Inside the Rig
On this crisp, clear mid-February afternoon, the mechanical colossus - the so-called topsides of the Hibernia drilling rig - towers over the shimmering waters of Newfoundland's Bull Arm. Just around the bend, hidden by snow-dappled rocks and trees, sits another engineering wonder - a 580,000-tonne concrete-and-steel behemoth with the even more prosaic designation of "the gravity-based structure," or GBS, that will anchor the topsides to the ocean floor. The mating of the top and bottom of the Hibernia rig, scheduled to take place this week, marks the consummation of six years of engineering and construction that, at its height, employed more than 5,000 people working on three different continents. "I don't think," says Hibernia's construction general manager Henk van Zante, "that a more complicated civil construction project will ever be built."
Ever is a long time. But there is no doubt that the $5.8-billion Hibernia platform is in a class of its own. Much of the project's complexity - and cost - is directly attributable to the owners' decision to opt for a huge concrete platform that will remain locked in place over the 20-year life of the drilling operation. Moreover, Hibernia will be drilling for oil off the Grand Banks, an area famous for wind, fog, 30-m waves - and, of course, icebergs. The platform is to be parked 900 km north of where a giant berg struck and sank the Titanic in 1912, in a channel that is often called "Iceberg Alley." If Hibernia is to function safely, explains David Luther, engineering manager for the GBS, it must be able to absorb an iceberg's impact, which he likens to "600 automobiles pushing up against a one-square-metre area of space."
There are about 20 gravity-based offshore platforms operating worldwide, most of them in the North Sea. But Hibernia's is the first to be constructed with the threat of roaming icebergs in mind. Its chief defence will be an outer wall consisting of 16 concrete teeth, each one 1.5 m thick, that are meant to distribute the force of the iceberg over the entire structure. According to its designers, the platform could withstand bergs of up to six million tonnes. And because Hibernia will be located in relatively shallow water - 80 m deep - they calculate that intruders of that magnitude should only show up once every 10,000 years. Impressive odds, but University of Toronto engineering professor Michael Collins cautions that "nothing is unbreakable." It may only occur once every 10th millennium, he adds, "but that doesn't mean it couldn't happen next year." Having said that, Collins, who is a leading authority on gravity-based platforms, says that Hibernia is "as safe as any comparable structure in the world."
But nothing about Hibernia, it seems, was done on a modest scale - starting with its main 1,600-hectare construction site at Bull Arm, 130 km northwest of St. John's. Prior to 1990, this was just another picturesque pocket of Atlantic Canada - ancient rocks, wind-blasted trees, undisturbed waters. But then the bulldozers and dynamite crews moved in, clearing the way for 14 km of paved roads connecting Bull Arm to the Trans-Canada Highway and a construction camp that included accommodations for 3,500 workers. A small community soon sprang up, complete with a water and sewage plant, softball diamond, library, post office - and a helicopter landing pad.
The next step was to create a dry dock for the GBS by erecting a berm across Great Mosquito Cove and pumping out 145 million litres of water. About one kilometre to the north, a pier was built for the topsides facilities. Near the pier, workers drained a small lake to make room for a fabrication yard; as part of an attempt to protect the environment, some 280 trout were caught in nets and moved to neighboring ponds.
Construction of the GBS began in September, 1992. Two years later, the base of the GBS - the length of two football fields and weighing 120,000 tonnes - was ready to be moved to its present site, about a mile offshore, where the water is 200 m deep. The plan was straightforward: water would be pumped into the dry dock and, at a certain point, the berm on Great Mosquito Cove would be removed. As the water pressure rose, the GBS would begin to float. It would then be towed out to the deeper waters of Bull Arm and anchored in place with six kilometres' worth of mooring chain. At this point, says van Zante, some of his corporate masters were expressing doubts: could something so heavy really float? Not only did it do so, but it started to rise within four centimetres of the level engineers had predicted.
Once the GBS was secured in the deeper waters, workers continued to pour concrete and reinforcing steel into the mould until it reached its full 85-m height. During this period, as many as 2,000 workers were being ferried out to the construction site every day, while up to 40 barges circled the ever-expanding GBS. The barges included a floating batch plant where the concrete was mixed, a power barge and another one holding 80 offices. "It was quite a floating city out there," recalls van Zante.
As the massive base of the Hibernia platform was being fashioned, the pieces that would make up the even taller topsides began to arrive for assembly at the nearby pier. The topsides consists of five supermodules - two of them built in Korea, two others in Italy and the fifth one at Bull Arm - that contain all of the drilling, producing and power equipment, as well as the living quarters for the 280 workers who will operate the offshore platform on a 24-hour basis. It also includes the drilling derricks, the 115-m-long flare boom that will burn off gas released during drilling, two lifeboat stations, and a helideck that will be used for shuttling workers to and from St. John's for their three-week shifts.
The topsides pieces were all welded together at Bull Arm; the result is now perched on the pier, looking like nothing so much as a many-tentacled space station inexplicably plunked down in the stark landscape of coastal Newfoundland. This week - if the weather co-operates - two heavy-lift barges will carry the topsides over to the GBS, which has already been gradually submerged. This was done by opening up an underwater valve and pumping seawater into the structure to weigh it down. With only six metres of the GBS's uppermost shafts remaining above the water, the topsides will be floated over it. When the two structures are precisely lined up, workers will begin to pump the water out of the GBS, which will then lift and connect to the topsides. Once mated, the entire structure will stand 224 m tall - roughly the height of the Calgary Tower and half the height of Toronto's CN Tower.
The mating operation, which will take five days to complete, is extremely delicate - Collins describes it as "almost like weaving; you need a very specific pattern to fit them together." And the final steps towards it do not always go off without a hitch. In 1991, a gravity-based structure owned by Statoil, the Norwegian government oil company, collapsed under the pressure of being submerged in the North Sea and fell like rubble to the ocean floor. But if he was worried about such mishaps, van Zante hid it well during an interview shortly before the Hibernia mating began. When asked what could go wrong, he smiled. "Nothing can go wrong," he replied. "We have worked hard to make sure nothing goes wrong."
If van Zante's confidence proves well-founded, the Hibernia rig will be towed out to its drilling site by nine of the world's largest tugboats in late May or early June. There, 400,000 tonnes of iron ore ballast will be dumped inside the outer wall of the GBS to sink it to the ocean floor. The platform, then weighing a total of 1.2 million tonnes, will soon begin drilling up to 135,000 barrels of oil a day, thereby fulfilling a quest that began when the Hibernia oilfields were first discovered in 1979.
For the Dutch-born van Zante, who helped to build three earlier gravity-based platforms in the North Sea, Hibernia will be a swan song. He plans to retire in April at age 65, although he will stay on contract until drilling commences. At that point, he expects to feel much as he did when helicopters finally whisked him away from those other massive offshore rigs. "Everyone is saying, 'Oh, it's tremendous, magnificent,'" he says. "But then the chopper takes off and you have to be fast to look back, because in a couple of minutes, even though the platform is so big, it's nothing in the expanse of that ocean." And that, he adds, "brings you back to reality. It keeps you very humble."
Maclean's March 3, 1997