Tool deconvolution and borehole compensation of sonic measurements

Sonic well logging waveforms contain information about the viscoelastic properties of the formation such as the slownesses and attenuations of the compressional, shear, and Stoneley waves. Also affecting the waves is the borehole/formation interface at which the waves are coupled into and out of the formation. In this paper we present a method to estimate the slowness, attenuation and the coupiing from sonic array waveforms. We begin with the introduction of models which relate the unknown parameters to sonic measurements. The sonic measurements are travel times and amplitudes of the P, S and Stoneley waves. Once we extract the sonic measurements from the waveforms, the problem becomes one of estimating the unknown parameters from the measurements. Although the system to solve is large in scale, there is a direct method which can be viewed as an extension of the depth derived borehole compensation method. Results from field data are presented to illustrate the applications in high resolution slowness logging, attenuation logging and lithologic correlation using the coupling.