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TitreCombined controlled source electromagnetic, reflection seismic and borehole study at the shallow-water edge of gas hydrate stability offshore Vancouver Island, IODP Expedition Site U1329
AuteurGehrmann, R; Riedel, M; Schwalenberg, K; Scherwath, M
SourceProceedings of the 7th International Conference on Gas Hydrates (ICGH 2011); 2011 p. 1-9
Séries alt.Secteur des sciences de la Terre, Contribution externe 20110047
Réunion7th International Conference on Gas Hydrates (ICGH 2011); Edinburgh; GB; juillet 17-21, 2011
Medianumérique; en ligne
ProvinceRégion extracotière de l'ouest
Lat/Long OENS-126.7750 -126.6000 48.8300 48.7400
Sujetshydrate; carottes; résistivité électrique; levés électromagnétiques; interpretations sismiques; interprétations géophysiques; levés de reflexion sismiques; hydrates de gaz; géophysique; sédimentologie; géologie marine; combustibles fossiles; Quaternaire
Illustrationsseismic profiles
ProgrammeCaractérisation des Hydrates de gaz, Hydrates de gaz
Résumé(disponible en anglais seulement)
On the northern Cascadia margin offshore Vancouver Island abundant gas hydrate deposits have been found and characterized through various geophysical imaging techniques and by deep drilling of the Ocean Drilling Program (ODP) Leg 146 and Integrated Ocean Drilling Program (IODP) Expedition 311. The Site U1329 was drilled during IODP Expedition 311 to investigate the shallow edge of the gas hydrate stability zone (GHSZ) in water depths near 900 m and some evidence for a small amount of gas hydrate was detected near the predicted base of the GHSZ as pore-water freshening was observed after core recovery. Borehole wireline, logging-while-drilling (LWD), and core data from Site U1329 provide ground-truth information on the physical properties of the sediments. We calculated the gas hydrate content from the chlorinity data and electrical resistivity data using Archie's law. We compare the results to the regional information gathered by reflection seismic and Controlled Source Electromagnetic (CSEM) data. The preliminary analysis of the CSEM data along profiles intersecting at Site U1329 show lateral variability in the inverted apparent resistivity values which may indicate a variable gas hydrate or free gas concentration within the top 100 mbsf. A pronounced resistivity anomaly further upslope at the edge of the gas hydrate stability zone that cannot be explained with the seismic data acquired in 1999 can be related to the dynamic change of the gas hydrate system as it has been observed in 2005 and 2006 on the CSEM data.