Documenting channel features associated with gas hydrates in the Krishna–Godavari Basin, offshore India.

Riedel, Michael , Collett, T.S. and Shankar, U. (2011) Documenting channel features associated with gas hydrates in the Krishna–Godavari Basin, offshore India. Marine Geology, 279 (1-4). pp. 1-11. DOI 10.1016/j.margeo.2010.10.008.

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Abstract

During the India National Gas Hydrate Program (NGHP) Expedition 01 in 2006 significant sand and gas hydrate were recovered at Site NGHP-01-15 within the Krishna–Godavari Basin, East Coast off India. At the drill site NGHP-01-15, a 5–8 m thick interval was found that is characterized by higher sand content than anywhere else at the site and within the KG Basin. Gas hydrate concentrations were determined to be 20–40% of the pore volume using wire-line electrical resistivity data as well as core-derived pore-fluid freshening trends. The gas hydrate-bearing interval was linked to a prominent seismic reflection observed in the 3D seismic data. This reflection event, mapped for about 1 km2 south of the drill site, is bound by a fault at its northern limit that may act as migration conduit for free gas to enter the gas hydrate stability zone (GHSZ) and subsequently charge the sand-rich layer. On 3D and additional regional 2D seismic data a prominent channel system was imaged mainly by using the seismic instantaneous amplitude attribute. The channel can be clearly identified by changes in the seismic character of the channel fill (sand-rich) and pronounced levees (less sand content than in the fill, but higher than in surrounding mud-dominated sediments). The entire channel sequence (channel fill and levees) has been subsequently covered and back-filled with a more mud-prone sediment sequence. Where the levees intersect the base of the GHSZ, their reflection strengths are significantly increased to 5- to 6-times the surrounding reflection amplitudes. Using the 3D seismic data these high-amplitude reflection edges where linked to the gas hydrate-bearing layer at Site NGHP-01-15. Further south along the channel the same reflection elements representing the levees do not show similarly large reflection amplitudes. However, the channel system is still characterized by several high-amplitude reflection events (a few hundred meters wide and up to ~ 1 km in extent) interpreted as gas hydrate-bearing sand intervals along the length of the channel.

Document Type: Article
Keywords: gas hydrates; channel systems; levee deposits; East Coast of India
Refereed: Yes
Open Access Journal?: No
DOI etc.: 10.1016/j.margeo.2010.10.008
ISSN: 0025-3227
Date Deposited: 17 Nov 2015 10:48
Last Modified: 17 Nov 2015 10:48
URI: http://oceanrep.geomar.de/id/eprint/30078

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