Page 328 - Principles of Applied Reservoir Simulation 2E

Part V: Technical Supplements 313

= 7 £ (B 0\ (30.14)
* 0
A Jt=l
is the average oil formation volume factor for all connections in which the well
is completed. Given Eq. (30.13), we simply proceed as in Eqs. (30.1) through
(30.3) above.

Case 5: Injection Rate Specified
If the well is a water or gas injector, the user must specify the total water
or gas injection rates Q w or Q g, respectively, and a well injectivity index (WI)
for each connection. The injection rate for each connection is then allocated as
follows:
Water Injection Rate

(30.15)

Gas Injection Rate
[WI(A, 0 + X w + A,p] t
gk g
~ ~K~ ~ (30.16)
k~ 1
It is important to note that allocation of injection fluids is based on total
mobilities, and not just injected fluid mobility. This is necessary for the
following reason: If an injector is placed in a block where the relative permeabil-
ity to the injection fluid is zero, then the simulator using injection fluid mobility
only would prohibit fluid injection even though a real well would allow fluid
injection. A common example would be water injection into a block containing
oil and irreducible water. To avoid the unrealistic result of no fluid injection,
we assume the total mobility of the block should be used. For most cases, the
error of this method will only persist for a few timesteps because, in time, the
mobile fluid saturation in the block will be dominated by the injected fluid.