Distribution Patterns of the Main Structural-Group Parameters of Crude Oils from the Timan–Pechora Oil-and-Gas Basin, According to 1Н NMR Data

A representative set of crude oils from the Timan–Pechora oil-and-gas basin (OGB) (75 samples of crude oils and natural-gas condensates from 51 fields) was studied, and data on the structural-group composition of the crude oils from this field were obtained. The distributions of all the parameters are far from the normal distribution. Therefore, only methods of nonparametric statistics can be used for the data processing. Among Timan–Pechora crudes, there are samples with abnormally high content of unsaturated compounds of radiogenic nature. Their highest concentration corresponds to the irradiation dose of no less than 11 MGy. On the whole, Timan–Pechora crudes differ from those studied previously (from the West Siberian, East Siberian, Volga–Urals, and North Caucasus OGBs) primarily in the content of monoaromatic components. The Timan–Pechora crudes occupy an intermediate position between those from West Siberia and Volga–Urals, on the one hand, and from East Siberia and North Caucasus, on the other hand. As compared to crude oils of the second group, Timan–Pechora crudes have considerably higher content of aromatic compounds. In the content of bi- and polycyclic aromatic components, Timan–Pechora crudes are close to those from West Siberia and Volga–Urals. All the large tectonic structures are combined in four groups with respect to crude oil composition: (1) Varandei–Adzva zone + Khoreivei and Kos’yu-Rogovskaya depressions; (2) Izhma–Pechora syneclise + Upper Pechora depression; (3) Pechora–Kozhva aulacogene; and (4) East Timan megalithic bank.