Summary

The Upper Jurassic organic-rich siliceous shales of the Bazhenov Formation occur in the West Siberian Basin, Russia. Geochemical analyses of Bazhenov core samples revealed TOC values of 2.1 to 12.6 wt.%, consisting predominantly of amorphous kerogen. Rock-Eval™ Hydrogen Indices range from 233 to 794 depending upon the level of thermal maturity (Tmax: 429°-446° C). These source rocks were solvent extracted, analyzed for biomarkers (chemical fossils) as well as stable carbon isotopic compositions, and statistically correlated with 300 West Siberian oils produced from UJ and LK reservoirs. Six oil families were recognized and mapped, representing various lateral and vertical organofacies of the Bazhenov, laid down under different depositional environments with respect to degree of anoxia and regions of upwelling. In addition, a number of maturity-sensitive biomarker ratios were statistically combined and converted into a vitrinite reflectance equivalent (VRE) value for each oil. Only 16% of analyzed Bazhenov-sourced oil was generated at maturity levels above 0.75% VRE.

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