Successful Time Lapse Studies on the Gullfaks Field, North Sea—Statoil
Gullfaks is a large tilted fault-block reservoir on the western margin of the North Viking Graben in the Norwegian North Sea, discovered in 1979, and with remaining reserves of some 120million cm. of oil. The recovery factor is around 53%. Production is from Brent, Cook, and Statfjord Jurassic sandstone units, with the top at about 1800m depth. The major fault throws are up to 300m in the north-south direction, and there are smaller east-west faults which could further compartmentalise the reservoir.
It has been surveyed by four 3-D seismic surveys, in 1979, 1985, 1995, and 1996. Platforms were moved into place shortly after the 1985 survey, and production commenced in December 1986. The oil-water contact has moved upwards by about 50m since start of production, and is rising at about 13m per year.
Gullfaks supplies some 20% of Norway's production, delivering 585,000 bbl/day. Production peaked in 1994. There are 102 production wells, and 127 water injection wells.