Fracture spacing in horizontal well multi-perforation fracturing optimized by heat extraction

Multi-perforation fracturing in horizontal wells is the key procedure in the operation of enhanced geothermal system (EGS). However, two questions remain unclear: 1) what are the similarities and differences between three fracturing methods; and 2) how to optimize fracture spacing (FS)? Here we established a three-dimensional hydraulic fracturing model to unveil fracture initiation and propagation mechanisms. The fractures obtained by hydraulic fracturing were subsequently embedded in a geothermal mining model. Heat extraction was used as an evaluation indicator to optimize FS and geothermal mining. We found that the initiation pressure in multi-perforation fracturing is higher than that in single-perforation fracturing. The stress shadowing increases with increasing time and decreasing FS. FS not only changes the complex fracture network, but also affects the low-temperature area of hot dry rock. Quantitative analysis of heat extraction shows that the optimal FS in simul-taneous, sequential,and alternate fracturing are 30 m, 40 m, and 50 m, respectively. Our study benefits fracturing method selection and construction parameter optimization in EGS operation.