25th International Meeting on Organic Geochemistry IMOG 2011

P-106
Organic geochemistry of naphthides of the Anabar-Khatanga
saddle
Natalya Kim, Vladimir Kashirtsev, Oksana Dzuba
Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russian Federation (corresponding
author:KimNS@ipgg.nsc.ru)
In the Anabar-Khatanga saddle, several small oil
fields are known and numerous bitumen shows have
been revealed in heterochronous deposits of natural
outcrops of the Nordvik Peninsula. The first
suggestions regarding the genesis of these
naphthides have been stated by one of the authors as
early as 2003 [1], based on the detailed molecular
analysis of oil from Permian deposits of well Yuzhno-
Tigyanskaya-102R. The present work is the
continuation of naphthide investigation in this area.
Using gas-liquid chromatography and gas
chromatography-mass spectrometry methods, oil from
well Nordvik-42 (T2) and natural bitumens from the
outcrops of Cape Yuryung-Tumus of the Nordvik
Peninsula (J1-2) have been analyzed.
The chromatograms of naphthides of the Nordvik
Peninsula show a ―naphthene hump‖ that suggests
biodegradation processes. In oils and some bitumen
extracts, where normal alkanes have still preserved,
the peak falls on n-C17 hydrocarbons. The Pr/Ph ratio
values are equal to 0.70-1.00. С30 squalane is present
in significant concentrations.
С27-С29 sterane hydrocarbons are dominated by С29
ethylcholestanes (45-47 %), and the value of
diasteranes to regular steranes ratio is not high, 0.13-
0.19.
Terpane hydrocarbons contain the highest
concentrations of hopanes, among which С29
adiantanes are predominant. С35 homohopanes
dominate over С34 homohopanes. Naphthides are
characterized by higher concentrations of
gammacerane. 28,30-bisnorhopane have been
identified, the appearance of which usually is related
to the existence of specific bacteria at the early
stages of OM transformation [2]. Besides, a series of
25-norhopanes (m/z 191, 384, 177, 355) have been
identified, which form due to microbial oxidation of
regular hopanes [2]. 3�-methylhopane, synthesized
by specific methanotrophic bacteria, has been found
in all of the studied naphthides. Tricyclic
hydrocarbons are dominated by С23-С24
cheilanthanes. Significant concentrations of С24
tetracyclic terpane are marked.
The values of isotopic carbon composition are equal
to -28.2 ‰ in Nordvik oil, and in the bitumens of Cape
Yurung-Tumus, the values vary from -29.6 to -29.2 ‰.
In these naphthides, the content of sulfur is 1.2-2.4 %.
The geochemical parameters indicate a single
genetic nature of the studied naphthides as well as
Yuzhno-Tigyanskaya oil, examined earlier [1].
Thus, the initial OM of naphthides of the Anabar-
Khatanga saddle has formed under the conditions of
highly saline Proterozoic-Lower Paleozoic marine
basin. According to geologic information, in the
considered region, salt strata are associated with
Devonian deposits [3] that require their further
investigation to establish naphthide – oil source rock
relationships.
References
[1] Kashirtsev V.A. Organic geochemistry of naphthides in
the east of the Siberian Platform. Yakutsk: SB RAS, YaD,
2003. – 160 p.
[2] Peters K.E., Walters С.C., Moldowan J.M. The
biomarker guide. 2 nd ed. – Cambridge University Press, New
York , 2005. – V. 2. – 1155 p.
[3] Kalinko M.K. Geologic history and petroleum potential of
the Khatanga depression // Proceedings of NIIGA, v. 104, L.,
Gostoptekhizdat, 1959, 353 p.
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