Hydrocarbon Prospects of Growth and Inversion Related Structures of the Naga Frontal Fold Belt, Assam-Arakan Basin

Pulin C. Goswami¹ and Pradeep Goswami^2
1Oil & Natural Gas Corporation, Ankleshwar, India
²Oil & Natural Gas Corporation, Rajahmundry, India

The Naga foothills region, which constitutes the frontal fold belt of Assam-Arakan basin, is about 20-35 km wide and 200 km long narrow morpho-structural zone adjoining the Upper Assam foreland. This structural zone is bounded by two planes of major tectonic dislocations known conventionally as the Naga thrust in its northwest and the Disang thrust in its southeast. A number of near parallel longitudinal faults have dissected this zone exposing progressively older Tertiary sedimentary sequences in inner fault blocks.

Difference in opinion exists as regards to its structural style and evolution. The school of ‘thin skin tectonics’ favors extension of Upper Assam foreland sedimentary sequence along with its foreland structural imprints below the thrust-sheets of Naga Schuppen Belt for several kilometers. The up-thrust and sub-thrust stratigraphic and structural framework is, thus, distinctly different and the less disturbed foreland structures below the thrust sheets are prime targets for hydrocarbon exploration in light of structural style. The school of ‘vertical tectonics’ favor vertical movements of fault-blocks with no significant horizontal displacement.

This work presents evidences in favor of syn-sedimentary structural deformation, structural growth and inversion related structural style in the Naga frontal fold belt. The foothills region differs from adjoining Upper Assam foreland in degree of inversion which gradually increases in down-the-basin direction. Structural plays such as brow zone anticlines, pop-up structures, fault-closures in association with extensional and compressional faults etc., are identified as prime targets for structural exploration. A focused exploratory effort for these plays in India’s premier oil-gas province is expected to contribute significantly towards reserves accretion.

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