Study On Array Acoustic Logging Attenuation Factor Inversion Method

The elastic wave has attenuating phenomenon when it propagates in the underground medium.The attenuation coefficient of the wave is of great significance for the evaluation of gas content,pore fluid saturation,lithology and permeability of the underground medium.The attenuation factor of the compressional and shear waves is generally used to evaluate the formation in logging.In this paper,we study the attenuation analysis of the compressional wave and dipole shear wave using array acoustic logging data.This thesis introduces the theoretical analysis method of the acoustic wave by the multipole sound source in the well,simulates the full waveform of the multipole sonic logging,and completes the forward modeling of the attenuation simulation.we analyze the attenuation factor of the compressional wave by factor-spectral ratio method,however,the calculation of the shear wave attenuation is limited.In the hard formation,the shear wave is affected by the pseudo Rayleigh wave and the Stoneley wave,the shear waveform is difficult to extract.In the soft formation,the shear wave does not exist.From what we have discussed above,we know that the attenuation of shear wave analysis is infeasible when using monopole source.Based on the research of dipole shear wave dispersion analysis,we improve the high-precision amplitude phase method and propose a method for dipole shear wave attenuation analysis in order to get the shear wave attenuation,the method can estimate the attenuation of the signal well by processing the mathematical signal model and the simulated data,which proves the accuracy of the method for estimating the dipole shear wave attenuation,and the processing of oilfield data further illustrates the feasibility of evaluating the formation combining with compressional and shear waves attenuation which provides a new idea for evaluating the formation with attenuation.