Western Siberian Artesian Basin

one of the largest artesian basins in the world, situated in the area of the Western Siberian Lowland. Area, approximately 3 million sq km. Aquiferous complexes of the basin are linked to a rock mass of sedimentary deposits from the Mesocenozoic period and rock of the folded foundation of the Western Siberian platform. Aquiferous complexes from the Mesocenozoic period are characterized by general submersion, increased thickness, and deteriorated seepage properties of deposits from the periphery to the inner part of the basin. Two hydrogeological levels may be identified in a cross section of the inner part of the basin. These levels are divided by a thick (up to 800 m and more) rock mass of argillaceous marine sediments from the upper Cretaceous and Eocene periods.

The upper level is represented by aquiferous complexes from the Oligocene, Neocene (southern part of the basin), and Anthropogene periods. Subterranean waters of this level are formed under conditions of intensive drainage (active water exchange) and are intimately associated with climatic factors and the hydrographic system of the territory. Primarily fresh waters are found in the central and northern parts of the basin (mineralization of the compounds HCO₃-Ca and HCO₃-NaCa up to 1.0 gram per liter [g/l]); they are suitable for water supply. In the southern part of the basin (approximately 55° N lat.), in conjunction with the widespread process of continental salinization, mineralization of water frequently approaches 10-15 g/l, and its chemical composition is more variegated.

The lower level joins aquiferous complexes of deposits from the Cretaceous and Jurassic periods with those of the near-surface part of the foundation. Aquiferous layers surface only along the periphery of the basin and extensively in the eastern area (the Ob-Enisei interfluve). The subterranean water supplies of the basin’s lower level are replenished here. Fresh waters, suitable for water supply, are widespread to depths of several hundred meters (in some cases up to 1,200 m and more—Tomsk Oblast, for example). General deterioration of conditions for water exchange and increased mineralization of subterranean waters occur from the periphery to the center of the basin in conjunction with submersion and increased amounts of argillaceous sediments. In the inner part of the basin, lower level subterranean waters occur at depths of over 1,000 m. When they are unsealed by wells the waters frequently gush and pour out. Mineralization of subterranean waters approaches 20-30 g/ l and more.

In Jurassic deposits and formations of the platform foundation northwest of Tomsk at depths of more than 2,500 m brines have been unsealed with dry residue of up to 80 g/ 1. Composition of the waters is Cl-Na and Cl-Ca-Na. Bromine content of up to 150-200 mg/ l and iodine content of up to 30-40 mg/ l are characteristic of highly mineralized waters and brines of the central part of the basin (Tobol’sk, Surgut). The temperature of subterranean waters at depths of 2,500-3,000 m (Malyi Altym, Tobol’sk) approaches 100°-150°C. Very large supplies of oil and gas are linked to aquiferous complexes of the lower level.

Study of the basin’s underground waters began in the late 19th century with the investigations of a route for the Siberian railway and the operations conducted by the Administration for Transmigration. There has been important hydrogeological research in the last 20 years during explorations and surveys of oil and gas deposits and during the development of virgin and fallow lands of the steppe zone of the Western Siberian Lowland.