Planned maintenance has affected gas output at Norway's Ormen Lange Field, operator Shell has announced.
Gas production at Langeled has declined from nearly 52mcm/day on 17 September to 33-37mcm/day late in the afternoon, according to data from the National Grid.
Ormen Lange, which is anticipated to generate up to 70 million cubic metres (mcm) of gas per day, primarily exports to the UK through the Langeled pipeline.
Output can be routed to continental Europe through the Norwegian North Sea pipeline network.
A Shell spokesperson told Reuters that maintenance work is affecting production.