Saturation Hysteresis During Cyclic Injections of Immiscible Fluids in Porous Media: An Invasion Percolation Study

Cyclic injection of immiscible fluids in porous media is a key process in applications such as carbon geosequestration and underground hydrogen storage, where understanding and predicting the residual trapping efficiency are critical. This study develops a modified invasion percolation algorithm incorporating a pore coupling coefficient to simulate quasi-static, cyclic fluid displacement in porous media. The coefficient captures the effects of pore-scale cooperative pore-filling mechanisms by modifying the capillary pore entry pressures based on the filling status of neighboring pores. Systematic simulations reveal that the displacement morphology and saturation hysteresis are strongly influenced by the pore coupling strength. Phase diagrams highlight regimes for which cyclic injections significantly enhance residual gas trapping. Results also establish connections between the pore coupling coefficient and physical parameters such as wettability and porosity. This work provides new insights into the pore-scale origins of saturation hysteresis and its implications for optimizing fluid injection strategies in subsurface applications.