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

Abstract

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.

Molecular dynamic simulation of asphaltene co-aggregation with humic acid during oil spill

“…During the last decade, great efforts have been made to interpret the asphaltene aggregation process using experimental techniques and molecular simulation approaches. For instance, the effects of temperature and pressure (Espinat et al, 2004), solvent (Aslan and Firoozabadi, 2014), inhibitors (Safaie and Nazar, 2014), molecular structures (Jian et al, 2013(Jian et al, , 2014 and concentrations (Haji-Akbari et al, 2014) on the asphaltene aggregation were investigated. However, our understanding on the driving force and inhibition factors on the asphaltene aggregation remains limited.…”

Aggregation of asphaltene model compounds using a porphyrin tethered to a carboxylic acid

“…Model compounds under study to probe aggregation based on the interactions of an acid (3) and base(4).49 …”

Multiscale Approach Linking Self-Aggregation and Surface Interactions of Synthesized Foulants to Fouling Mitigation Strategies

“…According to their work, below the CNAC asphaltenes are found either as molecularly dispersed entities (monomers) or as oligomers of asphaltene molecules with a lateral dimension of ~1.5 nm. 28 As the concentration increases towards the CNAC (~50 mg L -1 ) 39 , asphaltene molecules adhere to each other forming nanoaggregates. These nanoaggregates grow, but it is postulated that steric hindrance prevents them from containing more than approximately 6 asphaltene molecules and hence they have a maximum lateral dimension of ~2 nm.…”