Counter-current spontaneous imbibition dynamics: Combined effects of wettability, fracture flow, and pore structure

Spontaneous imbibition plays a crucial role in various engineering and industrial applications, with its efficiency significantly influenced by a range of factors. To unravel the intricate mechanisms behind these factors, our study employs pore-scale numerical simulations. Utilizing a color gradient model within the framework of the lattice Boltzmann method, we delve into how pore structure, wettability, and flow velocity within fractures collectively impact spontaneous imbibition. Our findings reveal that the dynamics of drainage and imbibition interfaces during countercurrent spontaneous imbibition are key determinants of imbibition efficiency. Specifically, the synergy between wettability and pore structure markedly affects the penetration depth and distribution characteristics of the imbibition interface, which, in turn, influences the imbibition's speed and duration. Moreover, the interaction between the flow velocity inside fractures and the configuration of adjacent pore structures significantly shapes the evolution of the drainage interface. This interplay is crucial as it can either enhance or hinder countercurrent spontaneous imbibition. These insights deepen our understanding of the pore-scale processes governing countercurrent spontaneous imbibition, laying a solid theoretical foundation for optimizing its application in engineering and industrial settings.