Water Percolation Threshold in Porous Media Modulated by Geometry and Interfacial Physics

Abstract Water percolation threshold in porous media marks the critical saturation where fluid transitions from isolated ganglia to a full‐scale cluster, essential for understanding transport in porous media. This onset of connectivity is crucial for fluid transport in natural and artificial porous systems such as hydrocarbon reservoirs, electrodes, and membranes. Traditionally, determining this threshold relies primarily on laboratory experiments and empirical curve fitting. Percolation theory offers a theoretical foundation for locating this threshold in an ideal, randomly occupied, and infinite system. However, real porous media deviate from these assumptions: (a) water‐phase connectivity is restricted within pore space as a subdomain of the full 3D space, and (b) even under static or quasi‐static conditions when dynamic flow or the invasion process is neglected, fluid occupancy departs from ideal random occupation because of pore geometry, wettability, and capillary constraints. Here, we employ Monte Carlo simulations to assess porosity and geometrical effects on thresholds under random occupancy. We find that restricting connectivity to the pore space of a porous structure, instead of the full 3D space, increases the threshold relative to classical random‐occupation models. Based on physically constrained fluid configurations, we then simplify the porous media into basic units, each containing a single meniscus, and derive the lower and upper bounds for the water‐phase connectivity threshold as a function of wettability and meniscus coordination number. Statistical analyses based on X‐ray micro‐CT data sets and pore‐scale observations support these bounds. This study offers new physical insight into the critical saturation required for connectivity in porous media.