Introduction

Common-azimuth migration (CAM) is a 3-D prestack depth migration technique based on the wave equation Biondi and Palacharla (1996). It exploits the intrinsic narrow-azimuth nature of marine data to reduce its dimensionality and thus manages to cut the computational cost of 3-D imaging significantly enough to compete with Kirchhoff methods. Based on a recursive extrapolation of the recorded wavefield, CAM is potentially better able to handle multi-pathing problems induced by complex velocity structures.

Elf Aquitaine provided us with an interesting dataset recorded in the North Sea, which shows a salt dome and other 3-D structures. The complexity of the wave propagation in the medium, resulting from high lateral and longitudinal velocity contrasts, yields multi-pathing and illumination problems. Vaillant and Sava (1999) have already illustrated how this model is both a serious challenge for imaging and an interesting test case for the CAM method.

In this paper, we present our latest imaging results that cover the whole vertical extent of the salt body with the CAM technique, as a complementary study to Vaillant and Sava (1999). At the same time, we compare the CAM-migrated cube to the image obtained using a state-of-the-art Kirchhoff algorithm and discuss the specificities of both approaches.