Hydrogeological prerequisites of Kizil oil-region in the Southern Urals

The article discusses a debatable problem of oil-bearing Kizil structural facies zone of Magnitogorsk megasinclinorium in Southern Urals from a hydrogeological point of view. The discussion is based on the results of exploration deep drilling (up to 5010 m) in the Urals profile involving information on ore and hydromineral deposits. We present the analysis of the abyssal hydrogeochemical zoning and our ideas concerning the formation and genesis of ground waters. We showed that the oxygen-nitrogen fresh waters at the depth of more than 1000 m were replaced by salty waters and > 2000-3000 m - by methane brines of chlorine-calcium type. They are associated with fractured reservoirs of sedimentary and volcanic-sedimentary Carboniferous strata and occur in a very complex hydrogeodynamic regime and shielded from the effects of supergene factors by regional thrusts. The brines are the product of sedimentation in Carboniferous evaporite paleobasins and subsequent metamorphism in the rocks due to epigenetic processes. The tangential forces affected not only the style of tectonics and hydrogeodinamics of the Southern Urals, but also played a key role in the formation of filtration-capacitive properties of the rocks. The prospects of the oil-bearing zones are associated with Kizil buried anticlinal structure, particularly with its eastern subthrust part. The exploration works are complicated due to anisotropism and irregular fractured reservoirs.