Study on the Seepage and Heat Transfer Characteristic of Single Rough Fracture and Intersecting Fracture in Hot-Dry Rock

Abstract

The efficient extraction of geothermal energy from fractured hot dry rock reservoirs requires accurate prediction of subsurface thermohydrodynamic processes. In this study, a novel simplified mid-plane fracture model was developed and validated as an approach that bridges the computational efficiency of two-dimensional approximations with the physical accuracy of fully three-dimensional simulations. Three distinct fracture representations were systematically compared: full 3D models, simplified 2D plane fractures, and the proposed rough mid-plane fractures. Discrepancies in flow dynamics and heat transfer predictions were quantified using coupled steady-state and transient numerical simulations. The influence of “X”-type and “V”-type fracture intersections on thermo-hydrodynamic processes was further examined. The results show that the rough mid-plane model accurately captures permeability and flow channeling effects inherent in realistic 3D fracture geometries, outperforming traditional plane approximations. Flow fields and velocity distributions are substantially modified by surface roughness, directly governing heat exchange efficiency. Flow and temperature fields are shown to be dramatically redistributed by variations in fracture aperture and intersection geometry, with heat extraction significantly enhanced by optimal aperture and injection rate combinations. Notably, “X”-type intersections are found to exhibit 40%–60% greater effective heat conduction areas than “V”-type configurations, highlighting their preferential heat transfer characteristics. These findings provide critical insights for the optimization of HDR reservoir performance, contributing to improved strategies for efficient geothermal energy extraction.OPEN ACCESS Received: 14/09/2025 Accepted: 21/10/2025 Published: 29/05/2026

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