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Volcanic Intrusions and Their Implications from Petroleum Systems in Andaman Basin, India

Vinod Dangwal, R. S. Warraich, Siddhartha Sengupta, D. K. Srivastava, A. V. Sathe, and M. Asthana
BSD, KDMIPE, ONGC Ltd., Dehradun, India

The Andaman Basin evolves through polyphasic, multigenetic tectonic events from early Cenozoic to recent. Major tectonic events - subduction/oblique subduction, magmatic intrusion and backarc spreading led to the development of major three tectonic zones, viz. fore arc , volcanic arc and back-arc. The back arc spreading and Andaman rift from Late Miocene to Recent caused the formation of intra volcanic arc rift which were filled with 2.5-3.0 km of Irrawadi fan sediments covering an area of 10,000Sq Km approximately.

Number of ash beds within the Miocene section of drilled wells, indicate frequent volcanic activities in Andaman Basin which corroborates with dating of tuffaceous sediments ranging from 23mybp to 11.5mybp (Early to Mid Miocene). Peak volcanic activities have been reported from 21.8 to 17.6 mybp. Barren Island volcano is still active and frequently spews volcanic material.

Number of seismic signature and some of the amplitude burst in the volcanic arc basin of Andaman are possibly related to igneous intrusions (sill/dyke) analogous to Myanmar Blocks in Irrawadi Delta. The Mio-Pliocene sediments in this area are pierced by relatively small igneous intrusions which possibly have caused localized enhanced thermal maturation accelerating the process of hydrocarbon generation. Some of the seismic signatures which are interpreted as sills / intrusives are overlain by faded/ transparent zone and high amplitude anomaly / DHI; indicating migratory path ways (gas chimney / volcanic gas) and hydrocarbon accumulation. More over, volcanic clasts and ash beds at porous and fractured part may act as reservoir for hydrocarbon.

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