Identification and characterization of marine geohazards in the deep water eastern offshore of India: constraints from multibeam bathymetry,side scan sonar and 3D high-resolution seismic data |
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| Authors: | Rabi Bastia M Radhakrishna Satyabrata Nayak |
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| Institution: | (1) E&P Division, Reliance Industries Ltd, Navi Mumbai, India;(2) Department of Earth Sciences, Indian Institute of Technology Bombay, Powai, Mumbai, 400076, India |
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| Abstract: | The eastern offshore of India covers a vast stretch of sedimentary tract fed by major rivers like Ganges, Brahmaputra and
Mahanadi in the north, Krishna and Godavari in the center, and Cauvery and Palar in the south, which led to variations in
shelf-slope characteristics, degree of slope and hence slope instability. The structure as well as seismic attribute maps
prepared from multibeam bathymetry and high-resolution 3D seismic data set has been analyzed to identify various geohazards
in the deep water offshore regions of the east coast of India. These can be categorized as slope instability, slope canyons,
shallow gas, mass transport complexes, sediment waves, gas hydrates, gas chimney, mud volcanoes and shallow faults. The slope
instability is primarily related to rapid sedimentation by the active river systems while the other geohazards are often developed
in association with shallow gas flows and leakages. The bottom simulating reflectors (BSRs) identified in the seismic sections
indicate the presence of gas hydrates. Rapid sedimentation, BSR formation, dissolution and expulsion of water as well as gas
and their subsequent vertical migration are responsible for the formation of shallow gas-related hazards. The results from
the above analysis are of immense help in minimizing the risk of shallow hazards during exploration, drilling and subsurface
installation activities along the eastern Indian offshore. |
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