Evaluation on the properties of broad-molecular-weight polymer/surfactant flooding system

When waterflooding reservoirs are in the development stage of high water cut and high degree of reserve recovery, they are faced with the difficulties of stronger heterogeneity and obvious interlayer and intralayer contradictions, and separate injection cannot be fulfilled. In order to solve these problems, the broad-molecular-weight polymer/surfactant flooding system was proposed in this paper. In addition, its properties were evaluated by means of theoretical calculation and laboratory experiment. It is indicated that broad-molecular-weight polymer has better viscosity increasing effect and it is better compatible with the surfactant. This broad-molecular-weight polymer/surfactant flooding system gives the full play to the sweeping enlargement effect of broad-molecular-weight polymer and the displacement efficiency increasing effect of surfactant, and its applicability to reservoirs is better. By virtue of this system, the recovery factor is increased by over 15% on the basis of water flooding. The molecular weight proportion of broad-molecular-weight polymer shall be determined according to the reservoir permeability. The best displacement efficiency cannot be realized unless the compatibility between the broad-molecular-weight polymer system and the reservoir heterogeneity is the best. In conclusion, the combination flooding system of broad-molecular-weight polymer is an effective displacement system. The research results can be used as the reference for EOR of heterogeneous oil reservoirs in the development stage of high water cut and high degree of reserve recovery.