Polymer augmented alkaline flooding (PAAF) is a relatively new EOR process, and its first version has been defined as injecting an alkaline slug chased by a polymer slug. During the early 1980's the second version of PAAF was introduced, being composed of a single slug of alkaline and polymer blended together, followed by a polymer slug.
A series of corefloods was conducted with alkaline solution, polymer solution, and a blend solution of alkaline and polymer in linear and radial Berea sandstone cores for studying the mechanisms of the second-version PAAF process. Sodium hydroxide was used as the alkaline agent, and the polymer was 30-percent hydrolyzed polyacrylamide. The efficiency of the second-version PAAF was compared with that of both alkaline flooding and polymer flooding alone.
Results showed that the synergistic effect of the second-version PAAF provides better efficiency than either alkaline or polymer alone for enhancing oil recovery. This chemical system of alkaline and polymer blended together yielded more oil recovery with increasing blend slug size.
Also, a phenomenon never before reported was observed. It is a visible residual oil saturation ring next to the region cleaned of oil adjacent to the injection sand face, and it was observed in both linear and radial cores after the application of the second version PAAF process. The size of this oil ring is similar to the size of the blend slug of alkaline and polymer.