Geochemistry of hydrocarbons in bottom sediments of the Laptev Sea shelf

UDK: 550.4.

DOI: 10.24887/0028-2448-2025-5-68-73

Key words: Arctic shelf, Laptev Sea, oil and gas potential, methane, thermogenic gas, carbon isotope composition

Authors: Yu.A. Petrichenko (IGIRGI JSC, RF, Moscow); Z.A. Tembotov (Arctic Research Centre LLC, RF, Moscow; Lomonosov Moscow State University, RF, Moscow); I.V. Goncharov (TomskNIPIneft JSC, RF, Tomsk; National Research Tomsk Polytechnic University, RF, Tomsk); D.K. Komissarov (Rosneft Oil Company, RF, Moscow); M.A. Veklich (TomskNIPIneft JSC, RF, Tomsk); N.A. Smirnova (National Research Tomsk Polytechnic University, RF, Tomsk); V.E. Verzhbitsky (Rosneft Oil Company, RF, Moscow)

The article presents the results of geochemical studies of bottom sediment samples which were collected in the license areas of Rosneft Oil Company on the Laptev Sea shelf. In order to identify gas anomalies that may indicate hydrocarbon migration from oil and gas deposits, a set of laboratory studies was performed to study the component composition of gases using the method of equilibrium concentrations (Head-Space Analysis - HAS) and the isotopic composition of carbon in gas components was determined using the GC-C-IRMS method (mass spectrometry of isotopic ratios using a gas chromatograph). Based on the results of complex geochemical studies, evidence was obtained of migration of deep fluids into the bottom sediments. This is indicated by the wide variability of the isotopic composition of methane carbon (-73-102 ‰), which is due to the mixing of thermogenic isotopically heavy (-30-50 ‰) methane with microbial gas (-100-110 ‰), the presence of methane homologues (C2-C5) in the degassing gases, as well as the detection of isotopically heavy (thermogenic) ethane. The conducted studies are good indicators of the presence of oil-and-gas source rocks in the sedimentary section of the Laptev Sea, which confirms the idea of the significant oil and gas potential of the offshore area.

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