Stress-Dependent Permeability in Oil–Water Displacement Through Sandstone: A Sequential Hydro-Mechanical Numerical Study

Oil–water displacement in sandstone is commonly simulated with fixed absolute permeability, although pore pressure changes can modify effective stress and the connected pore-throat network. This study proposed a sequential hydro-mechanical workflow that links incompressible oil–water flow, Biot effective stress, and an exponential permeability update. A five-state deterministic numerical dataset generated from the converged hydro-mechanical simulations over a mean effective stress range of 0.20 to 18.84 MPa, rather than from independent experimental measurements, was used to calibrate the stress-dependent permeability relationship, and a transparent one-dimensional waterflood screening model was then used to evaluate its flow consequences under a fixed pressure difference. Effective permeability decreased from 1.50 × 10−13 to 1.33 × 10−13 m2, a reduction of 11.3%, and was described by a stress sensitivity coefficient of 0.00639 MPa−1 (R2 = 0.992). In the screening calculation, this change reduced the mean total rate from 48.0 to 41.7 m3 d−1, delayed water breakthrough from 24.4 to 27.5 d, and lowered 45 d cumulative oil production from 1227 to 1203 m3. These results show how even moderate stress sensitivity can change rate- and time-based interpretations of oil–water displacement. The two-phase calculation is a reproducible sensitivity case, not a field forecast; sandstone-specific relative permeability, capillary pressure, and coupled simulator validation remain required.