Impacts of Waterflooding Erosion and Fluid–Solid Coupling on Porosity and Permeability Evolution in Offshore Unconsolidated Sandstone Reservoirs

Abstract

Aiming at the significant pore structure reconfiguration and mechanical response evolution of offshore unconsolidated sandstone reservoirs during long-term high-intensity waterflooding development, this study proposes a novel fluid–solid coupling mathematical model incorporating waterflooding erosion effects. This method enables coupled simulations of reservoir deformation, fluid flow, and waterflooding-induced pore structure evolution. Compared with conventional methods, the proposed method not only accounts for the influence of mechanical responses on reservoir seepage parameters, but also incorporates pore structure evolution induced by waterflooding erosion under high-intensity waterflooding conditions. The model is validated against MRST, demonstrating its reliability. Multiple case studies are further conducted to systematically investigate the impacts of waterflooding erosion and fluid–solid coupling on the evolution of reservoir properties. The results indicate that under long-term high-intensity waterflooding conditions, waterflooding erosion dominates the evolution of reservoir petrophysical properties in the vicinity of injection wells. Although the fluid–solid coupling effect is weakened under high-porosity conditions, waterflooding erosion remains across different porosity reservoirs. It is a key factor controlling reservoir petrophysical property evolution during long-term high-intensity waterflooding.