The 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.

Applications

• 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.

Components

• 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.

Attributes

• 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.
• Modular construction methods and liberal tolerances are utilized in the construction of the VLT to provide cost savings and reduced construction time.