The effects of saturation and pore structure on acoustic properties of carbonate rocks

This paper highlights the methodology, analysis and models developed to understand the effects of saturation and pore structure on the acoustic properties of carbonate rocks at various confining pressures (5, 10, 15 and 20 MPa) and fluids (dry, brine an oil) in a Saudi Arabian field. Obtained models are based on empirical relationships between core-derived acoustic velocity measurements (Vp & Vs) and petrophysical properties (porosity, permeability, grain density, mercury porosimetry, pore size and petrography) from one hundred and fifty plugs. A very important observation from this study with respect to applicable velocity models for the specific field is that at low velocities brine saturated samples correlated with Pickett model while oil saturated samples correlated with Castagna. On the other hand, there is no correlation at high velocities with both published models. This implies that one must be careful in choosing the model to use to reflect the velocity range and the reservoir fluid-type.