Reconstruction of facies conditions of the sedimentation of bitumen-bearing sandstones according to granulometry data (Volga-Ural oil and gas province, Russian Federation)

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For 60 years in the Volga-Ural oil and gas province, the study of Paleozoic sediments was carried out taking into account their industrial oil and gas potential. Therefore, the most studied are deposits of the Devonian and Carboniferous periods. Today, most of the Devonian and Carboniferous oil fields are close to depletion. In recent years, in order to maintain production volumes, oil companies are increasingly focusing on the study of Permian deposits, in which significant resources of natural bitumen and super-viscous oils are concentrated. Their industrial resources are associated with psammite (sandy) deposits of the Sheshmian horizon of the Ufimian stage of lower-Permian period. In this regard, the task of a more detailed study of the conditions for the formation of Sheshmian deposits, which are characterized by a complex geological structure, is becoming ever more acute. Formation conditions affect the spatial distribution and features of geological structures, the definition and refinement of which is important for building high-quality 3D geological models and improving the efficiency of exploration and development of deposits. To determine these characteristics, facies analysis is successfully used, which is carried out on the basis of granulometric and mineralogical studies of sediments to obtain ideas about sedimentation conditions. Lithological-facies studies also make it possible to determine the structural features of the terrigenous rock and its reservoir properties.