Activation of Formation of Hydrocarbon Fluidizites under the Conditions of Shear Geodynamic Regime of the Caspian Region (Russian–Kazakh Sector, Russia)

Abstract

The paper presents the results of the study of objects spatially related to extremely high hydrocarbon (HC) emissions identified in the North Caspian Sea. The analysis of variable geological–geophysical parameters in these objects showed (i) a high correlation with large destruction zones of the crust, (ii) the occurrence in negative forms of the top of the consolidated crust, (iii) elevated Moho top in areas of their occurrence, and (iv) their coincidence with near-shear depressions in the sedimentary sequence. These objects are revealed on the basis of surface reflection. The study of their spatial location allowed them to be correlated with the main clusters of petroleum formation, which can be identified from geological prospecting data. In the South Caspian Sea, petroleum clusters are studied by both seismic survey and drilling up to 7 km. The results of these comprehensive studies substantiate the conclusion on the formation of excitation sources under certain conditions at a deep horizon of the crust favorable for HC generation. The summarized materials from the North and South Caspian Sea suggest that significant areas of higher HC emissions are caused by large-volume fluidizites that formed in the petroleum clusters. These objects occur in the southern areas of the North Caspian region under dominant shear geodynamic regime. The position of the negative structures of the platform cover near the zones of transregional strike-slip faults causes their near-shear type. The association of HC fluidizites with near-shear depressions is caused by their location in the extension areas of the crust favorable for the formation of pull-apart structures. The correlation of fluidizites with various structural-tectonic and sedimentation factors indicates the key role of the deep geodynamic regime in the formation of similar objects.