Environmentally Sustainable Large-Scale CO<inf>2</inf> Sequestration through Hydrates in Offshore Basins: Ab Initio Comprehensive Analysis of Subsea Parameters and Economic Perspective

Immediate measures are required to tackle global warming and climate change that may require the storage of enormous quantities of anthropogenic CO2 in geological and oceanic reservoirs. In terrestrial storage sites, CO2 is buoyant due to the subsurface temperature profile. Therefore, if the reservoir is not adequately sealed, stored CO2 can escape from geological formations. Alternatively, oceanic sequestration has immense potential to facilitate long-term sequestration of CO2 beneath the seafloor, thereby assisting the wider scientific and industrial community to make the world carbon neutral. There is a far-reaching scope for discussion in this aspect that will open up new avenues for future developments in this area. This article discusses the long-term viability, environmental sustainability and economic potential of CO2 sequestration in the form of hydrates into oceanic and subsea sediments. Analysis shows that at above 2800 m depth, CO2 is denser than seawater, which offers an additional gravitation barrier for CO2 to escape. This article offers an in-depth analysis of CO2 sequestration conditions, along with challenges and outlook with relevance to hydrate-based CO2 sequestration in oceanic conditions. Moreover, the crucial role of negative buoyancy and hydrate-forming zones (NBZ/HFZs) and analysis of depth criterion in oceanic conditions have been highlighted. The review also envisages that sequestration in NBZ region offers stable storage for years even in geological perturbation and earthquakes; however the depth of HFZ and NBZ regions depends on sedimentary type, storage conditions, temperature and pressure.