Asphaltene Precipitation is a perennial problem in production of heavy oils. Field condition conducive to precipitation includes normal pressure depletion, acid stimulation, gas-lift operation, and miscible flooding, just to mention a few. To avoid precipitation, it is useful to know the solubility of asphaltene in petroleum liquids as a function of temperature, pressure, and liquid-phase composition. The accurate prediction of phase behavior in multi-component hydrocarbon systems prone to asphaltene precipitation is, therefore, crucial for the economic and safe operation of any petroleum production scenarios.

In this study, the Soave-Redlich- Kwong equation of state (SRK EoS) has been modified based on perturbation theory in order to improve the phase behaviour predictions and develop a more flexible EoS to modeling asphaltene precipitation. The parameters of the new cubic equation of state considered to be reduced temperature and acentric factor dependent. These parameters have been determined using three phase behaviour calculations namely, saturated vapor pressure, vapor volume and saturated liquid density, for 40 pure hydrocarbon and non hydrocarbon compounds with an absolute average deviation percent of 0.814, 2.614 and 5.814, respectively.

Next, applying the newly modified EOS, the Flory-Huggins (FH) model is adjusted to predict asphaltene precipitation more accurately. The adjustable parameter is defined based on solubility parameter of asphaltene in heavy oil. The phase behavior of asphaltene was extended by these modifications and the precipitation of asphaltene is calculated while adding three n-alkenes solvents. The newly developed model predictions for amount of asphaltene precipitation have been compared with Flory-Huggins model as well as available literature data, showing the robustness and reliability of the new approach.

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