Environmentally Sustainable Large-Scale CO₂ Sequestration through Hydrates in Offshore Basins: Ab Initio Comprehensive Analysis of Subsea Parameters and Economic Perspective

Abstract

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.

A Perspective on the Effect of Physicochemical Parameters, Macroscopic Environment, Additives, and Economics to Harness the Large-Scale Hydrate-Based CO2 Sequestration Potential in Oceans

“…At a depth of approximately 2800 m, the density of CO 2 supersedes the density of seawater that offers an extra gravitational barrier. 39 A suitable justification for the formation of a possible CO 2 reservoir type has been provided henceforth. The temperature profile of thermocline in the Gulf of Mexico (GoM) and geothermal profile considering the average temperature rise and density profile in oceanic and subsea conditions is depicted in Figure 5.…”

“…In oceanic conditions, temperature decreases as the depth from the sea surface increases. 39 However, temperature increases as the depth increases in subsea sediments, owing to a geothermal gradient. Further, the density of CO 2 increases as we go deeper inside oceans more prominently than the density of seawater.…”

“…However, the density of liquid CO 2 is less than the density of seawater at this depth. At a depth of approximately 2800 m, the density of CO 2 supersedes the density of seawater that offers an extra gravitational barrier …”

“…Temperature and density variation in oceans and subsea sediments as a function of depth (data taken from ref ; thermocline (Gulf of Mexico) data taken from ref ; density data taken from ref ).…”

“…Figure provides a general understanding of the various possible CO 2 sequestration conditions in oceans and subsea basins at different oceanic depths. In oceanic conditions, temperature decreases as the depth from the sea surface increases . However, temperature increases as the depth increases in subsea sediments, owing to a geothermal gradient.…”