New Exploration Perspectives on the Jurassic of Southern Western Siberia

Hafizov, Sergei¹, Vladimir Shimansky², George Pemberton³, John Dolson⁴, Richard Herbert¹ (1) TNK-BP, Moscow, Russia (2) All-Russia Petroleum Research Exploration Institute (VNIGRI), St.Petersburg, Russia (3) University of Alberta, Edmonton, AB (4) TNK-BP, Moscow,

The Jurassic of Western Siberia contains at least 28 billion barrels of recoverable reserves. Many of these accumulations are combination valley-fill traps flanking paleo-hills which can have relief in excess of one kilometer. New data from biostratigraphy, ichnology, 3D seismic and regional geology reveals an extensive regional pattern of paleo-drainage networks which are particularly pronounced in the South. Late Paleozoic accreted terrains associated with the Uralian collision formed the basic tectonic framework controlling the location of the interfluves. Early Triassic rifting accentuated some of these structures and created strong controls on the position of the early Jurassic river systems. These valley networks have filled with non-marine, estuarine and marine strata which generally show a progressive southward onlap. Detailed core and seismic data, however, reveal numerous higher frequency fluctuations and the development of both local and regional unconformities which interrupt this transgressive fill. Estuarine valley fills are dominant in the south and production occurs from channelized sandstones, tidal inlets, flood-tidal and bay head deltas and barrier islands. World-class Bazhenov source rocks overlying the Jurassic reservoirs have charged much of the section from downward migration. Additional deeper source rocks contribute though vertical migration. Exploitation of these reservoirs is not without challenge, as facies relationships are complex, reservoir quality variable and only a detailed understanding of the micro-facies in each field will reveal the keys to additional production and new accumulations.