Page 339 - Principles of Applied Reservoir Simulation 2E

324 Principles of Applied Reservoir Simulation

pressures and potentials in the flow equations by using the capillary pressure
concept. Let us define the difference in phase pressures as
p = P P
cow o - w (32.8)

and

\~>^.J/
P ego = P g ~ P o - (32 9)
The differences P cow and P cgo are the capillary pressures for oil-water and gas-
water systems, respectively. Experimentally P cow and P cgo have been observed
to be principally functions of water and gas saturations, respectively. Using Eqs.
(32.8) and (32.9) lets us write the water and gas phase potentials as

Pw*
$ = P o ~ P cow - -2— (32 10)
J
*w
\J±.iv)
~ AA
144
and
p + p
® 8 * = o cgo - ~7 (32.11)
144
*
Combining Eqs. (32.5) through (32.7) with Eqs. (32.10) and (32.11) and
rearranging yields

Oil

a
%•„}
— ~. « I t A, 1 _ _ ?„ d . S }
V • K • — VP + CGL - ' ~ (32-12)
v ^ J Po,c 5r
Water

L
f — ^ = ~~ U~ (32.13)
w
\ i