EFFECT OF FLUID VISCOSITY AND SATURATION ON THE ULTRASONIC VELOCITIES IN A FONTAINEBLEAU SANDSTONE

Simultaneous measurements of the P- and S-wave velocities at 1MHz frequency as a function of temperature from - 80-degrees-C to 80-degrees-C have been made in a Fontainebleau sandstone saturated with glycerol. We investigated 8 saturation degrees, from fully saturated to almost dry state. Generally, the velocity decreases with increasing temperature; it is large between almost-equal-to 40-degrees-C and almost-equal-to 40-degrees-C. The velocity dispersion is attributed to viscous shear relaxation. The model of O'Connell and Budiansky modified by introducing the saturation parameter and a Gaussian distribution of crack aspect ratios is used to interpret the data. A trial and error method is used to estimate the model parameters. The model satisfactorily accounts for the data at high saturation.