Environmental Conditions, Sedimentation Cyclicity, and Architecture of the Productive Series Reservoirs

The orogenic processes took place at the end of the Pontian and gave rise to the Caspian surrounding land areas, and enormous sea-level lowering, according to information available, from 600 to 1500 m, led to the complete isolation of the Caspian Sea in the Lower Pliocene. The sedimentation at that time took place under conditions of the South Caspian, the most isolated basin that accumulated all the vast mass of terrigenous material supplied by the three largest river arteries: paleo-Volga, paleo-Amu-Darya, and paleo-Kur. Avalanche sedimentation at the rate of 2.5 mm/y and a high down-warping rate of the basin bottom led to the formation of a unique 7 km terrigenous productive series containing up to 90% of all oil and gas reserves in South Caspian oil/gas–bearing basin (SCB). The question arises: within more than 30 km thick sedimentary series represented by a wide stratigraphic range - from the Middle Jurassic Aalenian stage up to the Holocene inclusive, the horizons possessing top-quality reservoir properties have been formed exactly in the Lower Pliocene deposits.