Application Of Undulating Surface TTI Anisotropic Prestack Depth Migration In Mountain Seismic Imaging

With the development of seismic exploration,the targets have been transferred to areas which have more complicated structures underneath and irregular surface in western China.And the efficiency of pre-stack depth migration lies greatly on the precision of velocity model building.As to areas which have more complicated structures underneath and irregular surface with heterogeneous velocity laterally,pre-time migration cannot make a good effect.Pre-stack depth migration is valuable choice for the imaging of complex structures due to its advantages.However,pre-stack depth migration is only valid and can give correct image under accuracy velocity-depth mode.In the rolling topography,the static correction method changes the shot point and detector position.The real wave field has been destroyed.Meanwhile,the media have anisotropy,the depth of seismic physical model and the actual formation depth cannot be closed.The rolling topography and the complex geologic structure lead to inaccurate image generated by the conventional isotropic pre-stack depth migration in the mountain area of southern China.Aiming the problem,a kind of TTI anisotropy based full velocity modeling technology was studied,a set of thoughts and implementation procedures of TTI rolling topography pre-stack depth migration was established.First of all,an accurate irregular surface velocity model was built by the well-constrained first arrival tomographic inversion method.Secondly,build an irregular surface isotropic velocity model by matching stitching the near surface model and the mid-depth velocity model obtained by conventional data processing.Then obtain the anisotropy parameters through borehole-seismic joint method.Finally,the TTI anisotropic irregular surface velocity model was accomplished by integrating the dip,azimuth and anisotropy parameters into the existing irregular surface isotropic velocity.Apply TTI rolling topography pre-stack depth migration to the seismic image of DXC survey in the Sichuan Basin.The processing results show that anisotropic full velocity modeling can achieve reliable full velocity modeling in the mountain area;TTI anisotropy velocity model based Kirchhoff pre-stack depth migration from rolling surface can eliminate the effects of relief surface and reduce the impacts of complex structures and velocity anisotropy on the seismic image,and reduce the well mistie below 1%.