Numerical simulation and sensitivity analysis of EGS thermal extraction based on THM-coupled model

Abstract

The deep geothermal energy produced from Enhanced Geothermal System (EGS) has a great development prospect because of enormous potential and environmental friendliness. Deep geothermal energy development is a thermo-hydro-mechanical (THM) coupled process. Reservoir thermophysical properties and fractures are the primary factors governing fluid flow and heat transfer. Understanding these parameters is critical for the sustainable development and utilization of geothermal energy. Based on this, a numerical model incorporating THM coupling was developed for EGS. It evaluated heat extraction performance under the individual influence of key parameters, including reservoir thermophysical properties and fracture characteristics. Using the established SOA-RFR-GA intelligent prediction model, geothermal productivity was forecasted and sensitivity analysis was conducted for EGS. The results showed that: reservoir specific heat capacity prolongs thermal breakthrough time; geothermal gradient increases initial geothermal productivity; in the long term, geothermal productivity is positively correlated with bedrock porosity, but negatively correlated with the fracture roughness coefficient; optimal geothermal development efficiency is achieved at a fracture width of 0.6 mm and a fracture angle of 45°; geothermal productivity exhibits significant sensitivity to both geothermal gradient and bedrock specific heat capacity. Based on the sensitivity analysis results, a surrogate-model-based evaluation framework for geothermal design implications was established; these findings provide valuable guidance for EGS fracturing and geothermal resource development.