June North Sea oil output to fall sharply

* June daily output to average 1.657 mln bpd

* Lowest daily output since September 2012

* Extensive field maintenance across North Sea

By Claire Milhench

LONDON, May 12 (Reuters) - North Sea daily oil output tracked by Reuters is set to fall by over 8 percent from May to June, hitting a 19-month low as summer maintenance work gets underway.

The much tighter supply from the North Sea will come when European refineries start to return from maintenance and Libyan crude exports remain restricted - which should keep North Sea crude prices firm.

Output from 12 of the main British and Norwegian crude streams will average 1.657 million barrels per day (bpd) in June, down from a revised 1.809 million bpd in May. This is the lowest level since September 2012 according to Reuters' data.

The slump in production is due to maintenance affecting the Forties, Ekofisk, DUC, Gullfaks, Statfjord and Troll fields, but traders said this was not unexpected and daily loadings were in line with expectations.

The market is also taking comfort from the fact that the four crude streams underpinning the Brent benchmark - Brent itself, Forties, Oseberg and Ekofisk (BFOE) - will load 880,000 bpd in June, up 5.7 percent from May's revised 832,700 bpd.

May's total was boosted by deferrals from April for Forties and Ekofisk, and an extra cargo for Flotta. But the return of Oseberg output in June following the expected completion of gas field maintenance has boosted June loadings substantially.

Some traders and analysts warned against complacency, however, given that European refineries are beginning to return from their own spring turnarounds.

"The market usually hinges itself on the BFOE numbers which are up month-on-month, but the Forties numbers are down month-on-month and year-on-year," said Abhishek Deshpande, an oil analyst at Natixis (Paris: FR0000120685 - news) in London.

"This can provide some support to oil prices as refineries come back from maintenance. The low 12 (crude streams) loading number could help provide further support."

Forties loaded some 420,000 bpd in June 2013 compared with this year's projected 340,000 bpd, whilst the 12 crude streams in total loaded 1.683 million bpd last June, according to revised programmes.

Deshpande saw refinery demand increasing from mid-May, but added it would only reach its peak in mid-July/August.

Local (Frankfurt: OTQ.F - news) refiners will also benefit from more Forties remaining in northwest Europe as the Very Large Crude Carrier (VLCC) jetty at Hound Point will be closed for maintenance. This will prevent the shipment of Forties to Asia.

"The drop in overall volumes seems reasonably heavy to me given that refineries are on their way back," a trader said. "But the lack of Forties arbitrage exports does make a big difference."

OILFIELD MAINTENANCE

For light, sweet (low sulphur content) grades, the picture is clearer - differentials are expected to remain high given the dip in volumes and continued Libyan outages, and traders have been quick to snap up barrels for the first half of June.

"This is really a light, sweet support story," one said.

Summer maintenance has come earlier this year, making year-on-year comparisons more difficult, but the scheduled works appear to be more extensive for these fields.

Maersk Oil's production platforms in the Danish North Sea will shut for about 12 days in June for the replacement of two flare towers and a bridge, plus inspection and optimisation work, Maersk Oil said. The company schedules such maintenance work every four years.

Statoil (Xetra: DNQ.DE - news) is shutting its Statfjord and Gullfaks oilfields for maintenance and ConocoPhillips (NYSE: COP - news) has work planned for the J-Area fields, which feed into Ekofisk, and Eldfisk. As a result, June's Ekofisk output is the lowest since January, said Virendra Chauhan, an oil analyst at Energy Aspects.

"It is the seasonal low point, but the numbers do look punchy," he said.

(Editing by William Hardy)