Report Summary

This report contains the results of work completed during the sixth year of the Full
\nWaveform Acoustic Logging Consortium in the Earth Resources Laboratory at M.LT.
\nOver the last six years, our work have evolved from simply modelling an open borehole
\nin an isotropy, elastic formation to the study of logging under more complicated, realistic conditions, especially those that may be encounted in production and development environments.
\nIn the past year, we have modelled elastic wave propagation in a transversely
\nisotropic formation, in a formation where the borehole is irregular in radius, across an
\nopen fracture, and in a transversely isotropic porous formation, where the horizontal
\nand vertical permeabilities are different. All of these situations are rather common in
\nthe field. It is important for us to understand how these complications mayor may
\nnot affected our interpretation of the full waveform acoustic logs, and how large an
\nerror we are likely to make if our interpretation is based on a isotropy, elastic model
\nof the formation. Just as importantly, we need to learn to identify these situations in
\nthe field, so that we can make the appropriate corrections to our interpretation.
\nIn data analysis, we have refined the Extended Prony's Method to calculate the
\ndispersion and attenuation of the guided waves in the borehole, and have applied
\nthe technique to both laboratory and field data with success. We have also studied
\nthe sensistivity of the guided waves to a transversely anisotropic formation. These
\nsensistivities are critical in the inversion of the dispersion and attenuation obtained
\nby the Extended Prony's Method for the actual elastic and anelastic properties of the
\nformation.
\nIn a continuation of last year's work, we have studied the attenuation of solid particles
\nin a viscous fluid, applicable to the study of both drilling muds and unconsolidated
\nsands.
\nWe have studied the diffraction of a cylindrical transducer and its effect on the
\nmeasurement of attenuation in laboratory experiments using the spectral ratio technique.
\nWe are also continuing in our effort of scale model experiments to mimic field
\nsituations which are not readily modelled by analytic or numerical methods.
\nA field study and comparison of velocities from core measurement, borehole compensated
\nsonic log, full waveform acoustic log, and VSP in the Salton Sea Scientific
\nDrilling Program is included in this report. Also included is an extended abstract on an
\neffort to map fractures in the Canadian Shield using borehole geophysical techniques.
\nThe following is a summary of the papers in this report.

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