(1) National Institute of Oceanography, Dona Paula, Goa, India
ABSTRACT: Geophysical Evidences of Shallow Gas and Gas Hydrates Along the Continental Margins of India
The scientific interest of natural gas hydrates grew enormously in the last few decades, as huge quantity of methane is trapped in the hydrate accumulations of the world, which may become an alternate energy resource in the near future.
High-resolution seismic data reveal the presence of shallow gas occurrences in the form of anomalous seismic signatures such as acoustic masking, acoustic turbidity, acoustic blanking and gas seepages in the inner continental shelf and gas plumes, gas seepages and pockmarks in the upper continental slope off western India. Seismic data also indicate the presence of Bottom Simulating Reflectors (BSRs), which represent the base of gas hydrate stability zone underlain by widespread free gas, in the deep Arabian Sea. There, the upper few tens to hundreds of meters of seafloor sediments are characterized by pockmarks, pressure domes and acoustic voids or wipeouts, which are interpreted to result from fluid expulsion, probably due to gas. Bright, high-amplitude seismic reflections and distinct velocity pull-down structures or gas sags suggesting gassy sediments and/or gas-bearing sands occur along the southwestern continental margin of India. Seismic evidences (BSRs) also suggest the occurrence of gas hydrates along the eastern continental margin of India and in the Andaman offshore.
These findings are comparable with the world-wide occurrences. Integration of geological, geo-technical, geo-chemical, biological and geophysical evidences would help in better understanding of concentration, distribution and hydrate forming processes and its implications in hydrates exploration and exploitation. Acknowledgement: The author is thankful to DST (Govt. of India), for financial support (ProjectHR/UR/04/2001).
AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004.