Tectonic dislocation of Mesozoic-Cenozoic series as one of the main distinctive feature of oil and gas occurrence in the northern part of the West Siberian plate

This paper presents the results of paleotectonic analysis of the conditions the Mesozoic-Cenozoic series were formed in within the sedimentary cover of the West Siberian Plate northern part (administratively corresponding to the respective territory of Yamal-Nenets Autonomous Okrug). Paleotectonic analysis is conducted using the methodology of building paleothickness maps for the main lithostratigraphic sequences controlled by the most clearly defined reflections (“А”, “Б”, “М”, “М´”, “Г”, and “С3”). Basing on the paleoreconstruction results, the inversion nature of development of the area under investigation is revealed; i.e., during the course of geological time, the very same areas are subject to inversion of tectonic dislocation directions - stages of active upwarping change for downwarping, and vice versa. The paper explains the impact of inversion tectonic movements on formation of folds and faults, tectonic blocks movement, and associated sediment destruction; i.e., on formation of tectonic dislocation pattern of sedimentary cover deposits. The authors also explain the consequences of tectonic inversions on the formation of mechanism of fluid migration, fluid distribution and accumulation. Zones with the high tectonic dislocation are substantiated as the areas most favourable for formation fluid migration and, respectively, for the processes of oil and gas accumulation. The authors were the first to create the model of tectonic dislocation of sedimentary cover deposits and to reveal the relationships between the tectonic dislocation degree and oil and gas occurrence within the northern part of Western Siberia. It is found that about 75 % of the discovered hydrocarbon reserves are confined to the zones having a high degree of tectonic dislocation. The results obtained can be used in planning of exploration and prospecting activities within the considered territory