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| Development and application of a real-time high-temperature and high-stress true triaxial fracturing test system |
| GUO Wuhao1，2，GUO Yintong1，2，CHANG Xin1，2，WU Mingyang1，2，HE Yuting1，2，BI Zhenhui1，2，ZHANG Xinao1，2，TENG Shilong1，2，WANG Lei1，2，YANG Chunhe1，2 |
| (1. Key Laboratory of Geomechanics and Geotechnical Engineering Safety，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；2. University of Chinese Academy of Sciences，Beijing 100049，China) |
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Abstract To investigate the fracture initiation and propagation of fracturing in deep oil and gas and geothermal energy reservoir stimulation，a real-time high-temperature and high-stress true triaxial fracturing test system was developed independently，which narrows the gap between laboratory fracturing physical simulation test and the real deep reservoir conditions. This system is primarily used to simulate the fracturing and fracture propagation behavior of 300 mm cubic rock samples in the in-situ environment of deep reservoir. It also monitors and processes parameters such as stress，displacement，pump pressure，flow rate，and acoustic emission signals during the fracture propagation process. The maximum stress in X，Y and Z directions of the system can be loaded to 88 MPa，and the internal temperature of the sample can be heated to 350℃. The intelligent temperature control mode ensures uniform heating of the whole sample，and the maximum pump pressure is 210 MPa when slickwater is used as fracturing medium(120 MPa when supercritical CO2 fracturing). The hydraulic fracturing test of shale and supercritical CO2 fracturing test of granite under high-temperature and high-stress conditions have been completed by using the system. The test results show that the system has high accuracy and good stability. The post-peak fluctuation of pump pressure curve is intensified under high-stress. High-temperature reduces the breakdown pressure and improves the fracture complexity. When supercritical CO2 is used as fracturing medium，the breakdown pressure of granite decreases significantly，the number and energy level of acoustic emission signals weaken，and the fracture complexity increases. The relevant research results can provide theoretical and technical support for the optimization of deep reservoir reconstruction technology.
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