Parametric study of the geothermal exploitation performance from a HDR reservoir through multilateral horizontal wells: The Qiabuqia geothermal area, Gonghe Basin

Based on the geological data of the GR1 borehole at the Qiabuqia geothermal area, northeast Tibetan plateau, a novel EGS with multilateral horizontal wells is proposed to assess the heat production potential. By varying several parameters (e.g. well layout, reservoir naturally occurring, and human-controlled parameters), the sensitivity analysis is implemented. The levelized cost of energy (LCOE) is taken as the economic criteria to intuitively analyze the influence of various parameters on the economy of the system. It is evaluated that in a reservoir at depths of 2650-3650 m and an initial temperature of 151-190 degrees C, the production temperature can increase from 162.9 to 167.6 degrees C for 11.6 years and then decline. The basic multilateral horizontal well system attains an electric power of 2.28-2.52 MW, a flow impedance of 0.17-0.26 MPa/(kg/s), and an electric energy efficiency of 3.5-7.0 in 20 years. The saving in greenhouse gas emission is 0.09-0.32 Mt. Sensitivity analysis suggests that the branch number and branch length significantly affect the electric power and flow impedance. A longer branch length and the perpendicular distribution of the main injection and production well are more favorable. Reservoir permeability has a greater influence on heat production performance compared with thermal conductivity and porosity. High permeability can effectively reduce flow impedance, save internal en-ergy consumption and gain a better economy. Reducing the injection flow rate and injection temperature within a certain range can improve the economy of the system.