The Pashyian Regional stage (horizon) is the main productive unit of the middle Devonian clastic succession of the South Tatar arch. This article presents, for the first time, maps of the lower and upper parts of the Pashyian, including data on sand-shale ratio, number of sand layers (reservoirs) and thickness, based on the analysis of logging data from 25,000 wells. The maps were created by spatial interpolation of Natural Neighbor and ArcGIS Pro software.
The model of sedimentation of the Pashyian Regional stage reflects the interpretation of the plotted maps as well as the synthesis of the results of detailed core investigations (lithological, sedimentological, ichnotextural, petrophysical, etc.) and analysis of archive and published materials.
The main points of the proposed model are as follows. The Pashyian sediments were formed in a marine basin, in an environment comparable to that of the middle shelf of modern seas – in an offshore zone dominated by current activity. The basin floor was a relatively flat plateau, on which sandy, silty and clay sediments were simultaneously accumulated. Sediments of all types accumulated during sea transgression. Sea regression caused erosion and destruction of the already formed sediments.
Positive landforms of seabed relief, composed predominantly of sandy well-sorted material, comprised autochthonous underwater sand bars, formed by constant currents parallel to the bathymetric contour of the seabed. Underwater sand bars formed extensive systems nearly throughout the entire territory of the modern South Tatar arch. At the same time, allochthonous, poorly sorted, less mature sediments were formed in underwater troughs produced by transversal currents (directed from the shore towards the sea).
The proposed model explains the consistent thickness of the Pashyian Regional stage, the mosaic distribution of sand bodies over the area, and the lens-like shape of the sand and siltstone reservoirs. The model can be extrapolated to other stratigraphic intervals of the Devonian clastic succession with similar sedimentological features.
Vladimir V. Silantiev – Dr. Sci. (Geology and Mineralogy), Head of Department of Paleontology and Stratigraphy, Institute of Geology and Petroleum Technology, Kazan Federal University; Branch of the Kazan Federal University in the city of Jizzakh of Republic of Uzbekistan
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Marat F. Validov – Leading Engineer, Head of Petrophysical Department, Center for Excellence of Digital Technologies in the Oil and Gas Industry, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Dinara N. Miftakhutdinova – Assistant, Department of Paleontology and Stratigraphy, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Vladimir P. Morozov – Dr. Sci. (Geology and Mineralogy), Professor, Head of Department of Mineralogy and Lithology, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Bulat G. Ganiev – Cand. Sci. (Engineering), Head of the Department of Field Development, Tatneft-Dobycha, Tatneft PJSC
Lenin str., 75, Almetyevsk, 423450, Russian Federation
Azat A. Lutfullin – Cand. Sci. (Engineering), Deputy Head of the Department of Field Development, Tatneft-Dobycha, Tatneft PJSC
Lenin str., 75, Almetyevsk, 423450, Russian Federation
Kirill D. Shumatbaev – Cand. Sci. (Geology and Mineralogy), Chief Expert (on petrophysical research), Department of Field Development, Tatneft-Dobycha, Tatneft PJSC
Lenin str., 75, Almetyevsk, 423450, Russian Federation
Rishat M. Khabipov – Head of the Field Development and Subsoil Use Monitoring Department, Department of Field Development, Tatneft-Dobycha, Tatneft PJSC
Lenin str., 75, Almetyevsk, 423450, Russian Federation
Nouria G. Nurgalieva – Dr. Sci. (Geology and Mineralogy), Professor, Department of Oil and Gas Geology named after Academician A. A. Trofimuk, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Zoya A. Tolokonnikova – Cand. Sci. (Geology and Mineralogy), Assistant Professor, Kuban State University
Stavropolskaya str., 149, Krasnodar, 353400, Russian Federation
Eduard A. Korolev – Cand. Sci. (Geology and Mineralogy), Head of Department of General Geology and Hydrogeology, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Vladislav A. Sudakov – Deputy Director of the Institute for Innovations, Director of Hard-to-Recover Reserves Simulation Research and Educational Center, Institute of Geology and Petroleum Technology, Kazan Federal University
Bolshaya Krasnaya str., 4, Kazan, 420111, Russian Federation
Anastasiya V. Smirnova – Design Engineer, Center for Excellence of Digital Technologies in the Oil and Gas Industry, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Kseniya A. Golod – Engineer, Center for Excellence of Digital Technologies in the Oil and Gas Industry, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Aleksey A. Leontiev – Leading Engineer, Head of Well Logging Interpretation Department, Center for Excellence of Digital Technologies in the Oil and Gas Industry, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Ruslan R. Shamsiev – Laboratory Assistant, Center for Excellence of Digital Technologies in the Oil and Gas Industry, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Mikhail V. Noykin – Engineer, Center for Excellence of Digital Technologies in the Oil and Gas Industry, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Viktor E. Kosarev – Senior Lecturer, Department of Geophysics and Geoinformation Technologies, Institute of Geology and Petroleum Technology, Kazan Federal University
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Darya A. Nikonorova – Laboratory Assistant, Institute of Geology and Petroleum Technology, Kazan Federal university
Kremlevskaya str., 18, Kazan, 420008, Russian Federation
Radik F. Akhmetov – Laboratory Assistant, Institute of Geology and Petroleum Technology, Kazan Federal university
Kremlevskaya str., 18, Kazan, 420008, Russian Federation