Feasibility of Storing Heat in the Subsurface for Flexible Electricity Generation

Geothermal growth is limited by a lack of geographically dispersed high-temperature thermal resources and high initial upfront investment in characterization and well construction. Further, there is a need for the grid to be able to accommodate changing conditions and to improve grid reliability, flexibility, resilience, and security. This project will improve geothermal adoption, reduce initial project risk, and improve price competitiveness through utilizing existing oil and gas infrastructure such as non-productive wells, non-economic fields, dry holes, and orphaned wells. The ability to leverage existing infrastructure represents a significant reduction in geothermal exploration, well construction, and site permitting costs. Further, the project will address the lack of geographically dispersed thermal resources and enhance grid resilience, reliability, and energy security by introducing an economical method for storing energy provided from currently available renewable resources (i.e. solar) in the subsurface for use during at-peak energy demand. The project will demonstrate the feasibility of utilizing abandoned oil and gas wells as geothermal heat storage wells at field-scale. During Phase 1 the project team will investigate the heat storage and hydrogeological characteristics of subsurface reservoirs in the Illinois Basin to evaluate their response to heat injection for determining the evolution of temperature profiles and heat losses over time using existing and available data sets. The project team will then perform modeling and simulation to evaluate the heat losses of returning fluids during heat extraction. The project team will use this data to select an optimal candidate reservoir and location. The team will design and perform a small scale field test in an existing oil well to refine and calibrate the model and to begin to demonstrate the ability to navigate permitting and regulatory pathways necessary for the conversion of oil and gas assets towards geothermal use. The team will then take the information gained to develop project economics and lifecycle costs for a larger scale Phase 2 demonstration. If successful, the project will demonstrate the ability to leverage existing oilfield infrastructure, existing permits, and existing land access and leasing agreements, to enable geothermal storage projects to come online faster and cheaper than a greenfield development could. The Phase 1 project is intended to be a proof of concept of the process in Illinois, but the