Dispersion Characteristics Of Mode Waves In Borehole

Estimating the slowness of various mode waves in a full wave is a very important and fundamental sonic logging processing technique.Conventional time-domain analysis methods require time-domain separation and do not take into account the dispersion properties of waves.Therefore,it is of great practical significance to obtain the dispersion curve of the mode wave by using the method of frequency domain analysis,and then to invert the velocity of the formation mode wave accurately.In this thesis,the method of real axis integration is used to simulate the array acoustic waveforms in hard and soft formations.The monopole sound source adopts the rake wavelet with the main frequency of 12 k Hz,and the dipole sound source and the quadrupole sound source use the rake wavelet with the main frequency of 3k Hz.Solve the mode wave dispersion equation of monopole sound source,the dispersion equation of dipole sound source and the dispersion equation of quadrupole sound source.The dispersion curves of borehole mode waves of monopole,dipole and quadrupole sources are extracted respectively.Program the Prony method,the matrix pencil method,the weighted spectral coherence method and the differential phase similarity method.The dispersion curve of the borehole mode wave is extracted and compared with the dispersion curve obtained by forward modeling to verify the processing effect of different dispersion analysis methods.The dispersion curve of the mode waves extracted by the Prony method is inconsistent with the forward modeling results,and the matrix beam method processing monopole sound source mode waves is consistent with the forward modeling results.The flexural and helical wave dispersion curves extracted by the single-mode dispersion analysis method weighted spectral coherence method and differential phase similarity method are in good agreement with the forward modeling results,and the differential phase similarity method is more accurate.