Shell Curlew Mooring Replacement Project

Shell Curlew Mooring Replacement Project


Axis Energy Projects was contracted by DOF Subsea to provide Technical Management, engineering services and supervision to DOF Subsea’s team for the Shell Curlew Mooring Replacement project.  The objective for this fast-track Curlew Mooring Replacement Project was to change-out the upper mooring chains for the Curlew FPSO without first flushing and disconnecting the risers and umbilicals.  This presented significant challenges to the project due to the increased environmental hazards to be managed and the congested workspace for surface divers when working within the FPSO turret.  Nevertheless, the project was successfully completed within the allotted window, within budget and without injury or damage to asset infrastructure.


Work commenced in mid March to review information and prepare CTRs, a master document register (with list of deliverables) and a Basis of Design.  In parallel with this, method statements were prepared and long lead items identified and specified to enable orders to be placed.  Models of the existing and replacement mooring systems were created and used to analyse the sequence of operations for disconnection of the existing chain, and deployment and connection of the new chain, each including a section of dual chain.  With the required quantity of mooring chain taking the Skandi Iceman was close to her fully ladened capacity, loading plans were produced for mobilisation of the new chain and demobilisation of the existing chain and clumpweights on the Skandi Iceman.  These were further developed and refined, in conjunction with the vessel master, and the details fed into the mobilisation and operational procedures and equipment lists.  By late April, there was sufficient detail to enable an Operational Review to be convened to ensure buy-in from the whole team and to check that the required activities during mobilisation, air diving and chain handing were covered.  Comments from the Operational Review were addressed and procedures and storyboards issued in advance of the Project HIRA, a few weeks later.

The new permanent mooring equipment was offloaded in Dundee in early June, where it was identified, marked-up and laid out prior to being mobilised onto the Skandi Iceman.  Meanwhile preparations were underway on the FPSO for the dive system and mooring line winching activities.  Once heading control was established by the Skandi Admiral, all was ready for disconnection of the first mooring line on 20-June.

For each mooring line, the existing chain was disconnected and recovered onto the special handling drum; the 10 x 6.3Te clumpweights were removed and stowed on deck.  The socket on the mooring wire was cleaned and maintained and the new mooring components gradually assembled and deployed.  The top chain was cut to length and stoppered-off in the turret, before the process continued with the next mooring line.  There were some delays due to weather (mainly restricting diving activities), SIMOPs (with the Seven Atlantic also working in the field) and technical challenges with the FPSO Mooring Winch.  However, all 9 mooring lines were replaced and the partially buried clumpweights that had previously fallen off the existing mooring lines were moved clear of the new chains.


  • Liaison with the Client on technical matters throughout the project.
  • Development and review of CTRs and work packages.
  • Definition of variation order requests.
  • Management of the engineering team for the project.
  • Preparation of the Technical and Engineering Design Basis.
  • Prepared and review method statements, procedures, storyboards, drawings & equipment lists.
  • Participation in weekly project meetings and daily ops meetings.
  • Assistance and troubleshooting during mobilisation and operations.
  • Provided offshore engineering support and assistance.