Frigg cessation took ten years

Operating company Total has completed the largest removal project in the history of the Norwegian shelf. More than ten years have passed since work started to phase out the installations on the Frigg field in the North Sea.

Production from the Norwegian-British gas field ceased in the autumn of 2004, after 27 years of operation. One year earlier, the Norwegian authorities had approved the cessation plan for phasing out the five facilities on the Norwegian side of the field. The UK authorities did the same for the facilities on their side of the sector border

The work to prepare the cessation plan and secure the authorities’ approval took almost five years, according to Erik Hjelde, field cessation advisor in the operating company Total.

The field consisted of a living quarters facility (QP), two process facilities (TP1 and TCP2) and two drilling facilities (DP2 and CDP1).

According to the OSPAR convention, it was clear that the three steel jackets and all the topsides had to be removed. How to handle the concrete gravity base structures was more uncertain, and several alternatives were considered:

  • complete removal
  • dumping in deep water
  • cutting down structures to 55 metres below the sea surface to prevent obstruction to maritime traffic
  • abandoning them on site.

Extensive studies were needed, and were carried out in cooperation with the companies that designed the facilities. Experts from Sintef, Det norske veritas and a German university were also involved in verifying the studies. Technical feasibility, risk to personnel, environmental consequences and costs were evaluated.

Many involved
During the planning process, Total consulted frequently with environmental and fishery organisations in Norway and the UK.

”It was important for us to conduct an open, transparent process from day one,” says Hjelde.

”We often received good input and advice in our meetings with the various stakeholders.”

The company prepared a newsletter that was distributed to the stakeholders – written in a language everyone could understand.

The dismantling work started in 2005. In 2010, all topsides, steel jackets, pipelines and cables have been removed from the field. Two concrete gravity base structures in the UK sector and one in the Norwegian sector are all that remains.

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More than ten years have passed since work started to phase out the installations on the Frigg field in the North Sea.

Nearly 90,000 tonnes of steel have been brought to land for scrapping – some to the Greenhead base in the Shetlands, but most to Aker Solutions’ facility at Stord in Hordaland county. According to Hjelde, a dedicated environmental account was developed specifically for the removal project with the purpose of documenting that all the materials from the platforms – including hazardous waste such as asbestos – made it to the final disposal destinations. About 98 per cent of the material taken to land has been recycled or re-used.

A fishing boat trawled over the field in the summer of 2010 to check that no obstacles were left behind. This marks the completion of the project.

New knowledge
Hjelde explains that new knowledge and new technology have been developed during the work to remove the facilities.

New equipment had to be developed to measure the exact weight and centre of gravity in order to lift the 8000-tonne deck on the TCP2 facility. The 9300-tonne steel jacket, plus the DP2 module support frame, were lifted without using heavy-lift cranes and divers, but by fastening four buoyancy tanks to the steel jacket.

Toxic gases are formed in connection with hot work on painted surfaces. The protective gear for personnel performing this type of work was improved.

Material components from the steel platforms have been sent to a laboratory to examine corrosion and fatigue – information which could be useful for future development projects.

For Total, the project has yielded much useful experience.

”For example, the lifting lugs were the last thing to be removed in connection with the development, and the first thing that had to be installed when removing the platforms. If we plan for removal, such equipment will be maintained and inspected during the operations phase,” says Hjelde.

”We have learned that every new development must consider how the facilities can be removed. We must address the removal issue even in the development phase,” Hjelde concludes.