Modeling seismic attenuation and dispersion in partially saturated rocks based on fluid distribution from computed tomography scans

The anelastic properties of seismic waves (attenuation and velocity dispersion) in partially saturated rocks depend on the spatial distribution of pore fluids. We map the fluid distributions in three sections of a limestone core sample with X-ray computed tomography (CT) scans and obtain the radii and volume fractions of the gas patches. These statistical data are input into an infinituple-porosity model with partial saturation, the results of which are compared with the forced oscillation (from 0.004 to 100 Hz) and ultrasonic (1 MHz) measurements, and the results of other approaches (the fractal model, the continuous random media model, and the finite-element method). The anelastic properties indicate significant differences among different sections due to fluid distribution. We find that it is possible to effectively characterize seismic anelasticity in a partially saturated limestone by using actual fluid distributions from CT scans and an appropriate petroelastic model. The agreement between the theory and the experiment proves the validity of our approach.