The interaction between shale and various fluids is crucial as it modifies pore structures, which govern the effective development of shale gas and the geological storage of carbon dioxide in shale formations. In this study, samples from the Longmaxi Formation shale in Sichuan Basin of China were exposed to different fluids, including 6 MPa CO₂, 12 MPa CO₂, 6 MPa CO₂+brine, and 12 MPa CO₂+brine, at 45 °C for 100 days. Various methods, including X-ray diffraction (XRD), X-ray fluorescence (XRF), field-emission scanning electron microscopy (FESEM), and the low-pressure gas adsorption (N₂) test, were adopted to evaluate chemical and structural changes during the exposure process. After being treated with supercritical CO₂+brine and subcritical CO₂+brine, the shale underwent significant changes in its major element composition. The content of Ca, Al, and K in shale saturated with supercritical CO₂+brine decreased from 13.00% to 10.34%, from 3.65% to 3.36%, and from 1.56% to 1.37%, respectively. Meanwhile, the content of Si and Na in the same shale increased slightly after saturation. The amount of quartz and dolomite increased, while the levels of clay and calcite slightly decreased. The surface of the shale sample became rougher and small bumps and cracks appeared after saturation with different fluids, as shown by the FESEM analysis results. Furthermore, the changes in both the total pore volume and pore size followed a similar pattern to the alterations in the specific surface areas. The highest level of variation occurred with the shale that was saturated with 12 MPa of CO₂, indicating that gas pressure and CO₂ phase state have a significant influence on the shale’s pore structure. In addition, the distribution of pore sizes showed a bias towards larger sizes across all diameters; this suggests that the reaction resulted in a decrease in the number of micropores. This also highlights that the impact of varying fluid saturation was primarily focused on micropores and macropores. The results of this study provided experimental evidence to further test the mechanisms and permeability of geological storage of CO₂ in organic-rich self-sourced shale.

As mineral resource extraction progresses to greater depths, it has become imperative for geomechanical applications to understand the thermomechanical degradation mechanisms of rocks under thermal loading. To investigate the thermomechanical characteristics of granite subjected to thermal treatments ranging from ambient to 1000 °C, we conducted uniaxial compression tests integrating P-wave velocity measurements, digital image correlation (DIC), and acoustic emission (AE) monitoring. The key findings reveal the following: (1) the specimen volume exhibits thermal expansion while the mass loss and P-wave velocity reduction demonstrate a temperature dependence; (2) the uniaxial compressive strength (UCS) and elastic modulus display progressive thermal degradation, while the peak strain shows an inverse relationship with temperature; (3) acoustic emission signals exhibit a strong correlation with failure–time curves, progressing through three distinct phases: quiescent, progressive accumulation, and accelerated failure, and fracture mechanisms transition progressively from tensile-dominated brittle failure to shear-induced ductile failure with increasing thermal loading; and (4) the damage evolution parameter exhibits exponential growth beyond 600 °C, reaching 98.85% at 1000 °C, where specimens demonstrate a complete loss of load-bearing capacity. These findings provide critical insights for designing deep geological engineering systems involving thermomechanical rock interactions.