Petroleum Systems and Mixed Oil in the Barents Sea and Northern Timan-Pechora Basin, Russia
Meng He1, Kenneth E. Peters2, J. Michael Moldowan3, and Alla Rovenskaya4
1Geological & Environmental Sciences, Stanford University, Stanford, CA.
2Schlumberger, Mill Valley, CA.
3Biomarker Technology, Sebastopol, CA.
4Foundation for East-West Cooperation, Moscow, Russian Federation.
Biomarkers and diamondoids were used to identify petroleum systems and infer source rocks for 34 oil samples from the Barents Sea and northern Timan-Pechora Basin. Chemometric analysis indicates five oil families from Triassic, Devonian (carbonate), Devonian (marl), Lower-Middle Jurassic, and Upper Jurassic source rocks. Based on the method of Dahl et al. (1999), 14 samples are mixtures of mature oil and highly mature condensate from deep, previously undetected source rock. Compound-specific isotope analyses of biomarkers and diamondoids show that highly mature Devonian source rock contributes to most of the mixed oil samples.
The Triassic oil family occurs in Triassic and Permian reservoirs in the northern Timan-Pechora Basin and the southern Barents Sea. The oils have high extended tricyclic terpane ratios (ETR), consistent with Triassic source rock. The Devonian carbonate oil family occurs in Permian and Devonian reservoirs in the northern Timan-Pechora Basin and Pechora Sea. The oils show high C29/C30 hopane, pristane/phytane (Pr/Ph) <1, elevated C34-homohopanes and C29 steranes, and low dinosteroids. The oils from Devonian marl source rock occur in Devonian reservoirs in the northern Timan-Pechora Basin. They are similar to the carbonate family, but have Pr/Ph >1 and lack elevated C34 homohopanes.
The two Jurassic oil families have high bicadinanes and triaromatic dinosteroids, consistent with Jurassic source rock having terrigenous input. The Lower-Middle Jurassic oils occur in Lower-Middle Jurassic reservoirs in the Shtokmanovskoye field and on Spitsbergen Island. These oils have Pr/Ph >3, high C19/(C19+C23), low C22/C21, and high C24/C23 tricyclic terpane ratios, and elevated C29 steranes indicating paralic marine shale source rock with higher plant-input, similar to oil generated from the Tyumen Formation in West Siberia (Peters et al., 2007). The Upper Jurassic oil family occurs in Triassic and Permian reservoirs on Kolguyev Island and the Pechora Sea. The oils show geochemical properties like those previously ascribed to the Bazhenov Formation in West Siberia (Peters et al., 2007).
Dahl, J. E., et al., 1999, Diamondoid hydrocarbons as indicators of natural oil cracking: Nature, v. 399, p. 54-57.
Peters, K.E., et al., 2007, Circum-Arctic petroleum systems identified using decision-tree chemometrics: AAPG Bulletin, v. 91, p. 877-913.
AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.������������������������������������������������������������������������������������������������