Oil Cracking, Mixing and Geochemical Correlation of North Slope, Alaska, Oil Deposits
Ye Wang1, J. M. Moldowan2, Kenneth J. Bird3, Leslie B. Magoon3, and Kenneth E. Peters4
1Dept of Geological & Environmental Sciences, Stanford University, Stanford, CA.
2Biomarker Technology, Sebastopol, CA.
3U.S. Geological Survey, Menlo Park, CA.
4IES-Schlumberger, Mill Valley, CA.
Biomarker and diamondoid analyses of the thirty-six oil samples from the Barents Sea-Northern Timan-Pechora Basin show that fourteen of them are likely to be mixtures of cracked oil and non-cracked oil. These mixed-oil samples are identified using the diamondoid-biomarker method for estimating extent of oil cracking. Genetic relationships between oil samples and the possible source rocks, based on the published literature, are indicated by using detailed biomarker study and isotope studies. Compound specific isotope analysis of biomarkers (CSIA-B) and diamondoids (CSIA-D) are applied in an attempt to identify the deep source in some cases. Taxon specific and age-related biomarkers provide information on the depositional environment of the source rock, source input, source age and thermal maturity of these oil samples.
Four major oil families have been identified in this study. Family-I is characterized by a high ratio of specific tricyclic terpanes to the C27-neohopane (ETR parameter) suggesting a Triassic age source, with a relatively high concentration dinosteroids, indication Mesozoic. Family-II with a high C29/C30 hopane ratio, pristane/phytane < 1 and elevated C34-homohopanes, with very low levels of dinosteroids (Paleozoic indicator) and elevated C29/(C27 + C28 + C29)-steranes may be from the Devonian age carbonate source (i.e., Domanik?). Family-III shows similar “age-related” biomarker parameters as Family-II, but shows pristane/phytane > 1 and without predominance of the C34 or C35 homohopanes, suggesting it may be from a more clastic facies of the Devonian. Family-IV, with a low ETR and a high dinosteroid component could be sourced from a Jurassic source rock.
Many more parameters support these conclusions, which will be integrated into the stratigraphic and structural framework and the thermal history of the northern Timan-Pechora and Barents Sea basins
AAPG Search and Discover Article #90096©2009 AAPG 3-P Arctic Conference and Exhibition, Moscow, Russia