Transformation of deep-water methane bubbles into hydrate

TL;DR

This study investigates how deep-water methane bubbles transform into solid hydrate structures in Lake Baikal, revealing conditions that favor granular versus foam hydrate formation through in situ experiments.

Contribution

It provides new in situ observations of methane hydrate formation mechanisms and identifies environmental factors influencing hydrate structure types in deep-water settings.

Findings

Hydrate granular matter forms at lower depths and flux rates.

High porous hydrate foam forms at greater depths and higher flux rates.

Granular hydrate remains stable during ascent, while foam releases methane.

Abstract

The paper is dedicated to the mechanics of the methane bubbles in the gas hydrate stability zone of the basin. Transformation of deep-water methane bubbles into solid hydrate was investigated in Lake Baikal in situ. Released from the bottom methane bubbles were caught by different traps with transparent walls. It was observed that when bubbles entered into internal space of the trap, the bubbles could be transformed into two different solid hydrate structures depending on ambient conditions. The first structure is hydrate granular matter consisted of solid fragments with sizes of order of 1 mm. The second structure is high porous solid foam consisted of solid bubbles with sizes of order of 5 mm. The formed granular matter did not change during trap lifting up to top border of gas hydrate stability zone, whereas free methane intensively released from solid foam sample during it lifting. It was concluded that the decrease of the depth of bubble sampling and the decrease of the bubble flux rate assist to formation of hydrate granular matter, whereas increase of the depth of bubble sampling and growth of bubble flux rate assist to conversation of bubbles into high porous solid hydrate foam.