BP PLC (BP) Wednesday said its Valhall oil field in Norway will remain closed for weeks.

The field, which was closed down April 2 for checks and maintenance related to pipeline corrosion, produces about 50,000 barrels of oil a day, figures from the Norwegian Petroleum Directorate show.

Company spokesman Jan Erik Geirmo said the unplanned outage was caused by microbial corrosion of hundreds of meters of pipelines.

He couldn't be specific about when the field would restart, saying: "It's a question of weeks."

In briefing notes BP said microbial-induced corrosion had affected water pipes on Valhall.

The company is carrying out a series of inspections and will carry out repairs to get the field back to secure production. The bacteria will be removed with biocides.

Valhall is in the southern part of the North Sea and is routed via a pipeline to Ekofisk field from where it is piped to Teesside in northeast England.

BP, which operates Valhall, has a 28.09% stake in the field, as do Enterprise Oil Norge and Hess Norge. Total SA (TOT) has a 15.72% stake.

Company Web site: www.bp.com

-By Elizabeth Adams, Dow Jones Newswires; +44 (0) 207 842 9386; elizabeth.adams@dowjones.com