The article considers the geological structure of the Tengiz-Karaton uplift zone, the history of the geological development of this area and adjacent zones and analyzes information on 12 oil samples collected within the Tengiz-Karaton uplift zone and 2 oil samples collected at the South Emba high. The studies included analysis of the physical and chemical properties and composition of oil, analysis of gas chromatography data, biomarker analysis, and carbon isotope analysis. According to the results of the caried out analyses, two families of oils were identified, which correspond to two source rocks. Oil such as that extracted from the Serpukhov horizon of Tengiz field is characteristic of reef reservoirs that are widely distributed within the Volga-Ural and Timan-Pechora hydrocarbon provinces and are associated with Domanic source rocks. This high-carbon clay-siliceous-carbonate formation was formed in a relatively deep-water basin, during the formation of which the sedimentation conditions changed from deep-sea to shallow-sea. In terms of the amount of isoprenoids and normal alkanes, as well as the distribution of regular steranes, domanic oils are very similar to the deep oil of the Tengiz field, selected from the Serpukhov reservoir. However, the distribution of normal alkanes in this oil indicates the Early or Middle Devonian age of the source rocks, which suggests the existence of uncompensated sedimentation conditions in this time interval. Based on the geological structure of the territory, most likely, the source of generation is located in the Caspian Sea area. The other oils, both from the postsalt and from the subsalt horizons, probably have a single source rock according to the totality of geochemical characteristics. Presumably, these oils were generated in normal marine sediments of Carboniferous age (the Moscow time), and migration to the postsalt complex occurred in areas where salts are pinched out.
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