Modeling of precipitation considering multi-component form of Asphaltene using a solid solution framework

Abstract

Many investigations have focused on determining the precipitation conditions for Asphaltene content in reservoir fluids. In addition, there are experimental observations in reservoir fluids titration, using different normal alkanes, proving multi-component form for Asphaltene in crude oil. In this work, the thermodynamic modeling approach of Hosseinzadeh Dehaghani et al. (2018) is extended through replacing the multi-solid approach with a solid-solution approach, which is closer to the real nature of Asphaltene solid phase in estimation of phase behavior and precipitation conditions. Therefore, after characterization of Asphaltene content into a few sub-components, solid-solution framework was considered to model the solid phase. To do this, the UNIQUAC activity coefficient model was used to describe solid phase non-idealities. The liquid and high-pressure vapor phase non-idealities were modeled using both Peng-Robinson (PR) and perturbed chain statistical associating fluid theory (PC-SAFT) equations of state (EOSs). The results obtained from modeling of bubble point pressure, onset pressure and crude oil titration with n-pentane were compared with experimental data of two oil samples from literature. The analysis of the results shows that the multi-component modeling of Asphaltene content provides a higher accuracy in comparison to single component modeling. For multi-component analysis, the highest and lowest “mean absolute percentage errors” in calculation of precipitation amount for the first oil sample were 10.26 and 1.59, for PR + UNIQUAC and PC-SAFT + UNIQUAC, respectively; while values for the second oil sample were 4.15 and 1.02, for PR + UNIQUAC and PC-SAFT + UNIQUAC, respectively.