The field had originally been developed with pressure depletion as its drive mechanism, but this led to compression of the reservoir. Waterflooding in Eldfisk was based in part on horizontal injection wells, with gas also injected for periods.
Located in 68 metres of water, the Eldfisk reservoir lies about 16 kilometres south of the Ekofisk Complex. Five platforms are located on the field – 2/7 A, 2/7 B, 2/7 FTP, 2/7 E and 2/7 S. The Embla 2/7 D facility is tied back to 2/7 S by a flowline, and the combined output from the two fields is piped away – originally to Ekofisk 2/4 R, and then from 1998 to Ekofisk 2/4 J.
Eldfisk 2/7 E is a conventional steel platform with a jacket (support structure) fabricated at Aker Verdal, while the three-storey topsides measuring 55 by 35 metres were built by Aker Stord.
A bridge connects 2/7 E to Eldfisk 2/7 S, which operates the facility remotely. In addition to treating large quantities of water, the platform is equipped for gas lift and injection with a capacity of 120 million cubic feet per day.
Eldfisk 2/7 E was the world’s first offshore platform to use exhaust heat from gas turbines to generate electricity via a 10-megawatt facility.
This new waste heat recovery unit (WHRU) was installed in 2013 and utilises residual heat from five gas turbines to drive the water injection pumps and a gas compressor. Steam under high pressure and temperature is conducted to the existing turbine driving a generator.
Together with conventional diesel generators on 27/A, the WHRU installation supplies electricity to Eldfisk 2/7 A, Eldfisk 2/7 FTP and 2/7 E as well as the unmanned Embla platform.
The first water from Eldfisk was injected into the reservoir beneath Ekofisk 2/4 K on 31 January 2000. The 2/7 E platform has a capacity of 670 000 barrels of treated water per day. Roughly half of this is piped 25 kilometres to 2/4 K for injection at a pressure of almost 5 000 pounds per square inch (psi).
This helps to boost oil production and retard subsidence. The water is thoroughly treated to eliminate bacteria which can form hydrogen sulphide and thereby pollute the oil and gas in the reservoir.
Published 24. September 2017 • Updated 25. October 2019
The aim of this facility – an extension to the Ekofisk South project – was to increase waterflooding on the southern flank of the Ekofisk reservoir in order to maintain oil and gas production.
An amended plan for development and operation (PDO) of Ekofisk South was approved by the Ministry of Petroleum and Energy on 7 September 2017.
This involved installing a new seabed template with four water injection wells, and represented a continuation of the well-established Ekofisk production strategy based on waterflooding.[REMOVE]Fotnote: https://www.regjeringen.no/no/aktuelt/okt-utvinning-pa-ekofiskfeltet/id2570011/.
The template was installed in September 2017, with a technical solution similar to that used on the seabed facilities already installed – Ekofisk 2/4 VA and 2/4 VB.[REMOVE]Fotnote:Pionér, no 2, ConocoPhillips, 2018.
In addition to the structure itself, including wellheads and Xmas trees, the installation comprised control modules with umbilicals connected to the existing waterflooding system.
The 2/4 VC facility receives injection water from Eldfisk 2/7 E, while power and control signals come from Ekofisk 2/4 M. It is run from the Ekofisk 2/4 K control room.
When fully developed, overall injection capacity for this subsea installation will be 80 000 barrels per day through the four wells.
The water pipeline and umbilical to 2/4 VB were extended to 2/4 VC. Well operations on the latter began on 24 May 2018 with a view to starting injection before the end of the year.
Published 15. October 2019 • Updated 15. October 2019