Comparison with Experiment

In Figure 6 we compare the computed bulk and shear modulus data for dry and water saturated Fontainebleau sandstone with experimentally measured values [Han1986]. Although Han's measurements were made at ultrasonic frequencies, Han [Han1986] suggests that the frequency dispersions are minimal (the Biot-dispersions and the non-Biot dispersions neglectible for clean sandstones). The predicted velocities are in good agreement with the experimental data. Generally, we see a slight overestimation of the measured moduli, which is most likely due to the finite resolution of the images. Small cracks and pores may not be resolved by the tomographic images but may have an effect on the elastic properties. This effect is enhanced for the dry samples [ Han 1986], which is in accord with our numerical data. The results from the simulations may be considered to provide an excellent upper bound for the bulk and shear velocity data.

Figure 6: Comparison of the "continuum" prediction of the elastic simulations for the digitized images under dry and the water saturated (40 MPa) conditions to experimental data (Han, 1986). The figures give predictions for the (a) dry and (b) wet bulk modulus and (c) the shear modulus.