Salt Dissolution and Pore Structure Changes Induced by Fracturing Fluid in Shale Reservoirs

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Salt dissolution in shale increases pore connectivity, which helps improve the initial production of shale gas wells. In this study, shale soaking and imbibition experiments were carried out to simulate the process of rock coming into contact with hydraulic fracturing fluid. The results show that salt dissolution can promote the release space and communication of pores within the main pore size range of 0.01–100 μm; the number of mesopores in shale also increases with increasing salt dissolution. The dissolution rate of salts increases with the increase in specific surface area and time. After salt dissolution, the cation formed is mainly Ca2+, and the anion is mainly SO42–. The dissolution of salts promotes the connectivity between pores, which is beneficial for the transportation of shale gas. Shale gas wells should be shut in after hydraulic fracturing to increase the dissolution amount of salts.