The Occurrence Patterns Of Gas Hydrate In The Ulleung Basin, East Sea

total of 6,690 L-kms of two-dimensional and 400 km(2) of three-dimensional multi-channel seismic reflection data were collected in the Ulleung Basin, East Sea in 2005 and 2006. On the basis of the echo-sounding images of precision deepsea recorder and the multi-channel seismic interpretation, seismic indicators of gas hydrate and associated gas such as bottom simulating reflector (BSR), acoustic blanking, column structure, gas seepage, enhanced reflection were identified. Gas hydrate was detected in localized column structure and sandy layer as nodules, veins, layers, and as disseminated forms from the previous expedition in 2007. Fractures, faults, sandy layer could be the migration pathways transporting fluid and gas to stability zone. Upward diffuse fluid flow could also transport fluid and gas to stability zone. The occurrence types of gas hydrate based on the patterns of gas and fluid migration and the gas hydrate accumulation in the Ulleung Basin include: (1) nodules, veins, layers in muddy sediments and disseminated forms in sandy layer within localized column structure, (2) disseminated forms in sandy layer due to fluid and gas transport through faults, and (3) disseminated forms in sandy layer just above BSR due to fluid and gas transport by upward diffuse fluid flow and through sandy layer.