Page 40 - Fundamentals of Enhanced Oil and Gas Recovery

28 Amirhossein Mohammadi Alamooti and Farzan Karimi Malekabadi

Figure 1.12 Injection patterns used in enhanced oil recovery methods.

The effects of these factors on efficiency are discussed in many studies. In these
reports, physical and mathematical models are used for numerical simulation. These
factors have been reviewed below.

1.14.6.2 Effect of Gravity Segregation on Vertical Displacement Efficiency
Gravity segregation occurs because of the difference in the density of the injector and
displaced fluids. When the injector fluid has a lower density than the displaced fluid,
gravity segregation happens and the displacing fluid moves higher than the fluid dis-
placed, as shown in Fig. 1.13A.
This situation is observed in steam injection displacement, in situ combustion, car-
bon dioxide injection, and solvent injection processes. In the opposite case, when the
displacing fluid is heavier than the displaced fluid, the heavier fluid tends to move
from the bottom. This mode is presented in Fig. 1.13B. Here, gravity segregation
results in early fingering and reduced sweep efficiency.