Optimization of different chemical flooding injection slug after polymer flooding and remaining oil distribution

Since polymer flooding was carried out in Bohai X oilfield, the recovery increased quickly. However, due to the high viscosity of the crude oil, the water-cut after polymer flooding increased rapidly and the profile reversal was serious. To improve the development effect, according to the field geological and reservoir characteristics and development situation, different indoor experiments of chemical flooding and optimization of reasonable mode of slug injection after polymer flooding was carried out by flat core with three heterogeneous layers. The results indicated the polymersurfactant flooding could effectively overcome the profile reversal in the polymer flooding process and expand the sweep volume. The optimal chemical flooding slug was 0.1 PV(0.25% surfactant and 2 000 mg/L polymer) and 0.3 PV(0.2% surfactant and 1 500 mg/L polymer). The optimal polymer-surfactant flooding could improve the recovery ratio by 8.6% than that of polymer flooding.