A comprehensive review on mechanical responses of granite in enhanced geothermal systems (EGSs)

Understanding the mechanical responses of granites after various thermal shocks is of utmost significance for heat extraction through from enhanced geothermal systems (EGSs). In this research, the changes in the mechanical characteristics of granites after various thermal shocks are analyzed and determined following according to a comprehensive review of research. The change mechanisms of the mechanical responses of granites after various thermal shocks are revealed by microstructural observations. The normalized values of mechanical parameters decrease linearly with heating temperature, while the confining stress enhances the mechanical parameters. The thermal cycle markedly reduces the mechanical parameters of granites only in the first few thermal cycles. With the rise of heating temperature and confining stress, the failure pattern of various granites transfers from axial splitting failure to shear failure and multiple shear failure. The macroscale deterioration of the mechanical parameters of various granites after thermal shocks is closely associated with the initiation, development and coalescence of microcracks. It is hoped that the comprehensive data review of the mechanical responses of granites in this study will provide reliable parameter values for wellbore stability and reservoir stimulation in EGSs.