Выпуск: 11 , Год издания: 2024

The results of integrated isotope-geochemical and microbiological studies of reservoir waters from oilfields under development in the southern part of the West Siberian petroleum province are reported for the first time. The waters have mainly Cl Na chemistry, with salinity 13-72 g/L TDS, pH between 6.9 and 8.5, and reductive geochemical environment with Eh ranging from - 166.3 to - 90.1 mV. Salinity variations are due to the injection of waters from the Aptian-Albian-Cenoma-nian aquifer to maintain the reservoir pressure early during the development, and subsequent use of closed-cycle produced water, at increased water cutting of the production well stock. The presence of two main genetic types of groundwaters in the hydrogeological section is revealed: the ancient waters of infiltration genesis, and the waters of sediment genesis. In most of the sampled waters, the δD-δ¹⁸O pair indicates climate-induced 4-5‰ ¹⁶O depletion prior to burial, combined with later 2-3‰ ¹⁸O enrichment during prolonged water-rock interaction. In some water samples, dissolved inorganic carbon is of bacterial origin, as suggested by its isotope composition (δ¹³C_DIC). The waters hotter than 90°Cshow an evident positive δ¹³C_DIC shift to a range of - 8 to + 4‰ VPDB, which is common to thermal water values. The analyzed waters are characterized by lower ⁸⁷Sr/⁸⁶Sr ratios than those in the present-day seawater. A substantial Sr input from mantle sources is assumed, manifested up to different degrees in the waters of the studied oilfields. Microorganisms involved in the nitrogen, sulfur, iron, and carbon cycles are detected in the studied water samples. The products of the vital activities of nitrifying, thionic, and sulfate-reducing bacteria are nitric and sulfuric acids, and hydrogen sulfide. The joint action of these microbial groups poses large-scale corrosion risks to the oilfield facilities.