fluid Property Correlations - page 38

Table 3-2. Average errors in estimates of solution gas-oil ratio at bubblepoint pressure from field
data for this study are within expected experimental error.

Predicted solution gas-oil ratios from field data
ARE, % AARE, %
Valko-McCain (2003) equations (3.2) and (3.1) 0.0 5.2
Valko-McCain (2003) equation (3.3) 0.0 9.9
Rollins et al. (1990) a 9.9 11.8
Hanafy et al. (SPE 37295, 1997) b * 17.1 19.8
a Rollins, J.B., McCain, W.D., Jr., and Creeger, J.T. “Estimation of Solution GOR of Black Oils.” Journal of Petroleum Technology . Vol. 42
(January 1990) 92-94. Transactions . AIME. Vol. 289. b Hanafy, H.H., Macary, S.M., El Nady, Y.M., Bayomi, A.A., and El Batanony, M.H.
“Empirical PVT Correlations Applied to Egyptian Crude Oils Exemplify Significance of Using Regional Correlations.” Paper SPE 37295.
Presented at the SPE International Symposium on Oilfield Chemistry, Houston (1997). * Author restricted the correlation to a specific
geographical area.

Correlation

The data of table 3-1 were sorted according to separator pressures,
separator temperatures, and separator producing gas-oil ratios to
determine if the results of equations (3.1) and (3.2) are valid across
the data set. The results, shown in table 3-3, seem to be consistent
throughout the ranges of separator conditions and producing gas-oil
ratios normally expected in the oil field.

Table 3-3. The solution gas-oil ratios at bubblepoint pressures from field data predicted with
equations (3.1) and (3.2) are consistent across the data set.
Data set

Number of lines of data ARE, % AARE, %

All data 881 0.0 5.2

p SP ≤ 50 psig 359 -0.4 4.3

50 psig < p SP ≤ 100 psig 291 -1.9 5.0

p SP > 100 psig 231 3.0 6.9

T SP ≤ 80ºF 472 1.0 5.3

T SP > 80ºF 409 -1.2 5.1

R SP ≤ 300 scf/STB 294 1.3 9.6

300 scf/STB < R SP ≤ 700 scf/STB 287 -0.8 3.8

R SP > 700 scf/STB 300 -0.5 2.1

Weighted-average specific gravities of surface gases
Weighted-average surface-gas specific gravities may be calculated
with equation (3.4).

(3.4)

A method of estimating the stock-tank producing gas-oil ratio,
R ST , was given as equation (3.2). Unfortunately, the specific gravity