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

Abstract

Subsea sequestration retains a huge potential in terms of the longterm viability of stable CO 2 storage and, therefore, can contribute to global carbon neutrality by addressing global warming challenges. However, macroscopic parameters such as salinity, porosity, sedimentary types, and additives play a vital role in tapping the fullest potential of subsea CO 2 sequestration. This aspect offers a wide range of opportunities for discussion and will open new avenues for future development. Therefore, there is a wide scope for discussions in this area, which will lead to new technological innovations in the future. CO 2 sequestration in subsea sediments in solid hydrate form is discussed in terms of interaction chemistry and macroscopic environmental effects on pore-scale hydrate formation and growth. This Perspective presents insights related to CO 2 hydrate formation and its long-term stability with relevance to porous media, CO 2 -sedimentary interactions, the effect of additives, and possible cost estimates for large-scale CO 2 storage in oceans. Insights into hydrate formation behavior and the effect of physicochemical parameters (interfacial tension, water saturation, organic matter, salinity, and the chemical nature of the sediments) have been additionally outlined. Light is shed on the economics of transportation and injection using cost estimates from the literature along with the challenges and outlook associated with the current technologies. The chemical interactions between CO 2 and hydrate-bearing sediments, additives, and marine environments would aid in understanding hydrate formation in subsea sediments.

Enhancing the CO2 Sequestration Potential in Subsea Terrain by Hydrate Formation from Liquid CO2

“…Improving hydrate conversion efficiency, gas uptake and overall kinetics may solve the dissolution-related issue and foster hydrate nucleation rate. , It is evident that CO 2 trapped inside the hydrate cage would not affect marine ecology and pH. Therefore, improving kinetics using additives/promoters will reduce the harsh effect of direct CO 2 dissolution in seawater …”

“…17 The following are some advantages of hydrate technology for sequestering CO 2 : (a) higher volumetric efficiency; (b) negative buoyancy effect (ρ hydrate > ρ seawater ); (c) chemically not interacting with surrounding and behaving like ice molecules. 4,18 Another obvious benefit of ocean storage is that oceans cover 70% of the earth's surface and are able to store a humongous amount of anthropogenic CO 2 . The oceanic sequestration is stable too, as one study shows that around 97% of injected CO 2 remains trapped even after 100 years of injection.…”

“…Therefore, improving kinetics using additives/promoters will reduce the harsh effect of direct CO 2 dissolution in seawater. 18 Rheological investigations of gas hydrate offer valuable insights into the flow characteristics of hydrate slurry, focusing primarily on its yield stress, strength, etc. The impact of hydrate agglomeration or uneven growth on viscosity, viscoelastic properties, and viscosity fluctuations at varying levels of hydrate saturation is also studied through rheological investigations.…”

“…A literature analysis has revealed that, although numerous mechanisms for CO 2 hydrate formation at the molecular level have been proposed, no consensus has been reached. 18 To the best of our knowledge, even though several researchers studied rheological aspects of CO 2 hydrate slurry, investigation on the rheology of CO 2 hydrate in seawater in the presence of bentonite clay is not available in open literature, which can provide valuable insights for CO 2 sequestration in porous media. A comprehensive understanding of the rheological properties of CO 2 hydrate slurries will help in several aspects to solve flow assurance challenges in a sediment bound system at sea floor at the time of CO 2 injection and serve as a foundation for further in-depth research.…”

“…At standard temperature and pressure conditions (STP), CH 4 (approximately similar to CO 2 ) hydrate can accommodate approximately 160–180 volumes of CH 4 gas per unit volume . The following are some advantages of hydrate technology for sequestering CO 2 : (a) higher volumetric efficiency; (b) negative buoyancy effect (ρ hydrate > ρ seawater ); (c) chemically not interacting with surrounding and behaving like ice molecules. , …”