Page 91 - PVT Property Correlations

Wet Gases Chapter | 4 69

TABLE 4.1 Parameter Values for Two-Stage Separation Equations
Value Value
A B
1 1.4599 0 635.53
2 1.3394 1 0.36182
3 7.0943 2 1.0544
4 1.1436 3 5.0831
5 20.93446 4 1.5812
5 20.7913

Option 6—Two-Stage Separation (Practical)
In many wet gas systems, two-stage separation is applied. In general, it is
difficult to have stock-tank GOR and stock-tank gas specific gravity avail-
able. Gold et al. (1989) developed correlations to calculate the additional gas
production from the stock-tank oil and the vapor equivalent of primary sepa-
rator liquid. The use of these correlations allows engineers to estimate the
reservoir gas specific gravity from the knowledge of primary separator GOR
and specific gravity of primary separator gas, density of stock-tank liquid,
and primary separator conditions. Estimates of these inputs are usually read-
ily available. The correlations are given in Eqs. 4.8 to 4.10. Table 4.1 gives
the correlations parameter values.
γ 5 R 1 γ 1 4602γ 1 G pa
1
o
gw ð4:8Þ
R 1 1 V eq
A 2 A 3
A 4
G pa 5 A 1 p s1 214:65ð Þ γ API T A 5 ð4:9Þ
1 s1
B 2 B 3
V eq 5 B 0 1 B 1 p s1 Þ γ API T B 5 ð4:10Þ
B 4
ð
1 s1
Option 7—Three-Stage Separation (Practical)
As in the two-stage separation system above, if the three-stage separation
system (two separators and stock-tank) is applied, correlations similar to
those given above can be used (also developed by Gold et al., 1989). In these
correlations, the additional gas production accounts for the gas production
from the secondary separator and the stock-tank. The vapor equivalent of pri-
mary separator liquid accounts for the stock-tank liquid production and the
gas production from the secondary separator and the stock tank. The equa-
tion to calculate the reservoir gas specific gravity is similar to that of the pre-
vious option; however, the correlations for the additional gas and vapor