Page 95 - PVT Property Correlations

Wet Gases Chapter | 4 73

TABLE 4.4 Field Measured Parameters for the Two Example Fluids
Parameter Unit Sample 1 Sample 2
Initial reservoir pressure psia 10,000 5498
Reservoir temperature F 204 290
CGR STB/MMscf 69.81 15.7
Stock-tank gravity API 43.2 45.2
First stage separator gas gravity (Air 5 1) 0.78 0.72
First stage separator GOR scf/STB 13,079 64,780
First stage separator pressure psia 575 540
First stage separator temperature F 74 107
Second stage separator gas gravity (Air 5 1) NA NA
Second stage separator GOR scf/STB NA NA
Second stage separator pressure psia 250 NA
Second stage separator temperature F 74 NA
CGR, condensate gas ratio; GOR, gas oil ratio.

Calculation of Reservoir Gas Specific Gravity From Composition
The procedure described in the Dry Gases Chapter applies here. The molecu-
lar weight of the C7 1 is used in addition to the mole fractions and molecu-
lar weight of lighter hydrocarbons and impurities, and the following results
are obtained:
Sample 1: Gas specific gravity 5 27.43/28.96 5 0.95
Sample 2: Gas specific gravity 5 22.71/28.96 5 0.78
Calculation of Reservoir Gas Specific Gravity From CGR
Molecular weight of the condensate is estimated from stock-tank liquid grav-
ity using a correlation. Other information is obtained from Table 4.4.
Table 4.5 summarizes the results of the calculations.

Calculation of Reservoir Gas Specific Gravity From Separator
Data
Full information of first stage separators are available for both gases in
Table 4.4. However, the full information on other stages of separation is not
available for other separator(s). We cannot therefore use the option that
requires knowledge of full information of separator data. However, we can
use the practical method to calculate reservoir gas specific gravity from par-
tial separator information. Gold et al. (1989) procedures (Options 6 and 7)