pgs4dFirst Break March 2025 | Opportunistic 4D Using a Regional Non-Repeated 4D Monitor, an Ærfugl Case Study This case study from the Ærfugl field in the Norwegian Sea, shows that MultiClientSubsurface Monitoring Requires Strict Desn Thresholds. 4D seismic monitoring of reservoir depletion, often assisted by enhanced recovery processes, relies upon the acquisition