Rapid Heterogeneous Asphaltene Precipitation with Dispersed Solids

Inorganic solids are often present in real heavy oil systems, but are typically absent in asphaltene laboratory studies. For the first time, we investigate the influence of inorganic solids on the kinetic precipitation of asphaltenes. In contrast to potentially slow kinetics in homogeneous liquid petroleum mixtures, rapid kinetic precipitation of asphaltenes was observed when inorganic solids were present in the system. A combined homogeneous aggregation and diffusion-limited heterogeneous nucleation model was developed to quantify the rate of asphaltene precipitation under the explored experimental conditions. The rate of heterogeneous nucleation was generally observed to be faster than the rate of homogeneous aggregation; however, this trend was reversed as the solvent strength decreased and greater quantities of asphaltenes precipitated. The inorganic solids were characterized, and kaolinite clay was observed in the studied samples. This investigation leads to a clearer understanding of the complex asphaltene aggregation process that occurs in real and heterogeneous systems. The competing pathways of asphaltene precipitation provide novel insight into asphaltene precipitation and deposition, in addition to new experimental strategies to measure asphaltene solubility.