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TitreGas hydrates in the western deep-water Ulleung Basin, East Sea of Korea
AuteurRyu, B -J; Riedel, M; Kim, J -H; Hyndman, R D; Lee, Y -J; Chung, B -H; Kim, I -S
SourceMarine and Petroleum Geology vol. 26, issue 8, 2009 p. 1483-1498,
Séries alt.Secteur des sciences de la Terre, Contribution externe 2005520
ÉditeurElsevier BV
Documentpublication en série
Mediapapier; en ligne; numérique
Sujetslevés géophysiques; hydrate; levés de reflexion sismiques; carottages par piston; carottes de sédiment marin; carbone organique; analyses de carbone organique; données sismiques; prospection sismique; hydrates de gaz
Illustrationslocation maps; core logs; tables; graphs; seismic reflection profiles; seismic velocity profiles
Résumé(disponible en anglais seulement)
Geophysical surveys and geological studies of gas hydrates in the western deep-water Ulleung Basin of the East Sea off the east coast of Korea have been carried out by the Korea Institute of Geoscience and Mineral Resources (KIGAM) since 2000. The work included a grid of 4782 km of 2D multi-channel seismic reflection lines and 11 piston cores 5 - 8 m long. In the piston cores, cracks generally parallel to bedding suggest significant in-situ gas. The cores showed high amounts of total organic carbon (TOC), and from the southern study area showed high residual hydrocarbon gas concentrations. The lack of higher hydrocarbons and the carbon isotope ratios indicate that the methane is primarily biogenic. The seismic data show areas of bottom-simulating reflectors (BSRs) that are associated with gas hydrates and underlying free gas. An important observation is the numerous seismic blanking zones up to 2 km across that probably reflect widespread fluid and gas venting and that are inferred to contain substantial gas hydrate. Some of the important results are: (1) BSRs are widespread, although most have low amplitudes; (2) increased P-wave velocities above some BSRs suggest distributed low to moderate concentration gas hydrate whereas a velocity decrease below the BSR suggests free gas; (3) the blanking zones are often associated with upbowing of sedimentary bedding reflectors in time sections that has been interpreted at least in part due to velocity pull-up produced by high-velocity gas hydrate. High gas hydrate concentrations are also inferred in several examples where high interval velocities are resolved within the blanking zones. Recently, gas hydrate recoveries by the piston coring and deep-drilling in 2007 support the interpretation of substantial gas hydrate in many of these structures.