Abstract: The production practice of shale gas reservoirs shows that soaking the well can significantly increase the initial production after fracturing operation. However, there is a lack of a comprehensive review and summary of the existing literature when it comes to which scientific-soaking system should be selected in a specific situation. Based on the research results of domestic and foreign scholars on the mechanism of reservoir reconstruction and damage, model, influencing factors and engineering process of fluid-rock reaction during shale gas well soaking, we systematically summarize the yield-increasing mechanism and the existing soaking system. The results show that the fluid rock reaction is the essence of soak production under reservoir conditions, and the degree of fluid-rock reaction is the key to formulate soaking system. The interaction of fluid-rock during well soaking can both contribute and damage the reservoir. The transformation of the reservoir includes the initiation and expansion of micro fractures and gas liquid imbibition displacement; the damage to the reservoir includes solid phase plugging during fluid-rock reaction and water phase trap caused by fracturing fluid intrusion. Establishing an unknown bridge between fluid-rock interaction and effective pore structure parameters of reservoir is the key to the study of the systems of soaking. In view of the cross scale and highly nonlinear problems that restrict the research on fluid-rock interaction, the author proposed an effective fracture characterization model based on molecular dynamics and an industrial artificial intelligence optimization model for shale gas well soak.

Key words: shale gas, fluid-rock reaction, soaking system, micro-fracture initiation, formation damage