Report Summary

Abstract

This report contains the results of work completed during the ninth year of the Full Waveform Acoustic Logging Consortium in the Earth Resources Laboratory at M.LT. During the past year, we have started the evolution from purely full waveform acoustic logging to more problems dealing with the broader perspective of borehole acoustics. As of April 1, 1991, tills Consortium will be known as the Borehole Acoustics and Logging Consortium. Our research in the past year reflects the beginning of tills change. We have continued to work on the problem of logging in fractured formations. We have developed a method of calculating the reflection and transmission of Stoneley wave energy through a variety of different elastic and permeable formations using a onedimensional wave equation approximation for the Stoneley wave. By doing so, we are able to model isolated fractures, fracture zones, and porous zones. Tills method matches the field data from fracture zones much better than the isolated fracture approach. We have started to work in the area of source radiation from the borehole and the resulting radiation pattern observed in the formation. Tills is for applications in crosshole tomography as well as single hole imaging. As a part of tills work, we are studying the piezoelectric response of transducers. On a more microscopic level, we are also studying the crack and fracture surfaces in core samples, how the roughness of the surface is affecting seismic and flow measurements. This allows us to relate in situ seismic velocities and attenuation to petrophysical parameters which are the actual objectives of many geophysical measurements. There are two papers dealing with the processing of full waveform data, and a paper on the seismic imaging of a hydrofrac using travel time information. A summary of all the papers in this report follows.