Valhall Flank Water Injection Platform, Norwegian North Sea, Norway

The Valhall field was discovered in 1969 and came onstream in 1982. It is operated by BP (28.09%) on behalf of Amerada Hess (28.09%), Enterprise (28.09%) and TotalFinaElf (15.72%). At project sanction it had 247 million stock tank barrels of oil located in the Chalk reservoir. The field is due to become operational in 2010. Operator BP is building a new field centre at Valhall due to subsidence and the need to operate more efficiently.

The new centre will consist of an integrated processing and hotel platform and will receive power form shore via a 292km-long cable from Lista.

Plan for development and operation (PDO) was approved in the Storting June 2007. The project has awarded all the major contracts except contract for support with offshore hock up and preparation for start up.

The Valhall complex consists of four separate steel platforms, all bridge-connected.

The quarters platform (QP) was built in 1979 and put to use in July 1981. It has accommodation for 208 people.

The drilling platform (DP) is situated in the middle of the complex. It has 30 well slots. The platform started its activity on 17 December 1981, at that time with the first covered derrick.

The production platform (PCP) is built to process 168,000 barrels of oil and 350 million cubic feet of gas a day. The platform is 65m high and weighs 21,000t. The oil production is piped to 2/4-J at the Ekofisk Centre and goes to Teesside. The gas is transported directly via Norpipe pipeline to Emden in Germany. The platform also processes oil and gas that comes from Hod.

The wellhead platform (WP) was installed in April 1996 and first oil production started in June. WP has 19 well slots. Total cost, including drilling of the wells, is approx. NKr1.5bn. Drilling of the last few slots was planned to be completed by summer 2002.

Two new projects have been commissioned as part of the field redevelopment: the Valhall flank development and the wellhead injection platform.

VALHALL FLANK

Valhall flank development (VFD) consists of two unmanned wellhead platforms, each equipped with 16 drilling slots and located about 6km (one to the North and one to the South) from the existing Valhall facilities where wellstreams will be processed.

Initially, about eight wells will be drilled from each platform, one waste injector and seven producers. These eight wells are being drilled by West Epsilon in a timeframe that stretches from September 2002 throughout late October 2003. There is room for future water injection at either wellhead platform. The two wellhead platforms are to be powered from Valhall and monitored from the existing Valhall facilities via a fibre-optic cable.

Pipelaying for the north and south WHPs was performed as one continual operation during peak weather window in 2002. Heerema Tønsberg was principal contractor for the WHPs, however jackets were sub-contracted to Heerema in Vlissingen, Netherlands.

The 13% super chrome pipeline units specified were welded together by the pipeline contractor Coflexip Stena Offshore at their fabrication site in Orkanger, Norway before being reeled onto a vessel for offshore installation. Tie-in modification work to Valhall production platform was carried out by Aker.

WELLHEAD INJECTION PLATFORM

Water injection is expected to improve the oil recovery factor from 31% to 38%. This will yield roughly 29,000,000m³ in additional oil. The total investment for the project is likely to be NKr4.5bn.

The water injection project involves a fixed steel platform, linked to the existing Valhall wellhead platform. The integrated topside has water injection facilities, seawater and produced water treatment facilities and power generation. There is also a platform-based drilling rig, which can skid on beams from the wellhead platform to the wellhead injection platform, including a mud mixing module.

The platform configuration allows for drilling and maintenance of wells on the new platform (24 wells in total) and on the existing WP platform. The 4,000t platform was due to be installed by the heavy lift vessel Saipem S7000, however the company had difficulty driving some of the piles securing the jacket to the seabed. Once the piling is finished, the 9,500t topside will be installed.