Pure qP-wave least-squares reverse time migration in vertically transverse isotropic media and its application to field
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Pure qP-wave least-squares reverse time migration in vertically transverse isotropic media and its application to field data* Huang Jian-Ping1, Mu Xin-Ru♦1, Li Zhen-Chun1, Li Qing-Yang2, Yuan Shuang-Qi3 , and Guo Yun-Dong2 Abstract: The anisotropic properties of subsurface media cause waveform distortions in seismic wave propagation, resulting in a negative influence on seismic imaging. In addition, wavefields simulated by the conventional coupled pseudo-acoustic equation are not only affected by SV-wave artifacts but are also limited by anisotropic parameters. We propose a least-squares reverse time migration (LSRTM) method based on the pure qP-wave equation in vertically transverse isotropic media. A finite difference and fast Fourier transform method, which can improve the efficiency of the numerical simulation compared to a pseudo-spectral method, is used to solve the pure qP-wave equation. We derive the corresponding demigration operator, migration operator, and gradient updating formula to implement the LSRTM. Numerical tests on the Hess model and field data confirm that the proposed method has a good correction effect for the travel time deviation caused by underground anisotropic media. Further, it significantly suppresses the migration noise, balances the imaging amplitude, and improves the imaging resolution. Keywords: Pure qP-wave equation, vertically transverse isotropic media, LSRTM, finite difference and fast Fourier transform, field data
Introduction The vast majority of subsurface media exhibit anisotropy (Thomsen, 1986). If this phenomenon is ignored, a large difference in the travel time and phase between the synthetic seismic data and the field data is observed (Alkhalifah, 2000; Duveneck and Bakker, 2011; Zhu et al., 2018). If the anisotropic seismic data
are processed using the isotropic migration imaging method, the reflected wave cannot be accurately located and the diffraction wave cannot completely converge (Zhang et al., 2011). Therefore, the influence of anisotropy on wavefield propagation needs to be considered to obtain accurate imaging results. In view of the difficulties associated with elastic data acquisition, the complexity of wave pattern separation, and high computational costs, the anisotropic acoustic
Manuscript received by the Editor November 16, 2019; revised manuscript received June 18, 2020. *This study work was financially supported by the National Key R&D Program of China (No. 2019YFC0605503), the Major Scientific and Technological Projects of CNPC (No. ZD2019-183-003), and the National Natural Science Foundation of China (No. 41922028; 41874149). 1. Department of Geophysics, School of Geosciences, China University of Petroleum, Qingdao 266580, China. 2. Geophysical Exploration Research Institute, Zhongyuan Oilfield Company, Henan Puyang 457001, China 3. Sinopec Geophysical Research Institute, Nanjing 211103, China. ♦Corresponding Author: Mu Xin-ru (Email: [email protected]) © 2020 Chinese Geophysical Society. All rights reserved.
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