25th International Meeting on Organic Geochemistry IMOG 2011

P-092
Geochemistry of heterocyclic components from organic matter
and oils of West Siberia
Lyubov Borisova
Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russian Federation (corresponding
author:BorisovaLS@ipgg.nsc.ru)
Multiyear studies conducted by the author [1-3] in
IPGG SB RAS (Novosibirsk) have shown that the
parameters of asphaltenes and resins, along with
hydrocarbon indices, allow the effective solution of
fundamental problems of the theory of formation and
transformation of oil in the Earth‘s sedimentary cover.
In order to study in detail these complex highmolecular
compounds of oils and dispersed organic
matter (DOM), a single complex of physicochemical
methods has been devised (elemental, isotopic, x-ray
diffraction analyses, spectrometry in the visible and IR
regions, NMR, EPR, electron microscopy, and Rock-
Eval pyrolysis).
The composition and structure of resins and
asphaltenes of DOM of variable genetic nature from
petrographically pure rocks, like hydrocarbon (HC)
components of bitumen extracts, are essentially
different, depending on assigning to aquagene
(marine) or terragene (continental) type. Up and down
the section of the Volgian stage, a gradual
carbonization of heteroatomic components occurs,
carbon content increases, and hydrogen and sulfur
content decreases. At the same time, the
hydrocarbon potential value declines, and vanadylporphyrin
complexes almost completely disappear.
These differences in the composition and structure of
heteroatomic components of OM from Lower
Cretaceous and Lower-Middle Jurassic deposits
suggest that terragene components have been
contributed to the OM of these deposits.
Geochemical structural features of resins and
asphaltenes of DOM are substantially defined by
catagenesis processes. In mesocatagenesis, the
composition of asphaltenes undergoes directed
changes, similar to those revealed by A.E.
Kontorovich [4] for debitumenized OM of
corresponding genetic nature: carbonization of
heterocyclic components is accompanied by the
decrease in hydrogen and heteroatoms, and the
growth of the degree of aromaticity of their molecules.
No unidirectional relationship between the resin
composition of various genetic types of OM and the
level of OM thermal maturity during mesocatagenesis
is marked. Only the redistribution of resins occurs: the
content of benzene resins increases and that of
alcohol-benzene ones decreases. At the same time,
benzene resins are carbonized, and alcohol-benzene
ones become more aliphatic and oxidized. During
apocatagenesis, the carbonization process of
asphaltenes changes, on the one hand, into their
polymerization and transition into insoluble forms, and
on the other hand, into aliphatization and partial
transition of their lighter form into resins, and the latter
into aromatic HC. Thus, during catagenesis of DOM
not only kerogen, but also asphaltenes and resins are
destructed and newly form [1, 5].
Investigation of asphaltenes and resins of West
Siberian oils of variable age has revealed the genetic
features of their structure and variation under the
impact of biodegradation and categenesis.
Genetic relations have been established in the
series: asphaltenes, resins of DOM – asphaltenes,
resins of oils. They are most clearly defined in the
content of sulfur, oxygen, vanadyl-porphyrins, and
isotope carbon composition.
Asphaltenes are of complex significance in the
geochemical history of oil, being a source of new HC,
on the one hand, and the inhibitor, impeding the oil
transformation processes both in catagenesis and
hypergenesis zone, on the other.
References
[1] Borisova, L.S. (2004) Russian Geology and
Geophysics 45, N 7, 884-894.
[2] Borisova, L.S. (2009) Geologiya nefti i gaza, (in
Russian), N 1, 76-80.
[3] Borisova, L.S., Kontorovich, A.E. (2008) Dokl. RAN
420, N 3, 1-3.
[4] Kontorovich, A.E. (2004) Sketches of theory of
naphthide genesis (in Russian), SB RAS, Novosibirsk
[5] Kontorovich, A.E., et al. (1988) Sovetskaya
geologiya (in Russian), N 7, 26-35.
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