25th International Meeting on Organic Geochemistry IMOG 2011

P-108
Organic geochemistry and Mesozoic petroleum systems of the
Yenisey-Khatanga regional trough
Alexei Kontorovich, Natalya Kim, Sergei Yershov, Elena Kostyreva, Vasiliy Melenevskiy,
Aleksandr Fomin
Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russian Federation
(corresponding author: KimNS@ipgg.nsc.ru)
Recently, the northeastern part of West Siberia
attracts attention of a large number of investigators in
connection with the discovery of the Vankor group of
gas-oil fields with giant reserves. In order to reveal oiland-
gas source rocks in the Mesozoic section of this
area, the core from wells of the western part of the
Yenisey-Khatanga regional trough has been
examined: organic carbon content in rocks and
isotopic carbon composition of insoluble organic
matter have been determined, Rock-Eval pyrolysis
has been made, and vitrinite reflectance R 0
vt has
been identified by the coal-petrographic method. The
results of investigation of biomarker hydrocarbons in
bitumen extracts and oils of Mesozoic deposits of this
region were presented at the IMOG -2009 [1].
The organic carbon contents in Cretaceous rocks
(192 samples) are lower than those of Jurassic rocks,
and the TOC values for 70% of Early Cretaceous
samples are lower than the Clarkes. The organic
carbon content in Jurassic deposits varies from 0.5 to
10.2 % of rock, averaging 1.7 % for 206 samples.
The Vym, Malyshevka and Sig Formations are highly
enriched in organic carbon (average values of
TOCг >2.3 % of rock). For the stratigrapic analogs of
the Bazhenovo Formation, Yanovstan and Golchikha
Formations, the TOC values average 1.6 and 2.0 % of
rock, respectively.
Isotopic carbon composition was studied in 120
samples. Bitumen extracts, having aquagene nature
of lipids, are characterized by higher values of δ 13 С (-
26.6…-30.9 ‰) as compared to typically marine OM
of bitumen extracts of the Bazhenovo Formation (-
28.9…-32.0 ‰).
Data on vitrinite reflectance resulting from the
examination of 139 samples have shown that the
most favorable for liquid hydrocarbon generation are
deposits with the level of OM maturity corresponding
to grades MC1 1 –MC2 (R 0 vt=0.60-1.15 %) – the
Malyshevka, Yanovstan, Golchikha, Nizhnyaya Kheta
and Shuratov Formations. Judging from coalpetrographic
data, Jurassic deposits up to depths of
about 4.0 km have not yet passed out of the main
zone of oil generation and could be of interest for oil
pool exploration.
Pyrolytic data (387 samples) correspond to the
results of petrographic analysis of OM. The
established relationships between hydrogen index HI
and Тmax suggest that Mesozoic deposits occur mostly
in the main zone of oil generation and are
represented both by OM of type II (aquagene marine,
samples from the Malyshevka, Yanovstan, Golchikha,
Nizhnyaya Kheta, Shuratov and Sukhodudinka
Formations, HI to 380 mg HC/g TOC), and OM of type
III (terragene).
Thus, based on a set of geochemical parameters, it
has been established that the Yanovstan (J3–K1) and
Golchikha (J2–K1) Formations, and, to a lesser extent,
the Malyshevka Formation (J2) include the widely
distributed levels where OM of rocks is aquagene
(type II), and organic carbon concentrations and the
level of OM maturity in these rocks make it possible to
consider them as oil source rocks.
Lower Cretaceous bitumen extracts (Nizhnyaya
Kheta, Shuratov Formations) with aquagene nature of
OM are confined to thin regional deep-water members
of clays. Organic carbon concentrations in samples
from these members account for 0.5-2.3 % (averaging
1.6 %) of rock. For the rocks from the Nizhnyaya
Kheta and Shuratov Formations, analyzed by the
coal-petrographic method, the OM maturity suggests
that 78% of all samples have reached the main zone
of oil generation. Therefore, Lower Cretaceous rocks
of the Nizhnyaya Kheta and Shuratov Formations
could generate liquid hydrocarbons, but not in so
significant amounts as the above-indicated Jurassic
deposits. The other examined deposits contain
organic matter related to higher land plants and are
assigned to gas-generating ones.
References
[1] Kontorovich, A., Kostyreva, E., Kim, N. (2009)
IMOG 2009, Abstract Book, 252
251