STUDY OF COMPOSITION OF HIGH-VISCOUS HEAVY OILS BY METHOD OF NUCLEAR MAGNETIC RESONANT SPECTROSCOPY

Abstract

The work uses the nuclear magnetic resonance method to study the composition of heavy high-viscosity oils of various fields of the Volga Ural oil and gas basin. The spectra were recorded on a Bruker Avance III 500MHz high resolution NMR spectrometer with operating frequencies of 1H (500.1 MHz) and 13C (125.8 MHz) at a constant sample temperature in CDCl3. It is established that the oil of the studied field in its physical and chemical characteristics, structural group composition of resins, asphaltenes and oil components is a typical representative of aromatic oils. Oil samples are characterized by high density, a high content of tar-asphaltene compounds and sulfur. In the 1H NMR scale, methylene and methine signals appear in the range from 1.0 to 2.3 ppm: β-CH2, some β-CH groups in aromatic compounds and β-CH, CH2-groups in hydroaromatic compounds, and in the 13C NMR scale they are in the range from 22 to 60 ppm: methylene group (CH2-) in naphthenic fragments, etc. An analysis of the aromaticity coefficients obtained from the 1H and 13C NMR spectra shows a high convergence of the results and indicates a high degree of aromatic condensation in oil samples with a density of 950 kg/m3, a viscosity of 7200 mPa*s at 20 °C and a density of 948 kg/m3, viscosity 1000 mPa·s (FHA=0.046-0.081). With an increase in viscosity, there is a clear tendency to increase the aromaticity coefficient and the average chain length. It follows from the results of the 1H NMR spectra of oils with different origins, viscosities and processing that crude and refined oils may differ in water and olefin signals, and from 13C NMR analysis for oils the most important results were obtained when assessing the concentration of primary, tertiary and aromatic carbon.