Study On The Pre-Stack AVAz Inversion Method Of Seismic Anisotropic Parameters

To solve the exploration and development geological problems of unconventional reservoirs,seismic exploration technology needs to solve the problem that conventional isotropic medium can’t accurately describe unconventional reservoirs.The reason is that the conventional pre-stack seismic inversion technology is based on the isotropic medium model.Therefore,it is necessary to study the inversion method based on anisotropic media model to meet unconventional reservoir description.In this thesis,the pre-stack AVAz inversion methods of seismic anisotropic parameters are mainly studied,including the regularization method in pre-stack inversion,anisotropic parameters inversion based on VTI medium and Fourier’s coefficient inversion based on HTI medium.The synthetic data is used to verify the exactness of the inversion methods,and the actual data is used to test the feasibility of the inversion method in practical application.AVAz inversion of seismic anisotropic parameters has more inversion parameters than conventional pre-stack AVO inversion of isotropic medium,and the inversion method is ill-posed,so regularization is needed in the inversion process.The total variation(TV)regularization method is used to constrain the inversion,and the sparse solution conforming to geological rule can be obtained.By comparing several algorithms for TV regularization,the algorithm with strong stability,strong noise resistance and robustness can be selected.Conventional seismic exploration is not deep enough to study highly anisotropic of VTI media,so it cannot reasonably describe the anisotropic characteristics of shale reservoirs.Compared to conventional AVO inversion,this thesis uses AVAz inversion method to obtain the anisotropic parameter information of shale.At the same time,the study shows that the influence of anisotropic parameters on seismic wave propagation characteristics,and the seismic responsive characteristics under different AVO models.With the development of wide azimuth and multi-dimensional seismic acquisition technology,anisotropic parameter information can be inverted from pre-stack seismic data.Compared to conventional AVAz inversion,this thesis deduces the approximate formula of reflection coefficient based on Fourier’s coefficient expansion formula.It also analyzes the relationship among anisotropic parameters,fracture density and Fourier’s coefficient,and establishes the relationship between fracture and anisotropic parameters through rock physical modeling.In the process of pre-stack inversion of anisotropic parameters,the anisotropic parameter information of unconventional reservoirs is obtained by establishing rock physics model.At the same time,TV regularization algorithm is introduced to well describe the reservoir characteristics,which provides a reasonable interpretation basis for the unconventional reservoir prediction.