SAFT model for upstream asphaltene applications

The increasing incidence of flow assurance problems caused by asphaltene deposition during oil production has motivated the development of numerous theoretical models and experimental methods to analyze this complex phenomenon. Even more challenging are the prediction of the occurrence and the magnitude of asphaltene deposition. It is well accepted that precipitation of asphaltene is a necessary condition for deposition. Hence, a significant amount of work has been devoted to the understanding of the conditions at which asphaltene precipitate from the crude oil. Although, several models seem to work well for correlating available data of onsets of asphaltene precipitation, they usually lack good prediction capabilities. This article briefly reviews the properties of asphaltene and presents a thermodynamic model based on the Perturbed Chain version of the Statistical Associating Fluid Theory (PC-SAFT) equation of state, which is then proven to provide excellent prediction capabilities for the phase behavior of complex and polydisperse systems such as asphaltene, in a wide range of temperature, pressures and composition. Furthermore, several case studies are presented where the effect of gas injection, commingling of oils, and contamination with oil based mud, as well as the effect of asphaltene polydispersity are analyzed. Finally, the asphaltene compositional grading that can lead in some cases to the formation of tar-mat is studied using the same thermodynamic model. In all the cases, very good agreement with experimental data and field observations is obtained. From the results presented in this work, we are confident that the PC-SAFT equation of state is an excellent tool to understand the thermodynamic behavior of asphaltene in petroleum systems. (C) 2013 Elsevier B.V. All rights reserved.