25th International Meeting on Organic Geochemistry IMOG 2011

P-068
Aromatic hydrocarbons in the barents-kara shelf
Anna Kursheva 1 , Ivan Litvinenko 2 , Vera Petrova 3
1 Anna Kursheva, Saint-Peterburg, Russian Federation, 2 Ivan Litvinenko, Saint-Peterburg, Russian
Federation, 3 Vera Petrova, Saint-Peterburg, Russian Federation (corresponding
author:A.Kursheva@mail.ru)
Information about the content and distribution of
hydrocarbons (HC), including aromatic (AHC) in the
components of the geological environment of aquatic
ecosystems allows predicting of oil and gas presence
and simultaneously creates a basis for further
geoecological monitoring. However, be aware that
hydrocarbons are widely distributed in the lithosphere
and form a stable geochemical background due to the
specifics of the initial organic matter (OM), the terms
of the accumulation and transformation. Application in
the multi-geological survey of on-board study by
fluorescence spectrometry allowed not only identifying
the background geochemical parameters, lithologicalfacial
features of sedimentation, but also abnormal
zones of endogenous and exogenous genesis [1].
This study based on measurements of sea water
and sediments samples (> 500 geological stations)
from the Barents-Kara shelf during the expeditions
carried out by VNIIOkeangeologia in 2000-2007.
Analysis of data on the distribution and
composition of aromatic HC in sediments of Western
Arctic Shelf showed that the low content (Xave = 4.3
mg/g) is typical for sandy sediments, with a
predominance of bi- and tri-aromatic compounds
(�max270-310 nm). It corresponds with a low sorption
capacity of coarse-grained sediments and a lack of
organic-mineral complexes containing the source of
destruction of initial OM in them.
In clay sediments (Xave = 13.0 mg/g) is
dominated by tetra- and penta-aromatic structures,
typical components of OM lipid fractions on postsedimentological
and early-diagenetic stage of
transformation. In doing so, change of the spectral
characteristics of sediments in the stratigraphic
section fully reflects the processes of diagenetic
transformation of OM, including aromatization and
formation of several compounds, such as perylene (�
max 435 nm).
The presence in the sediments of highly maturated
(post-diagenetic) organic matter, forming a special
(petrogenic) type of spectrum (� max 370-380 nm),
which is fundamentally different from the appropriate
spectrum typical for modern marine sediments.
This type of spectrum, combined with
abnormally high content of aromatic HC (Xave =
349.1 mg/g), is characteristic for the Svalbard
offshore area, erosion and redeposition of coal rocks
which play a significant role in the sedimentation [3].
A similar composition of aromatic HC was recorded in
the sediments on the shelf of the Kolguev Island, in oil
producing region, where exogenous anomaly is,
apparently, the case of technogenic factors [2].
The influence of endogenous processes (seeping
migration of HC) can also lead to a distortion of the
background spectrum because of formation of the
intense stripe in the short-wave range (� max 240-260
nm). Thus, in the Prirazlomnoye oil field area
(Pechora Sea) abnormal distribution of aromatic HC
observed in the sediments and in the water column
where the aromatic HC content in the bottom waters
exceeds the background value of two orders of
magnitude. Endogenous nature of anomalies is
confirmed by seismic profiling data, which showed the
presence of gas saturation and gas fluid.
A significant role of aromatic compounds in
fluid makes the dubious assumption about the
diagenetic and/or gas hydrate nature of emanation,
the most typical components of which are to be
methane and its homologues. On the contrary, the
fluid relation with productive horizons of hydrocarbon
deposits to be consistent, because the high content of
benzole homologues in the produced water is a direct
hydrochemical measure of oil and gas presence.
References
[1] Galishev M. (2004) Integrated research
methodology of oil products dispersed in the
environment in emergency situations. St.
Petersburg.: St. Petersburg Institute of the State
Fire Service EMERCOM of Russia, 157. [in
Russian]
[2] Hovland M., Judd A.G. (1998) Seabed
Pockmarks and Seepages. Graham & Trotman,
175.
[3] Petrova V., et al. (2000) Correlation diagnostics
of HC anomalies in bottom sediments of the
arctic shelf. Geochemistry 3, 311-308. [in
Russian]
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