New Group-Contribution Parameters for the Calculation of PC-SAFT Parameters for Use at Pressures to 276 MPa and Temperatures to 533 K

Cubic Equations of State (EoSs) typically provide unreliable predictions for phase density and derivative properties at the high-temperature, high-pressure (HTHP) conditions associated with ultradeep petroleum reservoirs (that is, temperatures to 533 K and pressures to 241 MPa). The perturbed-chain statistical associating fluid theory (PC-SAFT) EoS returns improved predictions for density but still can overpredict the experimental value by up to 5% at HTHP conditions. Not surprisingly, when a modified set of the pure-component PC-SAFT parameters m, σ, and e/k are fit to HTHP experimental density data, density predictions throughout the HTHP range agree with reference data to better than ±1%. However, the lack of such HTHP density data for many hydrocarbons presents a hurdle to the more widespread use of this PC-SAFT method. This study presents a group-contribution (G-C) method for calculating PC-SAFT parameters that are designed to yield accurate HTHP density predictions. First- and second-order group con...