SEQUENCE STRATIGRAPHIC APPROACH TO RESOLVE THE LITHOSTRATIGRAPHIC DILEMMA IN HYDROCARBON EXPLORATION OF BANGLADESH

Lithostratigraphic dilemma in Bengal Foredeep is due to the current use of an outdated and infelicitous stratigraphic framework, which is based on Evans's (1932) classification of the Tertiary sedimentary sequence of Assam. Adopting Evan’s stratigraphic classification in Bangladesh has been challenged for years, due to the diachronic progradation of basin development, lack of regional marker horizons and spatial facies variation. Despite this, the current institutional practice of the old stratigraphic scheme causes difficulties in stratigraphic correlation and paleographic reconstruction that is of critical significance in resolving the challenges of assessing the hydrocarbon potentiality of the country, and to expand the goal of the exploration from structural to stratigraphic traps.

Sequence stratigraphy which includes a frame for integrated seismic interpretation, wireline logs and well data that is largely expedites the exploration by defining play boundaries and prospects. Sequence stratigraphy has already been successfully used in the Bengal Foredeep to locate the turbidite systems (lowstand systems tract) and incised valley-fills (lowstand and transgressive systems tracts). A tentative correlation between the offshore and the onshore fold belt sequences is also proposed. However, trapping mechanisms and timing of hydrocarbon migration in Bengal Basin still remains undetermined, an important issue of future prospect and risk evaluation.