Imbibition displacement mechanism of fracturing fluid in shale oil reservoir

The imbibition displacement of fracturing fluid is a key technique for enhancing oil recovery in shale oil reservoirs. This paper assesses the impact of fracturing fluid wetting modifiers on the efficiency of imbibition displacement and explores the underlying mechanisms at play in shale oil reservoirs. Tests were conducted on the surface tension, interfacial tension, and wettability of the treating agent, alongside investigations into its compatibility with conventional fracturing fluids. Additionally, the imbibition displacement efficiency of rock samples with varying pore sizes was evaluated. The results indicate that the anionic surfactant AOS proved to be the most effective treatment agent for improving the wetting properties of fracturing fluids. The imbibition displacement efficiencies observed were 8.17% for particles, 17.55% for matrix, and 37.37% for fractured rock samples. These findings demonstrate that the imbibition displacement force encompasses buoyancy, buoyancy-capillary, and capillary forces. By altering rock wettability, the modifier significantly enhances the capillary force, thus boosting oil displacement efficiency by approximately 152.9% compared to conventional fracturing fluids. The influence of pore structure on the dominant imbibition displacement force was also noted. Capillary forces were predominant in small pores, and buoyancy is the main force for natural and hydraulic fractures. The research on the imbibition displacement mechanism of fracturing fluid provides valuable guidance for the efficient development of tight shale oil reservoirs.