Effect of Pore Geometry and Heterogeneous Surface Wettability on the Nanoconfined Phase Behavior in Nanopore Networks of Shale Rocks

The phase behavior of hydrocarbons in liquid-rich shale formations deviates from their bulk phase behavior due to the nanoconfinement effects in the extensive nanopores of shale rocks. While the phase behavior in nanopores has been widely investigated, the macroscopic phase behavior in the complex nanopore networks of shale rocks remains poorly understood. To address this critical problem, we have recently developed a novel pore-network-based upscaling framework that allows for deriving the macroscopic phase behavior for shale rocks accounting for size- and geometry-dependent nanoconfinement effects (Chen et al., 2021). Here, we apply the pore-network-based upscaling framework to examine the influences of pore geometry and heterogeneous surface wettability on the macroscopic phase behavior using three example nanopore networks. The results show that pore geometry and heterogeneous surface wettability have a relatively minor impact on the macroscopic phase behavior, and (as reported in our prior study) pore size distribution is the primary controlling factor. Conversely, pore geometry and heterogeneous surface wettability are shown to significantly modify the spatial distribution of fluid phases and components in the nanopore networks, which further modifies the two-phase constitutive relationships (e.g., capillary pressure saturation curve and relative permeability saturation curve).