Stratigraphic Drilling in the Northern Kara Sea: First Case and Preliminary Results

摘要

Until recently, the sedimentary cover age and composition of the marginal North Kara Basin (northern part of the Kara Sea, Russian Arctic) remained uncertain because of the absence of direct data from parametric and exploration wells. Taking into consideration the absolute importance of these issues for understanding the regional geology of the Arctic shelf and evaluating its petroleum potential, Rosneft Oil Company, together with AO RosGeo, drilled ten shallow stratigraphic wells in fall 2020 using the research vessel (RV) Bavenit to reveal the complete stratigraphic range of the North Kara Basin. The ultrahigh-resolution (UHR) seismic survey was carried out by the RV Kapitan Voronin to adjust the well site locations and integrate the well sections into the regional geological model based on 2D seismic data during the drilling campaign. As a result, 300 m core was recovered from 11 Paleozoic and two Mesozoic stratigraphic units, previ-ously investigated by 2D seismic and outcrop studies of the Severnaya Zemlya Archipelago. Lab analyses (biostratigraphy, lithology, sedi-mentology, geochemistry, and other types of core analysis) were performed at Lomonosov Moscow State University. We present obtained lab results confirming that the main part of the North Kara Basin section belongs to the Paleozoic; late Cambrian-Late Devonian rock ages have been derived. Several Paleozoic units tend to be older than those in previously published models. Core samples include mainly terrigenous rocks with insignificant carbonate presence. Paleozoic units are overlain by a thin Mesozoic terrigenous section dated from Middle Triassic to Middle Jurassic above a distinct angular unconformity. After a thorough analysis of all the lab results, we will obtain data on the ages of sedimentary units, as well as their lithology and depositional environments, and establish elements of the hydrocarbon system (source rocks, reservoirs, and seals) to evaluate the North Kara Basin petroleum potential with lesser uncertainty. We suppose that our results will significantly contribute to establishing a stratigraphic framework, reconstructing the basin history, and evaluating the petro-leum potential of the whole Arctic region.