Nexans, the worldwide leader in the cable industry, has been awarded an 11 million Euro contract by BP Norge to supply a direct electrical heating (DEH) system for the Skarv field subsea production pipeline in the Norwegian Sea. Nexans is the only supplier with experience of this unique technology and has already supplied this type of system for 17 subsea pipeline installations. “DEH is a reliable, eco-friendly and cost-effective method of maintaining flow in production pipelines and there is increasing interest in electrical pipeline heating from a variety of companies and projects”, says Patrick Barth, High Voltage Activities Managing Director.
A 12” diameter production pipeline will be installed from one of the production wells at the field to the Floating Production Storage and Offloading (FPSO) vessel at Skarv. The distance between the well and vessel is approximately 13 km. At low production and shut down scenarios, a DEH-system will be used thus preventing blockage of the pipe. A number of methods may be used for maintaining flow, such as chemical injection, but DEH has proved to be both a reliable and eco-friendly solution to the problem.
Nexans will supply all cables and dedicated sub-sea equipment for the DEH system. The cables will be manufactured at Nexans’ Halden factory in Norway and should be delivered for installation in the spring of 2010.
The DEH system was developed through a partnership of Norwegian operators and suppliers, and Nexans is the only supplier so far to have delivered these systems. StatoilHydro is a major user of this technology and the Åsgard, Huldra, Kristin, Norne, Tyrihans, Alve and Morvin fields all now have Nexans DEH systems installed.
How does DEH work?
The DEH principle works by sending an electrical alternating current from the FPSO through a dynamic riser cable with two power cores to the seabed and in to 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 (far-end) where it is connected to the pipe. AC 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.
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