Subsea heating system

Nexans has been awarded an €11m (£9.7m) contract by BP Norgeto supply a direct electrical heating (DEH) system for the Skarv field subsea production pipeline in the Norwegian Sea.

The DEH system was developed through a partnership of Norwegian operators and suppliers, and Nexans is the only supplier so far to have delivered systems based on the technology.

It works by sending an electrical alternating current from a Floating Production Storage and Offloading (FPSO) vessel through a dynamic riser cable with two power cores to the seabed and into the production pipeline.

One insulated cable is connected directly to the pipe in the near end, while the other is laid along the pipeline in the direction of the template, or far end, where it is connected to the pipe.

Alternating current is supplied through the cable and returned partly via the pipe walls and partly through the seawater. This causes heat to be generated in the steel pipe, which ensures that the well flow is maintained above the critical temperature for hydrate formation.