Formation, origin and age of brines from Volga-Ural oil and gas basin

The article is devoted to the fundamental problem of modern genetic hydrogeochemistry and petroleum hydrogeology - to clarify the nature and age of the brines dominating in hydrostratisphere of epi-Karelian platforms. On the basis of more than 500 analyzes of macro- and micronutrients we made a geochemical typification of Volga-Ural brines and presented our ideas about their formation and origin. The genesis of calcium chloride brines was associated with the processes of density convection of uterine magnesium chloride brine from the Lower Permian evaporite paleoreservoir into the underlying Paleozoic complexes and its subsequent metamorphism mainly due to the metasomatic dolomitization of limestones. The epigenetic character of calcium chloride brines was confirmed by hydrogeochronological estimates made by a kinetic-geochemical method. The interpretation of geochemical genetic information indicated a possible contribution of the Urals in the oil and gas potential of the Volga-Ural region.