Page 96 - PVT Property Correlations

74 PVT Property Correlations

TABLE 4.5 Calculation of Reservoir Gas Specific Gravity from CGR for the
Two Example Fluids
Parameter Unit Sample 1 Sample 2
CGR STB/MMscf 69.81 15.7
Separator gas specific gravity (Air 5 1) 0.78 0.72
Stock-tank gravity API 43.2 45.2
Oil specific gravity (Water 5 1) 0.81 0.8
Molecular weight of stock-tank oil lbm/lbm mol 173.14 163.62
Reservoir gas specific gravity (Air 5 1) 0.997 0.770
CGR, condensate gas ratio.

TABLE 4.6 Calculation of Reservoir Gas Specific Gravity from Separator
Data for the Two Example Fluids
Parameter Unit Sample 1 Sample 2
Reservoir gas calculations 3 stages 2 stages
option practical practical

V eq scf/STB 1535.87 1167.06
G pa scf/STB- 940.31 619.93
gravity
Oil specific gravity (Water 5 1) 0.81 0.80
Reservoir gas specific gravity (Air 5 1) 1.02 0.77

are used to calculate the reservoir gas specific gravity for Samples 1 and 2,
respectively. Table 4.6 summarizes the important results of these calcula-
tions, and Table 4.7 compares the results of the reservoir gas specific gravity
calculated by the different approaches.

Problem 2—Calculation of Wet Gas z-Factor and Formation
Volume Factor

For the gas specific gravity obtained in Problem 1, calculate the gas z-factor
and gas formation volume factor at initial reservoir pressure and reservoir
temperature.