Due to the superior hydrothermal properties and CO2 geological storage, Super-critical carbon dioxide (ScCO2) has superior performance as working fluid in Enhanced geothermal system (EGS). In this paper, a three-dimensional fracture grid model is established to obtain the flow and heat transfer characteristics of ScCO2 in Hot dry rock (HDR). The influence of mass flow rate on heat extraction performance and flow characteristics in EGS is evaluated, and outlet temperature and flow resistance with operation time is obtained. The results indicate that the fluid temperature of production well begins to decrease when heat extraction operates two years. The greater the mass flow rate, the greater the decline speed and range. After ten years of operation, the maximum drop of the fluid temperature of production well is 65 K. With the increase of mass flow rate, the heat extraction capacity increases, the heat extraction of unit mass flow ScCO2 decreases, and both of them decrease with operation time. With the increase of mass flow rate, the flow resistance increases, which causes larger consumption of circulation pump power. In addition, the power consumption per unit heat extraction increase.
Keywords EGS, heat transfer, flow resistance, super-critical carbon dioxide