PHYSICAL/CHEMICAL PROPERTIES OF OIL FROM EASTERN AND WESTERN SIBERIA DEPOSITS: INTEGRATED STUDY BY DIELECTRIC SPECTROSCOPY AND NMR RELAXOMETRY METHODS

Abstract

The relevance of the research is caused by the increasing interest in an integrated interpretation of several methods data to determining the petrophysical and physical/chemical properties of rocks and intraformational fluids. The physical/chemical properties of oil are determined by a complex of data methods of dielectric spectroscopy, NMR relaxometry and geochemical analysis. The results of these methods are complemented each other, since they differ in different sensitivity to some characteristics of the rock and its saturating fluid. The main aim of the research is the sequential interpretation of dielectric spectroscopy and NMR relaxometry methods to determine the group composition and physical/chemical properties of oil samples, comparison of the obtained results with the results of geochemical analysis. Objects: oil and condensate samples from Eastern and Western Siberia deposits characterized by different physical/chemical properties. Methods: laboratory methods of dielectric spectroscopy aimed at determining the complex dielectric constant; NMR relaxometry which allows assessing the group analysis of studied fluid; standard geochemical methods including determination of physical/chemical properties, fractional and group chemical composition of oil. Results. 48 samples of oils and condensates from fields in Eastern and Western Siberia have been studied. The values were established for 29 samples: density at 20 ℃, viscosity at 20 and 60 ℃, content of temperature fractions above and below 200 ℃, content of methane-naphthenic and naphthenic-aromatic hydrocarbons, resins and asphaltenes. The dependence of the dielectric constant and the transverse relaxation time on the content of different hydrocarbon compounds groups was experimentally established, which showed a high sensitivity of the methods used in this work to the content of resinous-asphaltene compounds. Increasing their proportion in the composition of an oil sample leads to a significant decrease in the transverse relaxation times and a significant increase in the values of the dielectric constant. The NMR data was used to determine the group composition of oil samples, which is consistent with the results of geochemical analysis with an accuracy of 5 % at a temperature of 25 °C. Since the transverse relaxation times of aromatic compounds and saturated hydrocarbons characterized by high overlap, this does not allow us to establish in more detail the boundary transverse relaxation times for each group of hydrocarbon compounds.

Keywords

• group analysis
• dielectric permittivity
• relaxation characteristics
• rheological properties of oils
• sequential interpretation