Gaussian beam migration method with seabed four-component data in anisotropic media
The multi-wave and multi component Gaussian beam migration method based on the elastic wave equation presents high computational efficiency and accurate imaging,and is appropriate to be applied to com-plex geological structures.At present,it is mostly applied to terrestrial three-component data.However,for seabed seismic data,there exist obvious adaptability issues:①Incomplete seabed boundary conditions lead to incomplete separation of P waves from S waves,and the up-going and down-going waves will be aliased in the recording manner of the seabed,which results in false imaging.②The general anisotropy in underground media brings kinematic information errors,which leads to problems such as inaccurate reflection wave homing,poor convergence effect of diffraction wave,and non-focusing energy in the stage of final imaging.Therefore,an elastic Gaussian beam migration imaging method is proposed,by which the anisotropy characteristics are taken into account and the four-component seismic data of the seabed including the water pressure component are di-rectly used.Firstly,provided that the receiving interface of the seabed is isotropic,the wave field is extended based on the elastic wave equation and the complete boundary of the seabed,and the waveform separation ma-trix of the four-component data is obtained.Then,by joint use of anisotropic ray tracing and dynamic parameter approximation,the elastic wave Gaussian beam migration of VTI media is realized.The numerical results of the 2D layered model and the Gullfaks region model in the North Sea show that the Gaussian beam migration method adopted in this paper can suppress the imaging illusion caused by incomplete boundary conditions.It can automatically separate PP and PS waves in the seabed anisotropic media to achieve accurate imaging of con-verted waves,and can better recover and migrate seismic waves to improve the imaging resolution.Thus,the proposed method is especially suitable for seismic exploration of complex seabed under the conditions of large offset and wide azimuth.
万方数据
维普
