Regular solution theory applied to asphaltene related phase behaviour

Asphaltenes are the least soluble fraction of crude oil and they can phase separate from the oil upon a change in temperature, pressure, or composition. This phase separation, often described as precipitation, may be beneficial (eg, in a partial deasphalting process) or detrimental (eg, in pipeline and surface equipment fouling). A phase behaviour model that can predict the onset and amount of asphaltene precipitation and is compatible with process simulators is desirable for the design and operation of these processes. This brief review focuses on the regular solution modelling approach. The regular solution model is based on activity coefficients and therefore is well suited for liquid-liquid phase separations such as asphaltene precipitation. The model and its internal correlations are presented and its performance on asphaltene phase separation from mixtures of heavy oils and solvent is demonstrated. Recent updates to this approach are presented and potential future applications are discussed. The strengths and limitations of this approach for oilfield applications are highlighted.

Automated summary

Asphaltenes, the least soluble fraction of crude oil, can phase separate from the oil with changes in temperature, pressure, or composition. A phase behaviour model that can predict asphaltene precipitation onset and amount is desired for design and operation of processes. The regular solution modelling approach, based on activity coefficients, is suitable for liquid-liquid phase separations such as asphaltene precipitation in heavy oil mixtures. New updates and future applications of this approach are discussed with highlighted strengths and limitations for oilfield applications.