The Research Of Tomography Inversion Method Based On ADCIGs In VTI Media

In the early days of seismic exploration,scholars generally believed that the subsurface medium was isotropic,ie,it was assumed that there was no difference in the propagation velocity of the seismic wave field in all directions in the subsurface medium;as the difficulty of seismic exploration increased,the horizon of the target ranged from the middle to the deep.Deep and ultra-deep layer development,and with the increase of seismic imaging depth,anisotropy develops in deep media,and seismic wave propagation velocity varies in all directions.For large offset and wide azimuth data,if we do not consider the anisotropy of the subsurface media,it will cause problems such as non-convergence of diffracted wave and inaccurate horizon in imaging results,which will reduce the accuracy of seismic imaging and inversion.In this paper,starting from the Thomsen theory,the propagation characteristics of the wavefield in anisotropic media are discussed firstly,and the forward model is established to analyze the relationship between the input and output of the VTI medium forward operator,and the effect of the VTI media parameters on the observation data is established.The factors were analyzed;then,under the premise of ensuring the accuracy of the forward operator,based on the principle of time consistency,offset profiles were calculated and energy compensated by calculating the cross-correlation between the seismic source wave field and the received wave field,and the low-frequency noise was utilized.The Laplacian filter operator suppresses;in the wavefield continuation of VTI media RTM imaging,the velocity direction of the wave field is obtained by calculating the Poynting vector of the received wave field and the source wave field,and then calculating the two The angles of the Poynting vectors are used to calculate the angle of incidence of the wave field in the medium to extract the angular gathers.The retrieval of the tomographic parameters based on angle gathers is the main content of the thesis.When the initial parameter field is inaccurate,the angular gathers There will be a certain degree of curvature on it,and this curvature will be transformed into the residual while traveling in the inversion.The tomographic inversion equations were established by the ray tracing of the sensitive kernel functions and the transformed travel-time residuals.Using a reasonable numerical solution,the inversion solution was implemented to update the parameters.