Norway's Kollsnes gas plant to be partially shut in May and Sept

(Adds maintenance plans at Dornum, Emden, St Fergus terminals, other details)

OSLO, Dec (Shanghai: 600875.SS - news) 16 (Reuters) - Norway's largest gas-processing plant, Kollsnes, will be partially shut from May 6-20 and from Sept. 2-20 next year, gas system operator Gassco said on Friday, announcing its 2017 maintenance plans.

Norway exports natural gas from its offshore fields via a dense network of subsea pipelines to Britain, Germany, France and Belgium after processing it at onshore plants.

Norwegian gas meets about 25 percent of Europe's demand.

The Kollsnes plant in western Norway processes gas from the country's biggest offshore field, Troll, a key gas supply source for Western Europe.

The partial shutdown will reduce the plant's daily production capacity of 144.5 million cubic metres (mcm) by 38.5 mcm, Gassco said on its website.

The plant and the Troll field will be shut completely for one day on May 15, it added.

Maintenance plans showed most of Norway's capacity reductions will occur in June and September, while the total scope was smaller than in 2016.

Gas import terminals at Dornum and Emden in Germany were expected to be shut for yearly maintenance on May 6-24, while maintenance at St Fergus terminal in Scotland was to reduce export capacity by 5 mcm/day for three months starting July 1.

There were no plans announced for annual maintenance at the Troll field, Kaarstoe or Nyhamna gas-processing plants.

Gassco was not immediately available to comment. (Reporting by Nerijus Adomaitis; Editing by Dale Hudson and Terje Solsvik)