Suppression method of multi-source harmonic noise in magnetic resonance sounding based on simulated annealing method

When the magnetic resonance sounding (MRS) method is applied in an environment with high electromagnetic noise, the signal-to-noise ratio of the measured data is often reduced due to the interference of electromagnetic noise. As a result, it is difficult to accurately determine the aquifer distribution using the inversion results, thus reducing the application effects of the method. In this paper, aiming at the common problem of multi-source harmonic noise interference in the field data acquisition using the MRS method, this paper derives the grid search simultaneous removal method based on the model denoising and further proposes the more efficient simulated annealing simultaneous removal method. The simulation results show that both methods can effectively suppress multi-source harmonic noise. Compared with the grid search simultaneous removal method, the efficiency of the simulated annealing simultaneous removal method is improved by 2.35 times in the case of double fundamental frequency harmonics, which greatly reduces the time cost of the denoising process. Meanwhile, the simulated annealing simultaneous removal method allows for great denoising effects of multi-source harmonic noise. Finally, the proposed denoising algorithm was applied to a field example. The comparison of the inversion results and borehole data shows that the simulated annealing simultaneous removal method can effectively suppress the multi-source harmonic noise in the measured data obtained using the MRS method and can significantly improve the application effects of the method.