Viscosity Measurements of Two Potential Deepwater Viscosity Standard Reference Fluids at High Temperature and High Pressure

This paper reports high-pressure viscosity measurements for Krytox GPL 102 lot K2391 and tris­(2-ethylhexyl) trimellitate (TOTM). These two viscous liquids have recently been suggested as potential deepwater viscosity standard (DVS) reference fluids for high temperature, high pressure viscosity studies associated with oil production from ultradeep formations beneath the deepwaters of the Gulf of Mexico. The measurements are performed using a windowed, variable-volume, rolling-ball viscometer at pressures between 7 and 242 MPa and temperatures between 314 and 527 K with an expanded uncertainty of 3% at a 95% confidence level. The viscosity results are correlated using an empirical temperature/pressure-dependent function and a modified Vogel–Fulcher–Tammann (VFT) Equation. The present viscosity data for TOTM and Krytox GPL 102 lot K2391 are in good agreement with the available reported data in the literature at lower temperatures and pressures. The viscosity values of TOTM and Krytox GPL 102 lot K2391 are 9.5 mPa·s and 25 mPa·s, respectively, at 473 K and 200 MPa, whereas the desired DVS viscosity value at this condition is 20 mPa·s. Although the viscosity of Krytox GPL 102 lot K2391 is closer to the targeted value, a comparison of the present viscosity results with data obtained for lot K1537 indicates a very large lot-to-lot variation of the viscosity for this polydisperse perfluoropolyether oil, which represents a significant deficiency for a DVS