Biostratigraphy and lithofacies of the Middle-Upper Devonian in the Ayazovo oil field (North-Eastern of Bashkiria)

Abstract

Research subject. Oil-bearing deposits of the Middle-Upper Devonian in the Ayazovo oil field located in the north-east of Bashkiria.Materials and methods. A detailed description and subdivision of the section were carried out based on the borehole cores of the Rustamovskaya area using biostratigraphic and lithofacial analysis, micropalaeontology of spores and conodonts.Results. The sediments of the Pashian, Timan, Sargaevo, Domanic and Mendym horizons are identified, their lithofacial features are described, and sedimentation conditions are determined.Conclusions. The studied succession of the Devonian sediments demonstrates cyclical changes in terrigenous and carbonate shelf sedimentation environments caused by eustatic sea level change and complicated by the tectonic events associated with the formation of uplifts and troughs of the Kama-Kinel system at the end of the Frasnian.