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Canada's Terra Nova field to get ice-resistant FPSO this fall


By Judy Clark
Associate Editor
Oil and Gas Journal

HOUSTON, May 1 -- The first floating production, storage, and offloading (FPSO) vessel to operate in North American waters is scheduled to start production at Terra Nova field off Newfoundland this fall.

The field, in the Jeanne d'Arc basin 325 km southeast of St. John's, is one of 15 "significant" oil discoveries in the basin, the largest of which is Hibernia -- in production since1997.

"Hibernia and Terra Nova are the largest conventional oil pools found in Canada since the 1960s," said Gary Bruce, vice-president of offshore development and operations for Terra Nova operator Petro-Canada. Bruce described the Terra Nova project Monday at the Offshore Technology Conference in Houston.

He said that four fields dominate the basin. Hibernia has reserves of more than 700 million bbl, Terra Nova 400 million bbl, White Rose 200-250 million bbl, and Hebron-Ben Nevis, 600-700 million bbl -- half of which is heavy oil at about 22°-gravity.

"We have some interesting challenges," Bruce said.

When the four fields come on stream and the smaller fields are tied into them, the basin could produce 300,000 b/d over the next 25 years.

"The [Terra Nova] FPSO contains all topside oil production and processing equipment, as well as storage capacity for 960,000 bbl of oil," Bruce said.

"While there are nearly 70 FPSOs in service or under development in the world, the Terra Nova FPSO will be the first of its kind developed for the unique environmental conditions offshore Newfoundland, " he said.

The vessel has an exceptionally tough double hull and 3,000 tonnes of extra ice-strengthening steel to withstand contact with sea ice (mid-February-April) and icebergs (February-July), including any "unacceptable" iceberg of 100,000 tonnes.

As many as 600 icebergs break off the coast of Greenland each year and float southward on the Labrador current toward the Grand Banks, according to R. B. Dugal of Petro-Canada Oil & Gas.

He spoke at a separate OTC technical session on ice detection and management in Terra Nova. Workboats successfully deflect about 97% of the icebergs. Despite the intensive ice detection and management effort, in April 2000 there were 10 icebergs near the production areas, one within a half mile of Hibernia wells and one within a quarter mile of the Terra Nova wellheads.

Because iceberg scour is such a threat to facilities in this environment, all flowlines are buried under the seabed for protection, insulation, and stability, and wellheads in Terra Nova field are 10-12 ft lower than the seabed in "glory holes" dredged by trailer suction. The holes are 210 ft long by 80 ft wide by 30 ft deep.

Bruce said the Terra Nova FPSO is designed to stay anchored during a 100-year storm with 90-ft waves, withstand the impact of a 100,000-tonne iceberg, and, in less than 20 minutes, get out of the way of icebergs of about 2 million tonnes.

The FPSO is 958 ft long, 149 ft in breadth, and has a draft of 92 ft. Its operating draft is 42-61 ft. Maximum displacement at operating draught is 194,000 tonnes.

It reportedly has the largest disconnectable turret ever built, weighing 3,000 tonnes, standing 210 ft high, and having 19 risers attached. The turret is connected to a spider buoy, which has risers and anchor chains attached. When the FPSO moves off location, the spider buoy is released, using automated controls. It then floats some 130 ft below sea level until the FPSO returns to hook onto it and pull it into the turret for rejoining.

Petro-Canada operates Terra Nova on behalf of its partners ExxonMobil Corp., Husky Oil Operations Ltd., Norsk Hydro Canada Oil & Gas Inc., Murphy Oil Co. Ltd., Mosbacher Operating Ltd., and Chevron Corp. affiliate Chevron Canada Resources.

The FPSO is at Bull Arm, Newf., in the latter stages of hookup and commissioning. It has been docked there since May 2000 when it arrived from the Daewoo Corp. shipyard in South Korea where it was built. The project schedule calls for first oil by yearend.

Delays have increased costs by 35% since the project was sanctioned. Operating costs in Hibernia, however, are falling and are now at less than $1.50/bbl. "We expect a similar cost at Terra Nova during peak production years," Bruce said.

First phase of Terra Nova production calls for 24 wells -- 14 producers, 7 water injectors, and 3 gas injectors.

Meanwhile, the semisubmersible Henry Goodrich already has drilled the six wells needed for startup.

The Newfoundland offshore area is vast -- 225,000 sq miles -- and Petro-Canada believes that the Flemish Pass basin, in more than 3,000 ft of water, may contain the next large oil field. It lies in deeper water, at over 3,000 ft. Partners Norsk Hydro, ExxonMobil, and Chevron contracted a 1,500-sq mile 3D seismic program last year and are evaluating results.

Although a pipeline to produce offshore Newfoundland gas is not currently economically feasible and faces the technological challenge of iceberg conditions, the government is assessing potential routes for a $2.5 billion (Can.), 36-in., 1 bcfd line.


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