An early-out PSDM multi-azimuth (MAZ) stack is now available, just 16 weeks after completion of the GeoStreamer X Viking Graben survey, in a time scale comparable to conventional single azimuth processing. From acquisition through to imaging, GeoStreamer X has delivered on its promise of a significantly faster method of achieving offset- and azimuth-rich data than node-based exploration.
Using a single Ramform vessel, PGS piloted a towed-streamer survey design that incorporated all its latest innovative acquisition solutions to solve the imaging challenges in the Viking Graben. The acquisition was completed in November and Fast-track PSDM data was released in February 2020.
The GeoStreamer X Viking Graben project combined three acquisition directions with a wide-tow source configuration for advanced offset- and azimuth-rich data. The Ramform Vanguard towed 12 streamers, including two 10 km long tails to provide offsets for FWI, and a wide-tow multi-source with 225 m total separation. Close to zero offset was achieved and this has been used for optimal near-offset sampling and shallow imaging. The setup also provided dense spatial sampling for high-resolution imaging, offering improved illumination with a significant efficiency gain and reduced environmental footprint.
Solving Viking Graben Imaging Challenges
The main imaging challenges in the area are illumination below shallow channels and resolving a complex sandy interval in the Hordaland Group. This includes cemented sand injectites that introduce anomalously high velocities (called v-brights), and below this, a thin chalk layer that absorbs energy and generates multiples.
Full Integrity Processing to Enhance Target Resolution
GeoStreamer X Viking Graben exploits rich offset and azimuth information in the imaging sequence. The velocity model used for the fast track imaging was based on the underlying legacy survey using 6 km data, acquired in 2011.
The full-integrity MAZ products will maximize resolution and the usability for interpreters of any signals present in any acquisition direction. The 10 km long offsets will be incorporated for multi-azimuth full-waveform inversion, multi-azimuth high-resolution reflection tomography, and the final anisotropic PSDM.
Expanding GeoStreamer X Coverage on the NCS
“GeoStreamer X has great potential on the NCS, delivering a robust and efficient solution to provide the data quality step-change needed to discover new resources and add value for clients. We plan to expand the concept during the 2020 season and are currently reviewing opportunities in the Viking Graben,” avers Gunhild Myhr, VP New Ventures Europe at PGS.