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

Authors: N.I.L. Xie, N.I.L. Wang, N.I.L. Xiao and N.I.L. Latter
Event name: 80th EAGE Conference & Exhibition 2018 Workshop Programme
Session: WS07: Seismic Imaging with Ray and Waves - Where do we stand? Part II: Imaging
Publication date: 11 June 2018
DOI: 10.3997/2214-4609.201801915
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 468Kb )
Price: € 20

The presence of absorption (Q) anomalies in the overburden, typically associated with gas accumulations, can obscure seismic imaging 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 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.

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