Experimental investigation on heat transfer characteristics of single-well enhanced geothermal system

Abstract The single-well enhanced geothermal system (SEGS) is an innovative approach designed to overcome the limitations of traditional deep borehole heat exchangers (DBHEs). It achieves this by modifying the well structure and circulating working fluid through an engineered reservoir to enhance heat transfer. This study presents a laboratory-scale experimental investigation of a SEGS analog to identify key performance determinants. The research explores the impacts of injection flow rate, injection temperature, and the initial temperature of the sandbox on the system’s thermal performance and temperature distribution into the sandbox. A series of experiments were conducted under different conditions, and the results were analyzed to determine the optimal operating parameters for maximizing heat extraction while minimizing temperature decay. The study also investigates the influence of injection–production spacing on the thermal breakthrough and the overall efficiency of the SEGS. Based on the observed trade-offs within the tested range, a flow rate of 0.4 m 3 /h, an injection temperature of 31 °C, and a spacing of 120 cm provided the best compromise between high heat extraction rate and stable production temperature. These findings provide foundational insights into SEGS thermal behavior and a basis for optimizing system design, supporting the development of sustainable geothermal energy solutions.