Elastic prestack, reverse-time depth migration is applied to both synthetic data and four-component eld data from the Valhall area. Reverse-time extrapolation of the recorded multi-component data is by 2-D elastic nite di erence solution to the full wave equation. An eikonal solver is used to compute the acoustic traveltime from the source to the image points. By using horizontal inline and ver...

We demonstrate a method for 2D velocity estimation on real data with no assumption on the re ector geometry nor on the unknown background velocity eld. In the prestack depth migrated volume, locally coherent events are automatically picked without interpretation and characterized by their positions and two slopes. The velocity is estimated by optimizing the atness of these events in the Common ...

Common-reflection-point (CRP) gathers provide important clues in various migration velocity analysis schemes (Al-Yahya, 1987; Etgen, 1990). Conventionally, CRP gathers are obtained by prestack migration of shot records or constant-offset sections. This paper introduces a way to generate a CRP gather for residual velocity analysis using wavefront synthesis imaging. Compared to CRP gathers obtain...

I show that, by estimating local event slopes in prestack seismic reflection data, it is possible to accomplish all common time-domain imaging tasks, from normal moveout to prestack time migration, without the need to estimate seismic velocities or any other attributes. Local slopes contain complete information about the reflection geometry. Once they are estimated, seismic velocities and all o...

s). “Quantifying errors in fracture orientations estimated from PS converted wave” by Michelena (SEG 1995 Expanded Abstracts). “Stratigraphic inversion of poststack PS converted waves data,” by Valenciano and Michelena (SEG 2000 Expanded Abstracts). “Tomography + prestack depth migration of PS converted waves” by D’Agosto et al. (SEG 1998 Expanded Abstracts). “Pand S-wave separation ats). “Pand...

Joint inversion of different geophysical datasets is an effective way to eliminate non-uniqueness in geophysical inversion problems. In this paper, we focus on a case study of joint inversion of seismic traveltime and gravity observations. The results are encouraging and we can have confidence that, comparing traveltime tomography alone, joint inversion of seismic traveltime and gravity data im...

Wave-equation migration is an accurate and robust alternative to Kirchhoff migration when multipathing and other complex wave phenomena occur, such as in subsalt exploration. In these situations, images obtained by wave-equation migration are often superior to images obtained by Kirchhoff methods. However, 3-D wave-equation prestack imaging is an immature technology compared with Kirchhoff imag...

Prestack Stolt residual migration can be applied to seismic images that are depth migrated using wavefield extrapolation techniques. This method has significant advantages over other methods that estimate interval velocity functions for depth migration. It is more accurate than methods that are based on focusing the stack of migrated images by a residual NMO operation, so it provides a more acc...