Mammoth equipment again will be used to track down the proverbial elephant-sized natural gas discoveries believed to be located in the shallow waters of the Beaufort Sea. Devon Canada has told the National Energy Board that it is leaning toward resurrecting one of the biggest exploration systems devised by the late Dome Petroleum Ltd. and its offshore hunting arm, Canadian Marine Drilling Ltd.

The Dome empire, once an international-scale star on the Canadian energy scene, is fading into history 14 years after it floundered in a sea of debt and was taken over by Amoco Canada, now part of BP Energy Canada. But the engineering concepts pioneered by Dome, with considerable help from Canadian government exploration incentives in the energy boom years of the 1970s and early ’80s, remain a live part of the arctic exploration legacy.

Devon calls the 21st-Century version of the concept the IMI, short for Inshore Mobile Island. Giving credit where it is due, the company says the idea grew out of experience with a CanMar behemoth called the SSDC, or single steel drilling caisson. It arrived in the Beaufort 20 years ago this summer and chalked up a string of successes before the 1986 oil-price collapse put an end to Dome, CanMar and arctic offshore drilling. Devon’s plans call for it to be ready to start drilling for gas in the Beaufort by the winter of 2004-05, on 3,385 square kilometers (1,300 square miles) of prospects acquired with its 2001 takeover of Anderson Exploration. The engineers face the same problems now as then.

As on the Mackenzie Delta, where marshy tundra and abundant wildlife make it all but impossible to attempt drilling or any other type of work during summers, winter is the best season to operate in the Beaufort. There is more time to get the job done, no danger of interfering with migrating animals such as whales and seals, and less risk of serious damage from any spills.

Offshore, however, winter operations add a big challenge — ice. On land, it is prized material that drilling contractors use for roads and rig foundations. Offshore, the stuff shifts and exerts immense power when it moves. Devising a drilling platform capable of staying on station becomes an exercise in crafting an immovable object capable of besting irresistible force.

The Dome-CanMar answer was to convert one of the biggest vessels afloat into an offshore exploration giant. The hull of a discarded super-tanker (known as a VLCC, or very large crude carrier) was converted into a drilling platform and renamed the SSDC at a Japanese shipyard and towed across the Pacific Ocean. From the tip of a helicopter landing pad overhanging the bow to a crane platform tacked onto the stern, the steel structure was nearly 200 meters long (more than two football fields). The deck was 60 meters wide (65 yards).

In the Beaufort, the SSDC was towed in summer across open water to winter well locations. In shallows no greater than 10 meters deep (33 feet), compartments were filled with ballast to settle the hull on sand cradles built by dredges on the sea floor. The big platform’s capabilities were extended to sea 25 meters deep (82 feet) by adding another mammoth piece of equipment.

In the deeper water, CanMar first towed a pedestal called the MAT to well locations and sank it with ballast, then parked the SSDC on top. At the time, MAT stood out as one of the largest steel structures in the world. It was also one of the strongest, capable of holding a 200,000-ton weight.

Part of the reasoning behind the scale of the system was that it would serve as a production platform after discoveries were made. The latter-day version of the technology contemplated by Devon, while large, will not necessarily attain the scale of the Dome-CanMar giant. The plan calls for the new mobile island — or possibly two of them — to stay in an easier environment known as the landfast ice, meaning in coastal shallows where the frozen shelves are attached to the shore and shift around less than the highly mobile floating pack farther out to sea. SSDC and MAT were built to withstand more severe conditions in a “transition zone,” where the polar pack meets and rubs up against the land-fast ice.

In Devon’s thinking, the scale of the 21st-Century inshore mobile island depends on safety and environmental considerations. A unit capable of containing all the supplies for two seasons of drilling could be as compact as 95 meters in length (one football field), half the size of the SSDC. But the size might have to grow to 160 meters (520 feet), if Canadian authorities want the vessel to carry a second drilling derrick just in case a relief well has to be drilled in the event of a blowout.

As in the case of the Dome-CanMar equipment, Devon’s mobile island would be towed to drilling locations. Improvements would allow the new version to operate in water six to 16 meters deep (20-50 feet) with less preparation of the sea floor. The approach is recalled as one of the best inventions of a creative era by an official record of the era published in 1997 by the custodian of the Dome-CanMar era’s technical and historical records, the Arctic Institute of North America at the University of Calgary — Breaking Ice With Finesse: Oil & Gas Exploration in the Canadian Arctic. “The SSDC was a breakthrough in the development of Beaufort Sea technology — a giant leap.”

Among the wide variety of caissons, ice-strengthened ships and artificial islands tried out off Canada’s northern coastline, “no other drilling platform matched the success of the SSDC and MAT…the entire operation with the SSDC ran very smoothly and worked successfully throughout the winter for several drilling seasons in the Beaufort, conclusively demonstrating the feasibility of year-round oilfield operations offshore in the Arctic.”

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