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Imaging of Sumatra Gas-rich Region Using 2D Hierarchical Viscoelastic Waveform InversionNormal access

Authors: T. Belahi, N. Fuji and S. Singh
Event name: 79th EAGE Conference and Exhibition 2017
Session: FWI D
Publication date: 12 June 2017
DOI: 10.3997/2214-4609.201700795
Organisations: EAGE
Language: English
Info: Extended abstract, PDF ( 2.85Mb )
Price: € 20

Summary:
We present a hierarchical strategy of viscoelastic full waveform inversion and its application to a real dataset.We show first that, in synthetic tests, mid-offset and far-offset data are particularly sensitive to attenuation and thus purely elastic waveform inversion can fail to obtain a meaningful model, i.e. simultaneous inversion of both elastic and anelastic parameters is required in order to properly treat reflections and converted waves close to the critical angle. We then apply our viscoelastic inversion scheme to long-offset (15 km) data acquired offshore Sumatra. A previous study using (purely) elastic full waveform inversion using the same data on the Mentawai forearc basin dataset found a low velocity anomaly, which could possibly be interpreted as a gas pocket. We apply, rather, our viscoelastic full waveform inversion strategy to the long offset data. We inverted using refracted waves in combination with a frequency continuation approach. In the later stage of the frequency continuation strategy, we included long-offset reflection data that granted access to the smaller wavelength of the model. We inverted simultaneously for elasticity and anelasticity at every stage of the inversion. The final resolution of the velocity model is increased and the dipping structures are better imaged.


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