Petroleum and Source Rock Geochemistry of Krishna-Godavari Basin, India: a Case Study

Prasad, I.V.S.V.¹, M. Varshney², A.K.S. Madhavan³, B.S. Negi³, T. Chand³, S. Pahari¹, A.K. Sinha³, H. Singh³, A.K. Mittal⁴, B.G. Goswami³, R.R. Singh⁵ (1) KDM Institute of Petroleum Exploration, Oil & Natural Gas Corporation Ltd, Dehradun, India (2) KDM Institute of Petroleum Exploration, ONGC, Dehradun, Indonesia (3) KDM Institute of Petroleum Exploration, ONGC, Dehradun, India (4) ONGC, Dehradun, India (5) Oil & Natural Gas Corporation Ltd, Dehradun, India

The hydrocarbon potential of east coast of India is gaining global petroleum industry attention. Krishna-Godavari basin, a poly-historic basin situated on the passive eastern continental margin of India, spanning an area of 28,000 sq km on land and 145,000 sq km offshore, has made rapid strides in the field of oil and natural gas exploration and production during the last two decades.

The paper presents the summary of the results of systematic processing and evaluation of the source rock data of 225 wells, petroleum geochemistry of 202 oil/condensate samples and 169 gases. Statistical processing of the geochemical data and regional evaluation using spatial and temporal distribution of source rocks enabled to recognize 16 distinctly different potential as well as effective source rock sequences in 11 formations varying from Permian to Miocene age. Significant kinetic diversity has been recognized among different source rock facies.

Based on the distribution of API gravities, bulk compositional properties, stable carbon isotopic as well as molecular geochemical data of the oils/condensates produced from 12 distinct stratigraphic plays varying from Pliocene to Permo-Triassic age are grouped into 16 distinct families. The hydrocarbon gases discovered and produced from 16 stratigraphic plays varying from Recent-Pleistocene to Permo-Triassic age reveal 26 distinctly different gas families.

Source-reservoir relationship enabled to define six Tertiary and five pre-Tertiary major petroleum systems. The entire drainage area lying around the down-dip mature source kitchen comprising Eocene, Paleocene and Cretaceous sediments towards the basinal side need more attention to find the undiscovered hydrocarbons.