ИСТИНА

The Barents Sea shelf is assumed to contain considerable oil and gas resources both in Russian and Norwegian sectors. Triassic successions in this region have a great interest for scientists as potential source rocks for huge hydrocarbon accumulations. The present work is devoted to composition, characteristics and depositional environments of Triassic sediments of the Barents Sea shelf and their hydrocarbons’ generation potential. Connection between type and quantity of organic matter and paleogeographic situations was evaluated. Our studies of the Triassic oil and gas source rocks in the Barents Sea are based on 20 Triassic rock samples with presumably high TOC from the outcrops at the Franz Josef Land and Svalbard Archipelagos. Literature, well and seismic data have been used. Macro and micro descriptions were done to identify lithological composition of samples. Complex of geochemical methods was used to characterize quality and quantity of organic matter, its genetic type, composition and maturity: fluorescent bituminology tests, Rock Eval pyrolysis, extraction, liquid adsorption and gas chromatography. Paleogeographic maps of the Barents Sea region have been made for Early, Middle and Upper Triassic epochs. Triassic time provides an example of sedimentation in the vast extensional basin, where sedimentary environments were changed from alluvial to deltaic, coastal and marine ones. Shaly Triassic sediments in the north, north-west and south-west of the Barents Sea are characterized with significant organic matter content (TOC=1-2%), therefore they can be related to oil and gas source rocks. Anisian sediments (in particular in Svalbard) possess the highest organic matter concentration (maximum TOC=7%) and are characterized with high generation potential. The organic matter in Triassic rocks is usually of humic type (less frequently of humic- sapropelic type) which is indicating to the shallow-marine environment of their formation and a significant share of continental component. Gas will be dominating among the generated HC. Maturity of Triassic rocks varies from immature to high mature. These sediments are likely to be gas source rocks for huge gas accumulations both in the Triassic and Jurassic reservoirs in the discovered fields on the Barents Sea shelf. At the south of the Barents Sea and at Pechora Sea Triassic rocks have low petroleum potential due to negative depositional environment.