Peculiarities of paleototonic development of the Astrakhan cove and prospects of oil and gas efficiency of the west part of the Caspian Depth
Analysis of the results of geological exploration and paleotectonic reconstructions of this region confirms the prospects of the western part of the Caspian depression in the oil and gas relation. The discovery of a number of gas condensate and oil fields confirms scientific forecasts about the prospects of deep-seated low-studied subsalt deposits. Peculiarities of paleotectonic development are analyzed taking into account the thermodynamic processes that allow us to identify a number of factors that are favorable for the formation of a closed isolated gas-hydrodynamic system. The received results have allowed to specify structure of Astrakhan Anticline and to reveal new deposits. Paleotectonic reconstruction during the period since the end of emsky time of early Devonian to a Pliocene - quarternary time allow to track changes of the structural plan and to note features of a relief and influence of a salt tectogenesis which has complicated the regional structural plan, but hasn't processed it completely. The cove was a leveled surface with a shallow sea basin at the early Devonian, where carbonates accumulated. At the turn of the Middle and late Devonian there is a restructuring of the structural plan takes place. This has led to the rise of the southwestern part and the sinking of the north-eastern periphery of the arch and to the erosion of the Middle Devonian carbonate platform. In the Famennian-Tournaisian time, there was a calm tectonic situation. The Viseisk-Bashkir time is marked by an immersion and a southwestern periphery and an interruption of sedimentation. By the end of the Carboniferous period, the deposits of the lower and middle Carboniferous entered the main phase of oil formation and this led to the formation of an oil deposit. In the Mesozoic, there are numerous signs of oil in the gas-saturated part of the deposit. In the Oligocene-Miocene period, the cove was an area of intensive uplift, which led to erosion of the Paleogene and in the central part of the Upper Cretaceous deposits. The growth of salt domes is activated and localization occurs in the trap of a gas condensate deposit. In the Pliocene-Quaternary time, the amplitude of the cove increased by 100 m and there was an increase in structural differentiation. The further development of the Astrakhan cove led to the formation of a hydrocarbon deposit.