| Abstract |
Hot dry rock (HDR) fracturing is a critical stage in the development of enhanced geothermal systems (EGS). Vertical-fracture network, as a widely applied fracture system, has properties and morphology that significantly affect heat extraction performance. However, current studies exploring the effect of various fracture networks often lack completeness and accuracy, where chemical reactions, wellbore dynamics, and/or rock mechanical behavoirs are overlooked. In this study, combined thermal-hydraulic-mechanical-chemical (THMC) and wellbore heat loss models are developed to investigate EGS heat recovery under different vertical-fracture patterns. The impacts of fracture properties on heat mining are also determined. The results from the proposed combined EGS models indicate that EGS heat recovery improves with increasing fracture spacing, fracture number, and decreasing fracture conductivity, but the performance gains diminish as spacing and number increase further. Meanwhile, excessively low fracture conductivity may lead to ineffective fluid flow in the reservoir. Therefore, an effective design of these parameters is critical in the HDR stimulation process. Additionally, the interrupted complex fracture network demonstrates the highest power and electricity generation. Although interrupted fractures require higher injection pressure, this is effectively offset by the complex fracture pattern, resulting in a similar injection-production pressure difference to that of the continuous simple fracture network. Therefore, interrupted complex fracture networks are recommended when a vertical-fracture network is determined to be created. This study accurately improves the understanding of EGS performance under different vertical-fracture networks, offering operators valuable insights to operators for improved decision-making in EGS development. |