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Disconnectable Riser and Mooring Systems for Semi‐Submersible FPU

IP.com Disclosure Number: IPCOM000245425D
Publication Date: 2016-Mar-08
Document File: 6 page(s) / 187K

Publishing Venue

The IP.com Prior Art Database


For certain offshore applications where the environmental conditions (e.g., ice and iceberg) could be challenging to the Floating Production Unit (FPU)'s mooring/stationkeeping system, and the FPU is required to have disconnection capability for safe operation. Semi‐submersible Floating Production Unit (Semi‐FPU) is a mature technology for the offshore oil & gas industry. However, to‐date there is no known disconnectable Semi‐FPU in operation. This document described four (4) different methods for riser and mooring disconnections, which will enable the Semi‐FPU to disconnect and move away from the field in adverse environmental conditions. The four methods are: (1) A disconnectable buoy connected to one column of the Semi‐FPU; (2) A disconnectable buoy attached to an above‐water platform on the Semi‐FPU; (3) A disconnectable buoy attached to the Semi‐FPU at the pontoon level; (4) A Semi FPU connects to a turret moored ice classed/ice‐strengthened DP assist vessel.

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Disconnectable Riser and Mooring Systems for Semi‐Submersible FPU 


For certain offshore applications where the environmental conditions (e.g., ice and iceberg) could be  challenging to the Floating Production Unit (FPU)'s mooring/stationkeeping system, and the FPU is  required to have disconnection capability for safe operation. Semi‐submersible Floating Production Unit  (Semi‐FPU) is a mature technology for the offshore oil & gas industry. However, to‐date there is no  known disconnectable Semi‐FPU in operation.    

This document described four (4) different methods for riser and mooring disconnections, which will  enable the Semi‐FPU to disconnect and move away from the field in adverse environmental conditions.  

The four methods are: 

(1) A disconnectable buoy connected to one column of the Semi‐FPU; 

(2) A disconnectable buoy attached to an above‐water platform on the Semi‐FPU; 

(3) A disconnectable buoy attached to the Semi‐FPU at the pontoon level; 

(4) A  Semi FPU connects to a turret moored ice classed/ice‐strengthened DP assist vessel. 


Main Body 

For certain offshore applications (e.g., area with seasonal ice and iceberg intrusion) the FPU is required  to have disconnection capability for safe operation. Industry has mature experience using ship‐shaped  FPSO with disconnectable turret, such as Terra Nova and Sea Rose FPSOs currently in operation at  Hibernia.  However, a disconnectable turret is a long‐lead item and is also a significant CAPEX cost‐ driver.  Disconnectable Semi FPU, combined with SubSea Tank & Offloading (SSTO) system, may offer an  alternative to the disconnectable FPSO option. Semi FPU may also supplement a field development with  FPSOs. A disconnectable Semi‐FPU may offer both cost incentive and schedule benefit. Figure 1 shows  example base‐case and alternative configurations for offshore field developments where disconnectable  floater is required, using disconnectable floating production units (FPSO and Semi‐FPU).  

Details of Invention 

This document described four (4) different methods for riser and mooring disconnection, which will  enable the Semi‐FPU to disconnect and move away from the field in adverse environmental conditions.  

The four methods are: 

(1) A disconnectable buoy connected to one column of the Semi‐FPU 

(2) A disconnectable buoy attached to an above‐water platform on the Semi‐FPU 

(3) A disconnectable buoy attached to the Semi‐FPU at the pontoon level 

(4) A  Semi FPU connect to a turret moored ice classed/ice‐strengthened DP assist vessel 


After di...