Devon Canada Corp., a unit of Oklahoma City-based Devon Energy Corp., will spud the first well in 15 years in Canada's Beaufort Sea during the upcoming winter drilling season. The company has moved a steel-drilling caisson (SDC) into Beluga Bay, about 45 kilometers offshore the westerly outlet of the Mackenzie River, and set it in 13 meters of water. Once ice cover is solid and stable, Devon will begin drilling a 2,350-meter well on its Paktoa prospect. Devon owns a 100% interest in offshore Exploration License 420, which is divided into four blocks. The terms of the license require the company to drill successive blocks in successive years; Paktoa is the first obligation well on the license. If the weather cooperates, the well will spud in early December. The drilling must be timed so that the depth at which Devon could potentially hit sustainable hydrocarbons occurs when land-fast ice has formed. That's when the pressure ridges that form in the ice have built to the point that they are embedded in the sea floor, anchoring the ice. The Paktoa wildcat is estimated to cost C$58 million. The prospect will evaluate Taglu and Kugmallit sands around a shale diapir. Compared with previous rounds of exploration in the Beaufort, Devon has acquired a significant amount of 3-D seismic. "We can image the structures much more accurately than was possible in the past. We're targeting the onlapped sands on the flanks of the structures, instead of sands draped over the crests that were drilled previously," says Ian Freeland, Devon Canada's Beaufort Sea exploration coordinator. While the play concept is new for this area, the target reservoirs are well-known producers in the rest of the basin. "We have the potential to find similar-sized reservoirs offshore that have been found onshore, and if we do, it adds to the critical mass for the development of the Mackenzie Valley pipeline." The SDC was originally built in the early 1980s for Dome Petroleum. The mobile offshore drilling unit was constructed from a crude-oil tanker. The bow and engine compartment were removed, so the modified vessel is not powered and has to be towed. It can be deballasted, so it can sit on either the seafloor or a submarine berm. Shortly after construction, the SDC was further changed by addition of a base section. The unit was mated to the SDC II, which is essentially a huge rectangular barge. This second piece improved the stability of the unit and increased its operating depth capability. "This configuration gives the SDC a much more stable platform in weaker soils, and allows it to resist the ice loads that are imposed on it," Freeland says. The unit can drill in water depths of up to 24 meters without a subsea berm. The SDC has an 80,000-ton displacement; its deck measures 200 meters long and its base is 110 meters wide. Size-wise, the drilling unit is comparable to a World War II aircraft carrier. The SDC drilled two wells between 1982-84 in the Canadian portion of the Beaufort Sea, and five wells between 1986-92 in the Alaskan sector. It was mothballed after the 1991-92 winter season. During the 2002-03 winter season, EnCana Corp. refurbished the unit for a well that it drilled offshore Alaska. After the project concluded, EnCana towed the unit to Herschel Island, off the coast of the Yukon. At present, Devon is stocking the SDC with everything it needs for the drilling, casing and testing operations, which are estimated to take about 85 days. "If we have a tremendous success, we may look to further testing, which could add another 30 to 45 days," Freeland says. Helicopters will transport crews and perishable items between Inuvik and the unit. The crew complement will range from more than 60 to as many as 80 people each day. Inuvik, which lies about 180 kilometers from the Paktoa location, was chosen because it offers commercial air service and the route from it to the location was the shortest direct distance of any of the potential shorebases. "Our immediate challenge is to get everything working so that it runs smoothly, and to have everything onboard that we need to drill the well."