The role of geodynamic stress in the formation of oil and gas structures in the Caspian Sea (on the example of the Shah Deniz, Umid, Babek, Bulla Deniz fields)

Abstract

Relevance. The article considers the geodynamic stress in the formation of oil and gas structures within the Caspian Sea (on the example of the Shah Deniz, Umid, Babek, Bulla Deniz fields). Aim. A theory for the formation of the Caspian basin was proposed based on the “mantle plume” model. Methods. In this technique, it is assumed that within the mantle plumes there is an uplift of matter and heat removal from the mantle depths. It is also believed that in the head of the mantle plume there is a partial melting of the mantle material and a magma-generating area is formed. The magma that is formed in the head is usually alkaline-basalticcomposition. When the mantle plume reaches the base of the lithosphere, plume magmatism appears above it: intrusions are introduced into the earth’s crust and along the border of the earth’s crust and mantle. It is noted that in the area covered by the Paleo-Caspian, magma moved from the mantle layer to the Earth’s surface. Thus, it changed its structure near the Earth’s surface, and the area outlined by local anomalous fields in gravity and magnetic fields corresponded to the paleocaspian morphology. Zones of seismic activity and circular regional faults, under the geodynamic stress of the modern Caspian basin, are considered signs of a plume process. Results. It has been established that strong earthquakes with a relative magnitude of M≥6-8 occur in the depth range of 7-20 km. In the northern arc of the South Caspian, where plume activity is still present in the 55-65 km interval in the basalt layer, there are signs of deformation in this interval in accordance with the characteristic earthquake sources. Geodynamic stress accumulated as a result of horizontal, vertical and circular motions created by the plume in the mantle influenced the dynamics of the sedimentary layer to a depth of 25 km, the Conrad boundaries 20-32 km 40-53 km, and the Moho boundaries to a depth of 40-53 km. There the morphostructure of the sedimentary layer was constantly changing. The deposition process in the basin of the Caspian Sea began before the Mesozoic, and during the Jurassic period the earth’s crust continued to decline and the formation of the basin took place with approximately the same tendency. As a result of the vortex movement created by the magmatic plume in the Caspian basin, the circular spiral anticlinal structures (Bahar, ShahDeniz, Absheron, Shafag, Mashal, Babek, Umid, BullaDeniz, Asiman, Zafar, etc.) were built. There was accumulated the large amount of the country’s hydrocarbon potential. The stratigraphic and lithological features of deposits in the structure ofUmidare analyzed and it is shown that there are very large reserves of oil and gas.