Advances and perspectives on water imbibition behaviours in shales

Abstract The characteristically low flowback recovery in shale reservoirs stems from spontaneous imbibition, a governing mechanism for fluid retention and hydrocarbon production. Despite extensive research, the fundamental processes underlying aqueous-phase transport in shales remain poorly understood. This review synthesises recent findings by characterising imbibition as a dynamic, cross-scale transport phenomenon driven by the coupling of capillary suction, chemical potential gradients and clay hydration. Unlike traditional static descriptions of this process, this review highlight how imbibition induces continuous pore-network evolution via hydration-triggered microfracture propagation and mineral-scale blockage. Geological attributes, fluid chemistry and operational parameters are systematically evaluated. We further examine the methodological transition from macroscopic monitoring to in situ visualisation, and from classical analytical solutions to multiphysics numerical frameworks. Lastly, we conclude by identifying critical knowledge gaps and outlining future perspectives in high-pressure high-temperature in situ measurements, multiscale predictive correlations and intelligent fluid systems.