An Improved Molecular Thermodynamic Model Of Asphaltene Equilibria

  • V. A. Kamath
  • M. G. Kakade
  • G. D. Sharma

Abstract

In this study, a molecular thermodynamic model was developed to represent asphaltene equilibria and to predict the amount of asphaltene precipitation that would occur from a reservoir oil under influence of a miscible solvent or immiscible gas. The model treats the asphaltenes to exist in the crude in a large range of molecular weights represented by a normal distribution function. The properties of each asphaltene pseudo-component such as solubility parameter and molar volume are obtained based on their molecular weights at given pressure and temperature. Scott-Magat theory along with binary interaction parameter between asphaltene free liquid phase (solvent) and asphaltenes are used to represent asphaltene solid-liquid equilibria and to predict the degree of asphaltene precipitation, the molar distribution of asphaltene pseudo-components in equilibrium solid and liquid phases at various pressures, temperatures and solvent-oil compositions. The model is coupled with Peng-Robinson equation of state for vapor-liquid equilibria calculations. The model uses an iterative Newton-Raphson scheme to obtain solution. The model has four parameters which are determined by fitting the model to experimental asphaltene precipitation data for tank West Sak oil-solvent mixtures. The model is used to predict asphaltene precipitation for CO2-West Sak oil mixtures at various pressures.

Keywords

Clay Entropy Enthalpy Sludge Toluene 

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Copyright information

© Springer Science+Business Media New York 1994

Authors and Affiliations

  • V. A. Kamath
    • 1
  • M. G. Kakade
    • 1
  • G. D. Sharma
    • 1
  1. 1.Petroleum Development LaboratoryUniversity of Alaska FairbanksFairbanksUSA

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