25th International Meeting on Organic Geochemistry IMOG 2011

P-090
Hydrocarbon potential of the western Barents Sea – Evaluation
of sedimentary rocks of Spitsbergen
Ulrich Berner 1 , Bernhard Cramer 1 , Karsten Piepjohn 1 , Pjotr Sobolev 2
1 Federal Institute for Geosciences and Natural Resources, Hannover, Germany, 2 Karpinsky Russian
Geology Research Institute, VSEGEI, St. Petersburg, Russian Federation (corresponding
author:ulrich.berner@bgr.de)
Seventy-five potential source rocks from Upper
Permian to Lower Tertiary of Spitsbergen have been
sampled during a joint project of BGR (Hannover,
Germany) and VSEGEI (St. Petersburg, Russia). The
sample sites are associated with the Central Basin of
Spitsbergen, and are located along the coastline of
Isfjorden and the southern Advendalen.
Organic geochemical investigations have been
performed; the latter include pyrolysis methods,
molecular as well as stable isotope analyses of
organic matter and sediment extracts. The
investigations aim at a better understanding of
Spitsbergen sediments as indicators of hydrocarbon
source rocks within the western Barents Sea region.
Within the marine Upper Permian Kap Starostin, and
the Lower Triassic Vikinghøgda Fms. consists of clay
stones and marls, whereas the Botneheia Fm. is
dominated by marls. The organic matter in both
formations consists of mixtures of aquatic and
terrestrial precursors as seen from pyrolysis and
biomarker data. The quality of the organic matter of
the Botneheia Fm., which has been deposited under
anoxic to dysoxic conditions is very good, as it
contains a higher contribution from hydrogen-rich
aquatic precursors. The upper section of the Lower
Triassic (Tschermakfjellet Fm.) is influenced by
terrestrial organic matter, which is also true for the
Middle Triassic De Geerdalen Fm. and the Upper
Triassic Knorringfjellet Fm.
The Middle Jurassic Agardhfjellet Fm. contains locally
variable mixtures of terrestrial and aquatic organic
matter. The depositional environment was likely dys-
to anoxic as seen from the elemental and biomarker
data. The sediment samples of the Upper Jurassic
Rurigfjellet Fm. are however dominated by terrestrial
organic matter.
The sediments of the Lower Cretaceous Helvetiafjellet
and Carolinefjellet Fms contain abundant land plant
material, which is also true for the Palaeocene
Firkanten Fm.
Likely oil source rocks of the western Barents Sea
region as indicated by data from Spitsbergen are
Early Triassic Vikinghøgda and Botneheia Fms as
well as the Jurassic Agardhfjellet Fm. All other
organic rich sediments are rather gas than oil prone.
A general trend from marine (partly anoxic and
dysoxic) depositional conditions during Upper
Permian and Triassic times to terrestrial palustrine
deposits during Palaeocene is observed (Fig. 1).
The thermal maturity of the investigated samples
reaches peak-oil generation in the Lower Triassic and
is only slightly lower in the Jurassic sediments. The
samples of the Lower Cretaceous Helvetiafjellet Fm.
touch the onset of the oil window at the sites along
the Isfjorden but samples from Carolinefjellet Fm. and
the Palaeocene Firkanten Fm. reveal a higher
maturity due to the structural position of the sample
sites south of Advendalen. The thermal regime in the
larger area is likely very heterogeneous due to the
presence of igneous intrusions which have been
described at different site on Spitsbergen and are
likely to occur also in the larger western Barents Sea
region.
Figure 1: The terrestrial-aquatic ratio (TAR) derived
from light aliphatic compounds indicates a shift from
marine depositional systems to terrestrial/pluvial
environments during Cretaceous and Palaeogene
times.
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