High-Resolution Reflected Wave Extraction and Imaging Enhancement for Array Acoustic Logging

Array acoustic logging reflected wave imaging is an important technology to detect the geological structure and characteristics around the wellbore, especially in the evaluation of fracture-vuggy carbonate rocks and unconventional heterogeneous reservoir. Extracting the reflected wave from the logging waveform is a key part of the method, but it is quite difficult to achieve effective and high-resolution separation of the reflected wave from the mode waves due to the high impedance reflection of the borehole wall, the noise interference and other factors. In order to solve this problem, this paper introduces a reflection wave extraction and noise suppression method based on shearlet transform for image enhancement. This proposed method combines the shearlet transform with two-dimensional Fourier transform to achieve multi-scale and multi-directional decomposition of array acoustic logging signals. It can be found that mode waves are focused on the horizontal cone region at a smaller scale in the shearlet domain. Therefore, by selecting a hard threshold to separate the mode wave and reflected wave signals, different components in the acoustic logging signal are identified. Thus, after suppressing the noise interference, high-resolution reflected wave extraction is achieved, which can improve the quality and clarity of reflected wave imaging. Based on the synthetic data of numerical simulations, the effectiveness and accuracy of the proposed method were verified by comparing the processing results with other methods. Finally, the field data results further verify the correctness of the proposed method. This method has broad application prospects in the evaluation of fracture-vuggy carbonate rock and unconventional heterogeneous reservoir.