Influence of resins and asphaltenes on the structural and rheological properties of petroleum disperse systems

Abstract

The structural and rheological properties of resin-free model petroleum mixtures (MPM) with an asphaltene content of 0 to 6 wt % and the same mixtures with added 3.85 wt % petroleum resins have been investigated. The composition of the mixtures simulates the amount of the main hydrocarbon-group components and distillate fractions in light paraffin-base oils (ρ₄²⁰ = 747.7–789.1 kg/m³). Temperature–dynamic viscosity relationships for cooling the MPM have been obtained, most of which displayed abnormalities in the temperature range of ~40–60°C. Calculations of the viscous-flow activation energy (E_μ) have shown that there are abrupt changes in E_μ in this abnormality region, which are an indication of structuring processes. By means of Fourier-transform laser diffractomery of MPM solutions in kerosene, it has been found that the particle size of the petroleum mixtures is qualitatively related to the revealed abrupt changes in E_μ. It has been shown that these abnormalities correspond to the formation of paraffin–asphaltene associates and their existence is determined by the critical concentration of resins and asphaltenes in the mixtures.