Comparative study of flow-rate dependence and end effects in steady-state two-phase flow through model pore networks

This study investigates the influence of network geometry, wettability, and flow conditions on end effects during steady-state immiscible two-phase flow in model pore networks. Systematic co-injection experiments were performed in planar microfluidic networks with periodic and non-periodic geometries and varying wettability characteristics, enabling direct comparison over a broad range of flow conditions, expressed in terms of capillary number and flow-rate ratio. Using the DeProF theoretical framework, pressure-drop measurements were analyzed to evaluate the flow-rate-dependency of relative permeabilities, intrinsic dynamic capillary pressure, and energy efficiency. In parallel, sub-pore-scale imaging provided direct insight into the spatiotemporal evolution of interstitial flow structures under both steady and transient flow conditions. The study: (a) further validates the DeProF framework as a robust and efficient approach for analyzing two-phase flow in porous media, capturing flow-rate dependency and energy efficiency across diverse flow conditions, fluid pairs, and pore-network configurations; and (b) demonstrates its potential to infer interstitial flow-structure characteristics from ex-core (macroscopic) relative permeability measurements. The results show that system-specific correlations can be established between macroscopic flow measurements at critical flow conditions and the underlying interstitial flow structures. These findings support the development of flow-dependent relative permeability scaling models and improved special core analysis (SCAL) protocols that more accurately capture the physics governing two-phase flow in natural porous media.