科研之友
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摘要
In the enhanced geothermal system (EGS), an artificial fracture network can be formed in the geo-thermal reservoir by hydraulic fracturing for heat transmission fluids to be circulated in the reservoir to extract heat from hot dry rocks (HDR), which involves complex thermo-hydro-mechanical (THM) coupling processes in the fractured rock matrix. Therefore, THM coupling analysis is of great importance for studying the performance of the EGS. A THM coupling model was presented in this paper, in which the fractured rock was regarded as a dual medium (discrete fracture networks and matrix rock), and a fully-coupling finite element analysis was implemented in a commercial software, COMSOL multiphysics, for analysis of the temperature, pressure and stress distributions in the fractured rock system during geo-thermal recovery. The coupling model and the numerical approach were verified in comparison with a proven analytical solution method. The model was used to simulate the EGS process with a 2D randomly generated fracture network to study the characteristics of flow, heat transfer and mechanical behaviors in a HDR reservoir. The results show that the connected fractures in the reservoir form the main flow pathways for fluid circulation, in which heat convection is essential for heat transfer. High pressure water injection and fracture extension induced by temperature variation can increase the conductivity of the fractured rock matrix, thus affecting the heat extraction. It is important to consider the THM coupling effects for studying the efficiency and performance of the EGS process.
- 出版日期2016
- 单位中国石油大学（华东）
