Seismic anisotropy in dipping shale layers causes imaging and positioning problems for underlying structures. Two 2D anisotropic depth migration algorithms, anisotropic phase-shift-plus-interpolation (APSPI) and anisotropic reverse-time (ART), are presented for tilted transversely isotropic media (TTI). These two algorithms inherit the accuracy of wavefield extrapolation migration methods. Based on the analytical solution of the frequency-dispersion equation, APSPI algorithms can handle an arbitrary distribution of velocities and anisotropic parameters. We also derive the P-wave and SV-wave equations for tilted TI media using the frequency-dispersion equation.
APSPI belongs to the downward continuation method that uses one-way wave equation migration methods, while ART is a full wave equation method. We focus our research on the differences between accuracy and efficiency. In addition, we evaluate the difference between isotropic and anisotropic migrations. Examples demonstrate that APSPI and ART have excellent performance for arbitrary velocity and anisotropic parameters media. However ART does not suffer from the dip limitation of one-way downward continuation algorithms.
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