Micro-seismic monitoring using sparse planar array and a weak signal enhancement method

Traditional ground micro-seismic monitoring is performed by laying long survey lines. This is expensive and difficult to implement in complex mountainous areas and deep marine shale gas reservoirs in China. To address these challenges, this study has proposed a ground micro-seismic monitoring method using a sparse planar array that offers greater flexibility in implementation. This study has presented a weak signal enhancement method based on a broadband array adaptive beamforming algorithm to improve the signal-to-noise ratio (SNR) of micro-seismic data collected by sparse planar arrays and to suppress coherent noise. The proposed method involves establishing a signal model for a broadband planar array, estimating the direction of arrival (DOA) of broadband signals using a grid search method, and setting constraint conditions and objective functions based on the DOA results. The optimal weight vector is then calculated by solving the objective function to obtain the desired signal and suppress noise. This study has demonstrated that the proposed method effectively improved the SNR and suppressed coherent noise in synthetic and real data. It has also highlighted the effectiveness of the sparse planar array as a ground micro-seismic monitoring method and the adaptive broadband beamforming method as a practical weak signal enhancement technology.