ESTIMATES OF FORMATION SOUND SPEED FROM ULTRASONIC REFLECTIONS

This paper presents preliminary results from experimental research con cerning the ultrasonic reflectivity of rock samples. The goal is to de termine whether meaningful petrophysical properties can be obtained th rough the analysis of reflected acoustic signals of the type produced with the new generation of ultrasonic borehole televiewers. Present em phasis is on analysis of the full-reflected waveform. Time-domain samp les of the transmitted and reflected signals are transformed into the frequency domain by means of digital Fourier methods to determine the complex reflection coefficient of the rock A simplified viscoelastic w ave-propagation model converts the reflection coefficient estimates in to wave velocity estimates. Sound speed estimates in reasonable agreem ent with those determined by use of standard experimental techniques h ave been obtained for a variety of sandstone samples. Signal-processin g techniques for the analysis of waveforms recorded in an attenuating mud-filled borehole have been developed and tested in the laboratory.