At present, it is difficult to image small-scale abnormal geo-bodies near wells using borehole acoustic imaging, as information from scattered waves is neglected and that from reflected waves is mainly used, thus resulting in low imaging resolution. Imaging methods based on scattered waves can help obtain higher-resolution measurements. Herein, a 3D scattered wave spatial scanning imaging method is developed to make full use of multimode scattered waves for imaging small-scale abnormal geo-bodies near the well. The 3D finite-difference time-domain method is used to simulate the acoustic fields for borehole azimuthal acoustic imaging with a fluid-filled target borehole near a measurement well, and the imaging method is applied for the acoustic detection of nearby wells based on forward modeling and field measurement waveform data. The results find that, for the fluid-filled target borehole that is approximately parallel to and distant from the measurement well, the amplitude of the scattered PP wave is the largest followed by the mode-converted PS and SP wave; and the amplitude of the scattered SS wave is the smallest, which is related to the radiation, scattering, and reception of the monopole acoustic field. In this case, the scattered wave from the target borehole can be regarded as a plane wave. The spatial scanning imaging method based on single-mode scattered acoustic waves and the 3D plane-wave imaging method provide similar imaging results. The comprehensive use of multimode scattered acoustic waves can further improve the imaging signal-to-noise ratio and resolution. A field example is used to verify the correctness of the forward analysis and the effectiveness of the imaging method. This approach will help improve the imaging resolution for the acoustic detection of nearby wells and the evaluation of downhole hydraulic fracturing.

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