Performance of enhanced geothermal system with varying injection-production parameters and reservoir properties

Abstract

The injection-production parameters and reservoir properties significantly affect the heat extraction performance of the enhanced geothermal system (EGS), while quantitative rankings of the effecting parameters have been yet unknown. This paper is devoted to investigating numerically the heat extraction performance of EGS by three-dimensional reservoir models under the influence of varying injection-production parameters and reservoir properties. A thermal-hydro-mechanical (THM) coupled model is used to quantify the complicated heat extraction process of EGS. Three-dimensional geothermal reservoir models containing random fracture networks are established based on the Monto Carlo algorithm to quantify the effect of fracture numbers in the process of heat extraction. The parameter sensitivity of the injection-production parameters (injection mass flow rate and injection temperature) and the reservoir properties (rock matrix porosity, fracture permeability, and rock matrix permeability) on the heat extraction performance are ranked and evaluated over the Qiabuqia enhanced geothermal system. It is found the heat extraction performance shows non-monotonic relationships with the fracture numbers in the three-dimensional reservoir model, which indicates the necessity of EGS fracture optimization. The injection mass flow rate turns out the first while the fracture permeability and injection temperature are the secondary dominating factors affecting the heat extraction performance among the evaluated parameters. The outcomes are beneficial to the high-efficiency construction, operation, and optimization of the EGS especially those with similar conditions to the Qiabuqia EGS.