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Identification of Deep-Water Geomorphic Features in Relation to Hydrocarbon Exploration Using 3-D Seismic, Andaman Basin, India

Nandi, Arun K.1; Samanta, Braja G.1; Rajesh, Kotekal G.1
1 Exploration, Oil & Natural Gas Corporation, India, Kolkata, India.

The Andaman basin is situated towards southeastern part of Bay of Bengal associated with converging plate boundaries. The basin is part of a large geotectonic unit that extends from Sumatra (Indonesian) Islands in the south to Myanmar (Burma) in the north. Major geotectonic units from east to west are back arc, volcanic arc, fore arc, Island arc and fore deep; which are related to the subduction tectonics.

The deepwater frontier holds a promise for future prospectivity in the scenario of depleting resources in onland and shallow off-shore. However, due of their relative inaccessibility for direct observation and comprehension, deepwater depositional systems pose a greater degree of uncertainty in the exploration for hydrocarbons. The 3D seismic data with its seismic time slices, horizon slices and interval attributes provides images of deepwater depositional systems in a map view that can be analyzed in the light of classical geomorphological concepts (Posamentier and Kolla, 2003).

The present paper focuses on the various seismic geomorphic features identified in the deep waters of Andaman Basin to the east of Andaman island arc within Forarc and a portion of Backarc sub-basin. Neogene 3D seismic horizon slicing has indicated various seismic geomorphologic features like i) Turbidity-flow leveed channels , ii) Channel overbank sediment waves iii) Crevasse splay/ overbank splay deposits , iv) Frontal splays or fan lobes and v) Debris flow deposits. Besides, amplitude extraction maps, seismic facies maps, seismic trace coherence maps, voxel picking and opacity rendering have also confirmed the identified anamolies.

Different geomorphic features and their analysis have a great significance in the understanding of the basin evolution history. Shifting of the channel systems in response to the change of slope and direction of the sediment transport is quite clearly observed. These give an idea of past seascapes and depositional environments and provide key evidence for the interpretation of paleo-depositional settings.

Analysis of depositional elements in the light of the seismic geomorphological concepts has helped in reconstruction of the sediment fill history and tectonic evolution of the basin. Further, the application of seismic geomorphological concepts and quantitative analysis of various features has helped in predicting the location of reservoir facies and in reducing the uncertainty and associated risk.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009