ABSTRACT: Neocomian Progradational Sequence in the West Siberian Basin

VYSSOTSKY, VLADIMIR N., West Siberian Scientific Research Institute of Petroleum Geology, Tyumen, West Siberia, Russian Federative Republic; and J. FRANK KEITH, Jr.,* and JEROME A. EYER, University of South Carolina, Columbia, SC

The 3.5 million sq. kilometers West Siberian basin is a large epicontinental basin that contributes approximately 10% of the world's hydrocarbon production. Continental and marine basin-fill consists of Mesozoic and Cenozoic clastics. Neocomian regressive sandstones contain over 1000 oil and gas pools in 230 fields. The Late Jurassic-Early Cretaceous depositional cycle, or transgressive-regressive wedge, represents an important sequence of basin fill. The Neocomian progradational succession represents the final phase of the cycle and contains a variety of sandstones. Provenances for this generally westward progradational system are the Central Siberian and Kazakh highlands of the eastern and southern basin margins. Uralian provenance is noted only along the western margin.

In the Neocomian regressive phase of the clastic wedge, three segments of the depositional system tract are identified from seismic data: (1) a distal prograding complex of predominantly fine-grained marine terrigenous sediments; (2) a shallow marine/transitional succession of both coarse- and fine-grained clastics; and (3) a transitional-continental sequence of predominantly coarse-grained clastics. On regional and local scales, seismic stratigraphy was utilized to define the sequence stratigraphy of the prograding sediments. Potential reservoirs, identified by external geometries, occur in three positions of the prograding clinoform complex or seismic sequence: (1) upper, or "roof-type," sandstones of the deltaic/shallow-shelf phase; (2) mid-shelf and shelf-ridge sandstones that are detached from the shoreface; and (3) low-stand or shelf-bypass turbidite-fan sandstones of the distal shelf. The Neocomian regressive succession is ideal for hydrocarbon exploration because of the development of reservoir rocks in close proximity to mature source rocks that form both regional and local seals.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)