Direct Electrical Heating (DEH) is a flow assurance technology developed to safeguard the well stream through the flowline to the platform. Alternating current transmitted via the cables returns through the steel in the pipe, which heats up due to its own electrical resistance.
Nexans developed this technology in cooperation with Statoil and SINTEF in the 1990s. The collaboration led to the first DEH project Asgard.
The DEH system may consist of the following components:
DEH Riser Cable
The DEH Riser Cable supplies power from the platform down to the sea bed. It can be designed for one or more systems and may include hydraulic tubes and signal cables. The cable is designed, produced and tested by Nexans.
Armoured Feeder Cable
The Armoured Feeder Cable connects the DEH Riser Cable to the pipeline and to the Piggyback Cable. The cable contains two conductors, one connected to the pipeline at the platform end and the other connected to the piggyback cable.
DEH Piggyback cable
The DEH Piggyback Cable conducts current from the platform end to the far end of the pipeline. At the far end, the Piggyback Cable is connected to the pipeline and the current returns to the platform end through the steel in the pipeline in parallel with the sea water. The Piggyback Cable is strapped tightly to the pipeline to achieve maximum effect and it has an integrated fibre-optic system for continuous monitoring along the entire length.
Integrated Protection System (IPS)
The IPS surrounds the piggyback cable and protects it from external loads, such as trawl boards and abrasion.