International Conference on Gas Hydrates (ICGH) (6th : 2008)

ISOTOPIC FRACTIONATION OF GUEST GAS AT THE FORMATION OF METHANE AND ETHANE HYDRATES Hachikubo, Akihiro; Ozeki, Takahiro; Kosaka, Tomoko; Sakagami, Hirotoshi; Minami, Hirotsugu; Nunokawa, Yutaka; Takahashi, Nobuo; Shoji, Hitoshi; Kida, Masato; Krylov, Alexey

Abstract

Stable isotope of natural gas hydrates provides useful information of their gas sources. We investigated the isotopic fractionation of gas molecules during the formation of synthetic gas hydrates composed of methane and ethane. The gas hydrate samples were experimentally prepared in a pressure cell and isotopic compositions (δ13C and δD) of both residual and hydratebound gases were measured. δD of hydrate-bound molecules of methane and ethane hydrates was several per mil lower than that of residual gas molecules in the formation processes, while there was no difference in the case of δ13C. Effect of temperature on the isotopic fractionation was also investigated and it was found that the fractionation was effective at low temperature.

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