Subsea asset monitoring specialist, Omnisens, has provided Break Detection systems to check the integrity of the Direct Electrically Heated flowline system being installed in the Shah Deniz field.
The Shah Deniz field was discovered in 1999. It is located on the deep water shelf of the Caspian Sea, 70 kilometers south-east of Baku, in water depths ranging from 50 to 500 metres.
The world’s largest DEH system, with a total of 130 km of the cable system made by Nexans, provides flow assurance for 10 subsea flowlines.
DEH is a technology for flow assurance, developed to safeguard the wellstream flow 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. As a result, problem free and reliable transportation is achieved. Traditional methods for flow assurance, by the use of chemical treatments and pressure evacuations, have considerable operational costs with long down times and may present a risk to the environment.
The operators use the DEH system during shutdowns, to raise the temperature of the fluid from ambient to above hydrate formation temperature within a specified time period and during tail-end production.
An important safety requirement for the DEH is that a power cable failure should be detected and located quickly to avoid damage to the pipeline. The main threat to the DEH is from trawling, anchor drag and dropped objects, which could rupture the cable.