(414b) Volume Translated SRK and PR Equations of State for the Prediction of High-Temperature, High-Pressure Hydrocarbon Density

In an attempt to improve the performance of cubic volumetric equations of state for predicting molar volumes at extremely high temperature, high pressure (HTHP) conditions associated with ultra-deep petroleum formations, a volume correction term is employed in several common cubic equations of state (EOS). Temperature-dependent volume translation (VT) expressions have been proposed for SRK and PR equations of state. Rather than correlating the volume correction to saturated liquid densities, as is done in most prior volume translation methods, the volume translation term in the HTHP VT-SRK EOS and HTHP VT-PR EOS is correlated to pure component, single-phase density data for short- and long-chain alkanes, cycloalkanes and aromatics for pressures between 7 - 275 MPa and temperatures between 278 – 533 K. New HTHP density data for several hydrocarbons has been collected at VCU to enhance the accuracy of these models.

Density predictions of the new HTHP VT-SRK EOS and HTHP VT-PR EOS are compared to the predictions of the standard SRK and PR EOSs, temperature-dependent volume translated SRK and PR EOSs, and the PC-SAFT EOS. The accuracy of the predictions of each EOS is represented by the mean absolute percentage deviation (MAPD) for density data at HTHP conditions. The MAPD values obtained for the 17 hydrocarbons selected in this study with the HTHP VT-SRK EOS and HTHP VT-PR EOS are (1-2 %) and (1-3 %), respectively. These MAPD values are substantially better than those calculated with the SRK (1-50%), PR (1-45%), VT-SRK (1-21%), and VT-PR (2-32%) EOSs.  The PC SAFT EOS (which was based on fits of sub-critical liquid density and vapor pressure) had MAPD values of 0.5-5%.