Temperature effects in deep-water gas hydrate foam

Abstract

This study focuses on heat and mass exchange processes in hydrate foam. The foam was formed by methane bubble collection in Lake Baikal at a depth of 1400 m with a trap in the form of inverted beaker. The bubbles entering in the trap were transformed into solid hydrate foam due to low temperature and high pressure, i.e. thermobaric conditions preferable for hydrate formation. The boundary between forming hydrate foam and the water propagated slowly from top to bottom along the trap. As soon as the hydrate boundary crossed the location of temperature sensor, the temperature jump by ~ + 1.1 °C was recorded. After that during 3 h the temperature relaxes to an asymptotic magnitude which exceeded the temperature of ambient water by 0.3 °C. During the following ascent of the trap to the lake surface we recorded high amplitude oscillations of the temperature inside the foam. However the temperature was sharply stabilized on the constant level –0.25 °C once the trap left the hydrate stability zone located at a depth below 380 m. It was found that the temperature in the foam during the ascent is controlled by the performing of the work by foam gas against the forces of hydrostatic pressure and the absorption of heat by the decomposition of hydrate.