Staggered-grid High-order Finite-difference Numerical Simulation And Prestack Reverse-time Migration

Numerical simulation of seismic wave, which has an important role for researching the propagation of seismic wave in media, is the basis of seismic exploration. Seismic modeling has been applied to nearly every part of seismic exploration, so it is important to develop a simple and efficient numerical simulation method. As the development of seismic exploration, it is necessary to research the propagation of seismic wave in more complex and real media.Migration is always the key problem of seismic exploration. As the imaging objects become more and more complex, especially the image of salt structure and the subsalt encountered on seismic exploration, the migration based on ray tracing and one-way wave-equation can not image this kind of structure very well, but the reverse-time migration(RTM) can produce a good image. The RTM based on two-way wave-equation accords with the propagation law of wave equation thoroughly and can image all reflect waves, even the one with multiple paths, so the RTM is regarded as the most accurate imaging method.In this paper, the first order velocity-stress equations are derived in isotropic media, viscoelastic media, porous media, and anisotropic media respectively based on the previous research results. Then numerical simulation of seismic wave propagation is carried using staggered-grid high-order finite-difference method. Firstly, the validity of the modeling method is verified using a homogeneous model, a two layers model and complex Marmousi2 model. And then the characteristics of wave propagation are analyzed in other media using the similar models above. There are many differences of wave propagation characteristics and wave types between different media from the comparison of wave propagation in different media. Even in same media, there are some differences if using different boundary condition.Based on the numerical simulation, the elastic prestack reverse-time migration is carried using the staggered-grid high-order finite-difference method which is the same as numerical simulation. Then the paper analyzes the imaging conditions involving the reverse-time migration and elimination of artifacts during the reverse-time migration. The cross-correlation imaging condition with energy flux vector density using in this paper can eliminate the artifacts greatly. The validity of migration method is verified through the imaging tests of a diffraction model, a two-layer model, a fault model and metallic orebody model which can be imaged well. The paper also simulates the same geological model using in the isotropic media for vertical transversely isotropic (VTI) media and tilted transversely isotropic (TTI) media and then image them using the prestack reverse-time migration in different media. The results show that the structures in reverse-time migration images become distorted and the imaging location is not correct if using the incorrect migration method. Only using the correct migration method in corresponding media, the migration image is accurate and clear. This shows the importance of reverse-time migration in transversely isotropic media.