Assessment and Analysis of Mechanical Parameter Variations in Longmaxi Shale Formation Under the Influence of Slickwater Action

This study presents a comprehensive evaluation of shale, a pivotal reservoir type in hydraulic fracturing operations, focusing on its mechanical parameters critical for theoretical calculations and computer simulations of fracture propagation. Departing from conventional rock mechanics tests conducted in dry environments, the Silurian Longmaxi Formation reservoir shale undergoes immersion in two type slickwater formulations for 48 h in this research. The experimental framework encompasses an extensive array of tests, including frictional characteristics, elastic modulus, poisson’s ratio, compressive strength, tensile strength, and fracture toughness parameters. Comparative analyses with dry rock samples highlight significant outcomes. The study determined the clay mineral content in these samples, ranging from 10% to 30%, with an average of 23%. The clay mineral is mainly illite, accounting for 70%. Intriguingly, the influence of clay inhibitors in slickwater on the tested parameters is minimal, aligning with the illitecentric clay analysis results. Furthermore, the friction coefficient on the rock surface exhibits a 10–20% decrease following exposure to slickwater compared to dry rock samples. Under liquid influence, the rock samples experience a notable reduction in elastic modulus, compressive strength, and tensile strength, with no significant differences observed between the impacts of formation water and slickwater. The fracture toughness of the samples also significantly decreases under liquid influence, indicating heightened crack susceptibility in subsurface rocks compared to their dry counterparts. These findings carry crucial implications for hydraulic fracturing simulations and fault slip calculations, contributing to an enhanced understanding of shale behavior in diverse environmental contexts.