Influence of Supercritical Carbon Dioxide at Various Temperatures on Shale Mechanical Properties

During the production of shale oil and gas, the interaction between carbon dioxide and shale will have a significant impact on the rock properties. Using brazilian splitting experiments and uniaxial compression experiments, the mechanical properties of shale samples subjected to supercritical carbon dioxide (SC-CO₂) at different temperatures were investigated in this study. The results of this study indicate that the tensile and compressive strengths of shale decrease gradually after exposure to SC-CO₂, and the higher the temperature at which SC-CO₂ acts, the greater the decline in strength. The mode of shale failure has shifted from a single tension failure to a mixed tension shear failure. Shale samples have a critical damage threshold temperature of 350 ℃, and the SC-CO₂ effect significantly reduces shale strength. This is related to the alteration of the rock internal structure during the high temperature shale formation process, and it is also the underlying cause of the deterioration of the shale mechanical properties. The failure mechanism and fracture mode of the rock are largely determined by its mechanical properties. The study findings have significant theoretical value and a number of practical applications in the area of shale oil and gas reservoir engineering.