Statoil has initiated an investigation after the gas leak that occurred at Visund on April 9. The gas leak occurred in a riser carrying oil and gas from well A21 to the Visund platform.
On Friday April 8, Statoil decided to shut down production from the Visund field to carry out inspections on the risers, after damage to the inner layer of steel that protects the pressure barrier was found in some of the risers at Njord. The risers carry oil and gas from the production wells to the Visund platform. Some of the steel pipe risers on Visund have design and operational similarities to those at Njord.
On Saturday April 9, gas was observed on the sea surface near the Visund platform, and the emergency preparedness organisation was immediately mobilised. The gas emanated from a leak in a riser that had been closed for inspection. The leak was stopped, and the situation normalised. Production was at this time already shut down, and the volumes that leaked out were limited.
Investigating the incident
There were no injuries to personnel in connection with the incident, and before the extent of the leak was determined, personnel without emergency duties were evacuated to nearby installations. Once the source was identified and the leak halted, evacuated personnel were returned to the platform. However, production remains shut down awaiting further inspection of the risers.
“ Statoil is investigating the incident, and will also support the Petroleum Safety Authority (PSA) in their investigation of this incident. Safety is our first priority, and through our investigation we wish to secure further knowledge to avoid this type of incident in the future ,” says Executive Vice President for Development and Production Norway, Øystein Michelsen.
Similar risers
Snorre B has the same technical solution for risers as those on Visund and Njord, but these have already been inspected, and three of the pipes have been replaced. There are also equivalent risers in operation on five other installations where Statoil is operator: Veslefrikk, Snorre A, Norne and Åsgard A og B. The risers on these installations have other technical solutions and other operational conditions than Visund and Njord. This reduces the probability of a change in pressure leading to damage to the risers.
There are no observations that would indicate that any other risers are damaged at this time. Statoil has carried out a risk assessment of all such risers on other platforms, and we do not consider there to be any danger from continued production from these installations. However, the company will re-evaluate these risk assessments in the light of yesterday’s incident.
Risers on all of Statoil’s installations are subject to constant monitoring and routine inspections in accordance with the applicable inspection programmes.
[mappress] Source:statoil , April 10, 2011;