Injection-production coupling control method for polymer flooding of conglomerate oil reservoir and its parameter optimization

Conglomerate oil reservoirs are microscopically characterized by complex pore structures and macroscopically by strong heterogeneity, and smaller injector-producer spacing leads to the development of dominant pathways. As a result, polymer channeling is severe and the development effect of polymer flooding is poor. In this paper, the injection-production coupling theory and method for polymer flooding under the condition of small well spacing was put forward with the conglomerate oil reservoir in District 7E₁ of Karamay as the example. The injection-production coupling control method was adopted in injection/production sensitive well groups to enlarge the injector-producer spacing, change the flowline, control the polymer channeling and effectively activate the remaining oil screen by dominant pathways, so as to realize the fine polymer flooding of conglomerate oil reservoir and its precise control. It is indicated that after the conglomerate oil reservoir in the middle and late stage of polymer flooding is treated by means of injection-production coupling method, the return trend of its overall water cut is under effective control and the polymer channeling is inhibited. The injection-production coupling parameters of the target oil reservoir were optimized by adopting the symmetric structure with time scale of 1∶1. When the half period of injection-production coupling is 60 d, the degree of reserves recovery is increased by 1.89%, which is the best effect. This method is of great significance to guide the enhanced oil recovery of conglomerate oil reservoirs in the middle and late stage of polymer flooding.