Abstract：The paper first reviewed the P-P wave AVO response feature and its classification,then systematically expounded the P-SV wave AVO response feature from P-SV wave reflection coefficients and amplitude feature,normalized P-SV wave reflection coefficients and intercept-gradient feature and relationship between the variation trends of strata parameters and AVO types. The paper gained the following knowledge by selecting lithological parameters of 4 AVO types given by Castagna and Hilter-man and using Zoeppritz equation to compute the P-SV reflection coefficients:① there is more complex P-SV wave AVO response feature in different kind of gas-beds,using single reflection coefficient curve and amplitude feature cannot differentiate from each other among 4 AVO types, which indicated the insensitive to fluids component of reservoir by P-SV wave AVO response; the normalized reflection coefficient curve is monotonic character when introducing the conception of pseudo converted wave impedance and amplifies weak AVO anomaly, which showed that the normalized reflection coefficients in vertical incidence are monotone increasing with incident angles for Ⅰ, Ⅱ and Ⅲ AVO types either in water-bearing reservoir or in gas-bearing reservoir; for Ⅳ AVO type of gas beds,the feature of fluids in the reservoir does not affect the variation trends of reflection coefficients that are positive values and monotone decreasing with incident angle;③Ⅰ and Ⅱ types of gas beds are characteristics of negative intercepts and positive gradients, the intercepts and gradients of Ⅲ type of gas beds approach to zero and Ⅳtype of gas beds are characteristics of positive intercepts and negative gradients. The paper uses P-SV wave AVO intercept-gradient theory to implement the intercept-gradient analysis for different AVO types and 25 gas-(or oil-) bearing sandstone samples given by Castagna, which further proved the P-SV wave AVO response feature and the ability to identify different gas-beds. The study in the paper has important meaning for AVO forward modeling, replacement of reservoir fluids,AVO analysis and parameters inversion of multi-waves.
