Lagos — When a commercial vessel requires repair or refit work, time is critical; especially for those in the oil and gas sector, where even a single day off the water can result in costly downtime.
To maximize a project’s resilience to schedule or scope changes, Mammoet often uses its expertise to prove out several solutions to the challenge at hand.
This occurred when Mammoet was contracted by shipbuilder and ship repair company Damen Shiprepair to assist with a jack-up leg repair for the Noble Corporation drilling rig Noble Regina Allen.
Initially planned to be completed using one of Mammoet’s PTC large ring cranes, the project was instead performed by jacking-up the 22,000t drilling rig. With time ticking, Mammoet resourcefully navigated the project and came up with a solution to get the vessel back in service as soon as possible.
Three solutions; three teams
With offices in Rotterdam, Mammoet and Damen Shiprepair have a longstanding relationship that goes back more than twenty years.
As a trusted partner, Mammoet was invited by Damen Shiprepair to visit Noble’s offices in Houston and present three different methodologies for carrying out the repair work to the leg.
“The first option we presented was performing the lift using a Mammoet PTC210 crane,” explains Ruud Jansen, Commercial Manager at Mammoet. “It would see the crane positioned on the quayside and lifting and lowering the leg into the vessel from above.
The second approach was to bring a small crawler crane onto the deck of the vessel and have the repair carried out from above. The third solution was to lift the vessel using Mammoet’s Mega Jack 5200 system and carry out the repair from underneath.”
The Mega Jack 5200 has been used for jack-ups of great size and scale. The largest of these was a topside of 42,000t. It also offers quick mobilization and assembly, so this solution was chosen to fit the project schedule.
However, this would bring its own challenges, as Mammoet Project Manager, René van Lint, explains:
“We had to act quickly, especially as the drydock was only available for a relatively short period of time. Whereas normally we assemble the Mega Jack system in 15 days, we realized that we would have to do it in seven days.
“To achieve this, we scaled up and accelerated the schedule. This was possible due to our large fleet of equipment and by having a team of experts working in two shifts.”
Jacking and welding
The drydock was prepped and support blocks installed on its base before the 22,000t rig was floated inside. The dock was then drained, and the rig lowered onto the blocks. The team was then able to install the equipment underneath.
A configuration of six towers of the Mammoet Mega Jack 5200 were used, each with a capacity of 5,200t. Small mobile cranes and forklift trucks were used to assemble this equipment. Once all the jacks were in place, the rig was lifted to a height of 35 meters.
Because the leg section measured 70 meters tall, it was cut into two parts to fit underneath the rig. Each section was moved into position using Mammoet Self-Propelled Modular Transporters (SPMTs).
The first section was driven into position under the rig and then lifted by the rig’s jacking mechanism.
The process was then repeated for the second section, which was welded to the first by Damen Shiprepair, forming the complete jacking leg.
Team effort
Thanks to Mammoet being flexible and responding quickly to the client’s requirements, mobilizing the equipment and people needed to carry out the job in just three months, the downtime of the rig was significantly less than what it could have been.
“Damen Shiprepair are our neighbors and we have been working with them for a very long time on offshore-related projects,” says van Lint. “We work together closely, and this was especially evident during this project.
They trusted us and our methodology, and this has opened opportunities for similar projects to be carried out in the future, having showcased that this methodology is possible.”
