Study On The Rational Function Characterization Of Wide-Angle AVO

In geophysics,seismic exploration is an important method to explore the reserves and distribution of oil and gas resources.The essence of it is to predict the nature and shape of underground strata by observing and analyzing the response of strata to artificially excited seismic waves based on the differences of underground media properties.AVO(Amplitude Variation with Offset)technology is a seismic exploration technology that uses seismic wave amplitude data to study lithology and detect oil and gas resources.Since 1980,it has been extensively researched and developed.The theoretical basis of the traditional AVO technique is the Zoeppritz equation and its approximate formula,which is usually only applicable to the reflection coefficient of plane-wave within a certain angle range(usually below 40 degrees).However,with the continuous development of exploration technology,it is found that the properties of large amplitude and large phase shift of spherical-wave at wide-angle are more favorable for the inversion of density,and the Zoeppritz equation is no longer applicable.Therefore,it is very important to study the AVO characteristics of wide-angle reflection waves,how to characterize the wide-angle AVO is a worthy research topic.According to the fact that the reflection coefficient of seismic spherical-wave conforms to the rational function(especially at wide-angle),the rational function fitting technique(vector-fitting)is proposed to deal with the reflection coefficient of seismicwave.The zero-poles and residues properties of rational function representing wide-angle AVO are obtained and their feasibility is analyzed.This technique is applied to classify AVO and distinguish lithology.By testing different models,it is proved that the zeropole-residue property obtained by the rational function can effectively represent AVO.Compared with the traditional AVO attribute representation method,this method can extend the research range from near offset to far offset and can dig more information and analyze seismic data more accurately.