Preliminary Assessment of EGS Potential in South-Central South Dakota

Abstract

South-central South Dakota exhibits elevated heat flow (up to 130 mW/m²) and steep geothermal gradients (greater than 100 °C/km), indicating substantial geothermal potential. Nevertheless, the region remains underexplored; past development has been largely confined to small direct-use systems (e.g., hot-water heating). In our previous work (Ye et al., 2025), we compiled the most comprehensive dataset to date, nearly 3,000 borehole temperature measurements, to reconstruct higher-resolution geothermal-gradient maps, and then performed preliminary techno-economic analysis (TEA) of direct-use applications in two shallow aquifers. These results are encouraging and point to considerable opportunities for geothermal development in South Dakota. In this paper, we further evaluate the technical feasibility and economic viability of the deployment of enhanced geothermal systems (EGS) within the deep crystalline basement using a doublet well configuration with approximately 100 m injection-production spacing. Thermal transport analysis shows that realistic fracture apertures enable rapid heat transfer, allowing produced fluid temperatures to approach reservoir conditions at depths of ~3 km, and deeper. A grid-based techno-economic assessment quantifies the levelized cost of electricity (LCOE), net present value (NPV), and internal rate of return (IRR) under varying production flow rates and Investment Tax Credit (ITC) levels. The TEA results suggest that EGS in South-Central South Dakota are technically viable and hold considerable long-term potential, but their near-term economic success remains sensitive to reservoir performance and the presence of policy incentives. This study aims to provide a first-hand perspective on the techno-economic viability of geothermal energy development in South Dakota and highlights key parameters affecting its future development.