An injection/production rate allocation method applied for polymer-surfactant flooding

Polymer-surfactant flooding which is an effective technology to enhance oil recovery, has been widely applied in Shengli oil field of China. At the stage of subsequent water flooding after polymer-surfactant injection, the injectivity and productivity of wells recover gradually along with the production of chemical solution which provides the feasibility of increasing the injection and production rates. However, due to reservoir heterogeneity, a poor performance may be obtained if the injection and production rates are simply increased for all wells at a same percent. This paper treats the injected polymer as a tracer and a method to calculate the interwell connectivity is proposed according to the concentration curve of the production well. Then taking Gudong 7th reservoir in Shengli oil field which is developed by polymer-surfactant flooding for example, an injection/production rate allocation method applied for subsequent water flooding period is proposed. On one hand, well injection rates are allocated according to the remaining geological reserves and watercuts of different well groups; on the other hand, well production rates are allocated according to the watercuts of the wells in each well group and the interwell connectivity between the injection well and production well. At last, the performance of the method is analyzed according to numerical simulation method. The result shows that the method gains lower watercut and higher oil recovery compared to the conventional method, and it is helpful to get a bigger oil recovery at the subsequent water flooding stage.