Approaches And Application Of Inversion Q Value Inversion In Zero-offset VSP Data

The energy of the seismic wave will attenuate as it travels due to the none-elastic heterogeneity of the stratigraphy and spherical spreading of the wave front. The absorption decaying due to the former factor is more complex in the seismic data processing, so study the law of absorption decaying is always an important area for many geophysics experts. VSP-vertical seismic profiling approach can receive the properties of propagation of the seismic wave, observe the changing of seismic wave and get the progress of reflection and transmission, so this method is believed to be the only source which can supply the valuable data of seismic decaying.Based on the properties and influence factor of seismic wave decaying, the absorption decaying law in viscoelastic medium and the forward theory of Ganley, accounting for the reflection and transmission, this thesis has designed the algorithm of zero offset VSP logging in viscoelastic medium, built the zero offset VSP logging of horizontal layered viscoelastic medium and implemented the forward progress of zero offset VSP. Then compared it with the no decaying zero offset VSP model, this paper has implied the decaying property had lead to the losing of the energy of seismic wave. This paper have also paid much attention to variety of inversion methods of Q and combined the properties of real data to analyze the feasibility of each method. At last, the paper focused on ratio of frequency spectrum method and basic frequency shift method, then designed and implemented the algorithm for both approaches, at last used the forward model to inverse the Q value and compared them with the theory Q value. This paper also have discussed the strengths and weaknesses and the application conditions of these methods, then these result can supply the references to the inversion of Q value for the real data.Finally, this paper applied the method of Q value inversion to the real data. First the real VSP data should be preceded wave field separation and the direct wave should be extracted. Then this paper chose a proper algorithm of Q value inversion. Finally, the Inverse Q Filtering should be carried out, so the energy of the seismic wave has be compensated, the Quality of the seismic data have be improved. The effect of Q value inversion has been tested, and this would be helpful for the later seismic data processing.