AMOG contracted to assist during the development of a column turret mooring system to be integrated into an FPSO at a ship yard in Singapore.

AMOG's scope of work included detailed design verifications of work done undertaken by another offshore company, as well as review and approval of documentation to be submitted to the classification society (DNV) in accordance with the POSMOOR and 1A1 class notations. 

The FPSO operated in close proximity to the Eastern Pacific typhoon corridor. The weather patterns here are monsoonal in nature, with the prevailing monsoon winds blowing from the SW and NE. ROI intended to replace the existing SALM system aboard Intrepid with a permanent mooring system to avoid numerous disconnections during the monsoon season.

The turret had capacity to accommodate up to 4 risers and 2 umbilicals, in preparation of phase 2 of Galoc field development, supported from inside the turret. Station keeping was via the 9 mooring legs, arranged in a 3x3 configuration, each leg comprising chain-polyester rope-chain from the fairlead to a drag anchor. the 5000psi fluid swivels were installed for transfer of produced fluids from the wells to the process equipment. In addition suitable hydraulic and electrical swivel paths are provided for vessel and subsea controls. The FPSO was free to weathervane through 360°.

AMOG was involved from the early stages of the column turret mooring system design development through to fabrication and DNV approval. The following specific tasks were performed:

  • Development, review and approval of design load reports, including marine loads, turret breakout forces, bearing loads, green water and wave slamming loads, hull girder bending moments and shear forces
  • Development, review and approval of the design basis and structural design brief
  • Development, review and approval of structural detailed design, including outer turret and cantilevers, chain table and inner turret, fairleads, foreship modifications, slewing bearing supporting structure, turret and foreship fatigue assessment, gantry, bulwark, and secondary steel
  • Review and approval of specifications for cathodic protection, slewing bearing, I-tube pull test piece, installation winch and HPU, bend stiffener latch mechanism, lower bearing pad, wire rope, bend stiffener, production riser, fairlead, chain stopper, coating, swivel stack and ancillaries, mooring chain, wire rope, drag anchor, and electro-hydraulic umbilical
  • Review of forepeak structural condition survey
  • Review and approval of turret project execution plan, turret construction and integration scope of work, and turret fabrication specification
  • Review and approval of turret weight report and MTO