Gassco has used a completely new subsea technology developed by companies in Haugesund, north of Stavanger, for inspection of the Knarr gas pipeline during March.
The Surveyor Interceptor remotely operated vehicle (ROV) had its first commercial outing in the North Sea for the Knarr Gas Pipeline. This assignment was aimed at proving that the technology worked in practice and proved to be very successful.
Gassco is operator for the gas transport system, which delivers Norwegian gas to continental Europe and the UK through more than 8000 km of pipelines.As the company responsible for operating and maintaining this network, it is constantly looking for cost-effective solutions that provide the highest quality.
“Most of the gas pipelines lie on the seabed, and ROVs controlled from surface vessels must therefore be used for maintenance and monitoring work,” explains Kristin Kinn Kaste, Vice President for the transport network.
“Such operations are basically expensive. Factors affecting the price include the offshore vessel, the ROV’s efficiency and the choice of inspection technology. Using new, world-leading technology is therefore cost-efficient for us.”
Inspection of the 106 km Knarr gas pipeline took place in the northern North Sea at water depths of 140 - 400 m to check the external condition of the pipeline and rockberm protection after laying. That had to be done before beginning to fill the line with gas.
Specially built by Kystdesign in Haugesund for a joint venture between MMT and ReachSubsea, Surveyor Interceptor’s unique design and outfitting allow it to acquire stable data at high speed.
The Knarr inspection job took just 17 hours, giving an average speed of 3.33 knots (6.2 km/hr), and the ROV was operated at a top speed of 4.5 knots (8.3 km/hr).
This is about three times the speed normally achieved by a traditional inspection ROV in the water depths involved here.
Surveyor Interceptor performed stably during the inspection, and the data acquired was of good quality. Data was processed and analysed continuously on the Edda Fonn support vessel to be able to provide a field report to Gassco on demobilisation.
Knarr is a gas and oilfield located about 100 km north of Brent in the northernmost North Sea. Gassco is operator for the Knarr Gas Pipeline joint venture, which owns the facility.
This 12 in. pipeline has been tied into the existing Far North Liquids and Associated Gas System (Flags) pipeline, which will carry rich gas to St Fergus in Scotland via the Shell-Esso Gas and Liquids (Segal) system.
The technical capacity of the 106 km Knarr rich gas pipeline is 1.7 million standard m3/d.
Adapted from press release by Hannah Priestley-Eaton