Feasibility Studies on CO2Foam Flooding EOR Technique After Polymer Flooding for Daqing Reservoirs

Most of the high permeability reservoirs in the Daqing Oil Field have been conducted by water flooding and polymer flooding. Further development of such mature reservoirs has become a big challenge due to highly dispersed residual oil. Foam flooding, as a candidate enhanced oil recovery (EOR) technique, has been proposed. In this article, EOR evaluation of CO2 foam flooding after polymer flooding has been conducted on homogeneous sandpack cores flooding tests at the reservoirs condition. Results indicated that CO2 foam flooding could enhance considerable oil recovery, even if the oil recovery occurs after polymer flooding. It was also found that higher quality foam with higher pressure gradient could improve larger swept volume and, thus, recovered more residual oil than lower quality foam did. The influence of both the injection strategy and solubility of CO2 in brine on EOR of CO2 foam flooding was also studied.