4D Seismic in Grane – Adding Value over Generations

The Grane oil field is located in the Norwegian North Sea, about 200 km NW of Stavanger, Norway and contains heavy (19°API), high viscosity and under saturated oil with no initial gas cap. The field has been successfully produced since the start-up in September 2003. Present recovery factor is estimated at 65% (by 2044) with an ambition of ultimate recovery as high as 70%. 4D Monitoring program was initiated in 2005 to map reservoir dynamics. Accordingly, the field has been monitored till date with acquisition of conventional streamer seismic data every second year. The main contributions from 4D data have expanded over time including experience in need for better quality of 4D data and more frequent monitoring of the dynamic behavior of the reservoir than the present strategy. Based on the need, a permanent reservoir monitoring (PRM) system has been installed in Grane in 2014 with 300m cable separation and 50m between receivers. Initial plan is to monitor the reservoir every 6 months. Frequent harnessing of seismic data challenges the present implementation workflow and hence prompts for more efficient workflows in order to benefit from the better quality and more frequent 4D data.