Numerical Simulation Study on Pressure-Driven Waterflooding in Low-Permeability Reservoirs

Low-permeability oil reservoirs are commonly characterized by complex pore structures, low permeability, high threshold pressure gradients, and restricted fluid flow, all of which significantly constrain the effectiveness of conventional water flooding. These challenges lead to inadequate reservoir energy replenishment and limited fluid production capacity, making the development bottlenecks of “poor injectivity and low productivity” particularly prominent. To improve oil recovery, this study proposes a pressure-assisted water injection strategy analogous to hydraulic fracturing, aiming to enhance reservoir energy replenishment, optimize inter-well connectivity, and increase water injection efficiency. Based on numerical simulation methods, a detailed geological model was developed to systematically investigate the mechanisms of pressure-assisted injection and evaluate its long-term development performance. Sensitivity analyses were performed on key operational parameters, including injection rate, shut-in duration, and cumulative injection volume, to evaluate their impact on injection-production dynamics and oil recovery under various development scenarios. The results indicate that, under otherwise consistent development conditions, setting the injection rate to 1000 m3/d, with a cumulative injection volume of approximately 15,000 m3, a 10-day shut-in of the production well following injection, an initial injection pressure of 40 MPa, and an injection duration of 270 days, can yield a cumulative oil production of 29,700 tons over 15 years, corresponding to a recovery factor of 14.27%. This study identifies the key controlling factors and optimization pathways for pressure-assisted water injection in low-permeability reservoirs, providing theoretical insights and technical support for the efficient development of similar reservoir systems.