BP’s request to extend the operating life of the Valhall field quarters platform (QP), has been denied by the Petroleum Safety Authority Norway (PSA) stating that BP has failed to define realistic acceptance criteria for non-linear analyses.
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Valhall. From BP. |
BP currently has permission to use Valhall QP for accommodation until 31 December 2014. Valhall is a giant oilfield located in the southern Norwegian North Sea, in 70m water depth.
"The PSA considers that BP has underestimated the wave crest heights and the loads from steep waves. When determining demanning criteria, BP has failed to take account of higher-order waves and area effects. Based on the information provided by BP, the PSA cannot see that Valhall meets an acceptable level of safety which finds expression in the requirements for load-bearing structures as specified in section 56 of the facilities regulations on load-bearing structures and maritime systems, with guidelines, see also section 11 on load/actions, load/action effects and resistance, with guidelines,” the PSA said in a statement.
The supermajor applied for the PSA’s consent to extend to 31 December 2017, and thereafter as an end platform for escape and evacuation until it goes out of service. BP also requested to continue operating the facility with a demanning procedure for high waves, and to shut down the facility from 20 December to 15 February 2015 in order to avoid one of the months with the greatest probability of high waves.
The collapse of Valhall
Due to many years of oil and gas production, the Valhall reservoir has become compressed, causing the seabed to subside. The PSA says this subsidence means that the base of the topside on Valhall QP is nearer the sea surface than before, and no longer satisfies the air-gap requirements.
According to the PSA, previous to this extension request, BP applied for extensions for Valhall QP on several occasions.
The PSA says these applications were primarily justified by the need for accommodation capacity on the field until the new Valhall PH process and hotel platform became operational, and for preparing and executing well work on Valhall DP. The PH facility became operational in January 2013.
Valhall
The Valhall QP was built in 1979 and put to use in July 1981. According to Valhall’s plan for development and operation (PDO), the design life was 20 years.
The field was original developed with three facilities, but now has eight platforms. The Valhall complex consists of six separate steel platforms for quarters, drilling, wellheads, production, water injection, combined process- and hotel platform, respectively. The field also has two unmanned flank platforms, north and south, both 6km from the field center.
In January 2013, BP announced the successful start-up of oil production from new facilities at the Valhall field. At that time, BP's Bob Dudley said the Valhall redevelopment project was one of the company's most complex field expansion developments and gives Valhall a further 40-year design life with the capacity to handle 120,000bbl and 143MMcf/d of gas. The redevelopment project is expected to extend production from the field to 2050.
An inquiry for comments from BP have not been answered as of the writing of this article.
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