Sensitivity analysis of model parameters for geothermal energy applications in deep mines of thermal-hydraulic-mechanical coupling of spatially heterogeneous settings

With the increasing demand for mineral and alternative energy resources, as well as the gradual depletion of shallow resources, the exploitation and utilization of mineral resources and geothermal energy in deep strata is an effective way to solve the problem of resource shortage. In recent years, as a new type of resource mining mode, the co-mining of deep mineral and geothermal energy has developed rapidly. This method is effective in solving the of deep mines and can also provide convenience for geothermal exploitation with the help of the original equipment of the mine. However, in deep mines, the interaction of high temperature, high geomechanical stress and high-water pressure might lead to rock failure because of the co-mining of mineral and geothermal resources. The huge uncertainty of underground parameters also makes the engineering environment difficult to predict.

We have established a Thermal-hydraulic-mechanical coupling framework of co-mining of deep mineral and geothermal energy considering uncertainty in the model parameters including porosity, rock permeability, thermal parameters (heat capacity and heat conductivity), Young's modulus and their spatial heterogeneity, as well as boundary condition. 500 samples were generated within the prior uncertainty ranges, by means of Monte Carlo simulations, and simulated the spatial and temporal distribution of the temperature, pressure and principal stresses field for each sample with COMSOL. Using the distance-based global sensitivity analysis, the most sensitive parameters for deep mining are identified, and the heat storage capacity of the system is evaluated, including uncertainty.