The impact of a quick 4D seismic survey and processing over the Halfdan Field, Danish North Sea

Abstract

The quick turnaround of seismic processing of a 4D time lapse survey over the Halfdan oil field allowed for interpretation and integration of the new 4D results seven weeks after completion of the seismic acquisition. Analysis of the first fast track 4D dataset led to improved processing parameters and an additional demultiple application which yielded a significantly improved fast track dataset 11 weeks after the seismic acquisition was completed. The repeat 4D seismic survey was acquired in the summer of 2012 in order to provide a better understanding of the sweep efficiency from the line drive water flood, guide future well interventions and improve the reservoir model. The baseline 3D seismic data was acquired in 1992/1993, prior to field development, and the first monitor 3D seismic was acquired in 2005. The rock physics model shows that increased water saturation due to the water flooding along the injectors in the Tor oil-bearing reservoir dominates the 4D change in acoustic impedance yielding a hardening response. The rock physics model was used to convert the reservoir model pressure and saturation changes from the three time-steps to modelled acoustic impedance changes. Examples will be shown from the 4D time lapse and the reservoir model acoustic impedance changes.