Methodology Research Of PP And PS AVO Joint Inversion

AVO inversion is one of well established seismic inversion methods to predict the earth's elastic parameters and thus rock and fluid properties.With the combination of PP data and PS data,we can get more information from the earth.Hence ill-posed problems can be reduced and more accurate and reliable results can be inverted.This thesis focuses on the methodology research of PP and PS AVO joint inversion.Based on Bayesian theory,introducing the prior information to the three-term AVO can stabilize inverted results.Different types of prior information distribution lead to various inverted results.Comparing results obtained by different approaches which apply various prior information distributions,inverting AVO parameters via a Trivariate Cauchy prior distribution can have more reliable and high-resolution results.Long offsets are important to estimate reliable density information.However,NMO stretch will affect the accuracy of inverted results.Based on the Bayesian theory,this thesis adopts PP and PS joint three-term AVO waveform inversion that uses CRP gathers before NMO correction.With the help of this method,we can acquire more accurate results even when the data have noise.There will be accumulative errors when we calculate the modulus information via conventional method.Because the conventional method inverts the velocity and density information in the first place,and then get the modulus information by calculations.The thesis utilizes Zoeppritz approximation whose parameters are P-wave modulus contrast,S-wave modulus contrast and density contrast.Introducing the first order difference matrix,we accomplish the PP and PS three-term AVO simultaneous inversion method and get considerable inverted results including elastic modulus and density directly.