Geochemical characteristics of the hydrocarbon systems of the Pre-Caspian basin

UDK: 522.578
DOI: 10.24887/0028-2448-2023-5-26-30
Key words: Pre-Caspian basin, Pre-Caspian oil and gas province, geochemistry of organic matter, Rock-Eval method, oil-producing rock, subsalt floor, oil and gas potential, hydrocarbon system
Authors: S.F. Khafizov (Gubkin University, RF, Moscow), K.I. Dantsova (Gubkin University, RF, Moscow), A.S. Monakova (Gubkin University, RF, Moscow), E.R. Kasyanova (Gubkin University, RF, Moscow), E.A. Izmalkova (Gubkin University, RF, Moscow)

The Pre-Caspian basin has a high oil and gas potential. The sedimentary cover is divided into three complexes – suprasalt, salt and subsalt. The most studied to date is the suprasalt complex. It has the largest number of industrial hydrocarbon accumulations.

The Pre-Caspian basin has been studied unevenly in area and in section. The central part is the least studied because of the thick sedimentary cover, which reaches more than 20 km. However, there are positive prerequisites for the discovery of new oil and gas fields in the subsalt complex.

Basin modeling and modeling of hydrocarbon systems are used nowadays to establish oil and gas potential. When using these methods, maps of the distribution of total organic content (TOC), hydrogen index (HI) and kerogen type over the studied region are the basis for determining the foci of hydrocarbon generation and a necessary element of any basin model. For their construction, the generation characteristics of the oil-producing strata are needed. For these purposes, the authors additionally investigated the core using the Rock-Eval method, selected from wells Embinskaya 9, Kozhasai PGS 1, Vostochny Akzhar 5, Karakulkeldy P 21. But geochemical parameters directly of the well core are always insufficient, they are distributed unevenly over the area and section, which significantly reduces the reliability and detail of the constructions.

Thus, the lack of analytical data on rocks in most of the territory does not allow us to single out oil and gas-producing rocks by area, however, according to the analysis of the physico-chemical properties and composition of oil, biomarkers for the fields of the Tengiz-Karaton zone and the South Embinsky uplift, the approximate age of the oil-producing strata is Devon-middle carbon, it gives reason to assume their wide distribution and good generation potential.

Based on the analysis of published data and conducted studies, four oil-producing strata were identified as the Middle Devonian, Upper Devonian, Lower Carboniferous and Lower Permian, maps of the distribution of Total organic carbon, hydrogen index and kerogen type were constructed for subsequent modeling of hydrocarbon systems.


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