Page 124 - Primer on Enhanced Oil Recovery

114 Primer on Enhanced Oil Recovery

As propane progresses through the reservoir, its concentration in the slug
decreases. Over time, a significant decrease in the concentration of propane in the
slug can lead to a significant decrease in the efficiency of the process. To ensure
the efficiency of the displacement process, it is necessary to calculate the optimal
size of the propane slug.

10.2.2 Applicability criteria
Injection of hydrocarbon gases should be carried out at sufficiently deep-lying for-
mations. The minimum depth is determined by the pressure required to maintain
miscibility. The required pressure ranges from about 8 MPa when pumping lique-
fied gas to 20 35 MPa when pumping high pressure gas, depending on the compo-
sition of the oil.
For the implementation of the process, steeply dipping seams are preferred, pro-
viding gravitational stabilization of the displacement front, which usually has an
unfavorable mobility coefficient. The criteria for the applicability of the method are
shown in Fig. 10.19.
The disadvantages of the method include:
Viscous instability leads to low vertical and horizontal formation sweep efficiency;
A large quantity of expensive consumable products is required;
There is a significant loss of expensive injected material, which cannot be completely
recovered later.

Figure 10.19 Screening parameters for hydrocarbon injection.