Analysis of Full Waveform Acoustic Logging Data in "Soft" Formations

Abstract

Direct recording of formation shear wave travel time is not possible in "soft" formations where the shear velocity is lower than the borehole fluid velocity. The borehole Stoneley wave is quite sensitive to changes in formation shear wave properties and may be used to indirectly determine shear velocity. This paper presents a method to calculate formation shear velocity through inversion of the dispersion equation for the propagation of borehole Stoneley waves. The Stoneley wave group velocity and effective attenuation are also computed in this data analysis.