Effect of Asphaltene Concentration on the Aggregation and Precipitation Tendency of Asphaltenes

Destabilized asphaltenes can easily adhere to the oil well production equipment, the transportation pipelines, and also the refining and storage facilities, resulting in significant remediation costs. Therefore, it is of great importance to the energy industry to understand the factors that govern the kinetics of asphaltene aggregation and precipitation. In this study, the effect of asphaltene concentration on their aggregation and precipitation tendencies after their destabilization with heptane is investigated for three different types of asphaltenes. It is intuitively expected that any increase in asphaltene concentration will accelerate the precipitation kinetics after heptane addition. For asphaltene concentrations below 1 wt % in toluene, this expected trend is indeed experimentally confirmed. However, for asphaltene concentrations above 1 wt %, an increase in concentration leads to slower aggregation instead. We believe that this counterintuitive decline in the aggregation rate is due to the stabilizing effect of stable or soluble asphaltenes. This effect has been overlooked in the existing aggregation models, and our research provides a better understanding of the factors controlling aggregation process. Accounting for the solubilizing effect of stable asphaltenes can provide successful predictions for the aggregation rate of asphaltenes at different asphaltene concentrations using Smoluchowski's model.