Viscosity Models Based on the Free Volume and Frictional Theories for Systems at Pressures to 276 MPa and Temperatures to 533 K

Abstract

This study presents methods for accurate viscosity modeling using the frictional theory (f-theory) and the free volume theory (FV theory) of viscosity at temperatures to 533 K and pressures to 276 MPa, which are high-temperature, high-pressure (HTHP) conditions associated with ultradeep porous sandstone or carbonate layers that retain crude oil or natural gas. The perturbed-chain statistical associating fluid theory (PC-SAFT) equation of state (EoS), the HTHP-volume-translated (VT) Peng–Robinson EoS, and the HTHP-volume-translated-Soave–Redlich–Kwong EoS (HTHP-VT-PR and HTHP-VT-SRK, respectively) are used to provide input information for both the f-theory and the FV theory. Viscosity values returned by these models are compared to available experimental data for n-alkanes with carbon numbers 1–18, branched alkanes, single and double ring aromatics, and naphthenic compounds. As currently constituted, the f-theory model underpredicts viscosity by as much as 20% at pressures near 276 MPa, but this deficiency...