Abstract:In VTI anisotropic media, multi-parameter analysis is an effective method for pre-stack time migration velocity modeling of converted waves. However, for converted wave from complex structures with serious anisotropy, low spectral accuracy and multiple solutions make it very difficult to directly perform multi-parameter spectrum analysis. This paper provides a method which simplifies the multi-parameter velocity modeling process. Through stratigraphic interpretation of P-wave and converted wave, the average velocity ratio of P-wave to converted waves(γ0)can be obtained. The initial migration velocity of the converted wave(vC2) and γ0 are used to perform the isotropic pre-stack time migration of the converted wave, and the imaging gathers are used to iteratively optimize the vC2 with only finely tuning γ0, so that the near-offset event is flattened. Then, the VTI four-parameter analysis of the converted wave is performed, in which vC2 and γ0 is kept unchanged. The equivalent velocity ratio and the anisotropic parameter of the converted wave are sequentially iterated until the far-offset events are flattened. The application result shows that the method can effectively reduce the multiplicity of multi-parameter modeling of converted waves, improve the imaging quality, and lay a good data foundation for karst fracture prediction by using multi-wave data.
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YANG Zhe, WANG Xiaowei, SU Qin, BIAN Donghui, LIU Wei, YANG Wei. The velocity model of converted wave VTI pre-stack time migration and its application in complex zones. Oil Geophysical Prospecting, 2020, 55(s1): 33-40.
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