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Seismic Architecture and Characterisation of Deep Water Slope-Fan Channel Plays in the Northern Bay of Bengal: A Review Based from New Seismic Data

Kieran Ryan, David Beckett, and John Chambers
Santos Ltd, Adelaide, SA, Australia

Recently acquired closely spaced high resolution 2D seismic over 17,000km2 in the NEC Basin has allowed detailed analysis of the depositional geometries and architecture associated with a series of Plio-Pleistocene channel-levee complexes developed on the slope of the Bengal Fan.

Seismic character analysis has led to the identification of a number of potential trapping configurations with both structural and stratigraphic elements. These include channel-levee systems developed in a series of vertically stacked and laterally migrating high amplitude, chaotic seismic facies bounded by low amplitude, semi-transparent levee deposits with distinct gull-wing form. Separate channel-levee units are well defined by seismically continuous high amplitude reflection packages (HARPs) that are representative of channel overbank facies deposited during periods of increased sediment influx.

Traps are generated both by stratigraphic pinch-out of channel and overbank reservoir sands and in low-relief antiformal structures caused by differential compaction of channel-levee complex sediments. Reservoirs developed within this system are likely to be charged by hydrocarbons sourced from disseminated organic matter in underlying and adjacent sediments. Regionally defined seismic events are suggestive of temporary rises in relative sea level that may provide regional seals across the Northern Bay of Bengal. Potential exists for both biogenic and thermogenic processes to generate hydrocarbons in this environment.

Primary exploration targets within this regime include laterally stacked channel sands and interbedded overbank deposits. Source yield and volumetric analysis of seismically defined traps indicates potential for the existence of several multi-tcf hydrocarbon prospects within the area covered by this seismic survey.

Presentation GEO India Expo XXI, Noida, New Delhi, India 2008©AAPG Search and Discovery