Nexans heated cables to protect Lianzi subsea pipeline
Subsea 7 has awarded Nexans a $33-million contract for Chevron’s Lianzi oil field development.
The Lianzi fields, in a unitized offshore zone between Republic of Congo and Angola, will be tied back to the Benguela Belize Lobito Tomboco (BBLT) platform in Angolan block 14.
Nexans will supply what is claimed to be the world’s deepest water direct electrical heating (DEH) system to date, in depths between 390 and 1,070 m (1,279-3,510 ft).
The company will supply a comprehensive package including a DEH riser cable, armored feeder cable, and a 43-km (26.7-mi) long piggyback cable incorporating an integrated protection system. These will be connected to the pipeline linking the Lianzi subsea facilities with the BBLT platform.
DEH was developed to protect the well stream as it courses through the pipeline to the platform. Alternating current transmitted from the DEH cable runs through the steel in the pipe, which heats up due to its own electrical resistance.
By controlling the current, Nexans says, the pipeline inner wall can be maintained above the critical temperature for wax and hydrate formation. The DEH system eliminates the need for chemical injection, pressure evacuation or other flow assurance techniques that might have associated environmental or operational issues.
The Lianzi DEH cables will be manufactured at the Nexans factory in Halden, Norway, for delivery in summer 2014.