Gas-geochemical studies of seafloor sediments from the Laptev-Siberian Sea zones in East Arctic shelf and interpretation
of the data obtained resulted in revealing direct indicators of hydrocarbon accumulation formation in the region. The determined values of δ¹³С–СН₄, С₂Н₆ isotopic composition, molecular weight of hydrocarbon fraction, mass concentration of С₁–С₅ hydrocarbons and their ratios (water content and maturation coefficients) are indicative of the fact that epigenetic (migration) gases from different sources dominate in sediments, including coal, gas, and supposed hydrocarbon accumulations of condensate and oil series. It should be noted that epigenetic hydrocarbon gases of oil and gas accumulations have maximum gas-geochemical indicators, that is their average values are as follows: Σ С₂–С₅ — 323 g/kg in hydrocarbon fraction, molecular weight of the hydrocarbon fraction is 19.48 g/mol, water content coefficient — 32.3 %, maturation coefficient — 176 c.u., δ¹³С–СН₄ and С₂Н₆ (−42.3 and −22.4 ‰). At the same time, these values differ in gas-oil and oil accumulations: 452–500 g/kg, 21.25 and 22.18 g/mol, 45.2 and 50 %, 280 and 307 c.u., δ¹³С–СН₄ and С₂Н₆ (−43,.8…−41.9 ‰ and −22…−21.9 ‰). it is found that seafloor deposits in the areas of oil and gas, gas and oil, and oil accumulation occurrence also have maximum average concentrations of Σ С₂–С₅: 0.0186, 0.02627, and 0.02818 cm³/kg, respectively. On the basis of the information obtained, the predicted oil and gas, gas and oil, and oil accumulations are delineated, and petroleum potential of the study areas is evaluated.

Alexander I. Gresov  ORCiD  Scopus
Doctor of Geological and Mineralogical Sciences,
Chief researcher
V.I.Il’ichev Pacific
Oceanological Institute,
43, Baltiiskaya, Vladivostok, 690041, Russia
e-mail: gresov@poi.dvo.ru

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