Mitigating Thermal Breakthrough in Enhanced Geothermal Systems Using Nanofluids

Abstract

Early thermal breakthrough in Enhanced Geothermal Systems (EGS) significantly limits heat extraction efficiency, particularly due to preferential flow channels. While previous studies focused primarily on circulation rate adjustments, this paper demonstrates the superior effectiveness of nanofluids in mitigating thermal breakthroughs. Through a transient thermal-hydraulic coupled model, we evaluated CuO, Al₂O₃, and Cu nanofluids, finding that Cu-nanofluid with 5% volume fraction achieved optimal performance. This configuration extended thermal breakthrough time from 35 to 59 years and elevated production temperature by 26.32°C after 100 years of operation. Our analysis revealed a direct correlation between nanoparticle concentration and performance improvement, with temperature gains increasing from 6°C to 27°C as volume fraction rose from 1% to 5%, though showing diminishing returns at higher concentrations. System performance was further optimized through reduced injection velocity and temperature, which extended fluid residence time and enhanced thermal gradients. These findings establish nanofluids as a promising solution for improving EGS efficiency, offering practical insights for future geothermal energy development.