Some features of associated petroleum gases in the northeast of Volga-Urals

The composition of associated gases of the main oil and gas complexes of the Upper Devonian carbonate and terrigenous Devonian was studied for the purpose of identification of the sources of these gases. Molecular characteristics and their specific features were used together with carbon and nitrogen isotopic composition for determination of their genesis. The results showed the difference in molecular characteristics for the gases of Upper Devonian carbonate complex and Terrigenous Devonian. More contrasting results were found for isotopic composition of carbon and nitrogen. The analysis of obtained results suggests a presence of several sources of gases at the study area.