A black-oil-based multi-component model for polymer flooding

Abstract

Alternating injection of different polymers can further trigger the potential of enhanced oil recovery effect by polymer flood, but such process cannot be perfectly numerically modeled by current simulators. Thus a sophisticated black-oil-based multi-component model for polymer flooding is proposed in this study, which can not only improve the computational efficiency over the compositional model, but can also better capture the complicated physiochemical features, such as multi-component polymer mixing, competitive adsorption and the resulting permeability reduction to aqueous phase. Next, the mathematical model is implemented with a finite volume method and an efficient three-dimensional, triple-phase, multi-component polymer flooding research code is developed when combined with the constrained pressure residual (CPR) preconditioned GMRES algorithm. Research on mechanisms and cycle number of polymer altering injection is conducted for heavy-oil reservoirs. The results show that alternating injection can improve compatibility between the strength of injected liquid and reservoir heterogeneity, which makes the change law of flow resistance force of each layer tend to be the same and then contain the conformance reversion, leading to the transformation of injection conformance of heavy-oil reservoir from ‘V’ type to ‘U’ type, and finally boost the mobilization of remaining oil of low-permeability zone. Proper altering cycle number can best suppress conformance reversion, and enhances liquid suction of low-permeability zone by more than 11.1% as well as recovery factor by 3.1%. These can provide technical guidance for sustainable and efficient development of heavy-oil reservoir.