Abstract: Compared with the post?stack inversion,the extended elastic impedance is more sensitive to the reservoir and hydrocarbon.In this paper,the authors discussed the theory,key techniques and steps of the extended elastic impedance inversion.Wetake P1x1 and P1s2 in DND gas field of North of Erdos Basin were taken as the study objects.Based on a detailed analysis of logging data,the authors pro?pose fusion method for estimating data of shear wave.This method combines modeling method,formula method and neural network meth?od.It estimates the sandstone section using modeling method,and mudstone with formula method for low frequency model and,in combi?nation with neural network,predicts the mudstone section of shear wave information,thus avoiding the error of mudstone caused by total porosity measurement inaccurate prediction using Xu?White model. Based on cross pictures analysis,the authors deal with sensitive elas?tic parameters for EEI inversion and effective scale for interpretation of lithology and fluid and,according to deterministic extended elas?tic impedance inversion,determine the variation and range and complete the pre?stack stochastic extended elastic impedance inversion, thus meeting the requirements of thin reservoir prediction.At last,the inversion results are interpreted crossly and the distribution of gas sand is predicted accurately,with the drilling data matching rate reaching over 90%.