Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

ABSTRACT

Viscosity data are reported for n-hexadecane (C16), n-octadecane (C18), and n-eicosane (C20) at pressures between (3 and 243) MPa and temperatures between (304 and 534) K. These extreme conditions are representative of those encountered in ultra-deep petroleum formations beneath the deepwaters of the Gulf of Mexico. The measurements are taken with a novel windowed Inconel rolling-ball viscometer designed by our team that is calibrated with n-decane. A comparison of the reported viscosity values with the available literature data that cover limited pressure and temperature ranges, shows that the mean absolute percentage deviation, d, ranges between 1.1% and 4.8%. The reported data extend the database of viscosity to the high-temperature, high-pressure region where most gaps occur in the literature data for n-hexadecane and n-octadecane. To the best of our knowledge, the results for n-eicosane are the first reported viscosity values at pressures above 2 MPa over the entire temperature range. The viscosity results are modeled with the free volume theory model in conjunction with density values obtained using the Peng Robinson equation of state (EoS) and the PC-SAFT EoS. The d values obtained with this model range from 2.0% to 3.5%. The data are also correlated by a non-linear surface fit as a simultaneous function of temperature and pressure that yields d values of 0.40%, 0.43%, and 0.38% for C16, C18, and C20, respectively.