The Gullfaks C platform in the North Sea. (Photo: Øyvind Hagen)
The incident entailed change in pressure and loss of drill fluid, which resulted in the loss of one barrier in the well. There was also uncertainty about the integrity of the remaining barrier. Statoil decided therefore to shut down production.
“We’ve now installed three cement plugs and one mechanical plug in the well,” says Rune Gaasø, acting head of Gullfaks drilling and well operations.
“This isolates the well from the reservoir and a high-pressure zone in the Shetland/Lista formation. The barriers are now intact, and we have given the green light for normalisation.”
Thorough risk assessment
A hole has been identified in a casing at a depth of 1,400 metres. The well is stable and has no leaks.
“We’re now going to work to seal the hole before we temporarily abandon the well and facilitate re-use of the well slot,” says Gaasø.
In the work to put the barriers in place in the well Statoil has used methods with the lowest possible risk of escalating the situation, with good support from various specialist entities in the company, as well as from contractors and external partners.
Comprehensive start-up plan
The Gullfaks organisation has prepared a detailed start-up plan which is more extensive than is normal after a planned maintenance turnaround, for instance.
Acting operations vice president Helge Kjell Rørnes is happy that the barriers are now intact and that the platform is approaching normalisation.
“The situation has been demanding and has involved many people,” he says.
“Our work has taken time but spending time making completely sure that we’re taking the correct measures was the right thing to do.”
Statoil has appointed an investigation team to examine the incident of 19 May. On the basis of the team’s report the company will be able to draw relevant lessons about making well constructions more robust.