An interesting concept called VersaBuoy Platform System could be used for a deepwater “fence” to protect future floating liquid natural gas terminals (FLNG) installations and other potential offshore targets all over the world. The key to the VersaBuoy system is the articulating connection between the supporting buoy hulls and the topside structure. The length and geometry of the buoy hull keeps heave to a minimum while the articulating joint decouples the pitch and roll motions of the buoys from the topsides keeping the topside structure stable and level. Multiple units could be linked together providing expandable offshore real estate.
The VersaBuoy System comprises of four spar-like, self-stable hulls supporting the platform topside through articulated redundant pin-in-pin connection. The unique application of the articulated joint between the columns and the topside allows the column rotation relative to the deck and consequently results in a dramatically reduced topside rotation. The VersaBuoy articulated joint is fixed between the top of each hull and the underside of the deck. This connection allows each hull to pitch and roll independently from the topsides. Each hull is sized and ballasted so it is stable and requires no other constraint or connection. Mooring is by either conventional catenary lines or a taut leg system attached to fairleads located on each hull.
According to the company, based on model tests, the VersaBuoy Platform System improves topside motions in harsh marine conditions by a factor of 5-10. The modal analysis of a single module showed a system deck heave period of 27 seconds and a deck pitch/roll motion period of 34 seconds. The model testing program considered a single module, two combined modules to form a single 250 by 500 ft (76.2 by 152.4m) module and a four-module combined to form a single 500 by 500 ft (152.4 by 152.4 m) module.
The application proposed by the company is for the protection of critical offshore assets such as FLNG. Protection is achieved through the use of a continuous ring-type structure located around the asset. The current rendition assumes mono-column buoys spaced at 250 ft centers with a clearance of 1,500 ft+ from the asset. The buoys support open truss bridge structures which in turn support a chain curtain lowered into the water to prevent small vessel passage. In addition, the bridge arrangement allows for continuous personnel access and monitoring around the perimeter. Supply and support vessel access is managed through the use of swing openings at several points around the perimeter. Supply and support vessel access is managed through the use of swing openings at several points around the perimeter. Buoy mooring is via a single tension leg to the seabed reducing mooring footprint and clashing with the asset mooring spread and riser and umbilical infrastructure.
