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ABSTRACT: The Vadaparru-Ravva (·) petroleum system in Krishna-Godavari offshore Basin, eastern offshore, India

Rao, S. V.1, D. R. Ghosh1, C. S. Ramdas1, K. S. Bhushan1, M. S. Srinivas1, and Y. R. Rao2
(1) Oil And Natural Gas Corporation Ltd, Mumbai, Maharastra, India 
(2) ONGC, Chennai, India

The Vadaparru- Ravva (·) Petroleum system encompasses an area of about 4 Lakh , forming a part of the pericratonic passive margin Krishna-Godavari offshore basin. The inplace estimates of 81.84 MMt of oil and 21.8 Billion m3 of gas are from seven oil and gas fields discovered so far. The Tertiary geological history within which the system exists, is characterised by presence of four tectono-sedimentary zones typified by shale bulge related listric / growth faults and rollover anticlines with basin ward delimitation by toe thrusts,a resultant of Tertiary deltaic and deepwater sedimentation of the two major paleo drainage systems of the Krishna and Godavari rivers. The Ganges-Brahmaputra fan system is an additional sedimentary input during Mid-Miocene to Recent in deeper parts of the basin and occurs orthogonal to the Krishna-Godavari drainage.

The time transgressive Vadaparru shale ( Paleocene to Early Miocene ) is the established source rock , with the sandstones of the Ravva Formation being the main reservoir rock and the thick Godavari Clay of Pliocene to Recent age forming the seal element. The latter two also form the overburden rocks of the petroleum system. Burial history data indicates that hydrocarbon generation and migration has occurred from Mid.Miocene to Recent with the critical moment at Late Pliocene. The GAE ratio amounts to 0.03 % defining the efficiency of the system.This apparent inefficiency is more a reflection of the unexplored potential of the system , a large tract being predominantly in deep waters at present.

AAPG Search and Discovery Article #90913©2000 AAPG International Conference and Exhibition, Bali, Indonesia