Estimation of wavelet phase spectrum and its application in seismic exploration

Wavelet estimation is of principal importance for seismic exploration. The wavelet is used in a variety of standard data processing filters and for parametrization of geological media. The estimation involves determination of amplitude and phase spectra. Standard methods are available for finding the amplitude spectrum. Due to estimation problems the phase spectrum is not evaluated but assumed to be constant- or minimum-phase. Thus, actual phase information is not used.; This dissertation develops a new wavelet phase estimation method which practically requires no phase assumptions. High variance of seismic phase and unwrapping errors, significant problems of phase estimation, have been reduced using spectral analysis in short time windows. This method allows reliable non-parametric statistical estimation of arbitrary-phase wavelets and increases performance of conventional zero- and minimum-phase inverse filters.; Conventional methods of estimating seismic attenuation are based on wavelet amplitude spectra. They depend on true-amplitude restoration and accurate knowledge of velocity and density structures in the Earth. The causality principle predicts that phase spectrum is an additional source of attenuation information. Phase spectra may be less sensitive to transmission and reflection losses in the Earth.; A frequency dispersion parameter, relative decrement of phase velocity, has been successfully measured in a laboratory ultrasonic pulse-through experiment. The observed dispersion is close to that predicted by a minimum-phase phenomenological theory. The attenuation coefficient is consistent with a linear model, but is not constrained to constant Q.; Strong positive correlations were found between attenuation and porosity, as well as between attenuation and permeability of water saturated Glenn Pool sandstone. Attenuation in shale is much less than in sandstone. These relationships may be useful in reservoir characterization.