SC-CO2 fracturing in shale gas reservoirs considering in-situ temperature and mechanical heterogeneity

Supercritical carbon dioxide (SC-CO 2 ) fracturing, compared to water-based fracturing fluids, is a promising technology for developing shale gas because it can effectively solve problems related to shale swelling and increasing the fracturing complexity of rock matrix. However, the adaptability of this technology is unclear due to the influence of in-situ mechanics and environment for the shale gas reservoir. Then, a ‘microscopic-macroscopic’ cross-scale mechanical parameters transfer framework was established and the macroscopic mechanical heterogeneity model was obtained through nanoindentation testing and SEM mineral scanning, as well as comprehensively utilizing a deep convolutional generative adversarial network and Mori-Tanaka method. On this basis, a multi-physics coupled model of SC-CO 2 fracturing, integrating thermal, hydraulic, mechanical, and damage (THMD) effects was developed to study in-situ mechanical heterogeneity and in-situ reservoir environment. The core innovations of this work are threefold: (1) proposing a reliable cross-scale upscaling workflow from nanoindentation to field-scale reservoir simulation; (2) systematically unraveling the individual and coupled influences of in-situ reservoir temperature, mechanical heterogeneity, and injection parameters on fracturing performance; and (3) revealing the combined effect of injection temperature and natural fracture approach angle on the interaction between hydraulic and natural fractures, providing crucial insights for optimizing field-scale fracture network complexity. The research findings offer significant theoretical guidance for reservoir adaptability assessments and the optimization of SC-CO 2 fracturing treatments in shale gas reservoirs.