Canada's harsh-environment operators are ready for anything.

When defending against a swarm of icebergs off the east coast of Canada, the first rule for operators of rigs or platforms is to prevent the collision. The second rule is to survive a hit.
Offshore Canada presents some of the harshest weather conditions in the world, but oil and gas production operators take threats of wind, waves, icebergs, field ice and ice formation on superstructures into account in designing their operations.
The weather off the east coast of Canada can pose a threat to people and machinery if they aren't ready for it. That's why oil and gas operators make sure they're ready for it.
Those precautions use years of experience and research to determine the threat, and many of the precautions already were in place long before the Hibernia gravity-base platform anchored to the ocean floor on a concrete pedestal was put into place. That experience persuaded the operators to build a platform with a cement skirt that could take a hit from a 1-million-tonne iceberg without damage or from a 6-million-tonne iceberg with repairable damage. That size iceberg is the largest that could drift into the 262-ft (80-m) waters, and that would happen maybe once every 10,000 years.
The Terra Nova and White Rose floating production, storage and offloading (FPSO) vessels in the same area take a slightly different approach. If an iceberg gets too big, they will be able to disconnect all hookups in about 15 minutes and move out of the way under the power of their thrusters.
The operators would rather not have to do that, so they all have ice management strategies in place to avoid those uncomfortable situations.
Using Hibernia as an example, the platform takes advantage of airborne surveillance by the International Ice Patrol and the US Coast Guard. It also uses satellite pictures and long-range radar.
The radar system can spot an approaching iceberg from a distance of 18 nautical miles (20.7 statute miles or 33.3 km). Those early warning tools bring into play the first rule of ice management, avoid the collision.
When it appears an iceberg or icebergs represent a potential threat, the platform sends work boats to meet it. On the way, they measure ocean currents. Alongside, they use side-scan sonar to get an accurate profile of the iceberg and the size of the underwater portion.
They transmit that information back to the Agra Earth and Environment ice management trajectory computer model in St. John's, Newfoundland. The computer uses the information to predict which icebergs pose a threat and sends back an early warning.
In the event of a threat, the support boats go into action. If they only have to deal with small chunks of ice, the boat's propeller wash may be enough to divert them. For larger pieces, water cannons may be able to change the paths enough to avert a hit.
Those boats also have the ability to lasso the largest icebergs and tow them to a different path. If they can catch an iceberg 15 to 20 miles away from the production facility, even a slight nudge may be more than enough to send it on a new path that will prevent a collision.
The ice battle
Icebergs aren't the only problems posed by temperatures that can dip to 0°F (-17°C). Ice fields aren't a problem in this area, but ice forming on the superstructure might be. It shouldn't bother a platform like the one at Hibernia, but it could be a significant factor for FPSOs. Terra Nova partners considered several alternatives before deciding on an FPSO and found the closest comparisons with vessels such as Statoil's Asgard A in the North Sea and BP's Schiehallion west of the Shetland Islands.
After studying those vessels for sea conditions, the Terra Nova team added precautions for sea ice and icebergs, including the ability to disconnect and move out of the way.
The Terra Nova FPSO is, and the White Rose FPSO will be, double-hulled and ice-strengthened. Terra Nova has an additional 3,000 tonnes of steel on the superstructure to minimize the risk of ice damage. It can take a hit from a 100,000-tonne iceberg, and it can deal with ice 1 ft (0.3 m) thick over half of the superstructure.
Terra Nova also has more heat tracing and insulation than the eastern Atlantic platforms to keep oil and fluids flowing in extremely cold temperatures.
Like Hibernia and Terra Nova executives, key people with Husky and the Kvaerner SNC Lavalin Offshore joint venture carefully analyzed alternatives before settling on a solution similar to the setup that will be used at Terra Nova when it comes onstream in the fourth quarter this year.
They looked at a steel FPSO; a concrete FPSO; a steel floating production, drilling, storage and offloading (FPDSO) facility; a concrete gravity-base structure like the one at Hibernia; a steel semisubmersible with and without storage capacity; a concrete semisubmersible; a disconnectable concrete tension-leg platform (TLP); and concrete-barrier wells with a floating production unit (FPU).
The disconnectable concrete TLP, concrete barrier wells with an FPU and the FPDSO didn't make it past the first cut, because they either didn't meet the technical requirements for the project or they were prototypes with no operating history or harsh-environment locations to help the companies judge performance.
Husky and Kvaerner SNC then examined the remaining alternatives for favorable construction time, capital cost, concept maturity, concept deliverability and risk considerations.
Using those criteria, two choices remained - the steel FPSO and the steel semisubmersible with or without integral storage.
Development, operations considerations, decommissioning and the ability to deal with accidental events were graded about equal between the two choices.
Finally, the steel FPSO was chosen as the most cost-effective option with the lowest degree of technical risk.
Having made the choice, they went about the task of making sure it could handle the harsh weather of the North Atlantic. They gathered historical data and analyzed sea states, ocean currents, ice, winds, waves and weather variables. They also had to build in physical considerations such as ice accretion into the above-water loading calculations.
As at Hibernia and Terra Nova, they decided the harsh environment posed a risk not only to the surface facility but the subsea facility. They also decided to dig glory holes for the subsea equipment.
Those glory holes, with the top of the equipment a minimum of 7 ft to 10 ft (2 m to 3 m) below the mudline, keep subsea equipment below the maximum observed scour depth for an iceberg scraping the ocean floor.
In addition, the flow lines will be set in trenches, and they will be designed so they can be flushed and purged to avoid spills if a passing iceberg damages them.
Operations at Terra Nova were designed so the FPSO could offload its 850,000 bbl of oil into the shuttle tanker even when waves reach 16.5 ft (5 m) in height with the shuttle tanker standing 230 ft (70 m) behind the FPSO.
Unique conditions
Even with the care taken to date, Terra Nova could cost up to 15% more than the US $1.6 billion original cost estimate.
Norman McIntyre, executive vice president of Petro-Canada, said of the Terra Nova project, "This FPSO is the first to be built specifically for the unique environmental conditions offshore Newfoundland, and it has been a challenging project. We have successfully addressed issues in the excavation of glory holes and the installation of subsea flow lines on the Grand Banks."
White Rose will meet similar challenges. It also will use up to three tankers, and all of them will be double-hulled and ice-strengthened for safety.
Husky already has an ice-management plan for its exploration operations, and it adjusted that plan to the new production vessel. It also collected the experience of other operators working the Grand Banks off Canada.
According to the company's development plan, the ice-management plan will cover ice accumulation and icebergs and will allow for annual variations in conditions.
Kvaerner has some experience in this area. It recently delivered the Asgard B, the world's largest floating production platform, to Statoil. It's the first floating platform on the Norwegian shelf.
The additional harsh-weather requirements even extend to the Sable Island area off the east coast of Nova Scotia.
The last time that area saw an invasion of field ice was in 1922, and most icebergs that make it south past the Grand Banks are puny by the time they reach this area. But when the Labrador Current gets strong enough, field ice and larger icebergs are possibilities offshore operators on the Sable project take seriously.
Mobil Oil examined records from 1964 to 1979 in the Sable Island area and found the field ice edge hadn't gotten within 25 miles (40 km) of the island during that period. A subsequent study in 1996 offered the same results.
Harsh weather and even ice still are concerns in this area, because operations are growing. The Kvaerner SNC joint venture recently received an award for the front-end engineering and design work for the Alma platform, the first step in the second development stage for the Sable gas project. It should be ready for production in 2004.
While it's not as complicated or vulnerable to weather as operations farther north, it still involved a jacket, a wellhead platform and a subsea tieback to the main Thebaud processing facility for Sable.
Each area of the world has its own special set of circumstances. For instance, Canadian offshore operations don't have to worry about the hurricanes of the Gulf of Mexico. Shell's Auger TLP was built to withstand 71-ft (22-m) waves and 140-mph winds.
On the other hand, Gulf operators don't have to build in the northern North Sea capabilities of a Gulfaks operation that uses spare generating capacity to heat water to warm the flow line bundles.
Whatever the environment, oil and gas operating companies are taking elaborate measures to make sure they produce economically and safely.

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