Fracturing mechanism of granite by supercritical carbon dioxide under true triaxial stress

Abstract

Supercritical carbon dioxide (SC-CO2) fracturing, as a new environmentally friendly fracturing mining technology, is gaining increasing attention in the field of dry-heat rock geothermal resource extraction and geological storage. Little is known about the mechanistic aspects of SC-CO2 fracturing of granite, therefore, SC-CO2 fracturing of granite under coupled solid–liquid–mechanical conditions is investigated based on a large scale and high temperature true triaxial SC-CO2 fracturing system. The tests were carried out under different ground stress conditions, and the evolution of fluid injection pressure with time, the relationship between ground stress and fluid injection volume, and the variation law of pumping pressure and triaxial displacement were analysed. The four aspects of triaxial stress, fluid injection pressure, fluid injection volume and triaxial displacement reveal the mechanism of SC-CO2 fracturing in granite, which provides a theoretical basis for the application and promotion of SC-CO2 fracturing in dry hot rocks.