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GEOCHEMISTRY OF ORGANIC MATTER OF MIDDLE JURASSIC AND LOWER CRETACEOUS ROCKS FROM THE SHTORMOVAYA 125 WELL (GYDAN PENINSULA)

A. I. Burukhina, E. A. Fursenko

А. А. Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Novosibirsk, Russia

The paper presents the results of the geochemical study performed on the core material (30 samples) selected from the intervals of the Akh (K1), Malyshev (J2) and Vym (J2) Formations in the Shtormovaya-125 well. Based on the results of pyrolytic studies of the rocks, distribution of hydrocarbon biomarkers in the composition of bitumoids and data on the isotopic composition of organic carbon, the homogeneous terrestrial genotype of the organic matter contained in the studied samples was determined; the accumulation of this organic matter occurred in environments from weakly reducing (Akh Formation) to suboxidizing (Malyshev and Vym Formations). Moreover, the concentration and catagenetic transformation of organic matter in the studied rocks, on average, are shown to increase from top to bottom along the well section. The values of pyrolytic parameters and the Corg index allow us to estimate generation potential of the studied rocks from low (Akh Formation) to moderate and high (separate intervals of the Malyshev and Vym Formations). At the same time,taking into account the terrestrial genotype, the OM of these strata may be a source of gaseous hydrocarbons. In addition, the revealed features of individual and group distribution of components in the composition of saturated and aromatic fractions of bitumoids enable considering the studied section as a more transformedanalogue of the “terpane geochemical horizon” distinguished in the lower part of the Oxfordian-Valanginian Nordvik section (Anabar Bay).

Keywords: geochemistry of organic matter, hydrocarbon biomarkers, north of West Siberia, Gydan Peninsula.

DOI 10.20403/2078-0575-2024-1-57-65

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