Report Summary

Abstract

This report contains the results of work completed during the tenth year of the Borehole Acoustics and Logging Consortium in the Earth Resources Laboratory at M.l.T. This is the first year that the Consortium has been known under this name, and the first year where the focus of research is evolving to encompass more than just acoustic logging. In this year's report, we have included papers on the wavefield interaction with a borehole, downhole source radiation, flow in porous media, as well as full waveform logging. As we have indicated when we decided to change the name of the Consortium, we will be doing research related to elastic wave propagation and interaction with the borehole and the interpretation of the results. Thus we will be interested in projects from petrophysics to full waveform logging, to single hole imaging and measurement while drilling, to crosshole tomography. In this report we lead off with a comprehensive review of the theory and application of full waveform acoustic logging, followed by a paper on the combined interpretation of full waveform and shear wave logs. We also have a paper on testing our permeable zone model using ultrasonic model experiments. A major portion of this report is devoted to the modeling of fluid flow in fractures and porous rocks. There are papers using both the theoretical and the numerical approach to this problem. There is also a paper on the crack models for anisotropic media. On the borehole acoustics side there are two papers dealing with the interaction of an incoming wavefield with the borehole. One of the papers deals with the displacements and stress around and inside a borehole caused by an incident plane wave (P or S) in the formation. The other concerns the conversion of an incident body wave at a layer boundary intersecting a borehole and the conversion into tube or Stoneley wave energy. Both of these results are important in three component downhole measurements. There are also theoretical, numerical, and ultrasonic model papers on the radiation pattern of downhole sources. A summary of all the papers in this report follows.