Triassic source rocks of the Eastern Ciscaucasia

Abstract

Background. Triassic deposits of the Eastern Ciscaucasia belong to the upper part of the transient zone, which is considered promising for hydrocarbon exploration. The presence of numerous deposits, as well as non-commercial hydrocarbon flows in boreholes, indicate the existence of petroleum systems in this part of the section. However, issues related to the sources of hydrocarbons in the Triassic deposits still remain unresolved.Aim. To identify and study the possible source rocks for the Triassic deposits of the Eastern Ciscaucasia, as well as to assess their contribution to the hydrocarbon potential of the upper part of the transient zone.Materials and methods. Research materials involved all available geological, geophysical and geochemical data published on the section under study, as well as reports from the Russian Federation geological repository. The collected data were analyzed as part of the conducted basin analysis. Numerical basin modeling and paleogeographic reconstructions were performed.Results. The paleogeographic conditions of the Eastern Ciscaucasia and the adjacent areas of the Caspian Sea at the Triassic period were studied. The results of basin analysis were used to construct the distribution maps of Neftekumskaya, Kultaisko-Demyanovskaya and Kizlyarskaya source rocks and to assess their charging ability for Lower and Middle Triassic reservoirs.Conclusion. The conducted numerical modelling revealed several pods of still active source rocks in the Neftekumskaya, Kultaisko-Demyanovskaya and Kizlyarskaya sections. Lower Triassic reservoirs charged from both the Neftekumskaya and Kultaisko-Demyanovskaya source rocks, unlike Middle Triassic reservoirs that charged from the Kizlyarskaya source rocks. Thus, independent petroleum systems separated by the Anisian seal at the two stratigraphic levels in the Triassic part of the transitional complex of Eastern Ciscaucasia were identified.