Hydrogeology of the artesian basins of the southern part of the Kara sea and Yamal-Gydansk megasaddle

Abstract

Background. In hydrogeological terms, the territory of the Barents-Kara shelf has not been studied in sufficient detail. The data on its hydrogeological zoning are based mainly on the results of research undertaken in the 1970s, when attempts were made to isolate artesian shelf basins according to a set of hydrogeological indicators of oil and gas content. Currently, the position of the basin boundaries can be adjusted using current data from oil and gas and geological zoning and the hydrogeological testing of wells.Aim. To conduct the hydrogeological zoning of the territory of the southern part of the Kara Sea and the north of the West Siberian geosyneclise, including oil and gas structures — the South Kara syneclise and the Yamal-Gydan megasaddle, as well as to carry out a chemical analysis of groundwater of the Jurassic-Cretaceous aquifer complexes composing the sediments of the sedimentary cover of the West Siberian sedimentary basin.Materials and methods. A cartographic method was used to analyze earlier maps and schemes of hydrogeological and oil and gas geological zoning of the Russian sector of the continental slope of the Arctic Ocean, and then to determine the boundaries of the identified artesian basins. For a chemical analysis of groundwater, the results of hydrogeological testing of wells drilled at the Zapolyarnoye oil and gas condensate field were used.Results. The boundaries of two artesian basins — the South Kara submarine and the Yamal-Gydan semi-marine, corresponding to the same-name oil and gas prospective structures and having the same geological structure, were determined. Both basins are characterised by the presence of the main aquifer complexes of the Mesozoic hydrogeological floor of Western Siberia. When studying the composition of groundwater of the Zapolyarnoye deposit, it was found that the types of water change regularly with depth and an increase in the content of the hydrocarbonate ion due to the possible migration of fluids enriched with carbonic acid dioxide from the rocks of the foundation.Conclusion. The determined basins are characterised by a wide distribution of oil and gas-bearing structures and the exploration maturity of the sedimentary cover. Both artesian basins are characterized by the distribution of groundwater of a unified composition and genesis.