A specially-designed drilling facility could become a game-changing technology for harsh environment land drilling after being used for the first time on Alaska's Arctic tundra in a scientific quest to prove up theories about energy potential in gas hydrates.

Anadarko Petroleum took a specially designed rig to test out the reserves of frozen methane locked below Alaska's North Slope. Frozen methane is thought to hold huge gas potential.

Earlier this year, the US $10.5 million methane hydrates research program was carried out through a partnership between the US Department of Energy (DOE) Anadarko, and two Noble Corporation subsidiaries, Maurer Technology and Noble Exploration and Development.

Anadarko's goal was to obtain field data to verify geological, geophysical and geochemical models of the deposition of gas hydrates in the arctic region, and to plan and design an economic and environmentally safe drilling program to obtain gas hydrate cores without harming the arctic environment.

Anadarko had a clear strategy for the drilling project, partly to use the first well as the basis for other drilling tests.

No ordinary drilling platform would do the job. Instead, Anadarko, along with Noble and Maurer, designed a specially winterized rig conforming to American Society of Mechanical Engineers (ASME) standards for arctic drilling. Serving a dual role as a drilling platform and as a scientific laboratory, the facility was built with modular components for ease of assembly, earning the title of the Lego rig because of its simple construction. It was built around a lightweight mining rig from Dynatec, the Utah-based drilling services supplier. Radoil Incorporated in Houston engineered, designed and constructed the aluminum platform on which the rig was based.

Anadarko's Lego rig is intended to extend the drilling season for the North Slope by being able to operate outside the normal winter-only weather window, allowing more time for prospect evaluation and reducing overall drilling costs. With this new type of rig, more wells are possible per year, cutting time from leasing acreage, to exploration and eventual production.

"This is a game changer [rig] if this works in getting a number of new exploration wells drilled on the North Slope," Tom Williams, vice president for marketing and business development at Maurer, said.

Measuring 100 sq ft (30.5 sq m), the platform provides 10,000 sq ft (930 sq m) of deck space, built from 16 aluminum modules, which provide the base plate for the rig. The platform stands 12 ft (3.6 m) above the ground - high enough to allow grazing caribou to pass underneath the installation without hindrance - on steel supports which have coarse threads to allow it to be "screwed" into the ice-bound surface. This innovation avoids the need for gravel islands which have traditionally been used to provide the weight-bearing surface for land rigs operating on Alaska's North Slope tundra, but scar the landscape once drilling is over and cost a lot to clean up.

Rig components were transported to the drilling location by all-terrain Rolligon vehicles fitted with balloon-tires that don't sink into the surface, because they exert a surface pressure of just 7 psi. Rig components, weighing up to 15,000 pounds, are also light enough to be carried by helicopter.

Construction of gravel or ice-roads on the tundra, which are the traditional methods for moving heavy gear on the surface, can cost up to $100,000 per mile. Eliminating the need for these roads cuts a big slice from rig-up cost.

In this instance rig components were transported to Seattle, Wash., then shipped to southern Alaska. From there, components were carried on Rolligons to the drilling location 80 miles (130 km) south of Prudhoe Bay, south west of the Kuparuk field and west of the Alpine field.

After the steel piles were driven into the surface at the well site, penetrating up to 20 ft (6 m) below the frozen tundra, the aluminum modules were lifted on to provide the drilling deck. Each module or "bucket" has channels around its edge, so that any liquid spilled during drilling would drain to the edges rather than spill on to the ground.

Drilling started on March 31, but by April 21, after just 22 days of operations, the decision was taken with the support of the DOE to suspend drilling until the winter.

At present, the well remains suspended, after being drilled to a depth of 1,403 ft (427 m), logged and 7-in. casing run and cemented, and a BOP test.

"This stage of construction was deemed to be best point to stop for the season," Maurer Technology said in a drilling progress report.

"This platform is designed to extend the drilling season, but they have caribou on the North Slope when everybody has to get off. We got caught in that earlier than anticipated, but we plan to go back on location again before the frozen in period, and start again," Williams explained. "We have already applied for some permits to get equipment back on the tundra." Accordingly Anadarko could resume drilling the hydrates by October or November, when the well depth could be extended to 2,200 ft to 2,600 ft (670 m to 792 m).

"We drilled a very shallow well on this trial run as part of a methane hydrates research project," Anne Vincent, Anadarko spokeswoman, said.

Nevertheless the rig was well received by drill crews, even though it was also a mobile scientific laboratory with an adjacent 64 ft by 64 ft (19.5 m by 19.5 m) support camp, also on stilts. Apart from the drilling crew, dozens of scientists were crowded into the facility.

"One engineer said he had never seen so many Ph Ds (doctors of philosophy) in one place in his life!" Williams said.

He was pleased the way the design worked and no downtime was recorded due to the rig. "It was perfect. It was very efficient," he said. "Anadarko patented the rig design. They are planning on utilizing it a lot more in the future.

"This rig can make all the difference. Three exploration wells are planned for the arctic for the next year and the reason is that the drilling season is so short so that unless you take some new technology like this platform there, nobody will be able to go out and explore the North Slope," Williams continued. "This rig is key to the economics for companies like Anadarko to do it."

Winterizing the rig was no easy job. Every steel element of the platform had to be examined to see if it would withstand the severe freezing temperatures experienced during the winter drilling season, when the thermometer commonly drops to -30?C. On several occasions temperatures nudged -40?C. Even nuts and bolts commonly found on rigs that operate in the lower 48 states in the United States had to be changed for higher-grade steels which would not shatter on impact in such temperatures. Standard hydraulic hoses had to be changed for ice-operations to ensure the fluids inside did not solidify. The derrick features a wrap-around canopy to provide weather protection. "We went through every single thing," Williams said. Aluminum was both light and stronger for the freezing conditions, he said. "Under cold conditions the aluminum is stronger. The Russians have been using aluminum for arctic drilling for years and years. It is perfect."

Design changes are possible for another lightweight arctic unit, but essentially, the engineers appear to have got it right first time. "This was perfect for the gas hydrates project," Williams said. He conceded a more permanent but lightweight arctic production rig would require casing handling facilities. "But fundamentally this thing performed extremely well."

Some of the special features on board include a mud chiller, necessary to ensure the drilling mud which came into contact with hydrate cores was at the same temperature, around -5?C, to avoid melting the frozen cores on contact.

Also the rig's drill floor was deliberately kept cold rather than being artificially heated to prevent gas disassociating from the 10 ft (3 m) hydrate cores as they were removed from the well bore on wireline. After being retrieved, the cores were analyzed in Dead Horse, 60 miles (100 km) from the drilling location.
Anadarko's Hot Ice 1 well was a ground-breaking project in every sense. It is the first to test the potentially huge potential of gas hydrates, estimated to be 590 Tcf of gas in Alaska's North Slope region alone, without a harmful impact on the sensitive environmental location in which they exist.

Despite the early end to the hydrate research program, the news is not all bad.

"While this delay will be expensive, it will allow plenty of time for evaluation, well testing, Vertical Seismic Profiles (VSP) and other activities before operations are resumed this fall, and it will be an excellent test of the arctic platform," Maurer Technology said.

Government approval for the platform has been given too. After visiting the well site, Carl Michael Smith, the DOE's assistant secretary for fossil energy said, "We saw what could be the drilling platform of tomorrow tapping the energy resource of tomorrow."

Also, Anadarko believes that, if the rig can be successfully deployed in the Arctic tundra, it may also be suitable for swamps elsewhere, such as onshore locations.

Smith emphasized that the platform design could be adapted and used in other environmentally sensitive regions, such as the wetlands of Louisiana and the high plains of the Rocky Mountains. Ultimately, the technology could help companies fight the declining oil and gas production in the United States.

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