LOPATIN, NIKLOLAY, and TAMARA EMETS, Geosystem Institute, Moscow, Russia

Abstract: The West Siberian Bazhenov Petroleum System "In Situ": Geological Evolution and Generation-Accumulation Efficiency

The West Siberian basin is the most prolific oil- and gas-producing area in Russia. More than 80 % of oil commercial reserves located in the Neocomian sandstone reservoirs, genetically connect with Bazhenov Formation as classical prolific source rocks.

This source rocks are keeping also rather big oil resources into shaly reservoir. It is Bazhenov petroleum system "in situ."

Detail geochemical study of US0 oils and bazhenov suit core samples of the Surgut and Salym domes, historical-geologic reconstruction of oil generation and migration processes inside and high fracturing zones evolution and data set interpretation in term of petroleum system are of this paper.

The Bazhenov prolific source-rocks as classical petroleum system were described very detail by series of electronic maps and basin modeling. The petroleum generative depressions and mature area of the Volgain source, some vertical migration pathway, the timing of oil expulsion rocks were determined. The Bazhenov shales contain very rich type I and II kerogen. Organic carbon content and residual petroleum potential of the Bazhenov Formation are extremely high in the Middle Ob River area, decrease in the Southern and Northern parts, and the lowerest in the marginal zones of the basin. We defined the peak of oil window in the Middle Ob River region, and the late zone of oil window in Yamal-Taz megasincline. The oil expulsion efficiencies above 30% and the time at 40 mm. years ago for start expulsion processes are very typically for the Middle Ob river area.