Destabilization and Aggregation Kinetics of Asphaltenes

Destabilization and Aggregation Kinetics of Asphaltenes

Nasim Haji Akbari Balou & H. Scott Fogler

Asphaltenes comprise the heaviest and most polar components of crude oil and their precipitation and deposition can have serious economical impacts in the oil industry. For years it was believed that asphaltene mixtures reach thermodynamic equilibrium shortly after changing the operational conditions. However, recent work in our group demonstrated that kinetics plays an important role in the precipitation of asphaltenes from crude oil-precipitant mixtures- especially at low precipitant concentrations [1].  It is expected that the kinetics of precipitation depend on the properties of the crude oil; the goal of this research is to investigate this relationship. Due to the complexity of crude oil, model mixtures are used as alternatives for this purpose. Model mixtures are prepared by extracting asphaltenes from crude oil and dissolving them in various solvents with varying concentrations. The precipitation rates are then estimated by adding different quantities of heptane as precipitant and measuring the time needed for the particles to reach to a size of ~ 0.5 µm via optical microscopy. We show that model mixtures represent crude oils reasonably well in terms of precipitation kinetics and an exponential relationship exists between detection times and precipitant concentrations which is similar to what was previously reported by Maqbool et al [1] for crude oil-precipitant mixtures. We also investigate the effect of asphaltene concentration and the medium in which they are stabilized on the precipitation kinetics. The knowledge from this study can lead to a better understanding of the destabilization and growth processes which can in turn give rise to new predictive models to foresee precipitation kinetics under different operational conditions.

[1] T.Maqbool, A.T. Balgoa, and H. S. Fogler, “ Revisiting Asphaltene Precipitation from Crude Oils: A Case of Neglected Kinetic Effects,” Energy & Fuels, vol. 23, no. 7 , pp. 3681-3686, Jul. 2009.