Gas hydrate recycling: overview and future directions

Natural gas hydrates are an important component of the global and oceanic biogeochemical cycle. However, much remains to be understood about gas hydrate systems, including processes resulting in the accumulation of high-concentration deposits. Gas hydrate recycling is a prominent mechanism in producing elevated hydrate saturations near the base of the gas hydrate stability zone (BGHSZ). During gas hydrate recycling, the BGHSZ moves upward relative to a given interval of hydrate-bearing sediment (i.e., hydrate-bearing sediment moves downward relative to the BGHSZ), causing hydrate to dissociate into water and free gas that may be “recycled” by migrating buoyantly upward and being reincorporated into the new GHSZ. This iterative process progressively enriches hydrate deposits via successive hydrate destabilization and re-accumulation. The purpose of this review is to: (1) describe the gas hydrate recycling process, (2) outline potential drivers of hydrate recycling, and (3) discuss knowledge gaps and opportunities for future research.