Periodic states and their implications in gas hydrate systems

Abstract

Gas hydrates are one of the largest marine carbon reservoirs on Earth. The conventional understanding of hydrate dynamics assumes that the system, in the absence of external triggers, converges to a steady-state over geological time-scales, achieving fixed concentrations of gas hydrate and free gas phase. However, using a high-fidelity numerical model and consistently resolving phase states across multiple fluid-fluid and fluid-solid phase boundaries, we have identified well-defined periodic states embedded within hydrate system dynamics. These states lead to cyclic formation and dissolution of massive hydrate layers that is self-sustaining for the majority of natural marine settings. This previously unresolved characteristic could manifest as spontaneous gas migration and pressure release in, supposedly, unperturbed systems. Our findings show that the gas hydrate systems are not bound to have unique steady-state solutions. Instead, existence of periodic states introduces an irreducible, but, quantifiable uncertainty in gas hydrate dynamics which adds significant error bars to global gas hydrate inventory estimates.