||1 : Ifremer, france
||2007 Offshore Technology Conference, 30 April-3 May 2007, Houston, USA
||Offshore Technology Conference, 30 April-3 May 2007, Houston, Texas, U.S.A. ISBN 978-1-55563-254-0. OTC-18532-MS, pp.1-9
||Parameters affecting gas hydrate formation include temperature, pore pressure, gas chemistry, and pore-water salinity. Any change in the equilibrium of these parameters may result in dissociation (gas-hydrate turns into free gas/water mixture) and/or dissolution (gas-hydrate becomes mixture of water and dissolved gas) of the gas hydrate. While, gas-hydrate dissociation at the base of the Gas Hydrate Occurrence Zone (GHOZ) is often considered as a major cause of sediment deformation and submarine slope failures the consequence in terms of pore pressure and sediment deformation of the dissolution of the gas hydrate at the top of the GHOZ remains neglected. In this study, we quantify and compare the excess pore pressure resulting from gas hydrate dissociation and dissolution. Based on theoretical development it is demonstrated that excess pore pressure and shear discontinuities generated by hydrate dissociation is unlikely to be a hazardous factor. In natural environment, the excess pore pressure generated by hydrate dissociation is bounded by the gas hydrate stability law inducing for a natural temperature increase a limited amount of excess pore pressure and limited shear discontinuities at the base of the GHOZ. On the other hand, we show that under natural temperature changes hydrate dissolution at the top of the gas hydrate stability zone, which can occur at a regional scale, is a hazardous process that can lead to catastrophic landslides.
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