Estimating Compressibility and Density of Oil-saturated Rock Samples Using Higher Order Resonance Modes of DARS

We characterize the DARS measurement system in terms of different resonance modes, and 6 sandstone samples were used in the frequency measurements for the fundamental, second and third resonance modes. A least-squares inversion method is used to invert these measured resonance frequencies for the compressibility and density of the sandstones. The compressibilities inverted from different resonance mode frequencies show frequency-dependence for the sandstones with relatively high compressibility, suggesting that the elastic moduli of these samples depend on the frequency of seismic waves. With further accuracy improvement for samples with low compressibility, the DARS technique can be used to quantify the frequency dependence of the acoustic properties of sandstones, which would be beneficial to evaluating attenuation mechanisms of seismic waves propagating through reservoir rocks.