INTEG, GEOPIC, ONGC, Dehradun, e-mail: basupinaki72@hotmail.com P-105 Mud volcanoes in deep water of Andaman Forearc Basin Pinaki Basu1*, Rajeev Verma 1 , Rajiv Paul 1 & K. Viswanath 2 , ONGC Summary Mud volcanoes (MVs) are a natural phenomenon that has attracted geoscientists for a long time. They have lot of similarities in appearance to that of magmatic volcanism but widely differ in the origin. The term “mud volcano system” is coined to describe the set of structures associated with a constructional edifice (mud volcano) and feeder complex that connects the volcano to its source stratigraphic unit. Mud volcanoes are key features that reflect regional geological processes that are active in their place of occurrences. The majority of reported mud volcanoes occur at active plate margins which lead many authors to suggest that tectonic stress, mainly compressional, is the main driving mechanism for mud volcanoes. The Andaman Forearc basin is one such basin where occurrence of mud volcano is quite common. The Forearc basin of Andaman is situated along the obliquely converging boundary of the Indian plate and Burmese plate characterized by active tectonics. Important structural elements observed in the basin include transpressional faults and anticlinal structures (result of basin inversion). The interpretation of a 3D seismic survey from the study area helps in studying the structural elements , evolution and mapping of these mud volcanoes. These features are associated with high amplitude above a chimney of extremely chaotic seismic signature and data wipe out while their morphology is evident in RMS attribute map. Seismic data show that despite differences in form, mud volcanoes t end to have a „Christmas-tree‟ structures interfingering with back ground sediments. Mud volcanoes always occur at the top of extrusive edifices that extend at least few kms down below, into the subsurface, occupying subsidence depressions developed above older strata. In this study an attempt has been made to find out the role of mud volcanoes in petroleum systems of Andaman Forearc basin given the fact that they are often associated with petroleum seeps and has an intimate relationship with the petroleum reservoirs in the sedimentary basin. Apart from that, a model has also been proposed to explain their evolution within the basin. Introduction The deep water of Andaman Forearc basin always remains in news for being one of the future exploration locales for hydrocarbon exploration in India. The detail study of the 3D seismic data of the area within basin has revealed the presence of features interpreted to be of mud volcanoes. The Andaman- Nicobar island chain and associated basin is a part of large geotectonic unit that extends from Sumatra (Indonesian) Islands in the south to Myanmar (Burma) in the north. Numerous seabed anomalies were observed during early regional 2D seismic evaluations. They were generally characterized by positive topographic relief and very high seabed seismic amplitude above a vertical chimney characterized by partial to almost complete data wipe out. On seismic data, these anomalies always occur above deeper structural culminations. The seismic imaging associated with these features gives rise to ambiguity in their interpretation and consequently numbers of models were suggested for their formation. The basic objective of this paper is to present evidence supporting the interpretation that these features are mud volcanoes. Little has been published on mud volcanoes in deep water of Andaman Forearc. Earlier works on mud volcanoes are concentrated on onshore areas only. However, with the advent of the hydrocarbon exploration in vast deepwater area with improved 3D seismic data, it is now evident that mud volcanism do occur in the deep water of this basin. The basin has more than 5000m of thick sediments ranging in age from Cretaceous to Recent. Therefore, an attempt has been made to investigate the role of mud volcanoes in petroleum systems of Andaman in the light of an envisaged model proposed for their formation within the basin.