Optimization of polymer mobility control for enhanced heavy oil recovery: Based on response surface method

As an enhanced oil recovery (EOR) method, polymer flooding has been widely applied in heavy oil production. Polymer's viscosity and residual resistance factor (RRF) are the key parameters of mobility control, whose increment can both result in the increased oil recovery factor (RF) and worse injectivity. Aiming at oil with viscosities of 50-350 cP, recovery factor and injection pressure of polymer flooding are obtained in the reservoir numerical simulation model. Then we used response surface method to optimize the combination of viscosity and residual resistance factor. The results show that injecting polymer solutions can balance the injectivity gap among layers caused by permeability heterogeneity, while high permeability layers contribute most in oil recovery. For polymer solutions with different combinations of viscosity and RRF in research scope, analyses of growth rates of recovery factor and pressure show that increasing RRF is suitable for above three-fourths of polymers. In such a way, a greater incremental recovery can be achieved under a reasonable increased injecting pressure. This study indicates that polymer solutions with relatively low viscosity and high RRF are more applicable to heterogeneous heavy oil reservoirs.