Recent advances in Q model building and Q-compensating migration for imaging in the presence of complex gas clouds using P waves

The presence of absorption (Q) anomalies in the overburden, typically associated with gas accumulations, cause seismic obscured areas in our images and reduce our ability to see and interpret events inside the resulting “shadow zone”. In this paper we present our recent developments for addressing these challenges. We review progress made in the area of Q-compensating prestack depth migration (Q-PSDM) in order to deal with the co-existing multi-pathing and absorption effects for imaging through or under complex gas clouds using P-waves. In addition, to mitigate the problem associated with over-boosting of noise and migration artefacts introduced by Q-PSDM, more advanced imaging methods, such as least-squares Q-migration, have been developed to maximize the benefit of Q-PSDM. We then highlight a recently developed visco-acoustic full-waveform inversion (Q-FWI) model building technique for joint estimation of Q and velocity models. This has been applied to a production example from the Norwegian North Sea, where we see that the Q-FWI detects attenuating bodies of varying strength and scale throughout the survey and provides a clear uplift in the subsequent imaging process.