Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications



Abstract 032
On the Mechanism of Gas Hydrate Formation in Subsea Sediments
Tohidi, B., Danesh, A., Todd, A.C.
Abstract of Papers of the American Chemical Society, 213, 37-Fuel (1997).
The mechanism of gas hydrate formation in subsea sediments is the subject of some debate with diverse views on the required conditions. In this work, an in-house thermodynamic model has been used to investigate the problem by predicting the methane concentration in the water-rich phase in equilibrium with methane, methane-hydrate, and hydrate-water in the presence of distilled or saline water. The results show that the concentration of methane in the water-rich phase in equilibrium with the hydrates, is far less than the concentration of methane in the water-rich phase in equilibrium with the gas phase. The impact therefore, as far as hydrate formation in ocean sediments is concerned, is that hydrate can be potentially formed from dissolved gas as well as free gas. In this paper, two mechanisms for hydrate formation from dissolved gas and free gas have been suggested. The results show that in the formers case, the diffusion of hydrate forming gas to the hydrate stability zone controls hydrate formation, whereas in the latter case (i.e., the presence of a free gas phase), the diffusion of salt is likely to be the controlling factor.

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