Thermo-Hydraulic Optimization of Deep Geothermal Systems: Computational Methods and Classification

Deep geothermal energy forms an important part of a sustainable energy portfolio, providing baseload power and heat. A significant global expansion of DGSs is projected for the coming decades, thereby increasing use of local geothermal resources. This, together with a competitive energy market, creates an incentive to optimize DGSs with respect to large-scale design and operational control variables. In particular, simulation-based optimization can enhance both the sustainability and economic viability of geothermal projects. Key decisions include well placement, well spacing, flow rates, and reinjection temperatures, all of which interact through the coupled thermo-hydraulic behavior of the reservoir. This review provides an overview of thermo-hydraulic optimization methods for DGSs, with a focus on computational simulation-optimization pipelines. The reviewed literature is organized according to a newly proposed classification scheme; for each study, the underlying model, optimization methodology, and objective functions are reported. Finally, open challenges and research directions in the field are identified.