Application of rock physics models to evaluate dispersion and attenuation in carbonate rocks

This study investigates dispersion and attenuation effects on P-wave velocity in carbonate rocks from two geological settings: pre-salt samples (Santos Basin) and coquinas (Alagoas Sub-basin). Using ultrasonic tests at 1.3 MHz and static measurements, P-wave velocities were analyzed under dry and brine-saturated conditions. XRD identified calcite, dolomite, and quartz as dominant minerals. Elastic properties were modeled using the Gassmann and Geertsma-Smit equations, considering different frequency regimes and fluid types. The White and Biot models were used as frequency references. Results show that model predictions depend on rock heterogeneity and permeability. The White model best fit pre-salt data, while the Biot model matched some coquina samples. Samples exhibited high Q values and low permeability, reflecting the influence of pore structure. The study emphasizes that integrating lab data with rock physics models improves understanding of acoustic behavior in carbonates.