25th International Meeting on Organic Geochemistry IMOG 2011

P-120
The generation potential of the Bazhenov Formation and its
stratigraphic analogues in the east of Western Siberia
Ivan Goncharov 1 , Vadim Samoylenko 1 , Nikolay Oblasov 1 , Svetlana Fadeeva 1 , Vladimir
Krinin 2 , Vladimir Volkov 3
1 JSC «TomskNIPIneft», Tomsk, Russian Federation, 2 CJSC «Vankorneft», Krasnoyarsk, Russian
Federation, 3 SE «SAC RNM named after V.I. Shpilman», Tyumen, Russian Federation (corresponding
author:GoncharovIV@nipineft.tomsk.ru)
Bazhenov formation, the major hydrocarbon source in
Western Siberia, is part of the same regional horizon,
which, in its turn, is located within the top lower
Volgian and bottom lower Berriasian. In the east of
Western Siberia, the investigated area, Bazhenov
horizon includes bituminous Bazhenov formation
rocks (south-east) and partially rocks of Mariyanov
(east) and Yanovstan (north-east) formations.
Bazhenov formation thickness ranges from 5 to 40 m,
while Yanovstan formation thickness is up to 600 m.
More than 3300 Bazhenov formation rock samples
(cores and cuttings) from the east area of Western
Siberia were analyzed. Rock-Eval 6 results showed
that the rocks of Bazhenov, Mariyanov and Yanovstan
formations have S2 value of more than
20 mg HC/g rock, which indicate that these rocks are
of excellent generation potential. Rock organic matter
(OM) in the investigated area has different
catagenesis. Tmax value ranges from 423 to 448 °С
and 4MDBT/MDBT value ranges from 0.4 to 10.0.
Average hydrogen index value (HI) for Bazhenov
formation and its stratigraphic analogues in east of
Western Siberia changes from 225 to
710 mg HC/g TOC. Thus, in single areas, the quality
of OM even exceeds that of kerogen-type II, the HIo
value of which is 627 mg HC/g TOC.
Rock-Eval 6 determines only the residual generation
rock potential; however, it is necessary to know the
initial potential in order to evaluate the volume of
hydrocarbon generation. There were zones of low OM
maturity in each of the above-mentioned investigated
formations. The whole complex of molecular and
Rock-Eval parameters shows the low OM catagenesis
of these rocks, which, in its turn, allows evaluating
HIo. If the HIo value for rock OM of Bazhenov
formation in the south-east of Western Siberia is 600-
710, then for Mariyanov formation rock OM – 500-
600, and for Yanovstan formation rock OM – 400-500
(Fig.). HIo decrease in Bazhenov-Mariyanov-
Yanovstan formation series is accompanied by TOC
decline. If the average TOC content in Bazhenov
formation rocks is not less than 6.0%, then the TOC
content in Yanovstan formation rocks is rarely more
than 5.0%.
It is noteworthy to mention that for rock OM of
Bazhenov, Mariyanov and Yanovstan formations the
sterane ratio 29/27 St has sufficiently close and low
values (Fig.). This fact shows that marine OM
dominates throughout the Bazhenov horizon.
Probably, OM quality (HIo) was mainly determined by
the character of aerobiotic and anaerobic
transformations of initial biomass during
sedimentogenesis and early daigenesis, which is
verified by the pristane/phytane (Pr/Ph) ratio (Fig.).
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