Complex analysis of the geodynamic conditions of the Absheron-Balkhan oil and gas zone

Abstract

The Absheron-Balkhan oil and gas area is located in the contact zone of the Scythian-Turanian platform with the South Caspian basin (SCB). In recent years, in addition to theoretical considerations, scientists have conducted a number of geophysical studies to determine the structure of sediment cover in the South Caspian Basin. The information obtained about the depth structure has formed a new idea about the formation of the South Caspian basin. The purpose of the work is to study the features of geodynamics of the zone of the junction of the South Caspian basin and the Scythian-Turanian epi-Hercynian platform. The research methodology combines a complex analysis of geological, seismological, geomorphological, and geodetic data on the studied area. Geological and geophysical data in particular on regional profiles were used to link earthquakes to specific geological structures. The South Caspian Basin is surrounded by active mountain zones on all sides. The Kopeh Dagh, Alborz, and Talysh mountains, which connect the eastern, southern, and western sides of the basin, are observed with earthquakes not deeper than 30 km. In contrast, earthquakes were observed in the Absheron-Balkhan threshold, which covers the northern part of the basin, at depths greater than 30 km. Tectonically, the Absheron-Balkhan threshold is located at the junction of the South Caspian oceanic crust and the epi-Hercynian Scythian- Turanian continental crust. Seismic events, mainly in the northern part of the South Caspian Basin are necessary to study the geodynamic conditions of this area, and to determine the causes of earthquakes. It was observed that the strongest and deepest earthquakes, as well as tectonic processes, occurred in the northern flank of the South Caspian Basin, in the Absheron-Balkhan fold zone, and in the pre-platform area. Analysis of the focal mechanisms and depths of earthquakes proves that they are not specific to collision structures. The high seismic activity of the study area, the observation of crustal deformations at the edges of the basin (based on GPS data), and the development of mud volcanism indicate that the geodynamic conditions of the basin are active. Analysis of the seismic events data shows that the subduction of the oceanic crust of the SCB in the zone of the Absheron threshold under the continental crust of the Scythian- Turanian is the main geological event that caused seismic activity in modern times. KEYWORDS: Absheron-Balkhan fold zone, geodynamic conditions, South Caspian Basin, earthquake, deep structure.