An Assessment of Geomechanical Considerations in Thermal Energy Storage Systems Using 3D Coupled Thermo-Hydro-Mechanical Models

ABSTRACT: Thermal Energy Storage (GeoTES) systems are designed to store heated or chilled brine to be produced when needed for power generation or district heating and cooling. High permeability and porosity sedimentary reservoirs have the potential to store large quantities of brine. In this study we present a geomechanics workflow that integrates subsurface data, from a US Texas Gulf Coast field site, with a fully coupled 3D Thermo-Hydro-Mechanical (THM) model. Our geomechanical modeling approach incorporates THM coupled solutions to simulate flow through porous media and heat transfer while considering progressive formation failure. 3D geomechanical model results show that THM loading conditions can lead to progressive damage around the wellbore and mechanical/flow alteration. Results also suggest that operational parameters can be optimized to minimize these alterations with direct implications to flow channeling and fines migration. Furthermore, preliminary Thermo-Hydro-Chemical (THC) simulations explore the scaling potential of the same thermal storage system using brine chemistry from offset wells. In the model, brine with measured concentrations of the major chemical constituents from the nearby well is heated and cooled (under pressure) to simulate injection of the brine under temperature and pressure. The relative changes in concentrations of various minerals, quantified from THC models, suggest that chemistry can play a significant role in thermal storage systems. 1. INTRODUCTION Solar and wind power are key in our transition to a net-zero carbon future. While abundant and cost-competitive, they are variable, intermittent and their energy supply not always optimized to meet demand needs. For example, the shift to a clean, efficient, and modern grid is essential to California's economy and its environment. This transition to a low-carbon grid provides challenges and opportunities, as the state incorporates increasing amounts of renewable energy into the electric system. When renewable resources generate more electricity than is needed, markets automatically reduce the production of energy from renewable resources, or "curtail" generation. While curtailment is an acceptable operational tool, as increasing amounts of renewable resources, oversupply conditions are expected to occur more often. System Operators are seeking solutions to avoid or reduce the amount of curtailment of renewable power to maximize the use of clean energy sources.