Page 139 - Primer on Enhanced Oil Recovery
P. 139
Water altering gas injection 129
Figure 11.1 Water alternating gas (WAG) process.
Figure 11.2 Sequential injection of gas and water.
We can list various applications which differ in the way of injected materials:
a. The alternating supply of working agents (see Fig. 11.1) includes gas injection followed
by water injection. In this case, gas injection increases the efficiency of displacement, and
water increases the reservoir sweep efficiency;
b. Sequential supply of working agents (see Fig. 11.2), includes gas injection followed by
water injection. At the same time, water injection increases both the displacement effi-
ciency and the coverage of the formation by the impact;
c. Hybrid WAG (see Fig. 11.3) consists of big injection of gas followed by big injection of
water aimed at increasing formation sweep efficiency
d. Simultaneous WAG, when water and gas injected together after mixing at the surface, see
Fig. 11.4.
e. Selective simultaneous injection of working agents (see Fig. 11.5). In this case, the work-
ing agents are fed into the well through various pipes and mixing is achieved in the oil
strata.
