4D Seismic and Through Tubing Drilling and Completion Wells Extend Life on the Gullfaks Field

摘要

The Gullfaks Main Field is one of the largest oil fields in the Norwegian sector of the North Sea. Production started in 1986 and reached a peak in 1994. Today approximately 90 % of the base reserves have been produced from this mature field. Locating remaining oil reserves is therefore a challenging and important task for the future of Gullfaks. The reservoirs are comprised of middle and early Jurassic sandstones, possessing overall excellent reservoir properties. The structural setting of the field is complex, and represents one of the main factors of uncertainty concerning the drainage of the field. The paper describes how multiple time-lapse seismic (4D) have proven very accurate in identifying undrained oil pockets in the Brent Group. The importance of 4D/4C in the wells drilled is estimated to represent a reserve oil volume of approximately 4 Mill. Sm~3 per 2004, (25 Mill. Sbbl). TTD&C (Through Tubing Drilling and Completion), being a more flexible and less expensive technology, has also been crucial in reaching smaller oil pockets on the Gullfaks Main Field. The potential offered by these technologies has been optimized by multidisciplinary teamwork on Gullfaks, thus creating synergy and flexibility. These three key elements have contributed to reverse the oil production decline, establish a new plateau, reduce costs and increase profit.