Distribution Patterns of Main Structural-Group Parameters of Crude Oils from Lena-Tunguska Oil-and-Gas Basin According t13C NMR Data

The distributions of the 13C NMR-measured structural-group composition parameters of the Lena-Tunguska basin crude oils were obtained. All these distributions were shown to be far from normal, many of them being asymmetric and/or bimodal. These oils exhibit a significantly lower content of aromatics than the Volga-Urals and Western Siberia oils. The principal maximum of Car distribution lies in the distribution tail areas of the other two basins. The Lena-Tunguska oils are free of fluids with low content (below 14 abs %) of n-alkyl structures. It was also demonstrated that the crude oils sampled from the basin's two major tectonic structures, namely the Baikit anteclise and the Nep-Botuob anteclise, differ significantly from one another in the concentrations of aromatics and n-alkyl structures.