Maersk Oil’s maintenance programme
- The Danish North Sea diving work is part of the regular maintenance across Maersk Oil’s operations, and it seeks to ensure the protection of the facilities and minimise unplanned production losses.
- It is sometimes necessary to close down production to carry out more extensive work to keep the installations in top condition. This is done every fourth or fifth year; the most recent in the Danish North Sea was a 12-day planned shutdown in June 2014.
- This year in particular, major work is being undertaken across many production areas including the shutdown of all platforms in the Al Shaheen field in Qatar and GPIII in the UK for 60 days
In the murky waters far below the surface of the Danish North Sea, divers methodically review Maersk Oil’s production facilities. They check for and repair potential fatigue cracks in the primary structures, risers and pipelines in work that is carried out twice a year. It is demanding, requiring up to eight hours per shift for a maximum of 28 days for saturation divers, but vital for ensuring that Maersk Oil’s assets remain in top working condition.
It is no less tough when the saturation divers are not at work – as they live in a small isolated chamber kept at the same pressure as their work depth. The living chamber is however equipped with communications equipment and internet to stay in touch with the world outside.
“You need to be mentally strong to live together with strangers in the confined living chambers,” says Jan Bjarnø Lauridsen, who works in the Inspection, Repair and Maintenance (IRM) department at Maersk Oil’s Danish business unit in Esbjerg. Yet their sterling efforts are essential for the safe working conditions of those above the water manning the platforms, and they help to ensure production for years to come.
For work at depths down to 30 metres, divers breathing air can make single trips down and remain underwater for a given time dictated by dive tables. At a greater depth, the decompression process makes that process too inefficient and that’s where the saturation divers take over. They are lowered safely to their work points in a pressurised diving bell.
“There is quite a big team on the vessel to ensure the divers are working safely and effectively, and that everything is ok at all times,” says Lauridsen, who handles the practical planning and operation of the diving work.
“You can replace someone if there is a problem, but it is not easy due to the depth that saturation divers are living at, as a decompression from their storage depth and back to the surface takes days. However a medic can be pressured down relatively quickly and enter the saturation chamber to assist in case of problems.”
Jesper Smedemark, who works in the Structures Department, is responsible for the preparation and issue of Inspection Plans (I-Plans) and then handing the information over to Lauridsen in the IRM department. The I-Plans pinpoint the stress points in the installations’ structures most likely to suffer from fatigue cracks, which divers then investigate manually and repair if necessary.
A fatigue crack tip is infinitely sharp, causing large stress concentrations at this spot. Hence the crack must be removed or it will grow larger. The divers use a grinding tool to remove the surface cracks according to established procedures, and subsequently the area is kept under monitoring, Smedemark explains.
“We have biannual mobilisation and by targeting the most critical structural parts periodically, we maintain the safety level of our structures at not less than we originally designed them to be.”
What this adds up to is a vital cog in a wider operation to ensure Maersk Oil is playing to its strengths while maintaining its focus on safety.
Shut down for 12 days
Production at the Danish production sites was shut down in June for 12 days for checks on essential equipment and a major upgrade, during which two flare towers and a bridge were replaced on the Tyra Fields, the export hub from which most of Denmark’s gas transportation stems. Regular maintenance work is also being carried out this year in Qatar and the UK. And it’s not just Maersk Oil that focuses on keeping everything in top shape; the Group’s drilling contractor, Maersk Drilling, has an extensive yard stay programme in 2014. Rigs undergo service and upgrades and some also have their lifetimes extended, ensuring compliance and more efficient performance.