Thermodynamic models for asphaltene solubility and precipitation

A number of different models that have been applied to modeling of asphalte ne precipitation and estimating asphaltene solubility in various systems ar e critically reviewed. Particular attention is paid to the basic assumption s and the performance of the models as compared to the present knowledge of composition and phase equilibrium of asphaltenes. In all models a number o f parameters are tuned to obtain best fits to the experimental data. The ma in parameter was, as proposed in the reviewed works, the molecular weight o f the asphaltene and only a few models take the aggregating nature of the a sphaltenes into account. Even though the models are based on thermodynamic concepts, they remain empirical because of the number of parameters used in the calculations. When the solubility parameter is employed as the basis f or a model, the calculation of asphaltene solubility cannot be calculated o r estimated without extensive modification to the model. In summary, the mo dels employed for predictability of asphaltenes precipitation are lacking i n several respects and are not quantitatively accurate. (C) 1999 Elsevier S cience B.V. All rights reserved.