Sinking CO₂ in Supercritical Reservoirs

Area of Science:

• Earth Sciences
• Environmental Science
• Geology

Background:

• Geologic carbon storage is crucial for mitigating the climate crisis through negative CO2 emissions.
• Traditional CO2 injection occurs below 800m, but CO2's lower density than brine causes buoyancy-driven leakage, hindering deployment.
• The risk of CO2 escaping geological formations challenges the long-term effectiveness of conventional carbon sequestration.

Purpose of the Study:

• To propose and evaluate supercritical reservoirs as an alternative for geologic carbon storage.
• To address the challenge of buoyancy-driven CO2 leakage in conventional storage methods.
• To explore a new approach for safe and efficient carbon sequestration.

Main Methods:

• Investigated CO2 storage in supercritical reservoirs characterized by high pressure (>21.8 MPa) and temperature (>374°C).
• Focused on volcanic areas where these conditions are met at drilling-reachable depths.
• Analyzed the density of CO2 under supercritical conditions relative to resident brine.

Main Results:

• Supercritical CO2 is denser than water under specific reservoir conditions, mitigating upward migration.
• Supercritical reservoirs offer a storage capacity estimated between 50-500 Mt yr^-1 per 100 injection wells.
• This method significantly reduces the risk of buoyancy-driven leakage compared to traditional approaches.

Conclusions:

• Storing CO2 in supercritical reservoirs presents a viable and appealing alternative to conventional geologic carbon storage.
• This innovative approach enhances the safety and efficiency of carbon sequestration strategies.
• Further research and development in supercritical reservoir utilization are warranted for climate change mitigation.