On the Nature of the Heavy Oils From the North of West Siberia by Isotopic-Geochemical Data

A genetic unity of the Lower Cretaceous oils and the heavy oil reservoirs of the Pokurian series has been established within the Novoportovskoye oil field. It was shown that the original, genetically encoded isotopic fractionation in the heavy oil inherited from the organic substance of the Neokomian deposits has been changed as a result of biodegradation. The heavy oil from the Senomanian reservoir of the Russkoye oil field is identical to the biodegraded oil from the Novoportovskoye oil field in its isotopic-molecular properties. Apart from traditional methods of investigation of oil and organic substance by IR-spectroscopy and GL-chromatography, the methods of carbon isotopic analysis of both the net oil and bitumoid samples and their fractions differing by degree of polarity have been used.