Study On Elastic Wave Field Separation Method Of VTI Medium

The multi-wave and multi-component seismic exploration technology is one of the most promising scientific research value and development foreground technologies in exploration seismology.Compared with regular P-wave seismic exploration,it can better describe the underground structure and characterize oil and gas reservoirs,such as the localization of faults,pinch outs and structures,identification of bright spot,and analysis of the fracture zone etc.However,the anisotropic medium VTI multi-component seismic exploration technology still faces many difficulties: first,there is always anisotropic wave coupling,it is difficult to derive independent longitudinal wave equation;secondly,the polarization characteristics are anisotropic,caused by elastic wave field separation method of vector failure of traditional Helmholtz decomposition;thirdly,some current mainstream the wave field separation of high cost,difficult to meet the demand of high elastic wave vector imaging.Based on this,to anisotropic reservoir multi component seismic exploration,the key lies in the realization of VTI elastic vector wave field fast and accurate separation.Seismic imaging requires accurate reconstruction of the seismic wave field.In fact,the seismic wave is transmitted through the Earth as a special medium,the process of propagation will produce compressed waves and shear waves.Using elastic wave equation is usually more suitable and accurate for wave field reconstruction than acoustic equation.The traditional acoustic offset technique only represents the scalar wavefield imaging of the P-wave;in contrast,the elastic wave migration technique includes vector wave field imaging of P and S waves.The key component of the wave equation migration is the imaging condition,which extracts information about the discontinuity of the physical properties from the reconstructed wavefield at each location of the space.For elastic imaging,we expect the reconstructed vector field to be decomposed into pure wave type,so that the imaging conditions produce interpretable images that characterize the reflectivity of different reflection types.This requires wave field separation before application of imaging conditions.In the anisotropic medium,P-wave and S-wave are coupled together to spread,using the conventional Helmholtz decomposition method for seismic wave divergence and rotation cannot achieve P-wave and S-wave completely separated,so this paper study the Vertical and horizontal wave separation of seismic wave field in heterogeneous media.In this paper,the VTI medium is used to simulate the VTI medium and the high-order finite difference method of staggered lattice.The influence of parameters on the propagation characteristics of various types of seismic waves is studied.In this paper,the method of separating the longitudinal and transverse waves based on the wave field projection is studied.On the basis of previous studies,the space-wave number domain separation operator composed of polarized vector is processed by low-rank decomposition strategy,and then the vertical and horizontal wave separation is realized.Finally,the staggered-grid high-order difference scheme and the vertical and horizontal wave separation simulation Thinking of the organic combination of the formation of the VTI medium high-precision forward simulation and wave field separation integration process.On the basis of the realization method,the correctness,adaptability and advantage of the method are demonstrated by carrying out three types of typical model forward and separation tests.