Research On Seismic Wave Propagation And Reverse Time Migration In Transversely Isotropic Media

With the increasing difficulty in exploration of oil and gas resources,the contradiction has intensified between supply and demand.As a result,industry expectation is increasing for imaging accuracy.However,ignoring the anisotropy of seismic wave will not be able to accurately describe the wave field propagation characteristics in the media,which eventually gets low precision imaging.Based on the two-way wave equation,reverse time migration(RTM)imaging method can realize high precision imaging of complex structures.The underground media is characterized as transversely isotropic(TI)media with symmetrical axis,which accords with the objective reality.Therefore,this paper studies RTM imaging method in TI media.The following progress has been made mainly:(1)Based on the dispersion relationship of q P wave,a finite difference scheme of coupled q P wave equations and pure q P wave equation were deduced for VTI media.By coordinate rotation,the finite difference scheme of q P wave equation is obtained in TTI media.Through numerical simulation,the two kinds of equations were studied in the wave field kinematic characteristics and wave field propagation stability,and the influence of anisotropic parameters on the kinematic characteristics of seismic waves is analyzed.(2)RTM imaging method of ground seismic and VSP data is studied in TI media.Through the model and actual data test,it is shown that the anisotropic factors of seismic wave can not be neglected.(3)The target area imaging method is proposed,which can effectively improve the signalto-noise ratio of the target region,such as sheltered structure by salt mound.A angle domain common imaging gathers calculation method is proposed,which can suppress the RTM imaging noise.(4)The decomposition of seismic wave field is studied in TI media.The relationship between the different traveling wave components and the imaging noise is analyzed.The wave field which contributes to the imaging results is screened,and the imaging illusion of the strong reflective interface is eliminated.The imaging conditions of wave field decomposition can weaken the detection point traces in VSP RTM results.(5)Combining the checkpoint seismic wave field reconstruction strategy with CPU/GPU cooperative parallel acceleration technique,the accuracy of seismic wave field reconstruction is improved,the dependence of the algorithm on storage is reduced,the computational efficiency is improved.It provides a thought for RTM industrialization.