New Insight Into Petroleum Systems of Orenburgh Region, Volgo–Ural Basin

Authors have identified a complex Paleozoic petroleum system represented by 5 major source rocks with good up to excellent characteristics from the point of petroleum potential, reservoirs of porous and fractured types, regional and local seals. Processes of generation, migration, accumulation and conservation of HCs occurred within the limits of this system. Moreover, 2 potential hydrocarbon systems were formed: Mezo-Cenozoic oil system which source rocks within the main part of the area have not entered conditions favorable for HC generation; Ordovician-Silurian petroleum system which source rocks have mostly worked out their petroleum potential and have possibly carried out significant input in petroleum potential of the area. Main source rocks reached oil window zone, and Devonian rocks partially reached gas zone. Main critical moment for Paleozoic rocks – Early Permian time at maximal rock submergence at high geothermal gradient. Subsequently Paleozoic deposits did not reach the same temperatures, i.e. secondary activation of HC generation processes did not occur.