Numerical evaluation of heat extraction for EGS with tree-shaped wells

Abstract

A reasonable well structure can help to extract heat from the Hot Dry Rock (HDR) reservoir effectively. A tree-shaped well by the fracture-connected way is proposed to improve the efficiency of heat extraction from the geothermal reservoir. The numerical analysis of various factors based on the local thermal equilibrium method and the established model is verified by the Lauwerier’s solution. The production temperature, heat extraction ratio, reservoir impedance, injection pressure, heat production power and electric power are engaged in the paper as the assessment criterion. In addition, the comparison results show that the conceptual model is superior to doublet model. Because the conceptual model has a lower flow impedance of 0.13 MPa/(kg/s) and a higher extraction ratio of 0.47, which is greater than that of doublet model. The performance of the conceptual model is significantly affected by the average perpendicular distance between the injector and producer, rock matrix permeability and injection temperature. Based on the base model, what is really significant is that the distance set as 575 m and the injection temperature set as 333.15 K when the reservoir permeability is 1 × 10−14 m2. This study can provide an alternative plan to extract larger geothermal energy in the future.