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Mooring Systems - Very Large Turret (VLT)

The Very Large Turret (VLT) provides a single point mooring solution for ship-shaped FPSOs in deep to ultra-deep water. It is applicable for large field developments requiring the use of a large number of risers.

 For deepwater developments requiring 40 to 100+ risers to an FPSO.
 For harsh and/or multi-directional environments requiring a robust weather-vaning mooring system.
 For large FPSOs designed for high production throughput (100,000 to 250,000+ BFPD).
 For developments with substantial pigging, injection, gas lift, monitoring/control requirements.
 For staged developments requiring an FPSO with large capacity for future tie-backs from multiple wells.

 Lightweight, flexible turret structure accommodating high dynamic loading conditions generated from large quantity of steel or flexible risers, multi-leg deepwater mooring attachments, and heavy on-turret subsystems.
 Spacious main deck accommodating large on-turret components such as manifolding, pigging, injection, monitoring and control equipment.
 Bearing system consisting of a proven AmClyde-type wheel and rail assembly for vertical loads and radial bearings for horizontal loads.
 Swivel system located within a swivel torque tube that eliminates lengthy swivel torque arms and freeing more space for other turret subsystems.
 Chain table and I-tubes that receive the risers and guide them to the upper turret structure. The chain table also provides a means of securing the mooring leg chains to the turret.

 Well suited for field developments with minimal or no subsea manifolding where each wellhead receives a dedicated riser bundle.
 The VLT's inherent structural flexibility results in an improved bearing load distribution.
 The turret's unique arrangement has a turret steel weight per riser ratio lower than other existing turret systems.
 The VLT's passive fully weather-vaning mooring design allows for tandem offloading, eliminating the cost and challenges associated with a deepwater offloading buoy.
 Applicable water depth for the VLT is 500 to 3000 meters.
 No riser shadowing (risers in the same radial direction), thus simplifying riser and installation changeout.
 The mooring system includes grouped anchor legs into sets providing large corridors for the risers to approach from the seabed to the FPSO.
 The VLT arrangement provides generous space for placing turret equipment, much of which can be skid mounted rather than engineered around the turret structure.
 The vertical, radial and lower bearings are simple configurations that allow easy access for inspection and maintenance.
 Removal and replacement of bearing components can be accomplished in-situ without disturbing the turret operation.
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