Deep structure of South Caspian depression and connection of seismic-geological conditions with oil-gas bearing content

Abstract

The geological model of South Caspian depression is specified, the seismic-geologic and geodynamic conditions of deep layers studied, a basis for the exploration of oil-gas structures in a new aspect developed as well. A complex analysis of geological, geophysical and seismological data obtained recently has been conducted, the distribution of the depth of sedimentary, granite and basalt layers, as well as the maps of the borders dividing them – Mokhorovich (Mokho-M), Konrad (K) and base surface (F) developed. It was defined that the depth of M surface fluctuates within 40–55 km, K – 20–35 km and the base surface 5–25 km. The history of the geological development of South Caspian depression has been studied, magmatic processes (intrusion formation), seismic-geodynamic activity (earthquakes), geotectonic movements (horizontal, vertical and circle), as well as the oil-gas perspectives of the deep layers of the region estimated. It is shown that the thickness of the granite layer in South Caspian depression decreased from 5–25 km to 4–5 km, and disappears in the deepest (1025 km) part of the Caspian Sea. Corresponding changes in the seismic activity on the map of earthquake epicenter and the distribution of epicenters by the depth were observed in the circle scheme within the intervals mentioned above, and the violent earthquakes with М≥6–8 coincide with 7–20 km diapason.