The role of proterozoic sediments in the formation of oil and gas content in the northern part of the Volga-Ural oil and gas basin (based on the results of basin modeling)

Abstract

Two-dimensional basin modeling was carried out along regional profiles (sublatitudinal and submeridional). When modeling, the software package of Lomonosov Moscow State University was used. The models take into account the features of geological structure of the Riphean deposits of the Kama-Belsky aulacogene northern part and the Vendian-Paleozoic complexes that overlay it. Recent data on the features of region geology (taking into account the assessment of thickness of the eroded Riphean-Vendian deposits), as well as on the features of organic matter of the ancient Precambrian deposits were used. As a result, boundaries of the oil and gas window and geotemperature gradient were revealed. Main type of deposits according to the results of 2D basin modeling is anticlinal (reservoir-arch) and stratigraphically shielded. Data obtained testify, firstly, to two stages of hydrocarbon generation by the Riphean-Vendian oil source strata (the first stage occurs at the end of the Early Riphean, the second – at the Vendian-end of the Late Carboniferous), and, secondly, to prevailing share of the Riphean-Vendian complex of source strata in the formation of oil and gas content of sedimentary cover within the marginal zones of the Kama-Belsky aulacogen northern-northwestern part of the Volga-Ural oil and gas basin. Generation of hydrocarbons by source strata of the Riphean-Vendian and Late Devonian-Early Carboniferous continues to this day, however, it has rather an «inertial character».