Geodynamic development of structures of the North Absheron uplift zone within the South Caspian megadepression and oil-gas-bearing

Abstract

The article discusses the geodynamic development of the structures of the North Absheron uplift zone. The Pirallahi-Kelkor trough is a polyfocal sub-basin due to the fact that in its sedimentary section, at least the Jurassic, Lower Cretaceous, Lower Pliocene and Quaternary deposits, are characterized by favorable conditions for the accumulation and burial of organic matter. It follows from this that, in accordance with its paleogeotemperature regime, several main stages of hydrocarbon migration could have taken place here. For identifying the formation and further structural-tectonic development , the Absheron bank, the Arzu, Chilov, Palchig Pilpilasi, Chirag and Garabag uplifts have been studied. To solve this issue, paleoprofiles for the end of the Jurassic, Early Cretaceous, Miocene and Pliocene based on the seismic geological profile across the strike of the Pirallahi-Kelkor trough have been compiled. As a result of these studies we established that the uplifts are of syndepositional origin, formed simultaneously with the sedimentation process. The sedimentation and geotemperature regime of the subbasin play a significant role . İt was found that by the end of the Pliocene, the main oil formation zone (MOFZ) contained sediments from the second half of the Lower Cretaceous to the second half of the Lower Pliocene, and both Lower Cretaceous and Lower Pliocene deposits took part in the main stage of hydrocarbon migration. Finally, the MOFZ currently contains sediments from the tops of the Lower Cretaceous to the bottoms of the Upper Pliocene. As can be seen, the main stage of migration covered both Lower Cretaceous and Lower Pliocene deposits. İn addition, we concluded that the natural reservoirs of local uplifts that formed within the Absheron archipelago, regardless of the time of their formation, could be saturated with hydrocarbons depending on the level of their development, position in the structural-tec- tonic plan and reservoir characteristics of the strata. Due to the fact that the uplifts were formed no later than the Miocene, it was even considered that they began to appear by the end of the earlier Miocene, and that they could have captured hydrocarbons of the Lower and Later Cretaceous period.