FLAGS

This article is about the pipeline. For the x86 status register, see FLAGS register (computing). For other uses, see Flag (disambiguation).

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.

Far North Liquids and Associated Gas System
Location
Country	United Kingdom
General direction	north–south–west
From	Brent oilfield
Passes through	North Sea
To	St Fergus Gas Plant
General information
Type	natural gas
Partners	Royal Dutch Shell, ExxonMobil
Operator	Shell UK Exploration and Production
Technical information
Length	450 km (280 mi)
Diameter	36 in (914 mm)

Pipelines

The FLAGS system gas pipelines are:^{[1] [2] [3] [4] [5]}

FLAGS system gas pipelines

Pipeline number	From	To	Diameter (inches)	Length (km)	Notes
PL044	Brent D	Brent C	24	4.2
PL047	Brent C	Brent B	30	4.4
PL052	Brent B	Brent A	36	2.3
PL002 (FLAGS)	Brent A	St Fergus	36	450	FLAGS line
PL164 (NLGP)	Magnus	Brent A	20	79	NLGP
PL165	Murchison	NLGP tie in	6	3.2
PL166	Thistle	NLGP tie in	6	3.2
PL200	Statfjord B	NLGP tie in	6	3.2	From Norway
PL017 (WLGP)	Cormorant A	Brent A	16	40.5	WLGP
PL917	Ninian Central	WLGP tie in	10	17.7
	North Cormorant	WLGP tie in	10	22.5
	Tampen	FLAGS tie in	32	23.2	From Norway
PL3039	Knarr	FLAGS tie in	12	106	From Norway
PL2633	Gjoa	FLAGS tie in	28	130	From Norway

Installations

FLAGS provides the gas export route for the following installations.^[6]

• 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 36-inch (910 mm) steel pipe to API 5L, X60 specification and is 450.6 kilometres (280.0 mi) long. It starts at Brent 'A' and terminates at St. Fergus near Peterhead in Scotland.^[7] 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.^[7]

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.^[5]

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:^[1]

FLAGS gas properties

Parameter	Value
Carbon dioxide	1.6 % vol max
Hydrogen sulfide	2.5 ppmv max
Total sulfur	15 ppmv max
Water	35 ppmv max
Cricondenbar	105 bara max
Oxygen	10 ppm max
Mercury	0.01 μg/m3 max
Propane +	5.5 %mol min

Capacity and throughput

The FLAGS system has a capacity of 33 million standard m³/ day.^[1]

Up to the end of 1991 the total cumulative throughput of FLAGS was 49,757 million cubic metres of gas. The throughput over the period 1992 to 2014 (in million cubic metres) was:^[5]

References

1. "FLAGS pipeline" (PDF). Retrieved 9 November 2022.
2. Oilfield Publications Limited (1985). The North Sea Platform Guide. Oilfield Publications Limited. p. 138.
3. Shell: 2002 Northern North Sea Pipeline Systems
4. Department of Trade and Industry (1994). The Energy Report. London: HMSO. pp. 143–44. ISBN 0115153802.
5. "North Sea Transition Authority - Oil and Gas Activity". Retrieved 9 November 2022.
6. Shell UK Limited (2020) Brent field pipelines decommissioning programme
7. Collins, Alan; Field, Graham. "Shell Expro's Plant Optimisation and Systems Management Project" (PDF). Energy Solutions International. Retrieved 14 March 2010.