Abstract
<title>Abstract</title> <p> The microscopic seepage law of oil-water two-phase flow in porous media can directly reflect the formation process of residual oil. However, existing physical simulation methods are unable to accurately quantify the oil-water flow patterns under varying external conditions. To systematically investigate the pore-scale displacement behavior of oil–water two-phase flow under different controlling factors, matrix and matrix-fracture porous-media models were developed using the algebraic Volume of Fluid (VOF) method coupled with the incompressible Navier-Stokes equations. The results show that: ①Injection velocity affects water-phase migration pathways by regulating the relative contributions of viscous and capillary effects, and this influence is controlled by the specific pore structure. ②Wettability, pore-throat structure, and injection velocity jointly control fracture-matrix fluid exchange. When the injection velocity increased to 0.015 m/s, the oil recovery factor of the MWS mode decreased to 63.7%, indicating that an excessively high injection velocity may weaken matrix imbibition. ③Different water-injection schedules exhibit distinct advantages in terms of final oil recovery and oil recovery per unit injected-water volume. The oil recovery factors obtained using periodic intermittent, periodic variable-rate, and constant-rate injection were 36%, 40%, and 37%, respectively. Linear interpolation showed that, to achieve an oil recovery factor of approximately 35%, the required normalized cumulative injected volumes, N <sub>inj</sub> , were approximately 2.93, 3.61, and 5.25, respectively. Under the injection cycles and simulation conditions considered in this study, periodic intermittent and periodic variable-rate injection reduced the cumulative injected-water requirement by approximately 44% and 31%, respectively, compared with constant-rate injection. </p>