Techno-economic analysis of closed-loop geothermal system with multi-wing fracture

This research seeks to determine whether thermally conductive fractures can substantially enhance the heat extraction of closed-loop geothermal systems. A fracture-incorporated closed-loop geothermal system, featuring a multi-wing thermally conductive fracture, is presented. A thermo-hydraulic coupled three-dimensional model is established for the system, through which an extensive numerical investigation is conducted to assess its heat extraction under circumstances of various fracture heat conductivity, multi-wing fracture configurations, and operational settings. Results indicate that a system with a dual-wing fracture attains moderately greater heat extraction than a fracture-free closed-loop design, when the fracture has large height and thickness, with performance increasing as fracture heat conductivity rises. For an identical fracture cross-sectional area, increasing fracture height provides more substantial heat extraction enhancement than expanding fracture thickness. Elevating the specific heat capacity of circulating fluid reduces the produced-fluid temperature considerably, although the corresponding improvement in net power remains modest. As the fluid circulation rate increases, cumulative thermal output initially climbs but eventually decreases once a threshold flow rate is exceeded. Implementing a multi-wing fracture yields up to a 60.93% increase in cumulative heat output over 180 days, and this improvement reaches 187.25% when a thermal plug is additionally utilized. The thermal output increment associated with the thermal plug plateaus near 78.51% when the number of fracture wings is greater than four. Among all influencing parameters, the thermal plug, followed by the fracture wing number, exerts the greatest effect on the closed-loop system’s thermal performance. The F-CGS with a dual-wing fracture and plug exhibits superior economy.