Effect of gas hydrates melting on seafloor slope instability

Type Article
Date 2004-12
Language English
Author(s) Sultan Nabil, Cochonat Pierre, Foucher Jean-Paul, Mienert J
Affiliation(s) IFREMER Brest, Dept Geosci Marines, F-29280 Plouzane, France.
Univ Tromso, N-9001 Tromso, Norway.
Source Marine Geology (0025-3227) (Elsevier), 2004-12 , Vol. 213 , N. 1-4 , P. 379-401
DOI 10.1016/j.margeo.2004.10.015
WOS© Times Cited 257
Keyword(s) Storegga, Slope failure, GLE, Finite difference, Methane hydrate
Abstract We present a theoretical study of the thermodynamic chemical equilibrium of gas hydrate in soil by taking into account the influence of temperature, pressure, pore water chemistry, and the mean pore size distribution. The model uses a new formulation based on the enthalpy form of the law of conservation of energy. The developed model shows that due to a temperature and pressure increase, hydrates may dissociate at the top of the hydrate occurrence zone to ensure a chemical equilibrium with the surrounding bulk water. This original result confirms what has been already shown through experiments. The second part of the paper presents an application of the model through a back-analysis of the giant Storegga Slide on the Norwegian margin. Two of the most important changes during and since the last deglaciation (hydrostatic pressure due to the change of the sea level and the increase of the sea water temperature) were considered in the calculation. Simulation results show that melting of gas hydrate due to the change of the gas solubility can be at the origin of a retrogressive failure initiated at the lower part of the Storegga slope. Once again, the developed model leads to predictions, which are supported by laboratory experiment results, but contradictory to previous interpretations and beliefs considering that hydrate dissociation occurs only at the bottom of the gas hydrate stability zone.
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