Topological evolution: An unexplored aspect of hysteresis for multiphase flow in porous media

The role of phase topology in hysteresis during fluid injection and withdrawal in porous media is not fully understood. We address this by providing experimental and theoretical evidence on three key findings. (1) The topological evolution of the nonwetting fluid is distinct from the capillary pressure and the specific interfacial area, as shown by experiments and a generalized model. (2) Saturation paths with identical capillary pressure and interfacial area show different topologies, revealing insights into energy dissipation and phase connectivity. (3) The topological evolution of the nonwetting phase follows predictable trajectories captured by a piecewise non-linear model. These findings offer practical implications for optimizing subsurface hydrogen and carbon dioxide storage systems and provide a novel approach to study complex systems with topological singularities.