The advent of borehole shear slowness measurements in sonically slow formations has lead to breakthroughs in the subsurface profiling of geological bodies. In sand bodies, compressional and shear velocities depend predictably on porosity, mineralogy, grain contacts, and fluid saturation. An interpretation is best performed by decomposing the velocities into moduli that are intrinsic measures of the rock frame and pore fluid compressibilities. Careful experiments on pure materials (i.e., pure quartz sandstones) demonstrate two simplifying constitutive relationships. First, the bulk and shear frame moduli are simple functions of the porosity. A comparison of the measured shear frame modulus to the prediction for the pure material INTRODUCTION

We have measured the viscosity and density of certified reference material S20, with a nominal viscosity at T ) 298 K and p ) 0.1 MPa of 29 mPa‚s, at temperatures in the range of (273 to 423) K and pressures between (0.1 and 275) MPa. A vibrating wire viscometer, with a wire diameter of about 0.15 mm, was used for the viscosity measurements at pressures up to 70 MPa, and the results have an expanded uncertainty (k ) 2) of ( 2 %, while a falling sinker viscometer was used for measurements at pressures up to 275 MPa with an expanded uncertainty (k ) 2) of ( 2.3 %. The density was obtained from vibrating tube densimeters with an uncertainty (k ) 2) of about ( 0.2 %. The measured viscosity and density are represented by interpolation expressions. Our equation represents the measured viscosities to within ( 2.3 % and the densities to within (0.2 %. These differences are comparable with the expanded uncertainty (k ) 2) of our measurements. The measurements extend the pressure range by 275 MPa and the temperature range by 50 K over which the viscosity and density of these fluids are provided by the supplier. These measurements complement those reported in the literature for S20, at pressures and temperatures exceeding the certified values, and extend the temperature range by 30 K and the upper pressure by 220 MPa. The viscosities reported here differ from values reported in the literature for batches different to that used here by less than ( 4.5 %, which is within the combined estimated expanded (k ) 2) uncertainties of the measurements and places a plausible bound on the certainty of η(T, p) for another batch of S20 that might be used as a calibrant for other instruments.

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We have measured the viscosity of certified reference materials N10 and S20 with nominal viscosities at T ) 298 K and p ) 0.1 MPa of (16 and 29) mPa‚s, respectively, at temperatures in the range (298 to 353) K and pressures between (0.1 and 55) MPa with a vibrating wire viscometer. This viscometer had a nominal wire diameter of 0.15 mm and provided viscosities with an estimated expanded (k ) 2) uncertainty of (2 % over the viscosity range (3 to 70) mPa‚s. The latter value represents about half the upper operating viscosity of this vibrating wire that is about 150 mPa‚s. The measured viscosity was compared with values predicted by interpolation expressions for N10 and S20 that represents the measured viscosities of different lots of the same fluids to within (2 %. The results reported here have an average absolute deviation from those interpolation equations of about 2.4 % for N10 and 2.7 % for S20. These differences are within the combined estimated uncertainties of the measurements.