A First In Mooring Pile Fabrication

InterMoor delivers the goods for floating production spar.

Flexibility and problem solving are two vital qualities for success in offshore operations. InterMoor engineers called on both these characteristics to complete a challenging mooring pile fabrication job: the first project certified to American Bureau of Shipping standards that the company has undertaken at its Morgan City yard in Louisiana, USA.

The mooring piles were required for the development of a deepwater oil discovery in the Gulf of Mexico. The field will produce from two drill centres tied back to an FPS, which has a permanent taut-leg moored system with nine lines secured by suction piles and a spare for contingency: each mooring pile is 5 m in diameter, 30 m long and weighs 175 t.

Winning the contract to build these suction piles was important for InterMoor, as Matt Morey the company’s project manager, explains: “The award of the mooring pile fabrication contract at the end of 2011 was a major step forward for our fabrication capabilities. For the first time on a project of this size, we would control all aspects of the fabrication, including the can-rolling operations. From the outset, we knew that the project would help us to develop new skills in fabrication.”

Can-rolling experience
This pile fabrication work was the first InterMoor project to make use of the company’s new can-roller system. For previous jobs, the company had subcontracted this operation and taken delivery of rolled cans for stacking and welding.

Morey says, “There was a steep learning curve on the can-rolling operations. We wanted to ensure that the programme went smoothly from the start, so we decided to bring in an expert familiar with the new equipment. One of the key tasks for this person was training another staff member so that we would have two fully trained roller operators to support future projects of this kind.”

Certification by the American Bureau of Shipping meant providing inspection access to the classification society’s engineers and project managers to ensure that the project ran in accordance with accepted standards. Much of this inspection work was at the beginning of the project to assess the systems and capabilities at the Morgan City yard before any rolling started.

Overcoming challenges
Throughout the project, InterMoor coordinated the various alterations and tweaks to ensure the quality of the final product. For example, during the fabrication work, it became clear that the planned padeyes would have to be changed. Modelling revealed a change in the stress profile with important implications for fatigue in the component. InterMoor immediately contacted UK specialist supplier Vulcan SFM to source the 10 cast padeyes necessary.

A delay in the FPS installation schedule as InterMoor was beginning to stack and weld the final assemblies meant that the company had to hold off on completing the assembly. “Rather than completing the 10-can stacks, we had to store the partially completed stacks in the yard,” Morey explains. “This was not a problem, as we had the capacity to keep all the partially completed materials on-site. When the installation programme resumed, all we had to do was complete the fabrication and make preparations to transport the piles to the field location.”

Logistical challenges
In October 2013, following factory acceptance and electrical continuity tests, the piles were ready for loading. Each pile was more than 30 m high with connectors attached and weighed in at 175 t, including chains, connectors and other elements.

“These are difficult objects to move safely and efficiently,” says Morey. “We had recently purchased a 600-t crane and were well prepared for the lifting operation. However, the barge that was selected for the job was, at 30 by 120 m, substantially larger than might normally be used for a job of this kind. This presented a loading challenge and meant that the operation was in three phases at two locations.

“The first step was to load most of the piles onto the outside edge of the barge at the Morgan City yard. The barge then moved to an Ocean Marine Contractors’ facility where a special crane transferred the piles to the centre of the barge. Then the barge returned to the Morgan City yard to load the last few piles onto the outside edge of the barge,” he continues.

On 22 October 2013, the piles left the InterMoor slip to complete nearly two years of work for InterMoor in Houston and Morgan City. They were installed one week later with no issues. The spare pile was not required and is currently stored in the Morgan City yard.

Learning from experience
“Throughout the project, InterMoor grew. We added equipment and personnel, refined processes and procedures, and developed new company standards and tracking systems that will enable us to undertake larger fabrication jobs and helped us to overcome the challenges of the project,” Morey concludes. “These were all great strides in improving our production facility capabilities and proof that InterMoor is ready for large-capacity fabrication projects.”

The success of this project has led to further work, for example, the fabrication and installation of 12 piles with DNV classification for LLOG Exploration’s Delta House semisubmersible floating production system in the Gulf of Mexico.

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