EVALUATION OF DEPOSITIONAL HISTORY AND HYDROCARBON PROSPECTIVITY OF THE HINGE ZONE OF BENGAL BASIN USING SEISMIC SEQUENCE STRATIGRAPHIC MODEL

Exploration for hydrocarbons in the Bengal Basin has traditionally focused on the eastern fold belt region. However, the recent drilling of the Mobarakpur-1 well has opened up new possibilities for identifying potential stratigraphic traps in the western shelfal part of the Bengal Basin. Our comprehensive study involves an analysis of 30 regional 2D seismic lines, two well logs, and biostratigraphic data from the western shelfal area. The aim is to enhance our understanding of the sequence stratigraphic framework, depositional evolution, and hydrocarbon potentiality. Within the shelf prograding interval, we have identified and mapped eight seismic sequences, with all sequences being siliciclastic except for seismic sequence 4, which represents a carbonate-rich deposit in a platform and build-up type setting. Notably, the initiation of the Ganges-Brahmaputra-Meghna (GBM) delta system is marked by seismic sequence 5, signifying a substantial influx of sediments from the rising Himalayas. The subsequent deposition of seismic sequence 6 is characterized by a forced regression of sea level, resulting in the formation of the extensive Mobarakpur Canyon System. This canyon, formed through intensive erosion, later became a potential source for hydrocarbon reservoirs through the bypass and slumping of sediments, creating a large submarine fan in the downdip area. The progradation of the shelf edge extended approximately 40 km between the deposition of seismic sequences 6 to 8. Above sequence 8, the deposits in the study area are dominated by fluvial processes, featuring intense channel cuts that complicate seismic sequence stratigraphic subdivision. The thickness of each sequence increases towards the southeast, displaying an overall tilting in that direction. Abundant depocenter switching suggests multiple sources, positions, and phases of development within the interval of interest. Potential lead types identified in this area include shelf, slope fan, and basin floor fan. While the Mobarakpur-1 well tested a shelf lead, slope, and basin floor fan leads remain unexplored.