Spontaneous Imbibition in Dual Permeable Media Using Dynamic Pore Network Model.

Understanding preferential flow in porous media holds substantial theoretical significance on the design and optimization of hydrocarbon exploitation in shale reservoir. Previous researches discussed the competition of imbibition front in layered porous media while the underlining mechanism for interfacial dynamics and induced displacement efficiency of multiphase flow remains ambiguous. In this paper, we investigate the spontaneous imbibition in dual permeable media and analyze the flux exchange between the neighboring porous zones with permeability contrast using dynamic pore network model. The impact of fluid viscosity ratio and permeability contrast on the spontaneous imbibition preference have been addressed, and finally a phase diagram for displacement efficiency has been obtained. The results reveal that the dual permeable structure enhances the invasion rate of wetting fluid in the low‐permeable zone and induces unstable displacement patterns, leading to reduction of the long‐term displacement efficiency. The interfacial pattern transition from stable displacement to unstable pattern in dual permeable media could be ascribed into the flux exchange between dual permeable zones, which shows a contrary impact on the fluid flow within the low‐permeable zone under favorable and unfavorable viscosity ratios. The permeability contrast in dual permeable media intensifies this impact during spontaneous imbibition. These results help us to understand the occurrence and mutual interaction of multiphase flow in layered porous media, and provide a theoretical guidance for the hydrocarbon exploitation in shale reservoir. Plain Language Summary: The shale oil reservoir has emerged as a crucial contributor to the global energy supply, primarily attributed to stimulation techniques such as hydraulic fracturing. The geological composition of shale rock encompasses stratified layers characterized by varying permeability, leading to diverse multiphase flow patterns at the pore scale during the shut‐in period. These intricate flow patterns significantly impact shale oil recovery during subsequent exploitations. However, a gap exists in comprehending the optimal design of injection conditions by controlling the multiphase flow pattern for a high‐efficiency exploitation strategy. The elucidation of multiphase displacement mechanisms within the complex porous structure featuring staggered layers are imperative. To address this gap, pore‐scale modeling and analysis were conducted to visualize spontaneous imbibition behaviors across varying fluid viscosity ratios and permeability contrasts. The findings indicate that the imbibition flux in low‐permeable zone is augmented by fluid flow in high‐permeable zone. Furthermore, an escalating permeability contrast intensifies the flux enhancement and reduce the displacement efficiency in dual permeable media by changing the displacement pattern from stable to unstable distribution. These outcomes serve as a theoretical foundation, providing insights for the selection and optimization of an effective exploitation strategy to enhance shale oil recovery under complex engineering conditions. Key Points: A dynamic pore network model for studying spontaneous imbibition in dual permeable media is presentedThe contrary effect of flux exchange on spontaneous imbibition within low‐permeable zone under various viscosity ratios is observedTransition of interface dynamics from stable to unstable pattern is induced by unfavorable viscosity ratio and large permeability contrast [ABSTRACT FROM AUTHOR]