Cloud Points: Can We Measure or Model Them?

Abstract The terminology “cloud point” has been traditionaly adopted by the American Society for Testing and Materials (ASTM) D2500 to refer to the temperature at which “cloudiness” of a relatively transparent petroleum fluid is observed upon cooling. The cloudiness forms as a “finite and detectable” amount of wax and/or paraffins precipitates from the test fluid contained in a 1½-in (˜30 mm) diameter glass tube. Nowadays, more sophisticated techniques of differing measurement principles and varying degrees of sensitivity have been developed to measure cloud points of petroleum fluids including opaque hydrocarbon systems (dark oils). Alternative terminologies like wax appearance temperature (WAT) and wax precipitation temperature (WPT), amongst a few others, have also emerged and are used interchangeably. Meanwhile, numerous characterization and modeling efforts have been made to simulate “measured” cloud points of petroleum fluids. The goals of this paper are to provide an objective review of the concept of “cloud point” and to illucidate the adequacy and limitations of the measurement techniques and modeling approaches.

[1]  K. Karan,et al.  Measurement of Waxy Crude Properties Using Novel Laboratory Techniques , 2000 .

[2]  G. Chilingarian,et al.  Asphaltenes and asphalts , 1994 .

[3]  T. O. Allen,et al.  Production Operations: Well Completions, Workover, and Stimulation , 1978 .

[4]  Huanquan Pan,et al.  Pressure and Composition Effect on Wax Precipitation: Experimental Data and Model Results , 1997 .

[5]  G. G. Stokes.  "J." , 1890, The New Yale Book of Quotations.

[6]  William D. McCain,et al.  The properties of petroleum fluids , 1973 .

[7]  Ahmed Hammami,et al.  Paraffin Deposition From Crude Oils: Comparison of Laboratory Results to Field Data , 1997 .

[8]  S. Andersen,et al.  Prediction of solid–fluid phase diagrams of light gases–heavy paraffin systems up to 200 MPa using an equation of state–GE model , 2000 .

[9]  Karen S. Pedersen,et al.  A thermodynamic model for predicting wax formation in crude oils , 1988 .

[10]  Dale L. Schruben,et al.  Wax crystal size distribution versus composition , 2001 .

[11]  D. Dorset.  Crystallography of Real Waxes: Branched Chain Packing in Microcrystalline Petroleum Wax Studied by Electron Diffraction , 2000 .

[12]  Donald R. Stevens,et al.  Chemical technology of petroleum , 1960 .

[13]  João A. P. Coutinho,et al.  A Thermodynamic Model for Predicting Wax Formation in Jet and Diesel Fuels , 2000 .

[14]  João A. P. Coutinho,et al.  Predictive Local Composition Models for Solid/Liquid Equilibrium in n-Alkane Systems: Wilson Equation for Multicomponent Systems , 1996 .

[15]  J. E. Tackett,et al.  Comparisons of Cloud Point Measurement and Paraffin Prediction Methods , 1999 .

[16]  A. Hunt.  Uncertainties remain in predicting paraffin deposition , 1996 .

[17]  K. W. Won,et al.  Thermodynamics for solid solution-liquid-vapor equilibria: wax phase formation from heavy hydrocarbon mixtures , 1986 .

[18]  V. R. Kruka,et al.  Cloud-point determination for crude oils , 1995 .

[19]  J. Coutinho,et al.  Low-Pressure Modeling of Wax Formation in Crude Oils , 2001 .

[20]  S. P. Srivastava,et al.  Phase-transition studies in n-alkanes and petroleum-related waxes—A review , 1993 .

[21]  Kenneth R. Hall,et al.  An algebraic method that includes Gibbs minimization for performing phase equilibrium calculations for any number of components or phases , 2003 .

[22]  Albin Henry Warth,et al.  The chemistry and technology of waxes , 1947 .

[23]  V. Chevallier,et al.  Influence of the Distribution General Shape of n-Alkane Molar Concentrations on the Structural State of Multi-Alkane Mixtures , 2000 .

[24]  V. G. Niesen,et al.  Thermodynamic Measurement and Prediction of Paraffin Precipitation in Crude Oil , 1993 .

[25]  A. Hammami,et al.  Analytical Considerations Related to Asphaltenes and Waxes in the Same Crudes , 1999 .

[26]  J. Svetgoff.  Paraffin problems can be resolved with chemicals , 1984 .

[27]  Ahmed Hammami,et al.  Paraffin Deposition From Crude Oils: Comparison of Laboratory Results With Field Data , 1999 .

[28]  S. Kistler.  The chemistry and technology of waxes. , 1948 .

[29]  E Gimzewski,et al.  Monitoring wax crystallisation in diesel using differential scanning calorimetry (DSC) and microcalorimetry , 1993 .

[30]  J. S. Rowlinson,et al.  Molecular Thermodynamics of Fluid-Phase Equilibria , 1969 .

[31]  Abbas Firoozabadi,et al.  Thermodynamics of Wax Precipitation in Petroleum Mixtures , 1996 .

[32]  A. Hammami,et al.  Non-isothermal crystallization kinetics of binary mixtures of n-alkanes: ideal eutectic and isomorphous systems , 1996 .