A method of Fourier finite-difference preserved-amplitude prestack depth migration

Seismic data contain rich travel-time and amplitude information. In order to solve the problem of amplitude errors caused by geometric spreading and incidence angle variations, we propose a practical wave equation preserved-amplitude migration method. In this method, we derive the high efficiency direct-viewing one-way wave equation for preserved-amplitude migration from full acoustic wave equation using one-way wave's preserved-amplitude decomposition, which is extrapolated while facing the pressure component of the seismic wavefield. Then we derive a 6-item operator equation based on the method of Fourier finite-difference preserved-amplitude migration, and modify boundary conditions and imaging conditions to take amplitude compensation into account in modified boundary conditions and imaging equations. So we compensate for amplitudes affected by geometric spreading loss and incidence angle variations from three aspects above. Theoretical model testing and real data processing indicate that this method not only can make scattering energy be focused and migrated to the correct position to improve imaging accuracy, but also can output the amplitude information which reflects the correct subsurface reflection coefficients. So this method can provide more real seismic information for following attribute analysis, such as AVO/AVA.