Vertical distribution of alkanes in the lower cretaceous and Jurassic sediments of the Borovoye oil field

The distribution of alkanes in the Lower Cretaceous and Jurassic deposits of the Borovoye oil field, which is part of the East Sabun structural-formation zone of local compression in the eastern part of the West Siberian Plate, is considered. The core material of exploration wells was studied. The bitumoid of rocks contains C8-C40 hydrocarbons, including n-alkanes, isoprenoids, n-alkylbenzenes, naphthalenes, and phenanthrenes, this is determined by chromatography-mass spectrometry, and the molecular mass distribution of n-alkanes and isoprenoids is considered. The lithological and petrographic characteristics of the rocks were studied by optical microscopy. Based on the results of the analysis of hydrocarbons in the Jurassic sediments, a closed oil and gas complex is identified, it’s including: the parent rocks of the Tyumenskaya and possibly Marianovskaya formations, a reservoir in the upper Tyumenskaya and Naunakskaya formations, fluid barriers - the Marianovskaya formation at the top and the Radomskaya pack at the bottom. In the marginal parts of the complex, there is a drop in the concentration and depletion of the composition of hydrocarbons, which is characteristic of filtration. In the Cretaceous sediments, the transit movement of alkanes up to C21 from the Jurassic zone of oil occurrence is recorded. The composition and content of heavier hydrocarbons vary from layer to layer, probably a function of the syngenetic bitumoid of the rocks. In the considered sandstones of Cretaceous deposits, low concentrations of extracted organic substances are consistently recorded, without a significant trend within the section, which may indirectly indicate the absence of geological conditions for the accumulation of hydrocarbons and the formation of non-structural deposits in the Lower Cretaceous section of the Borovoye field.