Influence of soluble asphaltenes and oxygen on asphaltene aggregation kinetics and equilibrium solubility

Abstract

Asphaltenes are one of the most industrial problematic and least understood crude oil compounds. They have a high propensity to aggregate and deposit on surfaces which eventually clog pipelines and hinder the production capability. In this research, the influence of soluble asphaltenes and dissolved oxygen on asphaltene aggregation was investigated. To observe the influence of soluble asphaltenes, asphaltenes were fractionated into soluble and insoluble fractions, remixed at different proportions and dispersed in toluene. The model oil was investigated by Small-Angle X-ray Scattering (SAXS) technique and then destabilized by heptane to study the aggregation kinetics using microscopy technique and the equilibrium solubility using centrifugation technique. To observe the influence of dissolved oxygen, asphaltenic crude oils were mixed with degassed heptane under nitrogen and air atmosphere. The equilibrium solubility was investigated using centrifugation technique and the aggregation kinetics was investigated using microscopy technique. For the soluble asphaltenes, the results suggest that they are molecular dispersed in the medium, increase the hospitality of the medium for insoluble asphaltenes and delay the aggregation. For the dissolved oxygen, there is no significant effect of them observed on both aggregation kinetics and equilibrium solubility. These observations verify the aggregation model observed beforehand.