Page 44 - Fundamentals of Enhanced Oil and Gas Recovery

32 Amirhossein Mohammadi Alamooti and Farzan Karimi Malekabadi

1.15.1 Mobility Ratio Control Processes
1.15.1.1 Polymers Along With Water Injection
Water and polymer solutions with a high molecular weight can partially increase the
viscosity of water (Fig. 1.15). Two types of polymers can control water flooding:
(1) hydrolyzed polyacrylamide and (2) xanthan polymers.
In polymer solutions containing polyacrylamide, increasing the viscosity and
reducing the permeability of the rock that reacts to the chemicals causes the reduction
of mobility. Xanthan polymers decrease the mobility of the solution while increasing
the viscosity. In most cases, injecting polymers can improve macroscopic volumetric
displacement.
In the process of polymer augment water flooding, polymer is persistently injected
with its initial density for a specific time period. Polymer density drops regularly
during the injection of the PVs. After polymer injection, it is mobilized within the
reservoir via water.

1.15.1.2 Foam and Gas Injection
Employing foam is an efficient way to control mobility ratio of the miscible process
and the injection of gas. When gas leads the oil forward, foam occupies the porous
medium. Since foam has high viscosity, it compresses the gas into the water and keeps
them separated through a thin film. So the mobility of gas decreases in this area as the
outcome of reduction of permeability in the foamed area. A dry gas such as nitrogen
or methane can be injected along with steam to further expand the foam in this
process.

1
S or

Polymer
Saturation Drive 165 330 500
ppm
ppm
Water
ppm
0 Interstitial water

Distance
Figure 1.15 Polymer injection.