Interfacial phenomena in shale reservoirs: Molecular insights into adsorption, wettability, and nanoconfined flow.

Shale reservoirs, characterized by their complex nanoporous structures and heterogeneous mineral compositions, present ubiquitous interfacial phenomena that govern fluid behavior at the nanoscale. This review provides a comprehensive analysis of three critical interfacial processes (adsorption, wettability, and fluid flow) occurring in shale formations, emphasizing microscopic mechanisms gained from molecular simulations. The interplay between geofluids (e.g., CH4, CO2, C8H18, H2O) and diverse shale constituents (including silica, carbonates, clay minerals, and kerogen) is examined. Key findings reveal that adsorption mechanisms are strongly influenced by pore size, surface chemistry, fluid composition, and confinement effects, with competitive adsorption favoring heavier hydrocarbons and CO2 over methane. Wettability, governed by fluid-solid interactions, varies significantly across mineral surfaces and is modulated by factors such as surface functionalization, ion presence, and pressure conditions. Nanoconfined fluid flow exhibits slip behaviors, viscosity variations, and complex multiphase dynamics that depend on interfacial properties and pore geometry. This work provides fundamental mechanistic insights into the nanoscale interfacial phenomena governing fluid behaviors in shale reservoirs. These insights deepen the understanding of complex fluid occurrence and dynamics in heterogeneous porous media and offer theoretical guidance for the optimized design of energy extraction and carbon management strategies in shale systems.