The Terra Nova production ship won’t head to a dockyard to have its damaged swivel replaced this summer.
Suncor Energy, the operator of the oilfield, is postponing that repair job until 2012 as it tries to solve sour gas problems at some of its production wells off Newfoundland and Labrador.
The company said both rounds of repair work will be done at the same time.
Sour gas is hydrogen sulphide (H2S), which is flammable, poisonous and corrosive.
It can result naturally from decaying organic material in oil and gas.
Some Terra Nova wells where hydrogen sulphide was detected have been safely shut in.
“The 15-week dockside maintenance at Terra Nova originally scheduled for July this year has been deferred until 2012 so that plans to resolve the H2S issues may be implemented concurrently with that work,” said Steve Williams, Suncor’s chief operating officer as he presented the company’s first-quarter report Tuesday.
Instead, the production ship will undergo a month-long round of annual maintenance work sometime during the third quarter, which starts in July.
Rick George, president and CEO of Suncor, said the company is examining the integrity of the wellheads and flowlines and the ability of the production ship to handle production of H2S.
“We’ll be replacing flowlines and then going back through the whole system to make sure that we actually have the ability to handle the H2S on the vessel itself.”
He said that will take place over the next 18 to 24 months.
“The biggest single thing is replacing the flowlines and some of the subsea lines,” said George.
Flowlines are the flexible pipes that carry oil from the seabed to the production ship.
The work will coincide with the production ship’s departure from the Terra Nova oilfield next year for 15 weeks of swivel repairs at the Marystown shipyard.
“That’s when a lot of this offshore work will be done — 2012 will be a heavy year on Terra Nova,” said George.
At Marystown, the production ship will get a new swivel.
Located in the ship’s turret, the swivel is part of the production ship’s water-injection system that uses sea water pressure to flow oil from the reservoir.
Suncor has said no hydrocarbons — oil and gas — pass through the water-injection swivel.
It was damaged in 2006 and temporarily repaired.
Oil production decreases
The shutdown of some wells at Terra Nova cut the oilfield’s total production in half during the first three months of the year.
Total production dropped 49 per cent to 4 million barrels of crude.
Last year, the oilfield pumped more than 7.8 million barrels during the first quarter.
The company first encountered H2S problems late last year and shut down the wells.
They appear to affect as many as six wells at Terra Nova, according to production statistics available from the Canada-Newfoundland and Labrador Offshore Petroleum Board.