Experimental study of damage of shale mechanical properties under supercritical CO2

With the growing demand of clean energy, much attention has been paid to the supercritical CO2 strengthened shale gas development technology. This paper aims to investigate the effect of supercritical CO2 on the mechanical properties of the shale. Supercritical CO2 immersion experiments were carried out on the Silurian shale from Sichuan Basin Longmaxi for different durations. Besides, indirect tension tests (i.e., Brazilian disc tests) and triaxial compression tests were conducted to obtain the variation regularities of the strength and deformation of shale before and after immersion. Combing with the results of XRD, porosity and SEM tests, the effect of supercritical CO2 on the mechanical properties of shale was preliminarily discussed. The results showed that after supercritical CO2 immersion, the tensile strength, triaxial compressive strength, and elastic modulus (Young's Modulus) of the shale all decreased at various degrees. However, the amount of shale strength loss increased with increasing the immersion time. Meanwhile, XRD, porosity tests and SEM results indicated that supercritical CO2 degraded mechanical properties of shale by changing the structure of mineral constituent, reducing the degree of cementation, and changing the particle framework and pore structure.