The role of matching relationship between polymer injection parameters and reservoirs in enhanced oil recovery

In order to determine the role of polymer injection parameters in enhanced oil recovery (EOR), the laboratory experiment of polymer flooding adaptability with different water-wash degree natural cores is carried out based on coring interpretation data of xing12-3-jian3222 well of Pu I3 layer in Daqing Oilfield (China). The water displacement efficiencies of the cores are 70–80%, 40–50% and 10–20%. And the feasibility of reducing residual oil after water flooding with high concentration and high molecular weight polymer is explained. Besides, the EOR effect of polymer is studied by laboratory “co-injection and separated-layer production” experiment with three parallel cores. The results indicate that the adsorption of polymer molecule and the injection pressure gradient are affected more significantly by concentration than molecular weight in different water-wash degree reservoirs. Residual resistance coefficient and displacement pressure gradient increase with the concentration increase. The residual resistance can be met in both strong and moderate water-wash reservoirs, and the injection capacity in weak water-wash reservoir is better with the polymer of 1300 mg/L, 2500×104 molecular weight. The parallel cores displacement results show that the profile controlling methods before polymer flooding with high molecular weight can adjust the injection profile of both moderate and weak water-wash reservoirs effectively and the oil recovery would be enhanced. The recovery efficiency is enhanced by 21.12% when compound-ion profile control agent with 1/3 profile modification radius and 2500×104 molecular weight polymer with 1300 mg/L are used, which improved by 4.06% than using 0.64 PV polymer slug alone. It contributes to improve polymer flooding EOR in heterogeneous reservoirs.