Cretaceous Volcanism and Development of Hydrocarbon Pools in and Around Peninsular India

Misra, Kiran S.; Misra, Anshuman

Cretaceous volcanics are sandwiched between older Mesozoic and Tertiary sequences at innumerable places in and around peninsular India. Earlier, only Tertiary sequence was targeted for exploration and exploitation of hydrocarbons. However, last two decades have witnessed discovery of hydrocarbons, not only from underlying Mesozoic's, but also from the volcanic horizons. Seismic, gravity and drill hole data sets are interpreted and this new geological information is integrated with available details for understanding the mechanism of volcanic eruption, as well as development of hydrocarbon pools both in Mesozoic and Tertiary successions. Rift and grabens transecting the land areas of peninsular India, exhibit evidences of extensional tectonics responsible for basin forming due to subsidence, sedimentation and volcanism. Various evidences suggest that the volcanism is caused by decompressional melting of lithosphere. It has also emerged that thick sediments have accumulated in the intersectional areas of subsiding rifts and grabens. Most of the hydrocarbon pools are also located in these inter-sectional areas. Interpretation of seismic profiles processed by Pre-Staking and Depth Migration (PSDM) and high resolution gravity data in the adjoining Bay of Bengal has also brought out that entire bay region is underlain by Cretaceous volcanic and under and overlain uninterrupted Tertiary sediments. The North-South trending faults, developed during Cretaceous extensional tectonics have formed effusive zones which are now represented by oceanic ridges. These ridges are now located nearly around 82 degree E, 85 degree E and 90 degree E longitudes. The prominence and the degree of deformation increases from west to east. The 82 degree E and 85 degree E east regions are characterized by gravity low while 90 degree E ridge is marked by gravity high. Furthermore, the 82 degree E and 85 degree E east ridges are completely buried below the Cenozoic sequence and turn towards west in southerly extension. The 90 degree E ridge is rather straight and crops up above the sedimentary sequence. The present authors believe that the elongated restricted basins between these ridges were excellent for source rock deposition, while the ridge tops could have provided suitable locales for prolific growth of coral reef complexes as reservoir rocks.

AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013