The FLAGS (Far North Liquids and Associated Gas System) pipeline is a natural gas pipeline in the UK sector of the North Sea which, together with its associated pipelines, is used to transport gas and associated liquids from oil and gas fields in the northern North Sea to the St. Fergus gas terminal.
Pipelines The FLAGS system gas pipelines are:Shell: 2002 Northern North Sea Pipeline Systems +FLAGS system gas pipelinesPipeline numberFromToDiameter (inches)Length (km)NotesPL044Brent DBrent C244.2PL047Brent CBrent B304.4PL052Brent BBrent A362.3PL002 (FLAGS)Brent ASt Fergus36450FLAGS linePL164 (NLGP)MagnusBrent A2079NLGPPL165MurchisonNLGP tie in63.2PL166ThistleNLGP tie in63.2PL200Statfjord BNLGP tie in63.2From NorwayPL017 (WLGP)Cormorant ABrent A1640.5WLGPPL917Ninian CentralWLGP tie in1017.7North CormorantWLGP tie in1022.5TampenFLAGS tie in3223.2From NorwayPL3039Knarr FLAGS tie in12106 From NorwayPL2633Gjoa FLAGS tie in28130From Norway
Installations FLAGS provides the gas export route for the following installations.Shell UK Limited (2020) Brent field pipelines decommissioning programme
Cormorant A North Cormorant North West Hutton Ninian Central Ninian North & South Brent 'A', 'B', 'C' and 'D' Tern Magnus Thistle Murchison Statfjord Heather Gjøa Gas exported from West of Shetland oil fields (Foinaven, Schiehallion/Loyal and Clair) Knarr
Infrastructure The FLAGS pipeline is a steel pipe to API 5L, X60 specification and is long. It starts at Brent 'A' and terminates at St. Fergus near Peterhead in Scotland. Pipe laying was completed in April 1978 and finally commissioned in May 1982. The pipeline was laid by SEMAC 1.
At Brent A, the pipeline is connected with the Northern Leg and Western Leg transmission systems, carrying gas from a number of nearby fields.
The 20-inch Northern Leg Gas Pipeline (NLGP) runs for 80 km from Magnus to Brent A with spurs to Thistle A, Murchison and Statfjord B. It originally served as the gas export route for these installations and delivered gas to Brent A for onward transmission to St Fergus via FLAGS. As some of these installation have become gas deficient it has served as their gas supply route. The pipeline has depressurisation facilities at Magnus. Gas from the NLGP is heated before flowing via manual pressure let-down valves to the HP and LP flare systems. Pre-heating the gas ensures that it remains within the temperature limits of the flare pipework after
The 16-inch Western Leg Gas Pipeline (WLGP) transports gas from Cormorant A to Brent A. It also takes gas from Ninian Central and North Cormorant.
Natural gas from the Norwegian Statfjord field is fed through the Tampen pipeline, linking Norwegian and UK gas trunkline networks.
Inlet specification The inlet specification for gas transported in the FLAGS system is as follows: +FLAGS gas propertiesParameterValueCarbon dioxide1.6 % vol maxHydrogen sulfide2.5 ppmv maxTotal sulfur15 ppmv maxWater35 ppmv maxCricondenbar105 bara maxOxygen10 ppm maxMercury0.01 μg/m3 maxPropane +5.5 %mol min
Capacity and throughput The FLAGS system has a capacity of 33 million standard m3/ day.
Up to the end of 1991 the total cumulative throughput of FLAGS 49,757 million cubic metres of gas.
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