Stability Determination of Asphaltenes through Dielectric Constant Measurements of Polar Oil Fractions

Abstract

Asphaltenes represent the heaviest and the most polar fraction of crude oil. The interaction of asphaltenes with other fractions of crude oil can affect its overall polarity and stability. Because of the complex nature of the molecules constituting asphaltenes, determining the polarity of asphaltenes—and, thereby, predicting their stability—is, however, difficult. A more practical way to estimate asphaltenes instability would have important implications in predicting oil production performance. In this study, we present a method of combining dielectric constant measurements of crude oil fractions with a modified effective medium approximation to estimate the instability of asphaltenes. Furthermore, we show that the dielectric constant of resins fractions comprising mainly organic constituents with minimum impurities provide the best representation of crude oils, with regard to physical properties such as density and viscosity. Two new analytical correlations relating the overall dielectric constant of crude oil mixtures and their constituents are suggested. These correlations provide insight toward the stability of asphaltenes with crude oil and can be directly used to estimate the overall precipitation tendency of asphaltenes.