25th International Meeting on Organic Geochemistry IMOG 2011

P-099
Oxygen-containing compounds in crude oils of south-eastern
part of West Siberia
Eugenia Strelnikova 1 , Ivan Goncharov 2 , Olga Serebrennikova 1
1 Institute of Petroleum Chemistry SB RAS, Tomsk, Russian Federation, 2 TomskNIPIneft, Tomsk, Russian
Federation (corresponding author:seb@ipc.tsc.ru)
Crude oils contain about 1% of oxygen in form of
various oxygen-containing compounds (OC) which
are mainly distributed among high-molecular
petroleum components - resins and asphaltenes. At
present time numerous works prove the sulfur nature
in crude oils. Abundantly clear that petroleum nitrogen
is inherited from proteins, lipid compounds (pigments)
and complex fats (phospholipids) of primary
organisms. However there is no uniform point of view
about an oxygen origin in oils.
More than 50 tests of crude oils a southeast part of
Western Siberia of deposits in a range from the Lower
Cretaceous to a Paleozoic are analyzed. The content
of sulfur (S), nitrogen (N), oxygen (O), carbonyl
groups of ketones (CO), carboxyl groups of acids
(COOH) and hydroxyl groups of phenol (OH) was
defined.
It is known that the structure and quantity of formed
hydrocarbon fluids are influenced very strongly by
depth of oxidation of organic matter (OM) in initial
processes of depositions. Anoxic conditions promote
preservation of unstable and active moieties
containing O, S and N, inherited from live ОM which
give rise to oils heteroatom compounds eventually
(fig. 1). It is not so important that there is a negative
correlation between the content of various classes OС
and Pr/Ph as that there is a close interrelation
between oxygen and nitrogen compounds. It means
that their quantity in oil is supervised by the same
group of factors. As petroleum nitrogen is inherited
from connections of the albuminous nature of live
organisms hence petroleum oxygen also is relic, i.e.
inherited from a biomass, and has not been
introduced in petroparent ОM as a result of its
oxidation at stage of sedimentation. Negative
correlation between OC and Pr/Ph specifies that
biomass transformation at a stage of its deposition
proceeds with loss of basic oxygen functional groups
and the oxygen as a whole. Products of oxidation
formed thus aren't involved in structure OM, dropping
out on a bottom, and mineralized to water and
carbonic gas.
Thus, the high content of oxygen is characteristic for
oils, whose initial ОM wasn't exposed to deep aerobic
oxidation at a stage of sedimentation. Often these oils
Content, %
2.00
1.00
Marine Oils
Terrestrial Oils
0.00
0.0 2.0 4.0 6.0 8.0
Pr/Ph
O
CO
S
COOH
Fig.1. Relationships between Pr/Ph ratio and S, N, O and
OC content of the samples of oils from the south-eastern
part of West Siberia
are the heaviest and resinous that gives the grounds
to some authors to name them «oxidized, unripe, oils
of early generation» etc.
Now deposits of all investigated oils are on different
depths and at different temperatures (70-115 °С) that
also could affect quantity and structure of OC. The
Isoprenoid parameter (Ki) and dibenzothiophene ratio
(4МDBT/1МDBТ) are the convenient parameters
characterizing degree of thermal influence on ОM and
oils. It is remarkable that factors of correlation of
these parameters with content OC and others
heteroatoms have appeared not significant. This
result once again specifies that in a range of
temperatures in oil reservoir 70-115°С processes of
thermal transformations don't make essential impact
on the general properties of oil (density, viscosity,
quantities resins and asphaltenes and their structure).
Possibly, here the leading role belongs to processes
of primary and secondary migration (migration
distance, mineralogical and granulometric
composition of rock on a way migration).
OH
N
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