Introduction

The area currently known as the

National Petroleum Reserve–Alaska

(NPRA, fig. 1) was originally designated in

1923 as Naval Petroleum Reserve No. 4

(NPR–4). It was one of four U.S. regions

thought to contain significant amounts of

oil that were to be reserved for national

crises. Geographic and geologic knowledge

of the NPR–4 was only superficial in 1923.

Earlier exploration, however, had shown

that the region contained the ingredients

necessary for oil accumulations to exist:

source rocks, reservoir rocks, and geologic

structures that could trap petroleum. Oil

seeps on the coast and the size of the area

(some 37,000 square miles, about the size

of Indiana) reinforced the notion that significant quantities of petroleum were present.

Since 1923, various exploratory programs have been undertaken in the NPR–4,

first by the Navy, then by the U.S. Geological Survey (USGS), and, most recently, by

industry. The government programs resulted in the discovery of several small, noncommercial oil and gas deposits and the

accumulation of a vast array of data, which

have been stored in many locations by several agencies. Although reports and maps

documenting these programs have been

published, large amounts of the basic data

remain in hard-to-access paper copies or

deteriorating, old- or outdated-format magnetic tape or poorly archived rock samples.

Recent discoveries of oil near the

northeast corner of the NPRA have

renewed industry interest. In response to

this interest and the initiation of lease sales

by the U.S. Bureau of Land Management,

the USGS has undertaken a program to

ensure availability of the information accumulated since 1923. To the extent possible,

these data will be available in digital format.

Exploration History

For an area intended as a secure

source of petroleum, very little was known

in 1923 about NPR–4’s petroleum potential. Accordingly, the Navy requested that

the USGS map and assess the petroleum

resources of this area. The task was completed between 1923 and 1926, and results

were published in 1930. The report was

based on traverses along the larger rivers

and reconnaissance-scale maps of the geology and geography. Oil shale source rocks

and anticlinal and overthrust structures

were documented in the Brooks Range, but

prospectors were cautioned about the

adverse geographic factors and the consequential high costs. The report recommended drilling near the Cape Simpson oil seepages as the next step in evaluating the

petroleum potential, followed by geologic

field studies and then additional drilling in

areas that appeared favorable. 

In 1944, the Navy began a more

detailed exploration program that included

field mapping, seismic profiling, and aeromagnetic surveys; the geologic component

of this work was the responsibility of the

USGS. This pioneering effort in Arctic

petroleum exploration resulted in the

drilling of 45 shallow core tests and 36 test

wells. The program ended in 1953 and

resulted in the discovery of several small

oil and gas deposits. Even though no commercial deposits were found, the vastly

improved understanding of the geologic

history of northern Alaska served as a

foundation for future exploration and established the feasibility of petroleum exploration and production in the Arctic.

Motivated by private industry’s 1968

discovery of oil at Prudhoe Bay (the largest

oil accumulation in North America) and the

oil embargo of 1973, the Navy authorized a

new exploration program in the NPR–4.

Between 1974 and 1977, seven test wells

were drilled in the northeast corner of the

NPR–4; although they followed the trend

of Prudhoe Bay, no significant accumulations were found. In 1976, the NPR–4 was

redesignated as the NPRA. At the same

time, the USGS was charged to assess the

oil and gas potential of the NPRA and to

discover commercially producible petroleum accumulations. From 1974 to 1982,

extensive seismic surveys were conducted

(fig. 2), and 28 test wells were drilled,

nearly every one of which had shows of oil

and gas. Two gas accumulations were discovered that were later turned over to the

North Slope Borough to supply the village

of Barrow.

The National Petroleum Reserve–Alaska (NPRA) Data Archive

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet FS–024–01

March 2001

ALASKA

Trans-Alaska

Pipeline

Point Barrow

Prudhoe Bay

100 mi

Brooks Range Front

Arctic National

Wildlife Refuge

National Petroleum 

Reserve–Alaska

Canada Alaska

Chukchi Sea

Beaufort Sea

Cape Simpson

Approximate location of

3-mile boundary between

State and Federal jurisdiction

Figure 1. Location of the National Petroleum Reserve–Alaska and the Prudhoe Bay oil field.

The North Slope is north of the Brooks Range.

100 miles

Figure 2. Locations of lines in the NPRA along

which seismic data were acquired from 1974

to 1981 as part of the Government exploration

program.
When the NPRA government exploration program ended in 1982, responsibility for management and protection of the

NPRA was transferred to the U.S. Bureau

of Land Management. The U.S. Congress

authorized competitive oil and gas leasing,

and four lease sales were held between

1981 and 1984. One exploratory well was

drilled on a lease in 1985; it was a dry hole.

Technological Advances

In the two decades following the 1968

discovery of the Prudhoe Bay oil field,

exploration focused on similar-scale, multibillion-barrel fields because fields containing less than a billion barrels were not economically viable then. In the past 15 years,

technological advances—notably 3-D seismic profiling, sequence stratigraphy (a relatively new technique of geologic analysis), and advances in well-site development—have reduced the costs of exploration and development to the point that

now fields as small as 100 million barrels

that are tens of miles from infrastructure

may be economic. Exploration has

increased on the North Slope of Alaska in

recent years, and several small but viable

fields have been discovered, including the

429-million-barrel Alpine field (fig. 3).

With this discovery in 1994, industry interest in the NPRA increased, and the Federal

Government reopened part of the NPRA to

leasing in 1999.

Data Archive Problems

The Federal Government archives all

data from Government exploration in the

NPRA. Until recently, this archive existed

in a variety of forms in many locations;

accessing it in any organized way was

impossible. This material was in danger of

being misplaced or deteriorating to a point

that it was no longer usable. The data consist of the following:

• Demultiplexed seismic-reflection data

collected along about 15,000 line-miles.

The data and supporting files are on

about 3,500 9-track tapes and are

accompanied by about 14,000 pages of

paper documents.

• Processed seismic data and supporting

files on about 1,000 9-track tapes.

• Drill records for more than 100 wells

and including 745 mylar well logs.

These records occupy seven file cabinets.

• More than 1,400 geologic reports, maps,

and cross sections.

• About 10,000 feet of drill core, which

represents about 2 percent of the total

footage (500,000 ft) of wells drilled in

the NPRA. A split of about half of the

10,000 feet of core is in the USGS Core

Research Center in Denver, Colo. The

complete set of cores is at the Alaska

Geologic Materials Center, Eagle River,

Alaska.

• Aeromagnetic and gravity data, which

were available largely as paper records

consisting of interpretive maps and data

tables.

The 9-track seismic data are 20 or

more years old; over time, tapes deteriorate, are misplaced, or are separated from

the paper documentation. Well logs on

mylar and related paper drilling records are

accessible only by one person at a time and

thus have limited use. The well cores are

unprocessed and are not easily accessible

by USGS or other scientists.

Data Rescue

The USGS is capturing, cataloging,

and archiving the data to make them readily available in a usable form to USGS scientists and the public. Rescue methods for

different types of data are described below:

• Digital seismic data, supporting files,

and paper documentation.—The digital

seismic data are being copied from the

original 9-track tapes to compact discs

(CD’s). The paper documentation is

being scanned and converted to graphic

images. These items will be combined

with the ASCII supporting files on CD

and organized by acquisition year and

seismic line identifier.

• Drill records and geologic reports,

maps, and cross sections.—Drill

records, reports, maps, and cross sections are being converted to graphic

images and stored on CD.

• Mylar well logs.—The mylar well logs

are being scanned and converted to

graphic image files with appropriate log

curves selected and digitized into Log

ASCII Standard (LAS)-format digital

well logs. Both the images and the digital well logs are being cataloged and

archived on CD. 

• Drill cores.—The drill cores are being

slabbed, photographed, cataloged, and

archived at the USGS Core Research

Center in Denver, Colo.

• Aeromagnetic and gravity data.—The

data files are being scanned and converted to graphic images or transcribed

into spreadsheets or data bases. The data

are cataloged and stored on CD.

The first rescued information is available in USGS Open-File Report 99–015,

Selected Data from Eleven Wildcat Wells

in the National Petroleum Reserve in

Alaska. The CD contains the following

information:

• Drill core photographs (fig. 4)

• Depths to selected stratigraphic horizons

• Geologic and drilling reports, scanned

from originals

• LAS-format core gamma ray data

• LAS-format borehole log data

• Permeability, porosity, and grain-density

data

Open-File Report 99–015 also contains full reference information, including

metadata and sources of all information on

the CD. The information is accessible

through commonly used web browsers and

text readers. Future publication plans

include a combination of CD’s and Internet

access to the complete NPRA data set.

For more information, please contact:

Kenneth J. Bird

U.S. Geological Survey

345 Middlefield Road, MS 969

Menlo Park, CA 94025

E-mail: kbird@usgs.gov

Telephone: 650–329–4907

Alpine

Field

1999 Lease 

Sale 

Planning Area

well

Point Barrow

100 mi

Figure 3. Location of the Alpine oil field, Government-drilled wells, and the 1999 Lease

Sale Planning Area in the NPRA.

Figure 4. Drill core photograph from

USGS Open-File Report 99–015.