Acoustic Waveform Logs and the In-Situ Measurement of Permeability—A Review

Abstract

Full waveform acoustic logs are composed of two propagating head waves, the P and S waves, and two guided waves, the pseudo-Rayleigh and tube (Stoneley) waves. The measurement of P and S wave slowness provides information on the subsurface lithology as well as estimates of the in-situ dynamic compressibility and rigidity of those formations. Strong correlations exist between measured in-situ permeability and the slowness and attenuation of the tube wave. The tube wave slowness can provide a measure of permeability variations if corrections are made for any changes in the formation shear wave velocity and borehole radius, both of which also affect the tube wave slowness. The Biot model of wave propagation in a porous and permeable formation can be used to estimate absolute in-situ permeability values from tube wave attenuation measurements if all of the model parameters are accurately known. Permeability estimates obtained by using both of these methods on field data sets in two different lithologies are in good agreement with smoothed core permeability measurements. Because heavy drilling fluids are not used in most geotechnical boreholes, there is no mudcake buildup along the borehole wall, thereby removing one of the greatest causes of uncertainty in using tube waves to estimate in-situ permeability.