Print this pageDiscovery of One of the Thickest and Deepest Gas Hydrate Occurrences Yet Known Along the Indian Continental Margins
M. V. Ramana1, P. Kumar2, T. Ramprasad1, M. A. Desa1, and M. V. Lall3
1Geological Oceanography Division, National Institute of Oceanography, Panaji, India
2Institute of Engineering & Ocean Technology, Oil and Natural Gas Corporation Ltd., Mumbai, India
3Directorate General of Hydrocarbons, New Delhi, India
It is now well established based on seismic evidence and drilling that gas hydrate can occur in the permafrost regions and continental slope sediments, and methane is the primary source for formation of natural gas hydrate under certain pressure and temperature conditions. Though the passive margins once were considered as significant potential zones for gas hydrate deposits, experience reveals that gas hydrates do occur but not that abundantly along these margins, and if present, they contain lower concentrations of methane gas. Good example of this kind is the Blake Outer Ridge, eastern margin of North America. On the other hand, repeated investigations along active margins i.e., the Nankai Trough in Japan Sea and Cascadian margin, west of North America reveal the occurrence of gas hydrate in nearly horizontal layers, a few hundred meters beneath the seafloor of the continental slope region.
India undertook NGHP Expedition 01 during 2006 in two geologically distinct provinces i.e., passive margins of the Indian Peninsula and the Andaman convergent margin, under the aegis of National Gas Hydrate Programme based on geoscientific data. These efforts have led to the discovery of one of the richest marine gas hydrate accumulations yet discovered in the world (Krishna-Godavari offshore), and thickest and deepest gas hydrate occurrence yet known (Andaman Sea) in volcanic ash bed as deep as 600 meters below the seafloor. This program also established the existence of a fully developed gas hydrate system in the Mahanadi offshore. We present the results obtained from these investigations in the passive margin and marine accretionary wedge settings in the Indian offshore.
AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas