Energies, Vol. 18, Pages 6031: Feasibility and Operability of CO2 Circulation in a CO2 Storage-Enabled Geothermal System with Uncertainty Insights from Aquistore
Energies doi: 10.3390/en18226031
Authors:
Rangriz Shokri
Chalaturnyk
CO2 circulation between subsurface wells is a promising approach for geothermal energy recovery from deep saline formations originally developed for Carbon Capture and Storage (CCS). This study evaluates the feasibility, operability, and performance of sustained CO2 flow between an injector and a producer at the Canadian Aquistore site, a location with active CO2 injection and an established geological model. A high-resolution sector model, derived from a history-matched parent simulation, was used to conduct a comprehensive uncertainty analysis targeting key operational and subsurface variables, including injection and production rates, downhole pressures, completion configurations and near-wellbore effects. All simulation scenarios retained identical initial and boundary conditions to isolate the impact of each variable on system behavior. Performance metrics, including flow rates, pressure gradients, brine inflow, and CO2 retention, were analyzed to evaluate CO2 circulation efficiency. Simulation results reveal several critical findings. Elevated injection rates expanded the CO2 plume, while bottomhole pressure at the producer controlled brine ingress from the regional aquifer. Once the CO2 plume was fully developed, producer parameters emerged as dominant control factors. Completion designs at both wells proved vital in maximizing CO2 recovery and suppressing liquid loading. Permeability variations showed limited influence, likely due to sand-dominated continuity and established plume connectivity at Aquistore. Visualizations of water saturation and CO2 plume geometry underscore the need for constraint optimization to reduce fluid mixing and stabilize CO2-rich zones. The study suggests that CO2 trapped during circulation contributes meaningfully to permanent storage, offering dual environmental and energy benefits. The results emphasize the importance of not underestimating subsurface complexity when CO2 circulation is expected to occur under realistic operating conditions. This understanding paves the way to guide future pilot tests, operational planning, and risk mitigation strategies in CCS-enabled geothermal systems.