A good explanation of why we use ice roads. From Petroleum News (www.petroleumnews.com), Vol. 12, No. 34, Week of August 26, 2007, courtesy of Rose Ragsdale.
Frozen byways offer vanishing footprint
Ice roads, winter byways that disappear with breakup in spring, are efficient and indispensable aids to oil and gas exploration on the North Slope. These ribbons of frozen water have paved the way for explorers to venture into remote areas of the Arctic since the 1950s when the Royal Canadian Mounted Police first fashioned crude roadways out of snow.
In Alaska, ice roads have successfully served remote locations in the Arctic, even during winters characterized by minus 70 degree Fahrenheit temperatures, 20-foot snowdrifts and limited daylight.
Early road construction in the 1920s featured bulldozing the tundra, but the practice proved disastrous. After just one season, such a route was impassable when the permafrost thawed.
Pioneer explorers turned to gravel to insulate the permafrost and stabilize roadbeds, airstrips, and drilling pads, but soon found that gravel mining and construction are expensive and environmentally harsh.
Oil and gas explorers quickly realized that ice roads could get the job done without leaving behind harsh reminders of their passage, and they cost a fraction of their gravel counterparts.
As construction of the trans-Alaska oil pipeline drew to a close in the 1970s, winter exploration roads made of snow and ice gained popularity on the North Slope.
Ice roads enabled explorers to use the same equipment to conduct exploration development programs that they used on gravel year-round, while minimizing the impact of their presence in the Arctic environment.
Rough riding on early roads
But in the 30 years since the late 1970s, ice road and ice pad construction technology has come a long way. Thanks to the growing expertise of operators and contractors, ice road construction evolved from simply packing snow into crude pathways across the tundra to mixing ice, water and snow into surprisingly durable thoroughfares that can withstand the heaviest loads all winter long.
Early ice road builders just packed snow and basically drove on it.
The “ice” road was very rough, built with caterpillars and trucks, according to James Trantham, a project manager for ARCO Alaska Inc.
“Basically any time a truck went over it, you had to go back and roll over it again, because it just kind of ‘squooshed’ the snow up,” Trantham told participants in an oil and gas technologies conference in 2000.
“So it was really high maintenance and probably not as safe a road as we have today,” he added
The original North Slope ice road crews consisted of a couple of bed trucks with “suck-on” water tanks (tanks that had water pumps combined with the tank, that could be used for filling the tanks with water), a loader or grader and a dozer, according to contractors at Peak Oilfield Services Inc.
“The technique was to take snow on the road route, smooth it down with either a dozer, or a loader with a drag or a grader and then to put water on it. This produced a road that a rig could be moved across, but were not necessarily very wide or smooth. The average crew was between 14 and 16 people, half on days and half on nights,” they said.
The soils of the North Slope have a permafrost layer that is frozen from a depth of about 1,600 feet to up to maybe a foot below the surface. The top portion of the permafrost is called the active layer, and it thaws in the summer and refreezes in the winter. When snow is dumped on top of the active layer, heat is trapped in the top half-foot or so below the tundra.
“So by packing the snow, you remove the air and actually promote the freezing. We do that from a rolligon, and then in time the trucks come down the middle of the road and squirt water out to the sides and start moving around on the ice road,” Trantham said.
Regulators set guidelines
“In the 1970s, it was pretty evident to everyone that the slope was a very sensitive area, and there were plenty of examples of tundra damage throughout the slope,” said Leon Lynch, a specialist with the Alaska Department of Natural Resources Division of Mining Land and Water.
DNR responded by passing regulations giving the slope a special land use designation. As a result, activities such as off road travel that were generally allowed on other state lands require a permit on the North Slope.
Among stipulations of the permits:
• Ice roads and ice pads must be built so that they are thick enough to protect the vegetative mat;
• Vehicles must be operated so that there will be no damage to the vegetative mat;
• All rehabilitation must satisfy the DNR commissioner; and
• DNR or another applicable land manager must determine what travel openings and closures should be based on snow cover and frost depth.
In the 1970s and 1980s, ice road builders started adding more water, especially close to the drill pads because there was so much traffic around the pads.
Later, they began to add more water to the roads, and use graders and snow blowers to maintain the ice roads.
“In the mid-80s, we actually started adding ice chips using a machine with a big pump that threw water up into the air where it turned into snow or ice chips (in the subzero temperatures of the 24-hour Arctic nights) and deposited on the road or pad where we would pack it down,” Trantham said. “After awhile we started actually mining ice chips from lakes to use in ice road construction.”
At the same time, the first insulated pads were built at the Leffingwell where insulation and boards were placed on the tundra to support the rig, he recalled. Later, the insulated foam was moved over to the KIC No. 1 well within the Arctic National Wildlife Refuge, he said.
The addition of delineators in the 1980s to mark the sides of ice roads also lessened the environmental impact of exploration on the tundra. Delineators allow exploration and construction crews to continue working in all but the very worst visibility, and they help to keep traffic on the ice roads.
Regulation drives ingenuity
As regulations governing the construction of ice roads and ice pads became more stringent, operators and contractors have responded, using technology to extend the length of the drilling season and to minimize damage to the tundra.
Regulators monitor the condition of the tundra closely and over the years have shortened drilling seasons as warmer weather has shortened North Slope winters.
The standard that regulators use for opening the tundra is 12 inches of frost and six inches of snow. Opening dates in general allowed for a six-month winter drilling season, but in the last decade, warmer temperatures have shortened the exploration season to about three and a half months.
Explorers responded with proposals for pre-packing trails and developing a graduated system of season opening. With such a system, instead of waiting for 12 inches of frost, lighter weight vehicles with lower ground pressure could actually operate on six or eight inches of frost. That became important for loaders and smaller vehicles used in ice road construction.
Working with regulators, operators and contractors refined this system until much of ice road construction occurs prior to the general tundra opening. This means that the sooner the industry gets to work safely, without damage to the tundra, the sooner they can complete their projects, and get off the tundra in spring, before breakup becomes a concern, DNR officials say.
Ice-based technology proves its metal
“The construction and use of ice roads by the petroleum industry provided access into environmentally sensitive areas without permanent impact from gravel road construction,” said Scott Guyer, a researcher with the Bureau of Land Management in Anchorage.
Based on a study of ice roads and ice pads construction, including work done in 2001 and 2002 for the Puviaq exploration well, in the northeastern corner of the National Petroleum Reserve-Alaska, BLM concluded in 2003 that “ice roads and pads that support drilling operations, if built with care, can have no long-term effects to the fragile tundra environment,” according to Guyer.
Today, ice road construction is similar to gravel road construction in many ways, only it is done with snow or ice. Dozers and drags pulled behind loaders are no longer used because they damage the tundra. Graders and loaders combined with on- and off-road water trucks and haul trucks are used to build the roads. Both water and snow are hauled from lakes to where roads are being constructed. Average crews number 24 to 32 people, depending on the scale of the project, again with half on days and half on nights.
To get an early start, operators and contractors use rolligons — large vehicles with large, smooth, low pressure tires that have a roller drive rather than a direct drive — which regulators have approved for travel on the tundra in both summer and winter. The rolligons are used to pack down the snow and place a layer of water on top of the tundra.
Technology spurs more improvements
On remote projects, where ice roads cannot link explorers with the gravel road system, all of the ice road equipment as well as drill rigs and support equipment must be hauled to the drill site. Originally Cat trains were used, but the practice was discontinued in the 1970s because of their detrimental effect on the tundra. Rolligons or track vehicles with balloon-like rubber tracks are now used to haul most loads across the tundra.
Early researchers would test the delicate touch of the rolligons by lying down on the tundra and allowing operators to drive the huge vehicles over their bodies.
Recently, rolligon crews have demonstrated even greater environmental awareness by carefully monitoring their activities on the tundra and taking steps to remove all signs of their passage, according to Sharmon Stambaugh, wastewater program manager for the Alaska Department of Environmental Conservation.
Peak, for example, has focused on rigorous vehicle maintenance to prevent spills of hydraulic fluids and other substances on the tundra.