Temporal Evolution and Numerical Simulation of Water-Sensitive Reservoirs During Long-Term Waterflooding: A Case Study of the North 31 Wutonggou Formation

This study addresses the challenges of uneven recovery in strongly water-sensitive reservoirs through the development of a time-dependent two-phase flow model capturing the dynamic evolution of permeability and relative permeability. Based on laboratory core flooding experiments and integrated into a black-oil simulator, the model accurately reproduces reservoir behavior under long-term water flooding, significantly improving the history matching of water cut and pressure—especially in high water-cut stages. Results demonstrate that water sensitivity causes staged damage: initial reduction in heterogeneity is followed by intensified interlayer conflict and earlier water breakthrough. The relative permeability curve shifts rightward, accompanied by reduced residual oil saturation. These findings overcome the limitations of conventional static-property models and provide a reliable basis for optimizing enhanced oil recovery strategies. Further validation with field data will enhance the model’s applicability under diverse geological conditions.