Coupling carbon dioxide sequestration with geothermal energy capture in naturally permeable, porous geologic formations: Implications for CO₂ sequestration

Carbon dioxide (CO₂) sequestration in deep saline aquifers and exhausted oil and natural gas fields has been widely considered as a means for reducing CO₂ emissions to the atmosphere as a counter-measure to global warming. However, rather than treating CO₂ merely as a waste fluid in need of permanent disposal, we propose that it could also be used as a working fluid in geothermal energy capture, as its thermodynamic and fluid mechanical properties suggest it transfers geothermal heat more efficiently than water. Energy production and sales in conjunction with sequestration would improve the economic viability of CO₂ sequestration, a critical challenge for large-scale implementation of the technology. In addition, using CO₂ as the working fluid in geothermal power systems may permit utilization of lower temperature geologic formations than those that are currently deemed economically viable, leading to more widespread utilization of geothermal energy. Here, we present the results of early-stage calculations demonstrating the geothermal energy capture potential of CO₂-based geothermal systems and implications of such energy capture for the economic viability of geologic CO₂ sequestration.