Numerical investigation and optimization on dynamic power generation performance of enhanced geothermal system

The Enhanced geothermal system (EGS) is a crucial technology for the development and utilization of hot dry rock (HDR). However, current research typically overlooks the strong coupling characteristics of fracture seepage, wellbore transport, and thermoelectric conversion, leading to a lack of precision in describing the dynamic operational performance of EGS throughout its entire lifecycle. A dynamic numerical model of evaporator and condenser is established by the moving boundary (MB) method. Subsequently, the dynamic power generation process is integrated with a coupled thermal-hydraulic-mechanical (THM) model of the fractured reservoir, proposing a methodology for calculating the dynamic performance of EGS throughout its lifecycle. Traditional EGS models exhibit significant deviations between calculated results and actual performance due to the neglect of instantaneous changes in injection temperature and the failure to consider the nonlinear characteristics of heat exchangers. The production pressure difference is a primary factor influencing the net output power of EGS. Therefore, selecting an appropriate injection pressure is crucial to ensuring continuous power generation throughout the EGS lifecycle. By optimizing the operating parameters of the actual EGS project, the optimal injection flow rate, fracture aperture, initial fracture permeability and well spacing are 50 kg/s, 0.03 m, 1.5 x 10-10 m2 and 350 m respectively.