Blocks and production licences
- Block 2/4 - production licence 018, awarded 1965.
Development approval 01.03.1972
On stream 15.06.1971
Operator ConocoPhillips Skandinavia AS
- ConocoPhillips Skandinavia AS 35.11 %
- Eni Norge AS 12.39 %
- Petoro AS 5.00 %
- Statoil Petroleum AS 7.60 %
- Total E&P Norge AS 39.90 %
Original - Remaining as of 31.12.2011
- 552.7 million Sm³ oil - 120.9 million Sm³ oil
- 162.1 billion Sm³ gas - 21.5 billion Sm³ gas
- 14.9 million tonnes NGL - 2.1 million tonnes NGL
Estimated production in 2012
- Oil: 127 000 barrels/day
- Gas: 1.29 billion Sm³
- NGL: 0.15 million tonnes
Expected investment from 2011 84.8 billion 2011 values
Total investment as of 31.12.2010 84.0 billion nominal values
Main supply base Tananger
Ekofisk is an oil field located in the southern part of the North Sea. The water depth in the area is 70 - 75 metres. The field was initially produced to tankers until a concrete storage tank was installed in 1973. Since then, the field has been further developed with many facilities, including riser facilities for associated fields and export pipelines. Several of these have been decommissioned and are awaiting disposal. Today, the operative parts of the Ekofisk Centre consist of the accommodation facilities, Ekofisk H and Ekofisk Q, the production facility Ekofisk C, the drilling and production facility Ekofisk X, the processing facility Ekofisk J and the production and processing facility Ekofisk M. From the wellhead facility Ekofisk A, located in the southern part of the field, production goes to the riser facility Ekofisk FTP for processing at the Ekofisk Centre. The pipeline from Ekofisk B in the northern part of the field is routed to Ekofisk M. Ekofisk K is a facility for water injection. A plan for water injection at Ekofisk was approved in December 1983, a PDO for Ekofisk II was approved in November 1994 and a PDO for Ekofisk Growth was approved in June 2003. In June 2008 a subsea template for water injection wells was approved. These have replaced the water injection at Ekofisk W, which is no longer in use. In March 2010, the new accommodation facility, Ekofisk L, was approved. This will replace Ekofisk H and Ekofisk Q. Ekofisk L will be in operation from autumn 2013. Permanent cables have been installed on the seabed over the Ekofisk reservoir for acquisition of seismic data.
The Ekofisk field produces from naturally fractured chalk of the Ekofisk and Tor Formations of Early Paleocene and Late Cretaceous ages. The reservoir rocks have high porosity, but low permeability. The reservoir has an oil column of more than 300 metres and lies 2 900 - 3 250 metres below sea level.
Ekofisk was originally developed by pressure depletion and had an expected recovery factor of 17 per cent. Since then, limited gas injection and comprehensive water injection have contributed to a substantial increase in oil recovery. Large scale water injection started in 1987, and in subsequent years the water injection area has been extended in several phases. Experience has proven that water displacement of the oil is more effective than anticipated, and the expected recovery factor for Ekofisk is now approximately 50 per cent. In addition to the water injection, compaction of the soft chalk provides extra force to the drainage of the field. The reservoir compaction has resulted in subsidence of the seabed, which is now more than 9 metres in the central part of the field. It is expected that the subsidence will continue for many years, but at a lower rate.
Oil and gas are routed to export pipelines via the processing facility at Ekofisk J. Gas from the Ekofisk area is transported via the Norpipe Gas pipeline to Emden, while the oil, which also contains NGL fractions, is sent via the Norpipe Oil pipeline to Teesside.
Production from Ekofisk is maintained at a high level through continuous drilling of water injection and production wells from several facilities. A PDO for Ekofisk Sør was approved in June 2011. The project includes two new installations; Ekofisk Z, a production facility, and Ekofisk VB, a subsea template for water injection wells. Ekofisk Z is expected to start production in 2013.