Report Summary

Abstract

This report contains the results of work completed during the fourth year of the Full Waveform Acoustic Logging Consortium in the Earth Resources Laboratory at M.LT. This is the first year of the second phase of the Consortium, and the emphasis in our research has evolved from a primarily theoretical study of wave propagation in a borehole to a more balanced treatment of all aspects of the problem. As a result, theoretical models developed over the past years are now being applied to field data for the determination of the physical properties of formations in a variety of situations. The knowledge gained from these applications is in turn helping us to refine the theoretical models used. One of the most important parameters in formation evaluation is the in situ permeability. In this report we have a number of papers dealing with the subject, from theoretical papers investigating the Biot-Rosenbaum model in detail, to the application of the model to field data, and a field comparison of in situ fracture permeability obtained from pump test, full waveform acoustic log, and hydrophone VSP studies. We also have synthetic microseismograms generated for formations with fractures of different thicknesses using the finite difference method. We have continued our study of the use of full waveform acoustic logs in a poorly bonded cased hole. In this report we have one paper each on theory and on data analysis in this subject. We have also made initial attempts in the inversion of real data. In this particular case, we made use of the P wave and PL mode to obtain formation S-wave velocity in soft sediments. The preliminary results are very encouraging. Last, but not least, we have included a preliminary report on the model experiment setup in the laboratory. Modelling allows us to study complicated boreholes under controlled conditions. The following is a summary of the different papers in this report.