Temperature conditions and level of organic metamorphism in the south-eastern part of the Terek-Caspian trough

UDK: 558.98:556.314.7
DOI: 10.24887/0028-2448-2019-2-18-22
Key words: formation temperatures, vitrinite reflectance, organic matter, hydrocarbons, maturity
Authors: А.А. Feyzullayev (Institute of Geology and Geophysics Azerbaijan National Academy of Science, Azerbaijan, Baku), G.G. Ismaylova (Institute of Geology and Geophysics Azerbaijan National Academy of Science, Azerbaijan, Baku), A.N. Huseynova (Institute of Geology and Geophysics Azerbaijan National Academy of Science, Azerbaijan, Baku)

The Terek-Caspian foredeep is located between the epi-Hercynian Scythian Plate and the Alpine folding of the Greater Caucasus (the south-east periclinal of deflection). The deflection has an asymmetric structure. The offshore part of the Terek-Caspian trough occupies the western part of the Middle Caspian Sea and consists of two basins: the Terek-Sulak in the north and North-Apsheron in the south-east. These depressions are separated by Yalama-Samur horseback of the Turanian Plate. The average thickness of the sedimentary cover of Terek-Caspian foredeep is about 12 km. At Yalama-Samur horseback (offshore) organic matter of the Jurassic interval of the section is classified as early mature medium.

Methodology of the conducted analysis is based on the patterns of change of the current temperature and paleo-temperature (vitrinite reflectance) through the section, and direct assessment of the maturity of organic matter (pyrolysis) and hydrocarbon (biomarkers). According to the actual data on the Yalama-Samur zone the process of petroleum formation begins approximately with a depth of 3 km. Thus, based on these temperatures, the values of paleo-temperature target and the spore coloration index (SCI), we can conclude that the upper threshold of oil generation in the pre-Caspian-Quba region (land) is located in the depth interval of 2.5-3.0 km. These conclusions well correspond to the character changes in gas composition (the sum С2Н6+) in case of deposits of Siyazan monocline.

Within the Apsheron archipelago, the zone covering the Neft Dashlary and Palchig Pilpilas areas is of interest for performing exploration work on the underlying productive strata (main oil and gas object of the South Caspian basin) Miocene sediments (oil reservoir).

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