Can gas hydrates be transported at atmospheric pressure? A review of the self-preservation phenomenon in gas hydrates

Gas hydrates are a promising medium for natural gas storage and transportation due to their safety, high storage density, and cost-effectiveness. Traditional gas transportation often faces challenges such as leakage, leading to fugitive emissions. Gas hydrates can mitigate these issues by securely trapping gas molecules under phase equilibrium conditions. However, they release gas immediately when pressure or temperature deviates from the equilibrium zone, necessitating continuous, energy-intensive pressurization throughout the transportation process. The self-preservation phenomenon reduces the pressure requirements for gas hydrate operations, allowing gas to be stored and transported at reduced or even atmospheric pressure. Despite the large number of studies on the self-preservation effect in gas hydrates, there has been no comprehensive review of its research status. This paper presents the first comprehensive review of the research progress on the self-preservation phenomenon in gas hydrates. It provides an in-depth discussion of the fundamental characteristics of this effect, a thorough analysis of methods used to enhance it, and the mechanisms that lead to its absence. Additionally, the review summarizes current understanding of the microscopic mechanisms underlying the self-preservation phenomenon and explores the different dissociation models of hydrates in this state. By systematically reviewing related studies, this paper offers theoretical support for a deeper understanding and practical utilization of the self-preservation effect in gas hydrates, while providing valuable insights into future research directions and technological applications.