Report Contents
[Report #. SR/O&G/2000-02]


Executive Summary

1. Overview of the Arctic National Wildlife Refuge

Geographic Setting

2. Analysis Discussion

Resource Assessment
Method of Analysis
ANWR Coastal Plain Assessment

3. Summary








































Potential Oil Production from the Coastal Plain of the Arctic National Wildlife Refuge: Updated Assessment

1.  Overview of the Arctic National Wildlife Refuge


    The Arctic National Wildlife Refuge (ANWR) 1002 Area of the Alaska North Slope represents an area of 1.5 million acres. The ANWR Coastal Plain Area includes the 1002 Area, State of Alaska lands to the 3-mile limit from the coast line, and approximately 92,000 acres of Native Inupiat lands. The area is located between the Prudhoe Bay area of the Alaska North Slope (ANS) and the Mackenzie River Delta of Canada along the Beaufort Sea. The area contains the largest onshore, unexplored, potentially productive geologic basins in the United States. The 1002 Area is approximately 8 percent of the 19 million-acre ANWR.

    The original Arctic National Wildlife Range of 8.9 million acres was created in 1960 by Public Law Order 2214. In 1980 the Alaska National Interest Lands Conservation Act (ANILCA) created 16 National Wildlife Refuges in Alaska. ANWR was enlarged to 19 million acres including the 8.9 million-acre wilderness area. Section 1002 of ANILCA deferred a decision on the management of oil and gas exploration and development of 1.5 million acres of potentially productive lands in the coastal plain of ANWR (which is why it is called the "1002 Area.") Potential for oil and gas discovery is great because the area is an extension of the productive trends west of the area toward Prudhoe Bay and east toward the Canadian discoveries of the Mackenzie Delta. Congressional action would be required to open the land for exploration and development. In 1987 the Department of Interior recommended opening the area for oil and gas exploration and development. In 1995 the House and Senate approved ANWR 1002 Area development in the Budget Act that was vetoed by the President. Interest in the area has increased recently with the increase in crude oil prices, declining domestic production, and increasing imports.

    The U.S. Geological Survey (USGS) updated in 1998 a petroleum assessment of the ANWR 1002 Area and the State and Native lands of the coastal plain. Based on the new information from the USGS and increased interest in the potential for production from the area, this analysis is presented to show the range of potential production that can be expected from the development of the ANWR Coastal Plain.

    Geographic Setting

    The 1002 Area of ANWR covers an area of 1.5 million acres between the Canning and Staines Rivers on the west, the Aichilik River to the east, the Beaufort Sea to the north, and the Brooks Range to the south. The Canning River western boundary is approximately 60 miles east of the Trans-Alaska Pipeline System (TAPS) and Prudhoe Bay. The 1002 Area extends approximately 100 miles from the Canning and Staines rivers (west boundary) to the Aichilik River east boundary. The area extends inland from the coast line of the Beaufort Sea from 16 to 34 miles to the foothills of the Brooks Range.

    The Alaska native Inupiat have approximately 92,000 acres around the village of Kaktovik. These lands along with the State offshore lands to the 3-mile state boundary are included in this analysis. The study assumes that the resources of these lands also will be developed if and when the Federal lands of the 1002 Area are opened for development.

    The map of Figure 1 shows the location of the 19 million-acre ANWR along the eastern boundary of the state with Canada. The locations of the 8.9 million-acre Wilderness Area and the 1.5 million-acre 1002 Area are shown in ANWR. The 23 million-acre National Petroleum Reserve–Alaska (NPR-A) is shown to the west of ANWR. Parts of the northeast area of NPR-A were recently opened for exploration and development. Between ANWR and NPR-A are the areas that are currently producing, including Prudhoe Bay. The path of the northern portion of the Trans-Alaska Pipeline (TAPS) is shown as it heads toward Valdez in southern Alaska. Also on the map are the Mackenzie River delta in Canada and the trend of the Brooks Range across northern Alaska.


    The description of the geology of the Coastal Plain is based on outcrops and geophysical data from seismic surveys of the area. The extrapolation of known geology and information from wells drilled offsetting the area provide additional confidence that potential oil and gas resources are located in the ANWR 1002 Area and the Coastal Plain. The stratigraphic section of Figure 2 shows the source rocks and petroleum reservoir rocks of the area. The reservoirs that are productive in other areas of the ANS are indicated. The 10 plays (similar geologic settings) that were evaluated by the USGS are also included in the figure.

    The following discussion of the sedimentary rocks in the area is from the Arctic National Wildlife Refuge, Alaska, Coastal Plain Reservoir Assessment, U.S. Department of the Interior, November 1986, p. 51.

    "The area in and adjacent to the 1002 area is underlain by sedimentary rocks several tens of thousands of feet thick. These rocks range in age from Precambrian (greater than 570 million years old) to Quarternary (Bader and Bird, 1986). In northern Alaska, rocks prospective for petroleum (oil and gas) are mostly Mississippian to Tertiary in age and overlie folded and truncated pre-Mississippian rocks. These rocks are divided into two sequences: the Ellesmerian sequence of Mississippian to Early Cretaceous age, and the Brookian sequence of Early Cretaceous and younger age. Deposition of the Ellesmerian sequence occurred when the land area was to the north and the seaway was to the south. During deposition of the Brookian sequence, the geography was reversed—the land area was to the south (the ancestral Brooks Range) and the seaway was to the north, much as it is today. The differentiation of these two sequences is important in understanding depositional history, and in projecting trends of reservoir rocks. Futhermore, properties of the Ellesmerian sandstones are generally better than those of the Brookian sequence."

    The unique combination of source rocks and reservoir traps is similar to the geologic combination of events that caused the productive reservoirs to the west including the Prudhoe Bay Field. Therefore, similar results are anticipated.