PC-SAFT characterization of crude oils and modeling of asphaltene phase behavior

Asphaltenes are the heaviest and most polarizable components of crude oil. The phase behavior of these polydisperse components is important in both the upstream and downstream processing of crude oil because of their potential to precipitate, deposit and plug pipelines and production equipment. Predicting flow assurance issues caused by asphaltenes requires the ability to model the phase behavior of asphaltenes as a function of temperature, pressure, and composition. In this work we present a detailed procedure to characterize crude oil and plot asphaltene phase envelope, using the Perturbed Chain form of the Statistical Associating Fluid Theory (PC-SAFT). This work also demonstrates that the proposed procedure can model the asphaltene thermodynamic phase behavior better than using a cubic equation of state typically used in the industry, even with compositional data as low as C-9+. The results obtained with the proposed characterization method show a remarkable matching with the experimental data points for both the bubble point and asphaltene precipitation onset curves. A wide range of temperatures, pressures and gas injection percentages have been tested. In this work, the concept of lower asphaltene onset pressure is also clarified and a new representation of asphaltene phase plot is presented. The results obtained in this work are very promising in providing better tools to model asphaltene phase behavior. (C) 2011 Elsevier Ltd. All rights reserved.