Global Marine Systems, a specialist in subsea cabling and engineering projects, has recently delivered a T&I (transportation and installation) of a Cable End Module (CEM) in the North Sea.
Global Marine’s project engineering department was tasked by Tampnet with demands that included pre-planning, interfacing with project stakeholders, design engineering and precision installation.
When the contract from Tampnet was awarded to Global Marine in October 2014, the initial concept design for the CEM was very different to what was finally deployed.
The design changes requested by the project engineers were important to allow successful installation given the tight parameters set by the client. Essentially, the CEM had to be installed within a set distance of a pre-installed SSIV (subsea isolation valve) to allow jumper cables to be connected by divers at a later date. Additionally, the operation was to be performed in close proximity to surrounding structures, which added further complications to the offshore execution.
Throughout the design process, the project engineering team was involved in review meetings with all parties, including the field owner, and visited the fabrication yard to ensure the changes incorporated were satisfactory for the CEM T&I project.
The team was also able to offer its expertise to design the installation rigging, which allowed the methodology for subsea release to be developed by Global Marine. When engineering the rigging for subsea deployment, it is important to have a contingency for subsea release in the event that the primary system does not work. For this project, Global Marine engineered a primary, secondary and tertiary method for releasing the CEM rigging, with the primary method, using ROV hooks, successfully working as planned.
A further important aspect of installing subsea structures is positioning on the seabed. On the Tampnet project, tolerances of ±2.5m for position and ±2.5° for heading meant Global Marine used a Sonardyne Ranger 2 USBL (ultra-short baseline) acoustic positioning and tracking system (with transponders fixed to the structure), while EIVA Navipac template software was used to ensure precise placement.
The CEM was installed successfully in April 2015, achieving all of the necessary installation tolerances.
The CEM deployment for Tampnet builds on Global Marine’s historical success in similar projects, such as the T&I of subsea nodes for scientific research at VENUS
Namely, Global Marine was selected as the project contractor to lay the foundation for the laboratory off the coast of Vancouver Island, British Columbia, Canada. First, the company completed a desktop survey identifying the optimum location for node and sensor positioning, which was followed by system installation.
The first phase involved the deployment of 40km of cable and two node bases in offshore waters just north of Vancouver International Airport. At the ocean observatory site, the second phase was completed with the installation of nodes at three previously identified sites. The node in the Saanich Inlet is located 95m below the surface, while in the Strait of Georgia there are two nodes, one at 300m in the central strait and the second at 175m towards the Fraser River Delta.