Methane hydrate formation in porous media: Overview and perspectives

Natural gas hydrate (NGH) has recently received more attention as a cleaner alternative energy source that not only reduces carbon emissions caused by the use of conventional fossil fuels but also plays a key role in global climate change. Furthermore, hydrate-based technologies, particularly hydrate-based carbon capture and storage, have enormous promise for decreasing global carbon emissions, and porous media play an important role in all hydrate-based technologies. Accordingly, this paper reviews the recent applications of porous media in the field of methane hydrate (MH) formation and analyzes the influence of porous media systems on MH phase equilibria and formation kinetics. This is because the efficiency of hydrate-based technologies is determined mainly by the phase equilibrium and formation kinetics of hydrates. The influence of the nature of the media on MH formation in porous media systems is comprehensively summarized to understand how porous media can efficiently enhance the kinetics of hydrate formation. Promoters are necessary for rapid hydrate formation, and the effect of various promoters on MH formation was also evaluated. Based on the aforementioned overview and understanding, the mechanisms for MH formation in various porous media systems are proposed. Finally, the future perspectives and challenges of hydrate-based technologies in tackling global climate change were discussed. This review provides a fundamental understanding of the application and development of porous media in rapid hydrate formation, a fair evaluation of the performance of various porous media systems, and critical insights into major research foci.