GEODYNAMIC MODELING AND HYDROCARBON POTENTIALITY IN BENGAL BASIN, BANGLADESH

Bangladesh occupies most of the Bengal Basin and sits on the largest delta in the world, formed at the convergent plate boundary of India and Eurasia. It is also a potential gas rich province. The setting includes a Cretaceous passive margin to the west and the active Indo-Burma margin to the east in close proximity. The plate boundary divides Bangladesh into two broad tectonic units. The western delta plain includes a thinner coastal plain wedge landward of the Hinge Zone, the location of the Eocene shelf edge, while sediments thicken up to 16-19 km seaward of the Hinge Zone. These thick sediments are underthrusting beneath the Burma sliver and are being accreted to form the >200 km wide Indo-Burma accretionary prism. The Chittagong fold-thrust belt in SE Bangladesh are exposed anticlines formed from accreted Neogene sediments. Farther west, anticlines continue, but are buried by sediments of the Ganges-Brahmaputra-Meghna Delta. Our geodetic GPS and morphotectonic studies show the delta is subsiding and the anticlines are growing. Moreover, the tectonics create hydrocarbon (HC) migration pathways from sources to reservoirs in the folds. Exploration in Bangladesh indicates that structural closures are primarily in the accretionary prism, which have significant gas reserves, while no productive structures have so far been found farther west. However, the full HC potential has not yet been unearthed. Proven reserves will be depleted within 10 years, which is a prod for ongoing development activities in Bangladesh. Petroleum geologists believe there is significant “yet to find” natural gas and that these may be recovered with extensive exploration drive. The recent settlement of maritime boundaries open a new frontier for HC exploration in offshore Bangladesh. The HC potential in western non-tectonic onshore and offshore Bangladesh remain uncertain. As a megadelta basin, the western basin is likely to be dominated by stratigraphic plays, rather than the structural plays found in the eastern half of Bangladesh. Development of sand prone clinoforms related to delta progradation together with diversified prospects such as channel sands, pinch outs, and thin beds, have huge potentials for HCs. There are ample opportunities for undertaking research studies to improve the knowledge and database for exploration targets.