Study on optimization of thermal injection parameters in fractured reservoirs of HDR

To improve the heat recovery of hot dry rock (HDR) and realize the efficient and sustainable development of geothermal energy, it is necessary to analyse the factors affecting the heat recovery performance of HDR fractured reservoir. In this paper, a numerical model of heat recovery in fractured reservoirs with HDR is established. The effects of injection parameters on the heat recovery performance of the Enhanced Geothermal System (EGS) are compared and analysed by means of the average temperature, heat extraction rate, production temperature and heat recovery power of matrix rocks at different locations. The influence degree of injection flow rate and injection temperature on production temperature was analysed by grey correlation analysis method. The results showed that reducing the injection temperature is beneficial to fully extract the heat energy in the rock mass. The injection flow rate is positively correlated with the heat extraction rate and negatively correlated with the extraction temperature. In this simulation scheme, the optimal results are as follows: injection temperature is 298.15K, injection flow is 12 kg/s, and the influence of injection flow on production temperature is greater than that of injection temperature. This study provides a theoretical basis for the development and utilization of geothermal energy in HDR and provides a reference for the design of engineering operation parameters.