The Study Of One-way Pre-stack Depth Migration In VTI Media

At present,exploration targets in oil and gas exploration is becoming increasingly complex,the previous basic imaging theory based on the assumptions of the simple isotropic medium will not satisfy the current needs of oil and gas exploration gradually,as a result,it is very urgent to research the method of imaging to the complex medium that conforms with the practical underground geological model.On the other hand,because of the anisotropic medium in the crust,there are great significant to research the seismic anisotropy for the cognition of earth media configuration,the exploration and development of complex oil gas reservoir,the forecast of the geological disasterat the current geophysical research.The pre-stack depth migration technology based on anisotropic medium has the best effect of imaging complex geology.We can obtain the sophisticated imaging by using pre-stack depth migration technology at complicated or deeper structure area in seismic exploration.At first,I obtained one-way wave continuation operator which is directly upward or downward extrapolation by decoupling acoustic wave equation in isotropic medium.For complex medium,I respectively deduced the Split Step Fourier(SSF)?the Generalized Screen(GSP)and the Chebyshev Fourier(CF)by approximatively unwinding the vertical wave number in the process of continuation using different mathematical expansions..Further,I respectively deduced the Split Step Fourier(SSF)?the Generalized Screen(GSP)and the Chebyshev Fourier(CF)which are applying to VTI media by using the basic theory of seismic pre-stack depth migration and the dispersion property of seismic wave spreading in VTI medium dispersion property.Then by means of comparing of the three operators' relative error curve and impulse response curve,I summarized their advantages and disadvantages.With the aid of the theory of migration,I programmatically completed one-way pre-stack depth migration in VTI media.Finally using SEG VTI-HESS model,I verified the imaging effect and efficiency of the three migration methods.By means of comparing the relative error curve and impulse response curve of the Split Step Fourier(SSF)?the Generalized Screen(GSP)and the Chebyshev Fourier(CF),SSF operator will produce larger error,and GSP operator is better than SSF operator,and CF operator is the most accurate and its impulse response result is the most consistent with the propagation of the actual seismic wave in the rock with the larger horizontal velocity variation or larger dip angle.Theoretical model trial results show that we should choose CF pre-stack depth migration method if we need better,more sophisticated imaging in the complex medium;On the contrary,the SSF method can greatly save the cost where the geological structure is simple;And the effect of GSP method is in between of those two kinds of migration method.