Applications of Finite Difference Synthetic Acoustic Logs

Abstract

Finite difference synthetic acoustic logs are suitable for studying wave propagation in vertically varying boreholes and in boreholes with continuously varying properties. Snapshots for the traditional smooth bore in a homogeneous rock show the standard phases in the borehole (compressional and shear head waves, pseudo-Rayleigh waves, and Stoneley waves), and also display the complex wave interaction which occurs in the rock. If a simple gradient in elastic parameters and density replaces the sharp interface the shear head wave and pseudo-Rayleigh wave are strongly attenuated. Also, off-centered receivers, washouts and horizontal fissures can have significant effects on amplitudes. A thorough understanding of these effects by forward modelling is essential in order to avoid pitfalls in interpretation and in order to design robust schemes for obtaining elastic properties and attenuation from acoustic logs.