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A comparative Raman spectroscopic study of natural gas hydrates collected at different geological sites ArchiMer
Chazallon, B; Focsa, C; Charlou, Jean-luc; Bourry, Christophe; Donval, Jean-pierre.
Intact natural gas hydrates recovered on the West Aftican margin in the South Atlantic Ocean (ZaiAngo and Neris IIrojects) and from the Norwegian Sea (Hakon Mosby Mud Volcano) are investigated by micro-Raman spectroscopy at ambient pressure and low temperature. The gas hydrates collected at different geological sites contain a high methane concentration relative to other minor components that are slightly dispersed in the samples. They crystallize in a type I cubic lattice structure as also confirmed by our preliminary synchrotron diffraction results obtained on the ZaiAngo specimen. However, detailed analysis of selected microscopic areas reveals a variation in the gas distribution among the different specimens. Trace amounts of CO2 and H2S can be...
Tipo: Text Palavras-chave: Micro Raman spectroscopy; H2S hydrate; CH4 hydrate; Natural clathrate hydrates.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-4303.pdf
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Caractérisation physique et géochimique d'hydrates de gaz d'environnements géologiques différents. Apport des techniques de Diffraction X Synchrotron et de Spectroscopie Raman. Contribution à l'étude de leur origine, formation et stabilité sur les marges ArchiMer
Bourry, Christophe.
Clathrate hydrates are inclusion compounds consisting of an ice-like network of water cages surrounding occluded guest molecules. They occur beneath the oceans and in polar regions, where low temperature and high pressure conditions prevail. Natural gas hydrates, mainly composed of methane occur worldwide and may contain huge natural gas amount, but they can also play an important role in continental slope stability or climate change, due to the potentially enormous "greenhouse" feedback effect of methane. The knowledge of their occurrence in the natural environment, their physical, chemical or thermodynamical properties is essential to prevent geohazards, to anticipate their role in climate change or to develop technologies to take advantage of this...
Tipo: Text Palavras-chave: X Ray synchrotron diffraction; Raman spectroscopy; Geochemistry; Gas hydrate; Eau interstitielle; Diffraction X synchrotron; Spectroscopie Raman; Géochimie; Hydrate de gaz.
Ano: 2008 URL: http://archimer.ifremer.fr/doc/2008/these-6236.pdf
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Free gas and gas hydrates from the Sea of Marmara, Turkey Chemical and structural characterization ArchiMer
Bourry, Christophe; Chazallon, Bertrand; Charlou, Jean-luc; Donval, Jean-pierre; Ruffine, Livio; Henry, Pierre; Geli, Louis; Cagatay, M. Namik; Inan, Sedat; Moreau, Myriam.
Gas hydrates and gas bubbles were collected during the MARNAUT cruise (May-June 2007) in the Sea of Marmara along the North Anatolian Fault system, Turkey. Gas hydrates were sampled in the western part of the Sea of Marmara (on the Western High), and three gas-bubble samples were recovered on the Western High, the Central High (center part of the Sea of Marmara) and in the Cinarcik Basin (eastern part of the Sea of Marmara). Methane is the major component of hydrates (66.1%), but heavier gases such as C-2, C-3, and i-C-4 are also present in relatively high concentration. The methane contained within gas hydrate is clearly thermogenic as evidenced by a low C-1/C-2 + C-3 ratio of 3.3, and carbon and hydrogen isotopic data (delta C-13(CH4) of -44.1 parts per...
Tipo: Text Palavras-chave: Isotopes; Thermogenic gas; Gas bubbles; Gas hydrate; Sea of Marmara.
Ano: 2009 URL: http://archimer.ifremer.fr/doc/2009/publication-6844.pdf
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Natural gas hydrates investigated by X-ray synchrotron diffraction ArchiMer
Chazallon, B; Bourry, Christophe; Charlou, Jean-luc; Donval, Jean-pierre; Brunelli, M; Focsa, C.
Tipo: Text
Ano: 2007 URL: http://archimer.ifremer.fr/doc/00068/17924/15460.pdf
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X-ray synchrotron diffraction study of natural gas hydrates from African margin - art. no. L22303 ArchiMer
Bourry, Christophe; Charlou, Jean-luc; Donval, Jean-pierre; Brunelli, M; Focsa, C; Chazallon, B.
Natural gas hydrates recovered from the Congo- Angola basin and Nigerian margins are analyzed by synchrotron X- ray powder diffraction. Biogenic methane is the most abundant gas trapped in the samples and others minor components (CO2, H2S) are co-clathrated in a type I cubic lattice structure. The refinement for the type I structure gives lattice parameters of a = 11.8646 ( 39) angstrom and a = 11.8619 ( 23) angstrom for specimens from Congo- Angola and Nigerian margins respectively at 90 K. These values, intermediate between the lattice constant of less pure methane specimens and pure artificial methane hydrates, indicate that lattice constants can be affected by the presence of encaged CO2, H2S and other gas molecules, even in small amounts. Thermal...
Tipo: Text Palavras-chave: Synchrotron X ray diffraction; Thermal expansion; Natural clathrate hydrates.
Ano: 2007 URL: http://archimer.ifremer.fr/doc/2007/publication-3511.pdf
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