Numerical simulation of heat production potential from hot dry rock by water circulating through a novel single vertical fracture at Desert Peak geothermal field

Based on the geological data of well DP23-1 under the EGS (enhanced geothermal system) project at Desert Peak geothermal field, we numerically investigated the heat production potential from deep HDR (hot dry rock) at this site by water circulating through a novel single vertical fracture. A technically feasible fracture aperture of 2 mm is assumed. The injected water is assumed to sweep the fracture along the diagonal and the effect of high pressure and temperature on water density is taken into considerations. The results indicate that desirable heat production efficiency can be attained under suitable fracture permeability and water production rate, however the heat and electricity production power remains a relative low situation and the water flow impedance retains a relative high level during production process. The sensitivity analysis indicates that the electricity production power mainly depends on rock thermal conductivity, water production rate and injection temperature; water flow impedance mainly depends on the fracture permeability, the rock thermal conductivity, the water production rate and the injection temperature; and energy efficiency mainly depends on the fracture permeability, the water production rate and the rock thermal conductivity. When the fracture permeability and water production rate are under reasonable conditions, the energy output and production efficiency will be optimized. However, rock contraction due to temperature reduction and water–rock interaction are not taken into considerations in this study, so the practical heat output and efficiency through one single vertical fracture needs further study in the future. - Highlights: • We established a numerical model of heat production from dry rock through a single vertical fracture. • The stable stage lasts short, in which the heat production rate maintains as unchanged. • As the temperature drops, the resistance to water flow increases. • Fracture permeability will greatly influence the pump power and energy efficiency. • Higher injection temperature has positive effect in reducing water flow impedance