Effects of the eccentric tool and source mismatch on acoutic dipole logging

Tool deviation is frequently encountered in sonic logging, especially in an inclined wellbore. Hence the effects of the eccentric tool and mismatched dipole source need to be investigated. In the present study we assumed that the dipole source is composed of two point sources with different amplitudes and is located at an off-axis position. We computed the waveform responses of receiver arrays using the real axis integration (RAI) method. An eccentric mismatched dipole source can produce non-dipole modes in addition to the pure dipole mode. According to the comparisons, the monopole mode is the strongest wavelet in the full wave signals while the source is mismatched and eccentric. Its amplitude increases with increasing mismatch level as well as the tool deviation inside the borehole. Moreover both the in-line and cross-line responses vary as eccentricity orientation changes in the borehole.