Hydrocarbon Potential of the Western Barents Sea - Evaluation of Sedimentary Rocks of Spitsbergen
Ulrich Berner1, Bernhard Cramer1, Karsten Piepjohn1, and Pjotr Sobolev2
1Fed. Inst. of Geosciences and Nat. Resources, Hannover, Germany.
2Karpinsky Russian Geology Research Institute, St. Petersburg, Russian Federation.
In a collaboration between Russian and Germany seventy-five potential source rocks of Mesozoic to Paleogene times have been sampled on Spitsbergen. The sample sites are associated with the Central Basin, and are located along the coastline of Isfjorden and the southern Advendalen.
Inorganic geochemical analyses and organic geochemical investigations have been performed; the latter include pyrolysis methods, molecular/biomarker 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 lower Triassic the coastal marine Vikinghøgda Fm. 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 (as seen from the elemental data) is better, 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 see from the elemental 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 coastal-marine (partly anoxic to dysoxic) depositional conditions during Triassic times to terrestrial palustrine deposits during Palaeocene is observed.
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.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.�������������������������������������������������������������������������������������������������������������