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Vol. 12, No. 28 Week of July 15, 2007
Providing coverage of Alaska and northern Canada's oil and gas industry

Insulated ice pads extend winter season

Innovation minimizes environmental impact and shrinks exploration footprint on North Slope, while cutting drilling program costs

Rose Ragsdale

For Petroleum News

Regulations designed to protect the fragile Arctic tundra and shorter winters have given Alaska North Slope operators both economic and environmental impetus to develop clever ways to extend their drilling seasons.

One such innovation is insulating drilling pads to prevent them from thawing during the short Arctic summers. This technology succeeded in extending exploratory drilling seasons as much as 50 percent, and earned recognition from the U.S. Department of Energy as one of the Alaska oil and gas industry’s best practices.

Currently, Arctic drilling seasons are restricted to 135-170 days, at best lasting from late November until mid-May. Operators not only must quickly build temporary ice roads to drilling sites, they also are required to construct ice pads, often as large as an acre. Drilling rigs and the remote camps that support them rest on these pads.

Drilling crews confine their activities to these islands of ice all winter and are careful to not stray onto the tundra beyond them. By mid-May, all traces of the rigs, camps and equipment must be removed to non-sensitive areas.

In the 1970s, regulations on the North Slope were less strict and the first ice roads invariably ended at a drill rig resting on a gravel pad. In very remote locations, a gravel airstrip also might be nearby.

The approach resulted in a potential loss of eight to 10 acres of tundra habitat, and should the drilling program end with a dry hole, state regulators said operators could show no economic benefit from the lost habitat.

Operators switched to drilling pads made of ice in the 1980s, recognizing them as less costly and environmentally intrusive than their gravel predecessors. Still, by the 1990s, conventional ice pads were no longer meeting the needs of operators because they melted in spring and had to be rebuilt the following winter.

Adding prefabricated insulation to ice pad construction made ice pads last for multiple seasons. It enabled operators to build ice pads before a winter drilling season started, and preserve the site through the summer thaw for re-use the following winter.

More importantly, the technique gave the companies up to a two-month head start on conventional technology. Insulated ice pads, in effect, extended the available drilling season to 205 days and effective well operations to 160 days. This enabled drillers to complete at least one exploratory well, and sometimes two penetrations in a single season, operators say.

What’s the allure of single-season completions?

Completing a multimillion-dollar exploratory well in one season cuts mobilization costs considerably, not to mention reduces related environmental effects. It also shortens the time between initial investment and return on that investment, and gets valuable subsurface data to exploration teams sooner than otherwise would be possible. Such speedy feedback enhances planning, operators say.

DOE cites BP success with ice pads

When a BP Exploration (Alaska) Inc. engineering feasibility study indicated that constructing an insulated ice pad in March 1993 at Yukon Gold No. 1 on the North Slope would significantly extend the winter drilling season, BP built a 390-by-280-foot ice pad covered with nearly 600 wind-resistant insulating panels. Summer visits confirmed that the ice beneath the panels remained sufficiently frozen. When the panels were disassembled in October 1993, they had not bonded to the resting surface, or scattered, and nearly 90 percent were in excellent condition and reusable.

BP began drilling in mid-November, two months ahead of conventional Arctic practice. With such an early start, Yukon Gold No. 1 was completed and the company had time to begin drilling at nearby Sourdough No. 2, where the insulated panels were placed under the drilling rig to give BP the option of leaving the rig on location over the summer and avoiding remobilization if the well wasn’t completed before season’s end. This proved to be unnecessary since the Sourdough well also was completed during the same season.

Overall, BP netted a cost savings of more than $2.3 million from the two single-season well completions, according to DOE. In addition, the tundra endured significantly less impact than would have been the case had BP’s crews been required to move seasonal equipment back and forth between two or more drilling seasons.

DOE also reported that subsequent site monitoring showed no long-term environmental impacts from use of the insulated ice pads.



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Petroleum News March 2002 reprint

Following is abbreviated text from an article that appeared in the March 24, 2002, issue of Petroleum News by Kristen Nelson

Phillips Alaska is planning winter exploration drilling next year on some of the farthest west leases in the National Petroleum Reserve-Alaska. The company has applied to build a 1.5 acre insulated ice pad in order to keep a drilling rig in the area over the summer.

The Puviaq insulated pad, according to the U.S. Army Corps of Engineers, would be west of Teshekpuk Lake approximately 67 miles southeast of Barrow in section 35 township 16N range 10W, Umiat Meridian. The Corps said no drilling operations are planned for this site. The rig would be moved to a “nearby winter exploratory drilling site” after tundra travel is approved for the 2002-2003 winter season.

This prospect is some 45 miles west-northwest of the Trailblazer prospect BP drilled last year, and, other than development drilling at the Barrow gas field, will be the farthest west North Slope drilling in several decades. …

Phillips will mobilize a crew … and construction equipment by rolligon or other all-terrain vehicles to the site for pad construction, the corps said. The drilling rig will be moved to the site by rolligon after the pad is built but before the close of tundra travel this spring and then moved to a nearby winter exploratory drilling site after winter tundra travel reopens in late 2002 or early 2003.

The corps said the insulated ice pad would be approximately 245 feet by 265 feet by six inches thick. Construction is expected to begin in March. The ice pad will be covered with standard … 4 to 6-inch thick, 25 psi expanded polystyrene foam insulation. The panels weigh about 700 pounds each.

The polystyrene panels will be sandwiched between 8-foot by 24-foot sheets of 7/16-inch thick oriented strand board. Reinforced polyethylene film will be laid under the panels to prevent them from bonding to the ice pad to ensure easy pick-up.

Exposed panel surfaces will be covered with a white, opaque surface fabric that is designed to minimize thermal gain, minimize rainwater infiltration to the ice surface and minimize thermal erosion of the ice pad.

Standard rig mats will be placed on the insulated panels with the drilling rig sitting on the mats. Ice berms may be constructed to divert spring runoff from the pad. The berms will be about 3 feet high, roughly trapezoidal in cross-section with an 8-foot wide base and a 4-foot wide top.

Rope anchors will be used to resist wind uplift forces on the panels not protected by the rig and the site will be monitored every two to three weeks over the summer to collect data from 10 or more thermistor sensors monitoring ice-surface temperatures and to provide side maintenance. …