ИСТИНА

The structure of the Arctic Eurasian basins suggests that petroleum systems of Palaeozoic, Mesozoic and Cenozoic age may be present. Palaeozoic petroleum systems are well studied in the northern part of the Timan-Pechora. On the Barents-Kara shelf Palaeozoic petroleum systems are forecast, but no related hydrocarbon accumulations have been discovered, although the Palaeozoic section contains source rocks able to generate hydrocarbons. Mesozoic petroleum systems are studied in the Barents Sea and the Yamal Peninsula. They relate to Lower, Middle and Upper Triassic gas and oil source rocks, Middle Jurassic oil and gas source rocks and very rich Upper Jurassic oil source rocks. The formation of the petroleum systems and the oil and gas potential of the basins is directly dependent on the basins’ structure and geological history. Palaeozoic intracratonic rifting increased the heat flow of the basin and resulted in oil and gas kitchens in the extensional parts of the basins. Fault tectonics allowed vertical migration of fluids. In the deep sag basins, like the Central Barents, South Kara and North West Siberia basins, filled by both Palaeozoic and Mesozoic strata the Mesozoic petroleum systems provide significant volume of hydrocarbon, but they are influenced by Palaeozoic petroleum systems. In the Palaeozoic basins, such as Timan-Pechora, Svalbard and, probably, North Kara, the petroleum systems are linked with hydrocarbon migration from the deep Palaeozoic horizons or adjacent Mesozoic basins. Hydrocarbon generation started long before the present basins’ structural configuration formed, and oil and gas kitchens were associated mainly with extensional parts of the basins. Later phases of rifting and extension affected both the ancient oil and gas kitchens and the younger ones. Inversion caused trapping and affected fluid migration, mixing the petroleum systems. Inverted structures in the old rifts have the highest potential for large hydrocarbons accumulations but, in highly uplifted areas affected by faulting and erosion, exploration risk is high. Forecasting hydrocarbon distribution needs profound understanding of the geological evolution of petroleum basins, their structural units and petroleum systems, which control the location of giant fields.