Modeling asphaltene precipitation in live crude oil using cubic plus association (CPA) equation of state

Changing thermodynamic conditions, such as pressure, temperature, and crude oil composition causes asphaltene precipitation and deposition in both reservoirs and surface facilities. Therefore, prediction of asphaltene phase behavior is crucial for reducing asphaltene deposition problems. To do so, mathematical thermodynamic modeling has been performed in this study. In this article, the cubic-plus-association (CPA) equation of state was utilized to model asphaltene precipitation behavior in live oil samples. CPA considers both physical and association terms of mixtures. Owing to the association nature of asphaltene molecules, this equation is able to predict the amount of asphaltene precipitation at different environmental conditions. Two equations of state including Peng-Robinson (PR) and Soave-Redlich-Kwong (SRK) were used for the physical part of the proposed CPA model. The results of the developed CPA-PR and CPA-SRK models were compared with the experimental data. It is shown that using SRK as the physical part of CPA makes the developed model more accurate.