An Innovative Solution Method for the Evaluation of CO2 Disposal in the Seafloor Environment

Injecting carbon dioxide (CO2) into underground geo-structures, such as depleted oil and gas reservoirs, reduces man-made CO2 emissions into the atmosphere or removes what is already there. Studies have identified the risks of CO2 leaks from these underground geo-structures through wellbores back into the atmosphere due to the high mobility of CO2 in gaseous and supercritical states. This work aims at proposing a novel method of CO2 storage using the Joule–Thomson cooling effect to effectively produce CO2 hydrates on seafloors, with an objective to avoid the leakage risks of storage in depleted oil and gas reservoirs. Through the combination of thermodynamic data, analysis of hydrate stability, and engineering design with established working parameters, this study proposes an innovative concept and an enabling process for CO2 placement onto seafloors for safe storage. The results of case analysis of typical seawater conditions reveal that the appropriate seafloor depth ranges for different applications (>1900 m for liquid CO2 and 700–1900 m for CO2 hydrate). An engineering design procedure for real applications is outlined.