A combined production, drilling and quarters (PDQ) platform was initially envisaged by the plan for development and operation (PDO) of Valhall submitted on 4 October 1976. In addition came a small compressor platform with a bridge to the main structure.
In a series of letters, the government requested clarification of certain safety issues. These questions prompted the Amoco/Noco group to drop the PDQ and compression platforms. Instead, it proposed a combined drilling and quarters (DQ) platform with a process and compression (PC) structure. This solution still included a bridge to link the two units.
Although the Storting (parliament) approved this solution, the Norwegian Petroleum Directorate (NPD) remained dubious about its safety. The final plan approved in September 1977 comprised three platforms – including a stand-alone QP. Netherlands Offshore Company (NOC – acquired by McDermott later in 1979 – won the main contractor job for design and construction of this accommodation facility.
Stord Verft north of Stavanger built the steel jacket for the QP, which was installed on the field in March 1980 – one year before the other platform components were ready.[REMOVE]Fotnote: Myklebust, Alf Terje, 75 år på Kjøtteinen: 1919-1994: jubileumsbok for Aker Stord , Bergen, 1994, 209. The Franco-Norwegian UIE/Sterkoder partnership fabricated the module support frame, while the Vigor yard at Orkanger near Trondheim built the modules and carried out hook-up work.[REMOVE]Fotnote: Kostnadsanalysen norsk kontinentalsokkel , volume II, 275–276.
A temporary fifth storey containing 19 two-berth cabins was installed beneath the helideck in 1981-82, boosting the platform’s accommodation capacity to 208 people.
This extension was only intended for use during drilling on the field, which was expected to take no more than a few years but actually lasted longer than planned.
With work on six additional wells in 1989, the fifth storey became permanent. This is still in place, although the QP’s capacity has been reduced and it operates only in the summer.
The seabed under the Valhall platforms turned out to be affected by subsidence, although the position was not as critical as on the neighbouring Ekofisk field.
A careful eye nevertheless needed to be kept on developments, and the possibility of special measures had to be borne in mind (see separate article). Plans are currently being laid to remove the QP in the 2019–2025 period.
The steel jacket is 90 metres high, has four legs and weighs 3 000 tonnes, including the piles holding it to the seabed. With modules, the topside weighs 5 100 tonnes in all, measures roughly 36 x 29 metres, and is 23.5 metres high.
The QP was originally built in four stories and also incorporates a large crane, helideck and helicopter hangar.[REMOVE]Fotnote: Kostnadsanalysen norsk kontinentalsokkel volume I, 230.