Numerical simulation study on parameter optimization of crosslinked polymer flooding for enhanced oil recovery in heavy oil reservoirs

Abstract For reservoirs exhibiting severe heterogeneity due to prolonged water flooding, conventional polymer flooding demonstrates limited capacity to alter reservoir properties under such conditions. Crosslinked polymer flooding, characterized by its three-dimensional network structure, significantly enhances reservoir conformance, sweep efficiency, and oil displacement efficiency, making it a key technique for strongly heterogeneous reservoirs in the middle to late stages of development. In this study, a geological model based on a one-injection–one-production well pattern was constructed to simulate the crosslinked polymer flooding process. The model incorporates critical factors including formation heterogeneity, wall adsorption, and the inaccessible pore volume associated with polymer injection. Using the Computer Modelling Group’s Steam, Thermal, and Advanced Processes Reservoir Simulator (CMG-STARS), model was validated through grid independence analysis and calibrated via history matching. A systematic investigation was conducted to assess the influence of key parameters—namely, crosslinked polymer concentration, injection rate, and injection strategy—on oil displacement performance. The results indicate that, under the studied conditions, a well spacing of 200 m, a mass concentration of 0.55%, and an injection rate of 400 m³/d effectively reduce polymer adsorption and shear degradation while promoting the formation of a stable gel, thereby enhancing plugging efficiency. An injection strategy initiated at a 35% water cut, combined with 2–3 alternating cycles, was found to mitigate water channeling through early-stage reservoir modification. This study identifies the dominant factors controlling the oil displacement performance of crosslinked polymer systems, clarifies their relative advantages and limitations compared to conventional polymers, and offers a reliable reference framework for parameter selection in field-scale crosslinked polymer flooding operations.