GEOCHEMISTRY OF ORGANIC MATTER IN THE BAZHENOV FORMATION ON THE NORTH-EASTERN SIDE OF THE NYUROL MEGA-DEPRESSION ( <i>south-east of Western Siberia</i> )

The article presents the results of detailed organic geochemistry investigations being part of a comprehensive (lithological, geochemical, petrophysical) study of the Bazhenov Formation in the Tomsk Region applying the Trofimuk Institute of Petroleum Geology and Geophysics, Siberian Branch of the Russian Academy of Sciences methodology developed for organic matter-rich source rock. As the thermal maturity increases from PС3 to MС2, the content of “free micro oil” in source rock’s pore spaces has been observed to increase. In the same time, there are modifications to the composition of bitumoids (chloroform source rock extracts) from open and closed pores at both the group and molecular levels. Even “immature” organic matter has been established to show a difference in bitumoids composition from open and closed pores, which increases as it enters the main phase of oil generation (“oil window”).