[1] Review of the literature reveals that the nature of pore-scale interactions between gas hydrates and porous media remains a matter of controversy. To clarify the situation, nuclear magnetic resonance (NMR) measurements have been made on methane hydrate-bearing sandstones. The samples were synthetically prepared within the gas hydrate stability zone, at or near the seafloor in Monterey Bay, California. The method simulated natural hydrate deposition by gas flows that are not in thermodynamic equilibrium with the surrounding earth. The efficiency of hydrate production was variable, as has been observed elsewhere. When substantial hydrate saturations were achieved, NMR relaxation time measurements indicated that hydrate tended to replace water in the largest pore spaces. The relative permeability to water, as determined by an NMR-based correlation, was significantly reduced. The magnitude of this reduction was also consistent with formation of hydrate in the centers of pores, rather than with hydrate coating the grains. The growth habit suggested by these results is consistent with creation of hydrate nodules and lenses in coarse, unconsolidated sediments. It is also consistent with scenarios in which methane gas is delivered efficiently to the atmosphere as a result of seafloor slope failure, thereby strengthening global warming feedback mechanisms.

https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/2003JB002389

Deep sea NMR: Methane hydrate growth habit in porous media and its relationship to hydraulic permeability, deposit accumulation, and submarine slope stability

Gas hydrates have received considerable attention due to their important role in flow assurance for the oil and gas industry, their extensive natural occurrence on Earth and extraterrestrial planets, and their significant applications in sustainable technologies including but not limited to gas and energy storage, gas separation, and water desalination Given not only their inherent structural flexibility depending on the type of guest gas molecules and formation conditions, but also the synthetic effects of a wide range of chemical additives on their properties, these variabilities could be exploited to optimise the role of gas hydrates This includes increasing their industrial applications, understanding and utilising their role in Nature, identifying potential methods for safely extracting natural gases stored in naturally occurring hydrates within the Earth, and for developing green technologies This review summarizes the different properties of gas hydrates as well as their formation and dissociation kinetics and then reviews the fast-growing literature reporting their role and applications in the aforementioned fields, mainly concentrating on advances during the last decade Challenges, limitations, and future perspectives of each field are briefly discussed The overall objective of this review is to provide readers with an extensive overview of gas hydrates that we hope will stimulate further work on this riveting field

Gas hydrates in sustainable chemistry

https://www.eng.yale.edu/aflab/archive/pdf/induction.pdf

P. Skovborg

Papers

Measurement of induction times for the formation of methane and ethane gas hydrates