InterMoor completes chain tensioning, cutting on Stones FPSO in the Gulf of Mexico

Offshore staff

HOUSTON InterMoor, an Acteon company, has completed the final tensioning and chain cutting operations on the FPSO Turritella for Shell’s Stones project in the Walker Ridge protraction area in the Gulf of Mexico (GoM).

Having arrived in January 2016, the Turritella is a disconnectable turret moored FPSO with nine mooring lines consisting of chain and polyester, arrayed in three bundles of three. The mooring lines were attached to a disconnectable buoyant turret mooring (BTM) buoy in field, awaiting the FPSO’s arrival. Each mooring leg has an in-line mooring connector (ILMC) tensioning system, located approximately 900 ft (274 m) below the surface, which was pre-tensioned after connection to the BTM.

Once the Turritella arrived, and the BTM was recovered by the FPSO, InterMoor’s work scope consisted of chain final tension adjustments through the ILMC system, subsequent cut and removal of excess chain, and riser pull-in rope stretching and transfer to the FPSO.

The company used the Seacor Keith Cowan anchor-handling vessel to perform the first phase of the operations and later moved to a larger construction vessel already on charter and on standby.

Tom Fulton, global president, InterMoor, said: “We were able to successfully provide full project management and engineering, including: design, procedures, procurement, dock support, offshore equipment and personnel for all phases. Our team also designed installation aids and fabricated them in our Morgan City facility, in Louisiana.”

Acteon sister companies worked alongside InterMoor on the project. UTEC provided the positioning survey for the vessel and Mirage custom-designed and fabricated the diamond wire cutting saw and clamping system.

InterMoor also provided the following services for the Turritella installation:

  • Provision of tow masters on-board the FPSO  
  • BTM buoy clump weight rigging removal
  • Dock and equipment support to Shell contracted heading control tugs
  • FPSO heading control steering lines design, procurement and offshore installation
  • Dive support vessel mooring design, procurement, and offshore support for hook-up and disconnection.

The FPSO Turritella will connect to subsea infrastructure located beneath approximately 9,500 ft (2,896 m) of water, breaking the existing water depth record for an oil and gas production facility. This ultra-deepwater project marks the first FPSO for Shell in the GoM, and the second FPSO in the GoM


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FPSO Turritella
The Turritella is a disconnectable turret moored FPSO with nine mooring lines that will work for Shell in its Stones field in the ultra-deepwater Gulf of Mexico. (Courtesy InterMoor)

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