Azimuth Estimation Method for Borehole Acoustic Reflection Imaging Using an Acoustic Vector Array

Borehole acoustic reflection imaging uses acoustic receivers to detect geological structures but suffers from low accuracies when measuring the azimuths of anomalies. To address this problem, this research proposes an azimuth estimation method based on an acoustic vector array. The acoustic pressure and particle vibration velocity from borehole acoustic reflection imaging are utilized to suppress noise and improve the accuracy of azimuth measurement. The multiazimuth acoustic pressure waveform recorded by the acoustic receiver is synthesized into a multicomponent vibration velocity waveform for which components are paired off and the coordinates are converted to obtain multiple groups of orthogonal components. Subsequently, polarization analysis can be conducted on each group of orthogonal components to obtain the particle polarization direction on the horizontal plane and the vibration velocity waveform of the principal component. The particle polarization direction, amplitude of the multiazimuth acoustic pressure waveform, and type of echo signal can be used to determine the azimuth of an anomaly and obtain its spatial distribution. The proposed method was employed for processing logging data from the field, and the azimuths and spatial distribution of anomalies were obtained. Compared with azimuth estimation using only the amplitude of the multiazimuth acoustic pressure waveform, the proposed method can be used to calculate the incident azimuth with much better measurement accuracy and stability.