Silurian Organic-rich Rocks of the Russian Arctic

Olga Bogolepova

Silurian oil-prone source rocks are an important component of the hydrocarbon systems in many Arctic basins of Russia. Black shale sequences are known from Novaya Zemlya, the Northern and Polar Urals, Pai-Khoi, East Siberia, Taimyr, Severnaya Zemlya, the New Siberian Islands, Verkhoyansk-Kolyma and Chukotka. In north-western parts of East Siberia, the source rock quality is so good that the basal Silurian black shale was mined and used as a fuel, since it generally burns without any processing. Comparative geological studies are important both to find common patterns in the evolution of different regions and to reconsider their petroleum potential. As part of the CASP ongoing research on Silurian organic-rich source rocks, a database of Silurian black shales in the Russian Arctic is being compiled from the literature with a complementary data provided by fieldwork and associated samples. Some results of the work from Severnaya Zemlya are presented here. Severnaya Zemlya is located on the edge of the Arctic Ocean north of the Taimyr Peninsula, separating the Kara and Laptev seas. Our field studies focus on the central part of October Revolution Island, where the early Silurian sequences contain organic-rich black shale and bituminous limestone intervals. Field and analytical studies have been undertaken to map the rocks, document their stratigraphy, establish and describe facies, reconstruct the palaeogeography, and identify the fossils. Organic-rich black shale, ogranic-rich black limestone and migrated bitumen were analysed to obtain independent parameters on organic matter source, composition, thermal history and to investigate their possible oil-oil and oil-source correlation. The occurrence of hydrocarbons in the Silurian of Severnaya Zemlya is clear evidence of an active petroleum system in the region. This information provides an important insight into the likely nature of successions and petroleum systems of the North Kara Shelf.