Page 143 - Fundamentals of Enhanced Oil and Gas Recovery

Miscible Gas Injection Processes 131

X o 5 1 2 X s (4.50)
where V is volume fraction and μ is viscosity in cp. The subscripts O, S, and m stand
for heavy oil, CO 2 , and CO 2 /heavy-oil mixture, respectively. The empirical parame-
ter α is determined by Eq. (4.51) as follows [121]:
7:36
ð
e 2 e 7:36 12p r Þ
α 5 0:255γ 24:16 T 1:85 (4.51)
r 7:36
e 2 1
where
T
T r 5 (4.52)
547:57
p
p r 5 (4.53)
1071
where specific gravity of the heavy oil, temperature, and pressure are indicated by γ, T
in R, and p in psi, respectively. The volume fraction of CO 2 in the mixture (X s ) can
be estimated from the CO 2 solubility or swelling factor, which is as follows [67]:
1 F 0 F s 2 1
5 (4.54)
X s 5
=F 0 R S 1 1 α 1 F 0 F s 2 1
αF CO 2
is the ratio of CO 2 gas volume at standard conditions to the volume at
where F CO 2
system temperature and pressure, and F o is the ratio of oil volume at system tempera-
ture and 14.7 psi to the volume at system temperature and pressure.

4.12.2 Required Volume
The CO 2 storage capacity of a reservoir can be defined as the CO 2 remained in the
reservoir at the end of EOR operation and any extra CO 2 that can be injected after
the EOR project. It is showed that about 40% of the originally injected CO 2 is being
produced in the producer wells and can be reinjected [12,81]. Shaw and Bachu [81]
introduced an approach to determine the CO 2 storage capacity in the reservoir during
EOR process. At breakthrough time, the CO 2 storage capacity can be calculated as
follows [81]:
OOIP
5 ρ
CO 2 res
M CO 2 RF BT (4.55)
S h
where the CO 2 storage capacity in million tone (Mt), density of CO 2 at reservoir
3
condition in kg/m , the recovery factor in percent, and oil shrinkage in 1/oil forma-
, ρ
CO 2 res
tion volume factor are exhibited by the symbols M CO 2 , RF BT , OOIP, and S h ,