Modern structural and tectonic model of the Caspian Region

Abstract

The article analyzes the development and evolution of the structural and geodynamic systems of the sedimentary complex in the Caspian region, and the results of structural and tectonic modeling of individual tectonic zones in the region. Based on the modeling results, an important feature of the morphology and structure of the basement surface and sedimentary complex in the Caspian Sea is the tracked sea extension of many elements detected on land. The main features of the morphology and structure of the basement surface and sedimentary complex in the Caspian region are the presence of superdeep depressions of the earth’s crust, with the basement depth up to 16 km or more in the North Caspian and up to 20–24 km in the South Caspian, as well as the distinct longitudinal (sublatitudinal) tectonic zonality of the region. Constructed as a result of the implemented reconstructions, the gener alized geological and tectonic model of the uneven-aged basement surface comprises the sea and continental parts of the region under study. article reports the integrated analysis of the history, geodynamics, modern faulting system, internal structure and spatial occurrence of Paleozoic and Paleogene (Eocene) accumulations of oil in the promising Chezhen block of the Chezhen sag of the Jiyang depression in the Bohai Bay Basin in East China. After review of the new geological, geophysical and field studies, the authors find out that in this structurally complex system of faults and fractures of different age, orientation and types, the present-day spatial occurrence of oil reservoirs is governed by the neofaults which blanket the whole geological section, including the Paleozoic period. The studies (analysis of polished sections) into internal structure (micro fracturing) and oil saturation of rocks produce some new data of interest for the theory and practice. The studies of samples from the reservoir and non-reservoir rocks in exploration drilling in the Shahejie pay horizon show that oil saturation is connected with the presence of the younger age system of micro fractures (permeable) of horizontal and vertical (faults) orientation. The further exploration in the promising Chezhen block of the Shenli oil field is recom-mended to continue in the zones of the Cenozoic faults as any rocks (irrespective of their lithology, including low-porosity rocks) can be saturated with oil in these zones which con-tain the best-type reservoirs (fractured) and feature active fluid neodynamics.