关键词: 高温岩石, 水力压裂, 热力耦合, 近场动力学, 裂隙演化

Abstract: Based on the peridynamics method, the bond model was applied to treat the thermal diffusion of rock and the conventional state model was adopt to simulate the displacement evolution. According to the number of broken bonds between material points, the material damage was determined to track real-time fracture propagation. The interaction between water and rock was realized by applying pressure and temperature of water to fracture surface. And a numerical model was proposed to simulate hydraulic fracturing in high-temperature rock considering the thermal-mechanical coupling effect. The accuracy of the proposed model was verified according to the test results of rock heating fracture propagation. Finally, the morphology of hydraulic fracturing-induced rock fractures were discussed considering the effects of water pressure, rock initial temperature and elastic modulus, the sensitivity of each factor to fracture geometry parameters was analyzed based on the comprehensive sensitivity attribute identification method. The results indicate that under conditions of low water pressure or initial rock temperature, the primary fractures exhibit a near-symmetric distribution, and there is almost no fracture branching. With the increase of water pressure or initial temperature, the number of fracture gradually increases and the bifurcation occurs, the total length and opening degree of fracture also increase. When the mean elastic modulus of rock is small, the fractures are well developed and many tiny cracks appear. With the increase of the average elastic modulus, the number of fracture branches and micro-fractures decreases obviously, and the total length and opening degree of fractures also decrease accordingly, while the rock fracture initiation time increases approximately linearly. The comprehensive sensitivity evaluation of rock material parameters and environmental parameters shows that rock fracture propagation is highly sensitive to elastic modulus and water pressure, but insensitive to water temperature.

Key words: high-temperature rock, hydraulic fracturing, thermo-mechanical coupling, peridynamics, fracture evolution