* Work to start Thurs; curb “shorter than a week”
* Unclear how much output will be curtailed
* UK gas prices jump to three-week high
* Output at Oseberg South, East fields resume
(Recasts first two paras with crude oil context)
By Gwladys Fouche
OSLO, Jan 27 (Reuters) - Production at the giant Troll oil and gas field will be curbed from Thursday for repairs that would last less than a week, while two other North Sea fields have resumed production, operator Statoil (STL.OL) said.
The news on Troll, the largest gas reservoir off Norway, came as UK day-ahead gas prices surged to three-week highs, after flows of Norwegian gas dived, and North Sea crude oil reached its biggest premium over U.S. oil for two years. [ID:nL3E7CR07M]
“We will reduce capacity this afternoon due to planned short-term repair work,” Statoil spokesman Ola Anders Skauby told Reuters. “It will be shorter than a week.”
Skauby said that the repair work would be done on a power cable connected to a utility system at the field. He declined to say how much production would be cut during the repairs.
Day-ahead gas prices rose to an intra-day high of 58.35 pence per therm just before midday, the highest price paid for day-ahead gas contracts since Jan. 4, after flows from Norway plunged, but prices for gas delivered on Friday eased to 57.60 by 1645 GMT after Norwegian flows climbed again.
Imports from Norway via the Langeled pipeline dropped to just below 20 million cubic metres (mcm) on Thursday morning, from over 60 mcm still seen on Wednesday evening, according to National Grid data.
Imports then rose to close to 40 mcm at 1510 GMT.
Skauby said the work at Troll, which produces 31 billion cubic metres of gas per year and 113,000 barrels of oil per day, should not have affected Norwegian gas exports early on Thursday since it was scheduled to begin in the afternoon.
“It was planned for some time and it was scheduled to be done now,” said Skauby. “We are delivering in accordance with our obligation towards our customers.”
Separately, production at two other North Sea fields, Oseberg South and Oseberg East, resumed on Wednesday after being shut since Monday. [ID:nLDE70N1U9]
“The A, B and D platforms at the (separate) Oseberg field are still down,” said Skauby, repeating that a start-up was seen in “a few days”.
A gas leak led to the production centres being shut on Monday. [ID:nLDE70N1U9]
In November, the head of a Norwegian trade union representing some 2,300 Statoil employees warned that he expected more shutdowns at Statoil’s ageing installations this winter due to a backlog of maintenance. [ID:nLDE6A21BC]
Terje Nustad said the backlog had built up since Statoil merged with the oil arm of aluminium producer Norsk Hydro (NHY.OL) in 2007 [ID:nLDE6AH1GC]
Statoil said that, aside from Troll and Oseberg, there were no issues affecting the platforms it operates off Norway.
Oseberg South produces 39,000 barrels of oil per day and 370 million standard cubic metres of gas per year, while Oseberg East produces 7,000 barrels of oil per day.
The Oseberg field produces 74,000 barrels of oil per day and 2.77 billion standard cubic metres per year.
Statoil has a 49.30 percent stake in all three fields, Norwegian state-owned firm Petoro has 33.60 percent, Total (TOTF.PA) 10 percent, ExxonMobil (XOM.N) 4.70 percent and ConocoPhillips (COP.N) 2.40 percent.
Additional reporting by Karolin Schaps and Daniel Fineren in London; editing by William Hardy