Wave Equation Migration Improvements - Towards Reliable Quantitative Seismic Interpretation of the Pre-salt Play

Structural imaging in subsalt environments has been a major challenge for the geophysical industry in the last decades. Thanks to the tremendous improvements in acquisition, processing, model building and migration technologies, structural imaging subsalt has reached a quality level that allows today to go further and to exploit amplitudes of subsalt migrated images. For this purpose and in order to correctly handle the complexity of the wave propagation, wave equation migration methods have become the standard algorithm for subsalt environments and have largely contributed to the improvements of structural imaging subsalt. But amplitude fidelity of those migrated images is still a challenge that can be today overcome by the recent improvements added to these methods: I/ the ability to compute accurately and efficiently common image gathers, II/ the derivation of true amplitude image conditions and III/ the efficient implementation of preconditioned least squares migration. We will describe and illustrate theses improvements in the presentation.