Natural bitumen fields in the northeast of the Siberian Platform (Russian Arctic sector)

摘要

In the northern and northeastern Siberian Platform, within the Anabar and Olenek zones, there are a number of hypergene bitumen accumulations (fields) and natural bitumen seeps, whose total resources are estimated at >5 bln tons. Bitumen fields are confined to a wide stratigraphic range from Precambrian to Mesozoic. A detailed geochemical study was performed for bitumens of the largest Olenek field, whose naphthides are localized mainly in Permian sandstones of deltaic and coast-marine genesis. Chromato-mass spectrometric analysis showed that normal alkanes are drastically reduced in the saturated fraction of the bitumens and most of terpanes are a homologous series of 25-norhopanes, which evidences the intense bacterial degradation of hydrocarbon pools. Identification of bicyclic sesquiterpenes, tetracyclic onocerane, and other biomarkers testifies that the organic matter of source rocks was rich in higher-plants remains. The concentrations of steranes are low, whereas those of earlier unknown 8-14-secosteranes are rather high. The set of geochemical data on the Permian bitumens of the Olenek field, including the isotopic characteristics of carbon (delta C-13 of -25.8 to -31.3%), suggests that the coeval oil source rocks on the passive continental margin (at the place of the present-day Verkhoyansk fold belt) were the main source of hydrocarbons for the field. Assessment of oil and gas resources, including giant bitumen pools, and their exploration in the framework of "The fundamentals of Russian state policy in Arctic up to 2020" have become a top-priority problem. Petroleum refining products might be economically feasible raw materials in the eastern Russian Arctic sector to be supplied via the Northern Sea Route.