Oil & Gas

Case Study

Inter platform fibre connectivity in the North Sea, linking the Valhall and Clyde platforms

Valhall and Clyde

Global Marine Systems Limited was contracted by North Sea Communications for the marine installation works for the NSC-FOC-EXT-Clyde cable system. The cable network provides capacity services for the Valhall and Clyde platforms and incorporates approximately 110 kilometres of fibre optical cable installation.

The cable connects the NSC’s blind-end west of the Valhall platform to the Clyde platform, with an extension to a planned blind cable end near the Judy Platform. In addition to this, the project required the installation of a branching unit.

The installation took place in October 2008 and the completion to the Judy Platform took place a year later in 2009.

Project overview

• Vessel: CS Sovereign
• Submersible: Atlas and Hi-Plough
• Location: North Sea Cable
• Length: 110km

CS Soveriegn

The Challenge

The main lay installation operations were carried out by the C.S. Sovereign; utilising Global Marine’s state of the art subsea equipment using both the Hi-Plough and Atlas ROV.

The project involved cable plough installation to 1 metre below the seabed and a scope of work which included six pipeline crossings and a J-tube cable pulled through to the Clyde platform as well as a branching unit deployment.


Ship: C.S. Sovereign is one of the most advanced offshore engineering ships of its kind in the world. At 130 metres in length, DPS-2 C.S. Sovereign is capable of handling the wide variety of subsea tasks required by such diverse industries as telecommunications, oil & gas, and deep sea research.

C.S. Sovereign has worked on numerous projects, which include: Fibre to Judy in the North Sea providing installation services to the oil & gas market, SGSCS FOC installation in the Caribbean as well as undertaking charter contracts supporting a diverse range of offshore projects.

Submersibles: Atlas is a state of the art, ultra heavy work class remotely operated vehicle (ROV) designed for intervention, trenching, umbilical and power cable maintenance, post lay and inspection roles. With 400Hp of installed power Atlas ROVs have substantial intervention capabilities, and an operating depth range down to 2,000 metres.

Atlas completed a dive time total of 273 hours completing post lay inspection and burial work operating in soft sand to dense sand shale. Hi-Plough, has been designed to operate to depths of 1,500 metres and is capable of installing cable, repeaters and cable splice boxes. The plough is equipped with a cable tracking system and forward obstacle avoidance sonar.

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