Existing subsea pipelines in the North Slope area of Alaska are very difficult to replace.
The cost of shutting down a corroded line is substantial, requiring an extensive permit process and completing work before the coldest months of the year. ENI needed to come up with a plan to replace their existing line with minimal impact, eventually settling on the idea of inserting a 10” pipeline inside their existing 14” pipeline.
One of the primary challenges encountered in the North Slope was the extreme weather, with very low temperatures, high winds and snowstorms being the norm. Another challenge was the collection of AUT coupling to comply with environmental regulations.
Finally, there were unique logistical challenges in getting trucks and supplies to the project site, given the lack of infrastructure and communications on the route from Fairbanks to the North Slope. Temperature fluctuations were also very difficult to overcome. The truck canopy was insulated with Styrofoam, while heaters and biodegradable antifreeze were added to the AUT coupling system to prevent it from freezing solid.
During the tie-in phase of the project, an enclosure was built to ensure that the reference block would remain at same temperature as the welds for inspection: if the block was too cold, the welds could not be scanned on time. With high winds from the Arctic Ocean, portable wind blocks were constructed to protect the welds and the reference block during scanning.
Despite these challenges, the project was a success. It was a first for the industry and opens the door for other pipelines to be replaced in the same way.
Applus+ was integral in delivering a safe, high quality product, demonstrating its capability to meet the challenges specific to pipeline inspection in the North Slope area of Alaska.
Having learned valuable lessons in working successfully in extreme conditions, Applus+ looks forward to applying this learning to future projects.