Overview of how subsurface carbon dioxide promotes geothermal energy extraction

The properties of carbon dioxide (CO2) under deep geologic conditions make it an excellent subsurface working fluid in geothermal systems, including CO2-Plume Geothermal (CPG) systems, Enhanced Geothermal Systems (EGS), and deep closed-loop Advanced Geothermal Systems (AGS). Supercritical CO2’s low viscosity, high density, and high thermal expansion coefficient render CO2 a highly efficient energy transfer, extraction, and storage fluid. These properties typically overcompensate the lower specific heat capacity of CO2, compared to brine, which is the conventional working fluid underground. Furthermore, CO2 can also reduce fluid-mineral reactions, such as mineral precipitation, which often clog reservoirs, wells, and equipment. Applying geothermal energy extraction to CO2 Capture and Sequestration (CCS) in deeper reservoirs results in true CO2 Capture Utilization and Sequestration (CCUS), enabling these projects to ultimately sequester all initially injected CO2 underground at reduced cost. In this presentation, I give an overview of how CO2 can be used to efficiently produce geothermal energy, store surface-generated energy underground, and/or support CCS operations to promote energy security while combating climate change.