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Description:
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Knowledge of the critical state is important in any study of phase behavior ; therefore , the applications of critical state prediction methods can be found in many areas of the petroleum and chemical industries . However , the vapor -liquid and volumetric computations for reservoir fluid systems in the retrograde and near -critical regions still remain a challenge . As a precursor in establishing a predictive equation of state for compositional reservoir processes , a previously established four -parameter cubic equation of state reported by Lawal -Lake -Silberberg (LLS ) is used to predict orthobaric densities , second virial coefficient and critical volumes of pure substances (hydrocarbon , non -hydrocarbon , polar and non -polar fluids ) . The prediction results are generally within 0 .5 % of the experimental measurements .
A framework of the attractive temperature function is established for two parameter (Peng -Robinson and Soave -Redlich -Kwong ) and four parameter LLS equations of state . The temperature function is demonstrated to be internally consistent with the critical behavior of fluids at sub - and super -critical conditions and the function does not suffer the difficulty encountered with Soave -type of temperature function which hitherto has been major source of research in equations of state development .
An analysis of the thermodynamic constraint criteria of the critical state of pure substances and binary mixtures is used to establish a theoretical expression for the van der Waals critical point . The theoretical expression for the van der Waals criticality is validated by the prediction results of binary critical volumes of asymmetric substances and mixtures . This project offers an insight to the phase behavior of ternary and multicomponent mixtures and the challenge for the future work is to apply this robust method to the near -critical flash routine in ternary and multicomponent systems . |