Prospects of power generation from an enhanced geothermal system by water circulation through two horizontal wells: A case study in the Gonghe Basin, Qinghai Province, China

Abstract

This study numerically investigates the power generation potential from a fractured geothermal reservoir at Qiabuqia geothermal area in the Gonghe Basin, Northwestern China, by water circulation through two horizontal wells. In the numerical model, the non-equilibrium heat exchange between fluid in fractures and rock matrix are considered to improve the simulation accuracy of heat and fluid transport in the subsurface. It is evaluated that in a reservoir at depths between 2700 m and 3200 m and initial temperature of 180 °C, the production temperature can maintain at 180 °C for 8.6 years and a temperature drops by 7.3% in 30 years. The production rate can maintain at 40 kg/s. The exergy analysis showed that the designed geothermal system could yield an electric power of 3.05–3.59 MW, with the flow impedance of 0.137–0.156 MPa/(kg/s) and energy efficiency of 31.0–62.4 over a 30-year period. The operation of such a system could reduce the total greenhouse gas (GHG) emissions by 0.27–0.92 Mt when compared to a fossil fuel plant. The sensitivity analysis indicates that the electric power mainly depends on fracture spacing and injection temperature, while the flow impedance and energy efficiency are controlled by fracture permeability.