Tectonic Styles and Hydrocarbon Accumulation Characteristics of Concealed Thrust Belt in Eastern Margin of Pre-Caspian Basin

The Pre-Caspian Basin is located between the Eastern European platform and the Kazakh plate. The eastern margin of the Basin is the Ural piedmont thrust belt, which is a typical concealed piedmont thrust belt and related structures formed by the Ural orogenic movement. Based on the seismic and drilling data of the eastern margin of the Pre-Caspian Basin, this paper analyzes the geological structure of the area and reconstructs the tectonic sedimentary evolution process. The study shows that the area has experienced the transformation of extension and compression stress, forming four stages of tectonic sedimentary evlution. Affected by the differences of stress action mode and filling stratum attributes, the eastern margin of the basin has the tectonic deformation characteristics of “vertical stratification, east-west zonation, north-south segmentation and tectonic periodization”. Differential tectonism controlled the formation of different tectonic styles and trap distribution, and also controlled the temporal and spatial allocation of hydrocarbon accumulation factors. The tectonic units have their respective characteristics of hydrocarbon accumulation and distribution, forming the present petroleum system owing to differential hydrocarbon accumulation.