--> Abstract: Variations And Control On Deep Marine Clastic Systems Of The Neocomian Productive Units Of West Siberian Basin, Russia, by Oleg V. Pinous, D. L. Sahagian, and M. A. Levchuk; #90928 (1999).

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PINOUS, OLEG V.1, DORK L. SAHAGIAN1, and MIKHAIL A. LEVCHUK2
1Inst. of Earth, Oceans and Space., Univ. of New Hampshire
2Institute of Oil and Gas Geology, Novosibirsk, Russia

Abstract: Variations and Control on Deep Marine Clastic Systems of the Neocomian Productive Units of West Siberian Basin, Russia

Deep marine clastic systems represent a significant portion of the Neocomian productive complex of West Siberia. In recent times, exploration priorities in the Neocomian interval have been reoriented toward deep marine plays, because most structural-trapped shelf reservoirs have been significantly depleted.

Our sequence stratigraphic analysis led to understanding of the main factors that control depositional architecture and reservoir distribution in the deep marine units. It is based on drilling data (320 wells) and 6 regional seismic profiles that cover over 100,000 km2 in the central West Siberia. Twelve third-order sequences were identified within the Valanginian-Hauterivian strata.

The depositional setting was a shelf-break margin with well-developed clinoform units and a 1 to 2? slope gradient. In terms of grain size, the deep marine sedimentation occurred in mixed sand-mud systems and was dominated by turbidity currents. During the most significant sea-level falls the systems differentiated into lowstand fan and lowstand wedge systems tracts. In lowstand fans the largest sand units are concentrated in basinal positions comprising constructional lobes and channels. Individual submarine fans evolved from separate entry feeder points (canyons), forming separate compartments. However, where feeder channels were close to each other and sediment supply was abundant, individual fans coalesced into thick submarine ramps. In lowstand wedges the best reservoirs are present in shingled turbidites that formed on slope and slope toes as a result of gravity-driven sedimentation from shelf-edge deltas.

The developed sequence stratigraphic framework may serve as a model to predict plays in deep-marine systems of the West Siberian Neocomian.

AAPG Search and Discovery Article #90928©1999 AAPG Annual Convention, San Antonio, Texas