Sequence Stratigraphy and Depositional Process of Miocene Sediments in KD-structure, Deepwaters of Krishna-Godavari Basin, India

Detailed chronostratigraphic biodatums and lithofacies in combination with correlative seismic horizons recognized two 3^rd order depositional sequences designated as Sequence 1 and Sequence 2 in stratigraphic order within Miocene in KD field. The biostratigraphic correlation has brought out that the Sequence 1 in shelf well GS-AD is sandrich and bounded by unconformable sequence boundaries, whereas coeval sequence in slope wells KDA and KDB, bounded by correlative conformities are dominated by clay rich system deposited during highstand sea-levels in earlymiddle Miocene. The clays are planar bedded with glauconite and pyrite nuggets with abundant deepwater benthics in association with shelf derived foraminifera, inferring that these clays were derived into intraslope basins mainly as debris flow/slump process. The Sequence 2 in wells KDA and KDB is represented by multiple sands with mudstone alternations, deposited during lowstand Sea-Levels. Biofacies are mixed with dominantly shelf derived benthics and the tests are commonly broken, abraded and occasionally ferruginised, suggesting reworking into intraslope basins as a result of relative Sea-Level fall during middle and late Miocene. The occurrence of abundant Paleocene to early Miocene dinoflageIlate cyst assemblage are also suggesting reworking process into upper slope by network of active channel system and were redeposited by Gravity-Flow processes into intraslope basins. The present study indicates each intraslope basin acting as an independent petroleum system and matured organic rich Paleogene beds lying at the bottom are contributing hydrocarbons to middle Miocene reservoirs through active growth fault system.