The North Slope - A Current Overview
Authors: Davis Louis F. 
Published: December 2007

Seldom has a new petroleum discovery attracted the amount of attention as has the Prudhoe Bay discovery on the North Slope of Alaska. It comes at a time when the U.S. petroleum demand is increasing steadily and when crude reserves are decreasing. This demand is expected to continue to grow, and by 1980 it will be about 6.7 million B/D, more than the combined productive capacity of the U.S. (excluding the North Slope) and the present import level of 23 percent. It has been estimated that perhaps 12 to 15 billion bbl of oil have been perhaps 12 to 15 billion bbl of oil have been discovered on the North Slope to date including the Prudhoe Bay field and the other announced discoveries. While all of this cannot be placed in the proved category at this time, it does represent a potential that approaches one-half of the present proved reserves in the U.S. Even with this addition, proved reserves in the U.S. Even with this addition, however, a considerable improvement in the industry's recent finding record is needed to avoid undue reliance on foreign sources of supply.

NORTH SLOPE ENVIRONMENT

The Prudhoe Bay discovery focused the attention of people throughout the world on an area that is remote, hostile, and with which very few people were familiar" The Prudhoe No. 1 discovery well and the Sag No. 1 confirmation well an located in an area that is approximately 390 miles north of Fairbanks and 600 miles north of Anchorage. The Trans-Alaskan pipeline will extend 800 miles to reach the southern coast of Alaska, which is currently the staving point for shipments of Alaskan crude. The entire area running northward from the Brooks Mountain Range to the Arctic Ocean is commonly referred to as the North Slope. However, most of the industry exploration activity has been conducted in the area bounded on the west by the Naval Petroleum Reserve No. 4 and on the east by the Arctic Wildlife Refuge. Operations in this area encounter many unique and difficult problems. In the winter, temperatures can drop to a -60 degrees F, which causes some metals to become brittle and some machines to become inoperative. Much of the North Slope is a vast level plain that receives only 4 to 6 in. of precipitation a year and could be classified as an precipitation a year and could be classified as an Artic desert. Because it is essentially flat, travel over this area in the winter when the ground is frozen presents no particular problems. Winds of from 70 to presents no particular problems. Winds of from 70 to 80 mph are not uncommon, and the blowing snow can result in white-outs with near zero visibility and drifts that can cover trucks and camp buildings. The flatness of much of the North Slope results in very slow drainage, and in the summer it is transformed into a vast spongy bog dotted with hundreds of shallow lakes and covered with a thin carpet of grasses and flowers known as tundra. The tundra survives on a thin (2-ft thick) layer of nutrient-deficient silty top soil, with the permafrost or permanently frozen ground beneath it extending to permanently frozen ground beneath it extending to depths of 2000 ft. Other unusual features common in this area are ice wedges. The tundra cracks open in the winter as the extremely cold temperature causes the surface layers to shrink more than those underneath. When the thaw occurs in the summer, these cracks filled with water and then refreeze the following year, creating an ice wedge. If an ice wedge becomes exposed during the summer months, such as along the edge of a river, it will begin to thaw and drain and eventually the ground above it will collapse, creating a natural depression. When viewed from the air, an area with numerous ice wedges creates what is commonly referred to as polygonal ground.

In much of this area, the permafrost has a high ice content and if the tundra that insulates it from the summer heat is damaged, the ice thaws and subsidence begins. If the damage occurs on a slope and is not corrected, serious erosion can result. Vehicular movement across this surface in the summer could destroy a delicate balance. To preserve the tundra, Atlantic Richfield Co. instituted the following practices that are enforced in all of its North Slope practices that are enforced in all of its North Slope operations:

Prohibiting all vehicular traffic that causes permanent damage to the tundra; permanent damage to the tundra; Minimizing the number of roads and trails that are constructed; Taking necessary steps to prevent erosional deterioration to existing roads and contiguous lands; Practicing good housekeeping by keeping all cash collected; and Disposing of all sewage and garbage in proper facilities.

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