Depth migration velocity model building with wave equation imaging

摘要

In spite of impressive advances in the application of wave equation imaging technology to generate images of complex struc-tures, ray-based tools are generally used for the equally important step of velocity determination. Closing the experimentalloop, by using the same wave equation imaging algorithm to measure velocity and to obtain a final image, is more thanjust philosophically pleasing. In strata exhibiting complex velocity structure, wave equation migration algorithms may bethe only tools able to image some reflectors, so it stands to reason in such cases that only a wave equation velocity updatecan reliably measure velocity errors near these reflectors. In this article, we present a wave equation velocity update scheme,similar to depth focusing analysis, utilizing the time-shift imaging condition. We demonstrate the robustness of this approachunder salt and in a land fault shadow example with limited acquisition effort. A common criticism levied against waveequation migration is the difficulty in efficiently obtaining 3D angle gathers (incidence, azimuth, and dip angle). We alsopresent an efficient Fourier-domain angle decomposition technology for wave equation migration and demonstrate efficacyon synthetic and field data examples.