Research On Elastic Wave Finite-difference Modeling And Reverse Time Migration In Cross-hole Seismic

The conventional seismic exploration have not meet the requirements of petroleum prospecting in resolving the structure accurate imaging and reservoir accurate description and reservoir dynamic monitoring and prediction of residual oil and gas and so on , cross-hole seismic technology emerged in this context, it breakthrough the limitations of traditional technology and methods,and it's resolution is between the surface seismic and the logging, it is the combination and addition of surface seismic and the logging. Cross-hole seismic data used to receive three-component geophone ,the wave field of up-going and down-going can be observed at the same time ,and it is rich and complex and difficult to identify; Secondly, the stack of conventional imaging methods can not meet the high-precision and high-resolution rate requirements. Therefore, the dissertation on staggered grid finite-difference modeling in anisotropic medium and reverse-time migration in cross-hole seismic to do an in-depth study and exploration.This research was financial supported by the key project "study on cross-hole Seismic data processing methods about inclined well at sea", from the National Science and Technology. First, the paper have a derivation of three-dimensional elasticity tensor dielectric matrix, then the dissertation have a systematic derivation about the 3D3C first-order coupled elastic equations of particle velocity-stress on TTI medium, and discussed in detail the 2D2C first-order coupled elastic equations of particle velocity-stress and any order accurate time and space staggered-grid finite-difference scheme and its implementation process. by the paper ,the procedures are applicable to 2D isotropic and VTI and TTI media, and it can be arbitrarily any complex 2D geological model of the wave-field forward-modeling. At the border, the paper used perfectly matched layer absorbing boundary conditions, the absorption of the boundary conditions have a very good reflection of the absorption ,and it is the best so far absorbed the boundary conditions.Reverse-time migration includes two steps, one is the calculation of imaging conditions, one of the reverse-time extrapolation of the elastic field. Papers use of shot-instant imaging condition ,which is computed by non-linear interpolation ray-tracing methods for the first break, by the method, the procedure of the non-linear interpolation applies to any complex isotropic media; the extrapolation of wave field use of first-order velocity-stress staggered-grid finite-difference method to computing, reverse-time migration process by the paper applied to 2D isotropic and VTI and TTI media, it can be arbitrarily any complex 2D geological model of the reverse-time migration imaging of full-wave field and single-wave field. Furthermore, the paper model of the diffraction point model, horizontal layered model, annihilation stratigraphic model and fault model of cross-hole by deviated well observation way forward modeling and reverse-time migration imaging. By the modeling, we can see, the methods is accurate, it have good image quality and high precision; by the processing of the actual cross-hole (vertical well) seismic data, it obtain a credible result, to further verify thecorrectness of the implementation and effectiveness.