When oil companies drill for oil in the permafrost they must create stable surfaces for equipment, roads, pipeline routes, and personnel. Gravel pads are a common solution and have the added benefit that they can take advantage of local gravel deposits, reducing the time and cost of transporting material to the site. The pads are usually 3 to 6 feet thick and require large amounts of clean material to ensure the pad is stable.

For example, a recent proposal from Hilcorp Alaska seeks to expand H pad in the Milne Point unit by 4.7 acres, which would require approximately 60,500 cubic yards of gravel to be laid down on the north, west, and south sides of H Pad, according to the permit application filed with the Alaska Department of Natural Resources. The proposal anticipates gravel will be placed this spring, with compaction from June to August.

This pad expansion would allow Hilcorp Alaska to drill twenty-five new wells. If constructed, once the pad is in the place the first round of twelve wells is slated for drilling in September 2024, with the second round of thirteen drilled in 2025.

Gravel pads such as these are an essential tool in North Slope development. Aerial imagery of Alaska’s oil patch shows beige dots scattered among numberless ponds and a webbing of greenery. These are the footholds where North Slope producers confine their work as they tap into pools of petroleum. Advances in directional drilling have allowed operators to consolidate onto smaller and smaller footprints while wells extend horizontally for miles, saving costs on infrastructure and reducing the effect on the environment.

While all gravel pads provide a stable base, not all those industrial islands are on solid ground. Some are literally at sea.

The first artificial island built for North Slope offshore oil development was Endicott, part of the Duck Island unit just east of the Prudhoe Bay field. In waters about 15 feet deep, Alaska Interstate Construction piled gravel at the end of a causeway connected to shore. Built for BP in 1987, Endicott is now operated by Hilcorp Alaska.

After Endicott proved that offshore development in the Arctic was possible, BP followed up a decade later with Northstar. Royal Dutch Shell discovered the oil pool in 1984, but the site was 5 miles offshore—too far for a causeway, like at Endicott. By 1999, BP pushed the project forward by designing a subsea pipeline to bring Northstar’s oil ashore. The production well was built on top of 700,000 cubic yards of gravel poured through holes cut in the frozen Beaufort Sea. To protect the squarish shoal from shifting sea ice, the edges are reinforced with concrete mats. Northstar has been in production since the fall of 2001, also operated by Hilcorp Alaska.

The techniques that made offshore gravel pads possible were perfected by the crews who built them on the tundra.

Cruz Construction, a contractor with decades of experience working on the North Slope, provides solutions for exploration, ice roads, road and pad development, tundra transport, and snow trail development.

It has completed more than $1 billion worth of heavy civil, oil and gas, mining, and marine projects in Alaska and the Lower 48.

The company performs all of its gravel activities in-house, including drill and shoot—the time-honored method of drilling a hole to a good depth, placing a charge in it, packing the hole with dirt, then lighting the charge.

“The majority of projects mine gravel in the wintertime utilizing drill and shoot as the primary mechanism of the mining process,” says Miller. “We build ice roads from the material sites to the construction sites.”

In 2017, Cruz Construction completed the Moose Pad project, an expansion of the Milne Pit gravel mine in the Kuparuk oil field, to support the construction of a drilling and production gravel pad. The project cost $6.3 million.

Cruz’s comprehensive history in Alaska has led it to an interesting transportation solution when it comes to transporting material for gravel pads: four-wheelers.

“It is rare that we have to fly equipment in,” says Cruz Construction Senior Executive Vice President of Operations Jeff Miller. “The primary mode for mobilization for most oil and gas support projects is an ATV mob. The secondary is barging, but most barging mobilizations require ATV support, too.”

All-terrain vehicles are just the beginning of the equipment needed for such a project. “The equipment list is large and diverse,” Miller says, “but regardless of what you use, it needs to be Arctic rated.”

The 2017 Moose Pad project involved large-scale mine site development, including drilling and blasting overburden and gravel, winter hauling and placement of 315,000 cubic yards of gravel, construction of 3 miles of ice roads over tundra, cross drainage improvements, and summer post-thaw compaction and grading winter-placed gravel.

Ice and snow are the other way to insulate the tundra from damage. While the winter cover is down, contractors can build year-round armor for sensitive sward.

“Our biggest challenge is having the weather conditions to achieve the mining, hauling, and placing of the necessary volume of material,” Miller says. “The biggest challenges vary from year to year and project to project, but weather, terrain/environment, project financing, permitting, asset availability, et cetera are a few of the things that seem to always be present.”

Where the tundra hides a wealth of oil and gas resources, the workers who extract it can confidently stand on the sturdy surface of gravel pads.