Subsea 7 takes Nexans DEH system deeper than ever before for Chevron's Lianzi project

Nexans, a worldwide expert in the cable industry, has been awarded a 25 million Euro contract by Subsea 7, a global leader in seabed-to-surface engineering, construction and services to the offshore energy industry, to design and manufacture the direct electrical heating (DEH) system for the subsea pipelines serving the Lianzi oil field development located in a unitized offshore zone between the Republic of Congo and the Republic of Angola. The Lianzi field is operated by Chevron Overseas (Congo) Limited.

The Lianzi fields tie back to the Benguela Belize Lobito Tomboco (BBLT) platform located in Angola Block 14. With a water depth between 390 and 1,070 meters, this will be the world's deepest DEH system.

The contract with Subsea 7 covers the delivery of a complete DEH system, including DEH Riser Cable, Armored Feeder Cable, a 43 km long Piggyback Cable and all associated accessories for connection to the pipeline that will connect the Lianzi Development Project subsea facilities with the BBLT platform. The Piggyback Cable incorporates Nexans' field proven Integrated Protection System (IPS).

Direct electrical heating (DEH) is a technology for flow assurance, developed to safeguard the wellstream through the pipeline to the platform. Alternating current (AC) 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, the pipeline inner wall can at all times 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 methods that might have environmental or operational challenges. DEH allows the pipeline to be operated in a cost efficient and environmentally safe manner.

Source: Nexans