Evaluation of indices and of models applied to the prediction of the stability of crude oils

In this work, indices developed for verification of the stability of oils or fractions were evaluated, as the Colloidal Instability Index (CII), Heithaus Parameter (P), and Toluene Equivalence (TE), and models of prediction of the compatibility of oils, as the BMCI–TE and the Oil Compatibility Model (Wiehe and Kennedy, 2000), were applied to the prediction of the stability. Possible relations between onset of precipitation (OP) and contents of saturates, aromatics, resins and asphaltenes (SARA) were also considered as indicative of the stability of oils. With the exception of the CII, these parameters have as a main limitation the necessity of calculations which depend on the experimental determination of the onset of precipitation of asphaltenes. In some of the oils studied it was not possible to determine the OP, then it was not viable to verify the efficacy of the models in the prediction of their stability. However, the CII, which does not present such restriction, showed to be the least efficacious. These indices, therefore, proved inefficacious in the evaluation of systems containing the Brazilian oils considered in this study, which proves the necessity of more research for its improvement or the development of new models and indices.