Research And Application Of Time Frequency Spectrum

During the propagation of seismic waves in the formation medium,scattering and absorption attenuation are related to frequency.The power spectral density of the signals is time-varying and belongs to non-stationary signals.Time-frequency analysis is an important means to analyze them.In this paper,we make a preliminary analysis of the advantages and disadvantages of the time frequency analysis method,and select the HHT,the generalized S transform and the matching pursuit for applications.According to the HHT decomposition of a series of different frequency components of adaptive signal itself,without considering the interference function or window selection and other factors,the result can reflect the characteristic of the signal itself better;the adaptive HHT decomposition ability of seismic signal and frequency spectrum whitening with extension ability effectively and according to the model and actual data,this method can effectively expand the frequency band of seismic data,so as to improve its resolution.The accurate and effective time-frequency tool is based on seismic data multi-scale decomposition,by comparing and studying all kinds of time-frequency analysis,generalized S transform has good time-frequency resolution,frequency adjustable parameters,and has the characteristics of lossless and reversible transform,multiscale decomposition of seismic data is very suitable for.According to the characteristic of "high frequency attenuation and low frequency increase" of oil and gas spectrum anomaly,wavelet transform and generalized S transform are used to do high frequency attenuation and low frequency increase section for detecting gas anomaly.In the strong amplitude anomaly region,the matching pursuit and energy balance normalized generalized S transform are used to improve the effect of strong amplitude on gas detection.