In order to overcome the inconsistency of intercepts in different azimuths with conventional azimuth AVO gradient extracting method and the difficulty in obtaining azimuth AVO gradient as priori constraint from wells,we developed a steady azimuth AVO gradient unconstrained inversion method.The inversion method is divided into two steps:the first step is to assume that seismic data is reflection coefficient sequence for eliminating wavelet term which could result in instability in the least squares inversion equation,and obtain the self-exciting and self-receiving seismograms and seismic azimuth AVO gradient records; the second step is to search reflection interface locations exactly based on the least reflection layer assumptions in order to reduce the dimensions of deconvolution equation for seismic azimuth AVO gradient records.The model test shows that the method can improve the stability of the inversion equation and the ellipse analysis of azimuth AVO gradient is a good indication of fracture density and fracture strike.The application results of the actual exploration area show that the ellipse analysis of azimuth AVO gradients from above inversion method can more accurately predict the formation fracture zone and provide a favorable technical support for fractured reservoir prediction.
azimuth AVO gradientinversionthe least reflection layerellipse analysisfracture prediction
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