High Concentration Polymer Flooding Field Test With Well Infilling to Change Fluid Flowing Direction After Polymer Flooding

Abstract

Abstract There are about half reserves remaining underground after polymer flooding, which are huge reserves for further tapping. So how to enhance oil recovery greatly after polymer flooding has been a major technical challenge in china or abroad. According to the data of 20 pressure coring wells after polymer flooding, the places where remaining oil locate are precisely described in this paper and on the basis of laboratory research and numerical simulation and geological study, a new method has been developed that combines well pattern restructuring for changing fluid flowing direction and high concentration polymer flooding so as to tap remaining oil which scatters highly and enriches relatively in distributary streamline after polymer flooding. Field test which used this new method has been carried out at B2D block in Daqing oilfield after polymer flooding. In order to get optimum mobility control, a reasonable formula of high concentration polymer system is optimized and the molecular weight and concentration of polymer are respectively 25 million and 2500 mg/L. Some good responses have been obtained in this field test. The injection pressure has increased by 4.3 MPa and the fluid absorption thickness ratio has increased by 26.3% and water cut drop maximum of central well has reached 16% and its incremental oil recovery is 5%. Based on this field test, it can be concluded that whether a field test after polymer flooding can get a good development effect, well pattern infilling is a premise and remaining oil distribution is a major influential factor and reasonable mobility ratio and injection-production ratio are important safeguards. High concentration polymer flooding with well infilling to change fluid flowing direction is a very effective technology to enhance oil recovery after polymer flooding. This technology has gain very good technological and economic effect, its final incremental oil recovery is 6.77% predicted by numerical simulation and its internal rate of return is 21.9%. This technology has wide application prospects and can be widely applied in blocks of Daqing oilfield after polymer flooding.