Numerical Simulation Of Thermal Fluid-Solid Coupling Process In Enhanced Geothermal System

The development of dry-hot rock mainly adopts the artificial formation of geothermal reservoir.The cold water is injected into artificially generated and open fracture zones through injection wells.The injected cold water is heated after contacting with high-temperature rock mass,and then returns to the surface through production wells to form a closed loop,thus achieving the goal of continuously extracting heat energy from deep reservoirs.Enhanced geothermal system is an artificial geothermal system based on dry hot rock technology,which can economically extract deep thermal energy from low permeability rock mass.In many geothermal fields,a large amount of field evidence shows that in fractured reservoirs,injected water can migrate rapidly to production wells along the preferential flow path,but it is not clear how to migrate rapidly.Based on the verification of the problem,the following aspects are studied in this paper:?1?On the basis of TOUGH2 software framework,FLAC^3D is introduced to analysis the the relationship between stress and strain.Combined with TOUGH2,a general three-dimensional mechanically coupled hydrothermal model is constructed.The method of TOUGH2 and FLAC^3D sequentially coupling and how to modify and update porosity and permeability are also studied in detail,which lays a theoretical foundation for our later programming.?2?Based on the process of TOUGH2-FLAC^3D mechanical coupled hydrothermal model program,the accuracy of TOUGH2-FLAC^3D coupling process is verified by numerical simulation of one-dimensional consolidation settlement model and heating of a hollow cylinder;By applying the TOUGH2-FLAC^3D coupling process to the In Salah project in Algeria,the results of the program simulation of the simple mathematical model are compared with the field monitoring values.The data shows that the simulation results are about 19%higher than the field monitoring results,which confirms the engineering application prospects of the coupling program.?3?The ideal artificial geothermal reservoir is modeled and analyzed,and how the injected water migrates quickly to the production wells is analyzed.The influence of the artificial low-heat injection-production model on the thermal recovery efficiency is studied by setting different positions of injection wells and production wells.The analysis results show that the positions of injection wells and production wells are relative to each other.The nearer the location is,the lower the thermal recovery efficiency is.When the wells are arranged diagonally,the area swept by the injected fluid under the preferential flow path is the largest,that is,the reservoir development degree is high.Lawrence Berkeley National Laboratory in the United States is in the forefront of the world in the research and development of numerical simulation of Thermal-Fluid-Solid coupling process in deep reservoir engineering.This master's dissertation has successfully realized the TOUGH2-FLAC^3D coupling process and completed the preliminary validation of technology introduction and application analysis.It lays a solid tool foundation for further numerical analysis and modeling of deep dry-hot rock mining.The results of this dissertation can provide direct reference value for the team and colleagues who are carrying out and will soon carry out the research on the Thermal-Fluid-solid coupling process of reservoir engineering.