Advanced Geothermal Energy Storage System by Repurposing Existing Hydrocarbon Wells in Low-Temperature Subsurface Profiles
Advisor: Dr. Tugce Baser
ABSTRACT
This research focuses on the investigation of the feasibility of an advanced geothermal energy storage (AGES) system in low temperature geological formations using existing hydrocarbon wells for flexible electricity generation. AGES systems offer an alternative approach to traditional geothermal systems, but their deployment is still in its infancy because demonstration efforts are very scarce across the globe. In addition, existing feasibility studies often rely on hypothetical and conceptual models without validation through field experiments. To address these gaps, this research aims to (1) investigate the hydraulic, thermal, and geochemical properties of suitable geological formations of an AGES system via a full-scale field experiments in the Illinois basin, (2) develop a validated and calibrated numerical model that considers coupled thermal, hydraulic, and geochemical (THC) processes; (3) assess key design parameters that control the operational performance of an AGES system using the validated physics-based numerical models, (4) evaluate the system sustainability, and (5) understand the challenges, opportunities, and pathways to repurposing existing hydrocarbon wells.
To achieve the objectives, a full-scale field test is performed to characterize the subsurface thermal, hydraulic, and geochemical properties of a pre-select formation in the Illinois Basin. During the experiment, continuous temperature data along the well is collected and used to estimate the subsurface thermal conductivity by solving the inverse one-dimensional heat equation. Fully coupled thermo-hydraulic (TH) and thermo-hydro-chemical (THC) numerical models are developed and validated using the results from the field experiment to investigate the thermal behavior of an AGES system. A temperature-dependent porosity model is developed based on brine geochemistry and chemical interactions between rock and brine are accounted as a function of temperature. The model is integrated into the TH model to simulate the coupled THC behavior of the AGES system. The injection and production cycles, injection rates and configurations, are varied to assess the key design parameters for an efficient performance of the AGES system. The sustainability of the AGES system is investigated through the metrics of energy storage efficiency, levelized cost of electricity, and life cycle assessment. Policy tools and instruments are suggested to incentivize the development in geothermal energy storage systems and regulate the usage of existing hydrocarbon wells for geothermal purposes. The direct outcomes of this research are: (1) a predictive model for thermal conductivity estimation using well temperature data, (2) a validated THC numerical model that can simulate the thermal response of
an AGES system, and (3) a proof of concept that successfully demonstrating that the AGES system is a cost-effective and environmentally sustainable approach. The findings of this research will contribute to increasing the installation of geothermal systems in low-temperature basins by reducing the exploration and drilling costs. This research also contributes to climate change mitigation efforts by providing the tools and guidelines necessary for decarbonizing the energy sector and reducing the dependency on fossil fuel sources; and thus, moving toward a cleaner energy future.