Comparative study of P and S wave amplitudes of acoustic logging through solid formations : contribution to the knowledge of in situ stresses and fractures

摘要

In order to compare the ratios between the amplitudes of P and S acoustic waves drawn from various boreholes, we have defined a specific wave parameter called magnitude : for each shot, we have added the maximum positive amplitude values and the absolute values of the minimum negative amplitudes of a given wave recorded at different depths. In compact formations, the difference between the logarithms of the magnitudes of S and P waves provides a value that appears to be characteristic of the state of stress of the domain where a borehole is drilled. Accidents between those formations, such as fractures or sedimentary joints can be determined, and breakouts well distinguished.