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

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 (Eμ) have shown that there are abrupt changes in Eμ 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 Eμ. 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.