UPDATE 2-Refinery strike may halve UK NSea oil output

By Margaret Orgill and Daniel Fineren

(Updates throughout)

LONDON, April 24 (Reuters) - A strike planned this weekend at a major Scottish refinery would force the closure of the key Forties North Sea pipeline, its owner BP (BP.L) said on Thursday, halving Britain's crude oil output.

Talks to resolve the dispute at the 200,000 barrel-a-day Grangemouth refinery, which collapsed late on Wednesday, are unlikely to resume and the two-day strike over pensions is set to go ahead on Sunday, trades union officials said.

The refinery has been shutting down gradually all week and once a heat and power station on the site shuts on Saturday, the Forties pipeline will have to close as the power plant supplies the nearby Kinneil facility which processes Forties crude.

"Without the power and steam, we can't keep the Kinneil operation running and so we would have to shut down," a BP spokesman said, adding the Forties pipeline would also have to shut.

The 700,000 barrel-a-day Forties pipeline carries about half of Britain's North Sea oil production.

BP has said that it would need to start shutting the pipeline about 24 hours before the shutdown of the Grangemouth power station.