Biogenic Gas Systems in Indian Sedimentary Basins

R. R. Singh, Harvir Singh, Sukumar Pahari, and Ivsv Prasad
Geochemistry, ONGC, Dehradun, India

Biogenic gas is a huge energy resource that could potentially be renewable on a human timescale and it accounts for 20% of the world's natural gas resource. Biogenic gas deposits in Indian sedimentary basins have been evaluated to identify favorable locales for accumulaion, gas source system, assess controling factors for generation and accumulation and delineate potential areas for future exploration.

Indian biogenic gas deposits reveals that it is formed at shallow depths (<1000m) by anaerobic bacterial decomposition of Type-III organic matter at low temperatures and was subsequently buried to deeper depth. Conditions suitable for the formation and entrapment of biogenic gas are present in the East coast of India during Neogene time with rapid burial associated to huge sediment supply by Ganga-Godavari river system and biogenic gas deposits have been identified at depths 500-2500m. Biogenic gas accumulations in East coast are found in close proximity to their organic source, with negligible migration and change in sea level, uplift and erosion has also played role in biogenic gas accumulation. In Krishna Godavari, biogenic gases are found in Mio-Pliocene sediments of both on land and deep water areas. In Mahanadi deep water area, late forced regressive channels in Neogene sequences are very good locale for biogenic hydrocarbon at depth 433 to 1362m from sea bed. Biogenic gas has also been identified in Viraj, Motera, Gamij, Jhalora and Sanand areas in Cambay Basin. There is also indication of biogenic gas deposits in Rudrasagar and Safrai area of north Assam shelf.

The locales having the presence of biogenic gas and potential areas for exploration have been mapped to develop an exploration strategy for Indian sedimentary basins for future. Origin, habitat and controls of biogenic gas deposits in India corroborates with global biogenic gas systems.

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