Page 31 - Standard Handbook Petroleum Natural Gas Engineering VOLUME2

Basic Principles, Definitions, and Data 19

not much higher than the initial solution gas-oil ratio, since the liberated gas
stays in the reservoir in contact with the remaining oil [17].
Several correlations are available for estimating formation volume factors.
Single-phase formation volume factors can be estimated from solution gas,
gravity of solution gas, API gravity of the stock tank oil, and reservoir tem-
perature by using the correlations of Standing [1,2]. Figure 5-3 provides Standing's
empirical correlation of bubble-point oil formation volume factor as a function
of the variables mentioned. Total formation volume factors of both solution gas
and gas-condensate systems can be obtained from Standing's correlations given
in Figure 5-4.
Empirical equations have been developed [2 11 from Standing's graphical data.
These equations provide the oil formation volume factor and the solution gas-
oil ratio as functions of reservoir pressure [21]:

B = a ~1.17 + b
0 (5-9)
where a is a constant that depends on temperature, oil API gravity and gas
gravity and b is a constant that depends on temperature. Values of both
constants are given in Table 5-3; other values can be interpolated.
Solution gas-oil ratio can be estimated from:

Rs = Y P'." (5-10)

Table 5-3
Values of Constants for Equation 5-9
Values of a x lo5
Oil gravity T = 120°F T = 140°F
"API Gas gravity: 0.7 0.8 0.9 0.7 0.8 0.9
26 2.09 2.55 3.10 2.03 2.58 3.13
30 2.44 2.98 3.61 2.38 3.01 3.64
34 2.85 3.48 4.21 2.78 3.51 4.24
38 3.33 4.07 4.90 3.26 4.10 4.93
42 3.89 4.75 5.71 3.82 4.78 5.74
011 gravity T = 160°F T = 180°F
"API Gas gravity: 0.7 0.8 0.9 0.7 0.8 0.9

26 2.02 2.47 3.02 1.95 2.38 2.91
30 2.33 2.85 3.48 2.27 2.78 3.39
34 2.69 3.29 4.01 2.65 3.24 3.96
38 3.10 3.80 4.62 3.09 3.79 4.61
42 3.58 4.38 5.33 3.60 4.42 5.38
Values of b
T. "F b
120 1.024
140 1.032
160 1.040
180 1.048
~~
From Reference 21.