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58 PROPERTIES OF RESERVOIR FLUIDS
1.240
Oil formation volume factor (RB/STB) 1.180
1.220
1.200
1.160
1.140
1.120
1.100
1.080
0 500 1000 1500 2000 2500 3000
Pressure (psi)
FIGURE 3.5 Demonstration of the correlation in Equations 3.17 and 3.19 with properties
from Examples 3.2 and 3.3.
1.80
1.60
1.40
Oil viscosity (cp) 1.00
1.20
0.80
0.60
0.40
0.20
0.00
0 500 1000 1500 2000 2500 3000
Pressure (psi)
FIGURE 3.6 Demonstration of the correlation in Equations 3.20 through 3.23 with
properties from Examples 3.4 and 3.5.
Viscosity. The following correlation for oil viscosity requires two steps. First, the
viscosity (cp) of “dead” oil is estimated from API gravity and temperature (°F):
°
×
log ( µ + 1) = 733 10 − . 0 0251 API (3.20)
.
10 oD T . 0 564
Dead oil refers to oil that has little dissolved gas; it is equivalent to stock tank oil.
The second step accounts for the decrease in oil viscosity that occurs as gas dis-
solves into it:
