Fast 3D velocity updates using the pre‐stack exploding reflector model

Abstract

The fundamental idea of PERM is to synthesize areal shots whose migration describes the correct kinematics of a reflector in an isolated subsurface-offset common-image gather (SODCIG) computed with wave-extrapolation methods. This is achieved by extrapolating source and receiver wavefields starting from the prestack image at the vicinity of the SODCIG. The modeling of PERM source D and receiver U wavefields can be carried out by any wavefield-continuation scheme. Here, we use the following one-way wave equations: and where x is the spatial coordinates, x m is the coordinate of the SODCIGs used in the modeling, is frequency, h is the subsurface offset, s 0 is the background velocity also used in the migration of the initial image, and I D and I U are prestack images used as the initial conditions for the modeling of source and receiver wavefields, respectively, and are computed by rotating the original image according to the apparent geological dip.

Migration velocity analysis for anisotropic models

“…However, the wavefield method better approximates wave propagation in complex areas. We can also utilize the phase-encoded target-oriented image-space wavefield tomography (Guerra et al, 2009;Guerra and Biondi, 2010) technique to reduce the computational cost.…”

“…Several advantages drive us to use the image-space wave-equation tomography instead of data-space wave-equation tomography: first, WEMVA does not require as accurate an initial model to avoid the cycle-skipping problem as FWI requires. In fact, many studies (Guerra et al, 2009;Guerra and Biondi, 2010;Tang and Biondi, 2010) show that the resolution gap between ray-based tomography and FWI could be linked by the imagespace WEMVA method; second, the objective function is directly related to the final image; third, the migrated image is often much cleaner than the recorded wavefields. Therefore, we choose to extend image-space WEMVA from isotropic velocity building to anisotropic model building.…”

Target-oriented wavefield tomography using synthesized Born data

“…Therefore, the cost reduction cannot be substantial. Biondi (2006Biondi ( , 2007; Guerra et al (2009); Guerra and Biondi (2010) approach this problem in a completely different way. They synthesize a new data set based on the initial image using the concept of prestack-exploding-reflector modeling.…”