Shell unit uses S-Lay fairings for Independence Hub

Shell Global Solutions (US) Inc. and others have installed fairings during S-Lay installation of a 10-in. steel catenary riser pipeline in 8,000 ft of water.

By OGJ editors
HOUSTON, Feb. 16 -- Shell Global Solutions (US) Inc. and others have installed fairings during S-Lay installation of a 10-in. steel catenary riser pipeline in 8,000 ft of water.

Shell Global said this was the first successful such application of fairings.

The technique was used on Mississippi Canyon Block 920 in the Gulf of Mexico for Independence Hub, a semisubmersible platform yet to be installed. Initially, 10 gas fields will be connected to the platform, operated by Anadarko Petroleum Corp.

Shell Global Solutions is a network of technology companies. The crew of Allseas' Solitaire pipelay vessel and the Independence Hub project team also participated.

Helical strake devices previously were the only choice for installation during S-Lay operations. Pipe is rolled off a stringer, a structure on the ship that curves into the water.

By design, fairings rotate freely around the pipe and typically are unable to pass through the v-shaped rollers on the stinger.

Shell Global Solutions developed hardware and a rigging procedure that secured the fairing tail in a position away from the stinger rollers of the S-Lay vessel.

At the Independence Hub, polyurethane strakes would have provided too much pipeline insulation, and gas would arrive at the platform too cold for the processing equipment.

The gas is pressurized at the sea floor. As it rises and decompresses, it naturally cools and must be heated by the surrounding water.

Fairings, which allow water to flow around the pipe, were the only option to provide the necessary vortex-induced vibration suppression without the unwanted insulation.

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