Velocity Analysis And Modeling Method Research In TI Media

The anisotropy is the nearly ubiquitous phenomenon in sedimentary rock. The research of seismic anisotropy has been one of the newest scientific research topic in seismology, and also it is the great challenge for studying seismology theory and application. Seismic migration imaging is main way to realize construction of subsurface. In order to obtain a good image and accurate depth positioning of reflectors in the subsurface, it is essential to account for heterogeneity and velocity anisotropy. Existing anisotropic velocity analysis algorithms often approximate the subsurface with homogeneous or vertically heterogeneous anisotropic layers or blocks, which is suitable in time imaging. For depth imaging pueposes, however, lateral heterogeneous should also be accounted for.Bases on elastic wave theory, elastic wave equation can be established, and by solving Christoffel equation, the formula of elastic wave phase velocity and group velocity can be obtained. We adopted 25-points finite difference numerical simulation schemes and perfect matched layer artificial boundary to simulate the seismic elastic wave field in TTI media.After scanned nonhyperbolic moveout of P-wave reflections form horizontal interfaces in VTI medium we obtain zero-dip NMO velocity and an anisotropy parameter, with it we achieved satck real data in some areas.Embarking on qP wave equation in VTI media, we investigated one-way dual-domain generalized-screen propagator of qP wave in VTI media. The operator expands generalized- screen method of isotropic media, and divides anisotropic velocity field into homogenous anisotropic velocity field, velocity perturbation and anisotropic parameter perturbation. generalized-screen propagator of qP wave in VTI media is composed of free operator in background media and anisotropic parameter perturbation operator. The operator not only achieve adequate precision in large-angle propagation, but also be applied to the media of strongly transverse velocity change and the anisotropic parameter of strongly transverse heterogeneous perturbation.When visible anisotropy and velocity gradient presence in the subsurface, the medium parameters includes P-waves, velocity gradient and anisotropic parameter. In order to obtain a good image and accurate medium parameters, an iterative application of migration and velocity updating can be uesed. Migration creates an image of the subsurface for trial values of the medium parameters, and velocity analysis is used to update the model for the next run of the migration code. We achieved used this algorithm in synthetic model and real data in some areas, it can be realize most events in image gathers after prestack depth migration are flat, this implies that the piecewise factorized model is a suitable choice for imaging and velocity analysis in heterogeneous anisotropic media.