Cracking property and brittleness evaluation of granite under high-temperature true triaxial compression in geothermal systems

Abstract Cracking property and brittleness are critically important to the drillability of injection production wells enhanced geothermal systems. This paper is devoted evaluating cracking Gonghe granite under high-temperature true triaxial compression conditions through a series laboratory tests. Thermal–mechanical coupled tests were conducted on samples four representative temperatures (20 °C, 120 180 240 °C) three different minimum (5, 10, 30 MPa) intermediate (40, 60, 75 principal stresses that correspond in-situ reservoir. The strength, deformation, characteristics quantitatively evaluated from macro- micro-scales based experimental results. Meanwhile, novel index evaluation method considering both energy failure surface roughness proposed accurately assess strength granite. We found reduced by more than 20% when temperature increases room °C. Higher contributes smoother fracture thermal–mechanical compression. Our findings provide new insights for formation assist in efficient drilling design