GEOCHEMICAL CHARACTERISTICS OF ORGANIC MATTER IN CRETACEOUS- CENOZOIC SOURCE ROCK STRATA OF THE NORTHEASTERN LAPTEV SEA, BASED ON THE RESULTS OF SHALLOW STRATIGRAPHIC DRILLING
Z.A. Tembotov1,2, N.A. Malyshev3, V.E. Verzhbitskii3, A.A. Borodulin3, V.V. Obmetko3, D.K. Komissarov3, A.A. Kolyubakin4, A.V. Stupakova2, M.A. Bol’shakova2, A.A. Suslova2, A.G. Kalmykov2, N.V. Pronina2, E.A. Krasnova2,5, R.M. Gilaev2, A.V. Mordasova2, I.V. Kuvinov2
1OOO Arctic Scientific Center, Moscow, Russia
2Lomonosov Moscow State University, Moscow, Russia
3PAO NK Rosneft, Moscow, Russia
4OOO RN-Exploration, Moscow, Russia
5Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, Russia
Keywords: Stratigraphic drilling, new wells in the Arctic, petroliferous strata, generation potential, organic matter, maturity, Laptev Sea sedimentary basin
Abstract
The Laptev Sea sedimentary basin is located in the eastern part of the Russian Arctic shelf and has been fairly well studied by geophysical methods, but drilling data have been lacking until recently. In 2021, six new stratigraphic wells were drilled on the Laptev Sea shelf north of the Anzhu Islands by the order of PAO NK Rosneft. As a result, a unique core material was obtained, which was studied by a number of analytical methods. This paper is concerned with analysis of the geochemical characteristics of the petroleum source rocks of a Cretaceous-Cenozoic complex in the Laptev Sea sedimentary basin, which can be regarded as promising for hydrocarbon generation. The paper presents the main pyrolysis parameters characterizing the share of free hydrocarbons in the rock (S1), oil generation potential (S2), and maturity ( T max) as well as the maceral composition of rocks and vitrinite reflectance ( R o). We have established that the carbonaceous and clay-siltstone rocks of the Paleocene-Eocene complex are enriched in organic matter (OM) containing up to 20% lipid component and are capable of generating not only gas but also liquid hydrocarbons. In contrast to the OM of the rocks of the Paleocene-Eocene complex, the OM of the Lower Cretaceous strata is at a much higher stage of transformation, which corresponds to the oil peak zone and the beginning of the wet gas zone. Organic matter accumulated in different lithofacies conditions; therefore, both humic type III kerogen and mixed type II-III kerogen are found in the rocks. Based on the drilling results and studies performed in the section of the Laptev Sea sedimentary cover, we have obtained the first factual data on the characteristics of petroleum source rocks, which can be used to predict the petroleum potential of both the Laptev Sea sedimentary basin and the entire East Arctic region.
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