Temperature effects in deep-water hydrate foam

TL;DR

This study investigates the temperature dynamics of methane hydrate foam formation and decomposition during ascent in Lake Baikal, revealing temperature drops associated with hydrate formation and heat absorption at the GHSZ boundary.

Contribution

It provides detailed measurements of temperature changes in hydrate foam during ascent, highlighting the heat exchange processes involved in hydrate formation and decomposition.

Findings

Temperature decreases during ascent within GHSZ, reaching negative values.

Sharp temperature drop observed at the GHSZ boundary due to hydrate decomposition.

Temperature stabilizes near -0.25°C at the surface.

Abstract

This study focuses on heat and mass exchange processes in hydrate foam during its formation from methane bubbles in gas hydrate stability zone (GHSZ) of the Lake Baikal and following delivery of it in open container to the lake surface. The foam was formed as a result of methane bubble collection with a trap/container. The trap was inverted glass beaker of diameter of 70 mm and 360 mm long. Open bottom end of the beaker used as enter for bubbles ascended from the lakebed. At a depth of 1400 m all bubbles which fed to the trap were transformed here into solid hydrate foam. The sensitive thermometer was mounted in the middle of the trap and recorded the temperature inside trap. The fate of the bubbles in the trap was recorded by video-camera. During ascend within GHSZ with velocity of about 0.375 m/s we observed the continuous decrease of the temperature in the foam up to a level of negative magnitude in a depth interval of 1400 - 750 meters. Above 750 m temperature decrease was changed by small growth. However once the trap ascended above top boundary of GHSZ at a depth of 380 m, the temperature fell sharply. Falling to a negative values -0.25 oC, the temperature sharply stabilized and did not changed further until the trap reached the surface. The decreasing of the temperature during the ascent is due to the cooling of gas as a result of the performing of the work against the forces of hydrostatic pressure. The temperature drop at the boundary of the GHSZ is due to the absorption of heat by the decomposition of hydrate.