Browsing by Author "Sisco, Caleb"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Item
    Thermodynamic Modeling of Hydrocarbon Mixtures with Application to Polymer Phase Behavior and Asphaltene Precipitation
    (2018-08-23) Sisco, Caleb; Vargas, Francisco M
    A new equation of state framework is proposed that hybridizes the classical cubic equations of state (EOS) with the chain term of the SAFT EOS. This model offers an improved description of the molecular features of long-chain molecules, such as heavy n-alkanes and polymers, whose thermodynamic properties are often poorly described by standard cubic EOS models. This hybrid EOS, called the cubic-plus-chain (CPC) equation of state, shows promising results for the n-alkanes and polymers studied and could ultimately be used for improving predictions for solvent-polymer phase splitting and asphaltene precipitation. Additionally, critical property correlations for nonpolar components proposed in a recent work are tested for their application to mixed solvent phase behavior modeling. Because the standard cubic EOS and CPC models require critical properties as inputs, the proposed correlations provide a means to calculate thermodynamic properties for mixed solvents given information on only molecular weight and refractive index – measurements that are simple to perform for both pure substances and mixtures – and have potential application to crude oil systems for which composition is unknown. Phase behavior modeling studies with the mixed solvent approach and cubic EOS show exceedingly good agreement to standard modeling approaches that require a detailed compositional analysis. Also, an asphaltic crude oil phase behavior study with a high GOR and asphaltene-rich fluid produced from a deep-water environment is presented. Thermodynamic modeling with PC-SAFT revealed interesting trends with respect to the properties of the bulk and onset phases that suggest that, though asphaltenes may be unstable in the bulk fluid, phase-splitting that is classically viewed as a precursor to deposition might sometimes produce two liquids of relatively low density whose compositions are much leaner in asphaltenes than phases commonly associated with deposition problems. As part of this study, a new algorithm for calculating saturation pressures of asphaltic crude oils is presented. This algorithm uses reliable methods to generate excellent trial phase compositions for initializing the upper and lower asphaltene onset and bubble pressure calculations.