Analysis of influencing factors of production performance of enhanced geothermal system: A case study at Yangbajing geothermal field

Deep geological exploration indicates that there is a high-temperature fractured granite reservoir at depth of 950–1350 m in well ZK4001 in the north of Yangbajing geothermal field, with an average temperature of 248 °C and a pressure within 8.01–11.57 MPa. In this work we established a conceptual and numerical model of this granite reservoir, evaluated heat production and electricity generation potential from this fractured reservoir by means of numerical simulation, and analyzed main factors affecting the heat production performance. The results indicate that in the reference case the system attains an electric power of 29.5–25.1 MW, a reservoir impedance of 0.12–0.21MPa/(kg/s), a pump power of 0.7–1.6 MW and an energy efficiency of 41.1–15.7 during a 50 year period. Main factors affecting the electric power are water production rate and injection temperature. Main factors affecting the reservoir impedance are the reservoir permeability, the water production rate and the injection temperature. Main factors affecting the pump power are the reservoir permeability, the water production rate and the injection temperature. Main factors affecting the energy efficiency are the reservoir permeability, the water production rate and the injection temperature. Within certain ranges main measures to improve the reservoir performance are to increase the reservoir permeability or adopt more reasonable water production rate and injection temperature. - Highlights: • We established a numerical model of the 950–1350 m fractured granite reservoir. • Desirable electricity production performance can be obtained under suitable conditions. • The system attains an electric power of 29.5–25.1 MW with an efficiency of about 41.1–15.7. • Electric power mainly depends on water production rate and injection temperature. • Higher permeability within a certain range is favorable for electricity generation.