Page 24: of Offshore Engineer Magazine (Mar/Apr 2021)

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FEATURE SUBSEA TIEBACKS

Source: Equinor

Troll Phase 3 beneath the surface. to continue the operations, notes Steinar Helle, Troll Phase 3 were some of the largest spools it has ever manufactured and construction and commissioning manager. installed. “It was a world record being able to connect these

A large bore subsea production system was used to take the two pipelines. DeepOcean had to use both the Edda Freya’s gas from the reservoir through to the production facilities to vessel cranes simultaneously (for lifting and lowering this help minimize the pressure loss, so the existing power at Troll spool piece),” says Ramberg.

A didn’t need to be increased, notes Ramberg. The spools were installed using a subsea H-frame lifting tool

A 400m section was laid and pulled into Troll A through a in to align the two pipelines – tools, including a pig launcher pre-installed conduit using a 900mm wire fed up to a winch and receiver, which had been used at Aasta Hansteen some on the platform deck. The pipe was then connected to pre- years ago. The umbilical and MEG line were piggy backed installed risers using the pipe bends already available at the together and pulled through a J-tube installed at Troll A. bottom of the riser shaft. Once the rest of the pipeline was In total, the project clocked up about 650 vessel days, says installed it was then connected to the 400 m section via Ramberg. “It was a huge program, but a lot of pipe and steel a 90m-long, 36-inch diameter spool piece with 100-tonne went into the ocean,” he adds. “Troll Phase 3 is a genuine dry weight. kinder egg, providing a huge amount of energy with a very

According to DeepOcean the 36in spool and the 20in small CO2 footprint and it’s shown the subsea tieback is very spool installed at the well site end of the 36inch pipeline, proftable. Subsea technology is a part of the solution.” 24 OFFSHORE ENGINEER OEDIGITAL.COM