Organic geochemistry of Precambrian petroleum source deposits (by the example of the Siberian Platform)

Nowadays the problems of Precambrian petroleum prospects attract great attention of scientists. Their solution favor progress in the theory of petroleum formation, on one hand, and enables substantiating the prospects of ancient strata within petroleum areas and increasing hydrocarbon reserves, on the other hand. Geochemistry of organic matter in Late Proterozoic (Riphean, Vendian) deposits clearly demonstrates that biospheres of these epochs supplied organic matter (OM) to sedimentary basins, with its amount being close to the amount of OM fossilized in Phanerozoic deposits of different systems. The investigation of OM concentrations and regularities of its distribution in the Upper Proterozoic deposits of the Siberian Platform and adjacent folded structures shows that contemporary residual organic carbon there constitutes about 64% of its total amount concentrated in the Riphean-Devonian deposits. The Riphean dark-shale dominikoid deposits abundant within the structures adjacent to the platform and, to a lesser degree, in its inner parts are most enriched in OM. The available data show that the Riphean deposits of the Siberian and Russian Platforms are similar in the concentrations and distribution of OM. Calculations of petroleum formation intensity for the Lena-Tunguska Province (Siberian Platform) have shown that the Riphean deposits produced about 80% of liquid hydrocarbons (HC) and more than 90% of gas ones of.their total amounts in the sedimentary cover of the province. Thus, in the context of balance calculations, the Riphean deposits were principal HC-supplying strata in the Lena-Tunguska Province. At the same time, numerous literature data on relict hydrocarbons (biomarkers) indicate that the problem of genetic correlation between oils and oil source rocks of the ancient Siberian Platform strata is still unsolved.