The Gullfaks Field is located in the Norwegian Sector of the North Sea, block 34/10, and currently has the capability of producing more than 70,000 Sm3/d of oil (440,000 stb/d) from three CBS platforms. The reservoir sands comprise shallow marine to fluvial sediments of the Cook Formation, Statfjord Formation and Brent Group, ranging in age from Early to Middle Jurassic. Water injection is the major drive mechanism for maintaining reservoir pressure above bubble point.
Development wells have confirmed a complicated structural picture with numerous faults beyond seismic resolution, causing major impacts on predicting field reserves and flow patterns. Reverse faulting in an area of predominantly normal faulting further emphasises the structural complexity.
Complex geology along with field performance after water breakthrough resulted in several changes in the initial development strategy. Production from the highly productive Tarbert and Statfjord sands was accelerated in order to compensate for the loss of production from the Lower Brent sands caused by sand production after water breakthrough. Development of complex Ness and low productivity Cook sands have recently commenced.
Gravel packing, implemented in the Upper Brent field development, provided sand control and increased production rates. Various types of chemical sand control are currently being evaluated and tested in the field. Lowering pressure in gravel packed wellbore region below bubble point may increase the production rates even further.
Following advances in drilling technology, highly deviated/horizontal wells improve recovery and accelerate field development by combining production from several reservoirs in one single well. A test programme for surfactant and WAG flooding has been implemented on the field. Other EOR methods, such as gel and polymer flooding, are currently being investigated for potential use.