Pore structure and crack characteristics in high-temperature granite under water-cooling

The changes of porosity and microcracks of high-temperature granite under water-cooling have a great influence on the safety and efficiency of geothermal resources exploitation. To analyze the formation conditions of the pore structure and microcracks of granite specimens at different temperatures under water-cooling, the rock porosity was measured by NMR, and the rock microstructure was observed by PM and SEM. The results show that the closure of microcracks occurs at 150 °C and the grain boundary microcracks appear at 300 °C. And the porosity and pore size begin to increase, the number of pores remains stable, and intracrystalline microcracks appear at 450 °C. When T = 600 °C, macropores and trans-granular microcracks appear inside the rock. When 600 °C