Prediction of asphaltene phase behavior in live oil with CPA equation of state

Asphaltene deposition mostly occurs when the thermodynamic conditions, like temperature, pressure, and oil composition of crude oil change. Therefore predicting asphaltene phase behavior through thermodynamic modeling may help to control its precipitation and reduce the associated problems. In this work, the Cubic-Plus-Association (CPA) equation of state was used to model asphaltene precipitation in live oil. This equation is based on a combination of a physical part and an association term. Through the past decades, CPA equation of state has been successfully applied to several complex mixtures of water, alcohols, glycols, organic acids, and hydrocarbons. As asphaltene molecules have an associative nature, which leads to form aggregation and finally precipitation, this equation can precisely predict the phase behavior of asphaltene and other heavy components in crude oil. In this work, the results of Cubic-Plus-Association equation of state were compared to experimental data of three live oils and the results of two other models. The results showed that CPA equation of state can predict asphaltene precipitation with good accuracy.