利用零偏移VSP资料估计介质品质因子方法研究

利用峰值频率移动法估算零偏VSP资料的品质因子Q．该方法用Ricker子波和匹配地震子波分别逼近零相位和混合相位的震源子波，得到了峰值频率移动法估计Q值的公式．进而针对常规方法估计的地震子波峰值频率精度不高的问题，提出了估计地震子波峰值频率的特征结构法．通过合成零偏VSP资料的仿真试验，验证了峰值频率移动法估计Q值的正确性．仿真结果表明，与快速Fourier变换和Burg最大熵方法相比较，特征结构法得到的峰值频率和Q值精度高一些．仿真结果也表明，用峰值频率移动法估计Q值时需要选取恰当的子波参数,否则影响Q值估计的精度．

On the method of quality factors estimation from zero-offset VSP data

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.