On the method of quality factors estimation from zero-offset VSP data
利用零偏移VSP资料估计介质品质因子方法研究

Quality factors of zero-offset VSP data are estimated by peak frequency shift (PFS) method. The approach employs Ricker wavelet and matching seismic wavelet to approximate zero-phase source wavelet and mixed-phase source wavelet respectively, and formulas for Q-values estimation with PFS method are obtained. Moreover, focusing on the problem that peak frequencies of seismic wavelets calculated by common methods are imprecise, eigen-struct (ES) method for estimating peak frequencies of seismic wavelets is proposed. The validity of PFS method for Q-values estimation is verified through simulation of synthetic zero-offset VSP data. Results indicate that peak frequencies and Q-values derived from ES method are more precise than those derived from methods of fast Fourier transform and Burg's maximum entropy. Results also make clear that Q-values estimation with PFS method needs to choose appropriate parameters of wavelet, or precision of Q-values estimation will be affected.