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Disconnectable FPSO vessels

 

Depending on location, climate and the expected lifetime of the oil or gas field it might be preferable to have a disconnectable instead of a permanent FPSO. FPSO’s in the North Sea are normally permanent and designed for 100 year storm conditions. Offshore facilities in the in the Golf of Mexico (GOM) are also mainly permanent but are generally evacuated in advance of a hurricane. A detailed operation contingency plan with predesignated weather conditions, determines when operations should be suspended. Continuing work during storms is of course more effective than evacuating but requires more of the facility because it should remain a safe work environment during storms. Evacuation is not always safe either. Distance to shore can constrain the evacuation and brings increased risk of loss of life because of accidents during the evacuation.

 

A solution is found in disconnectable mooring systems. These systems offer an operator the ability to evacuate personnel and assets to avoid damage during harsh environmental conditions, such as hurricanes, typhoons and icebergs. After the weather has subsided sufficiently the FPSO can return and reconnect.

 

Turrets

Turrets are generally used to create a disconnectable system. The installation will take place in two phases: First the installation of the turret and its mooring legs. The second phase is the establishment of the connection between the vessel and the turret. By rising and lowering the buoy the turret can easily be connected to the vessel.

 

 

Hawsers between tower and vessel

 

 

Disconnectable Riser Turret Mooring (RTM)

External turret

 

Internal turret