Page 345 - Principles of Applied Reservoir Simulation 2E

330 Principles of Applied Reservoir Simulation

Oil and water compressibilities include the effect of gas:

(32,32)
B 0 dP o

B
4- £

W
^
Gas compressibility is

(32.34)

while rock compressibility has the form
1 ad:
r* (32.35)
0
Total compressibility for the system is the sum

c c + c s + c s + c s
t = r o o w » g g (32.36)
Employing these definitions, Eqs. (32.21) through (32.23) and (32.27) in Eq.
(32.31) gives
« A a
R
(*o - s + CG - —

V • K - —VP + CG

(32.37)

CG -
+
*
a/>
^ t -%
dt
Equation (32.37) is called the pressure equation. The pressure equation does not
contain any time derivatives of saturations. WINB4D is coded to solve the three-