Summary

Based on the stable carbon isotope analyses of saturates, aromatics, resins and asphaltenes of the extracted bitumens, and kerogens as well as Rock Eval data for the Oligocene Menilite Beds and Upper Cretaceous Spas Shales in the profile of Ku´zmina-1 well it has been determined that a mixture of two genetic components of organic matter: marine (aquatic) oil-prone and terrestrial gas-prone occurs. The former one dominates in the Menilite Beds, whereas the gas-prone one - in the Spas Shales. As the organic matter of the Menilite Beds is immature, no bigger quantities of hydrocarbons could be generated. The organic matter of the Spas Shales approached the ending phase of low-temparature of thermogenic processes (“oil window”) therefore was able to produce bigger amounts of hydrocarbons, mainly gaseous ones. Stable isotopic analyses of individual gaseous hydrocarbons from influxes from the Spas Shales indicate that they come just from this kind of environment.

AAPG Search and Discovery Article #90937©1998 AAPG Annual Convention and Exhibition, Salt Lake City, Utah