Oil and Gas Resources of the Arctic Alaska Petroleum 

Province

By David W. Houseknecht and Kenneth J. Bird

Abstract

The Arctic Alaska Petroleum Province, encompassing 

all the lands and adjacent Continental Shelf areas north of the 

Brooks Range-Herald arch, is one of the most petroleum-productive areas in the United States, having produced about 15 

billion bbl of oil. Seven unitized oil fields currently contribute to production, and three additional oil fields have been 

unitized but are not yet producing. Most known petroleum 

accumulations involve structural or combination structuralstratigraphic traps related to closure along the Barrow arch, a 

regional basement high, which has focused regional hydrocarbon migration since Early Cretaceous time. Several oil accumulations in stratigraphic traps have been developed in recent 

years. In addition to three small gas fields producing for local 

consumption, more than 20 additional oil and gas discoveries 

remain undeveloped.

This geologically complex region includes prospective strata within passive-margin, rift, and foreland-basin 

sequences. Oil and gas were generated from multiple source 

rocks throughout the region. Although some reservoired oils 

appear to be derived from a single source rock, evidence for 

significant mixing of hydrocarbons from multiple source rocks 

indicates a composite petroleum system. Both extensional and 

contractional tectonic structures provide ample exploration 

targets, and recent emphasis on stratigraphic traps has demonstrated a significant resource potential in shelf and turbidite 

sequences of Jurassic through Tertiary age.

Recent estimates of the total mean volume of undiscovered resources in the Arctic Alaska Petroleum Province by 

the U.S. Geological Survey and U.S. Minerals Management 

Service are more than 50 billion bbl of oil and natural-gas 

liquids and 227 trillion ft3 of gas, distributed approximately 

equally between Federal offshore and combined onshore and 

State offshore areas.

Introduction

The Arctic Alaska Petroleum Province, one of the most 

petroleum-productive areas in the United States, currently is 

an exploration target for new additions to reserves. New discoveries, along with the economic benefits of applying innovative exploration and production technologies, evolving industry demographics, rising oil and natural-gas prices, and the 

anticipation that northern Alaska natural-gas resources may 

become economic and marketable through a planned pipeline, 

have stimulated a renewed intensity in leasing and exploration 

activity. Until recently, this activity was focused mostly on 

State onshore and offshore areas of the central North Slope, as 

well as the Federal offshore area immediately adjacent to the 

Federal-State boundary. Exploration in these areas has been 

mostly for oil in relatively large structural or combination 

structural-stratigraphic traps similar to that at the Prudhoe Bay 

field (fig. 1), where approximately 12 billion bbl of oil has 

been produced and more than 3 billion bbl of reserves remains 

(table 1; Alaska Division of Oil and Gas, 2006).

Discovery of the 500-million-bbl Alpine oil field in 1994 

(fig. 1) on the Colville River delta and success at the nearby 

Tarn oil field (>100 million bbl recoverable) stimulated interest in exploration for stratigraphic traps. As a result, exploration since 1995 has progressed westward and southward from 

the main productive fairway into areas where new oil fields in 

stratigraphic traps may be discovered.

The purpose of this chapter is to provide an overview of 

known petroleum accumulations in the Arctic Alaska Petroleum Province and to review recent assessments of undiscovered, technically recoverable, conventional petroleum 

resources. Those resources associated with continuous-type 

(unconventional) petroleum accumulations, such as lowpermeability basin-centered gas, gas hydrates, and coal-bed 

methane, are not addressed.

Geologic and Tectonic Setting

The Arctic Alaska Petroleum Province extends about 

1,100 km from the United States-Canadian border westward to 

the maritime boundary with Russia, and from 100 to 600 km 

northward from the Brooks Range to an arbitrary boundary at 

the approximate edge of the Continental Shelf (fig. 1; Bird, 

2001). Although the edge of the Continental Shelf provides 

a well-defined physiographic boundary for the province, this 

edge does not represent a geologic limit to potential petroleum 

resources. The offshore part of the province is characterized 

Studies by the U.S. Geological Survey in Alaska, 2005

U.S. Geological Survey Professional Paper 1732–A
 Oil and Gas Resources of the Arctic Alaska Petroleum Province

by a relatively narrow (100 km wide) shelf in the Beaufort Sea 

(Scherr and Johnson, 1998) and a broad (600 km wide) shelf 

in the Chukchi Sea (Sherwood and others, 1998). The province is bounded on the south by the Brooks Range-Herald arch 

orogenic belt and offshore to the north by the passive continental margin of the Canada Basin (fig. 1).

The principle geologic features of the Arctic Alaska 

Petroleum Province are summarized in figure 1. The Chukchi 

and Arctic platforms are remnants of a late Paleozoic through 

early Mesozoic south-facing (present coordinates) continental 

margin. These features are separated by the Hanna trough, a 

north-trending structural sag characterized by extensional normal faulting, in which thick layers of sediment accumulated 

mostly during the Devonian(?) and Mississippian and into the 

early Mesozoic. Sherwood and others (1998) considered the 

Hanna trough to be a failed rift. The Barrow arch and adjacent 

hingeline fault zone formed during Jurassic to Early Cretaceous rifting. The oceanic Canada Basin and flanking passive 

margin resulted from this rifting event. At the southern margin 

of the Arctic and Chukchi platforms and overlapping in time 

with rifting to the north, an arc-continent collision created 

the Brooks Range, the adjacent Colville foreland basin, and, 

presumably, the Herald arch orogenic belt (Moore and others, 

1994). Contractional deformation in Tertiary time created the 

fold-and-thrust belt that extends northward from the Brooks 

Range and is expressed topographically as the foothills belt 

(Moore and others, 1994).

Stratigraphy

Although the stratigraphic record of the Arctic Alaska 

Petroleum Province extends into the Precambrian, rocks with 

a potential for petroleum accumulations are dated at Mississippian and younger (fig. 2). The traditional grouping of the 

rocks into tectonostratigraphic sequences, as proposed by 

Lerand (1973) and modified by later investigators, emphasizes 

tectonic history, provenance, and genetic relations. This section briefly describes the tectonostratigraphic sequences north 

of the Brooks Range.

The Franklinian sequence mostly includes Devonian and 

older sedimentary rocks representing diverse origins and a 

complex geologic history. These rocks have been buried and 

metamorphosed beyond the thermal stage of oil preservation 

across most of Arctic Alaska, and so they are considered to be 

economic basement.

B R O O K S

R A N G E

HERALD

ARCH

Trans-Alaska 

Pipeline System

R u s s i a

U n i t e d S t a t e s

Beaufort Sea

Chukchi Sea

N P R A

A N W R

1 0 0 2 A r e a

C a n a d a B a s i n

( o c e a n i c )

North Chukchi

Basin

Chukchi

platform

C o l v i l l e

( f o r e l a n d )

C a n a d a

U n i t e d S t a t e s

Hope Basin 0 100 200

KILOMETERS

Hingeline fault

zone

PA S S I V E

M A R G I N

H

a

n

n

a tro

u

g

h

100 m

North limit of contractional structures

Arctic

platform

PB

AF

Barrow

Arch

B a s i n

Figure 1. Arctic Alaska Petroleum Province, showing locations of principal geologic features. AF, Alpine oil field; ANWR, Arctic 

National Wildlife Refuge; NPRA, National Petroleum Reserve in Alaska; PB, Prudhoe Bay oil field. Modified from Bird (2001).
Figure 2. Generalized stratigraphic column for the Arctic Alaska Petroleum Province, emphasizing petroleum-prospective rocks and their tectonostand reflecting major stages in tectonic development of the region. GRZ, gamma-ray zone of the Hue Shale.

.

. .. . .

.. . ... .

. . .

.

.

. .

.

. . .

.

. .

. . .

. .. . .

.. . ... .

. . .

.

.

. .

.

. . .

.

. .

. .

ELLESMERIAN

FRANKLINIAN BEAUFORTIAN

BROOKIAN

< MEGASEQUENCES

KingakShublikGRZ? Lisburne? Canning

Endicott(gas)

Known andpotential oilsource rocks

359

AGE

(m.y.)

66

146200251299318

JURASSIC

CRETACEOUS

CENOZOIC

MISSISSIPPIAN

PENNSYLVANIAN

PERMIAN

TRIASSIC

PREMISSISSIPPIAN

Pebble shale unit

SW Gubik Fm. NE

Kingak Shale

Shublik Fm.

Endicott Group

Lisburne Group

Sadlerochit

Group

Basement

Sag River Ss.

Kuparuk Fm. Lower Cretaceous unconformity

Torok Fm.

Seabee Fm.

Canning Fm.

Sagavanirktok Fm.

GRZ

Hue Shale

Prince Creek Fm.

Schrader Bluff Fm.

Sagavanirktok Fm.

Fortress

Mountain

Fm.

Tuluvak Fm.

Nanushuk Fm.

Etivluk Group *

*Allochthonous rocks

MarinCondNonm

Marin

MetasCarboGraniHiatu

EX
 Oil and Gas Resources of the Arctic Alaska Petroleum Province

The Mississippian through Triassic Ellesmerian sequence 

consists of carbonate and shallow-marine to nonmarine siliciclastic deposits. On the Arctic platform, Ellesmerian strata are 

continental-shelf deposits that accumulated on a south-facing 

passive margin. From a northern pinchout or erosional edge 

near the Barrow arch (fig. 1), they thicken southward to about 

2 km (Moore and others, 1994). Westward, Ellesmerian strata 

thicken rapidly into the Hanna trough and, beyond, thin onto 

the Chukchi platform. In the Hanna trough, Devonian(?) and 

Mississippian rocks are interpreted as synrift deposits, and 

post-Mississippian strata as thermal sag-phase deposits (Sherwood and others, 1998). Although the Ellesmerian sequence 

contains both petroleum source and reservoir rocks, source 

rocks, which lie near the top of the sequence, did not generate 

petroleum until buried by Beaufortian and Brookian deposits.

The Jurassic and Lower Cretaceous Beaufortian sequence 

(Hubbard and others, 1987), consisting of synrift deposits 

derived locally or from the north, is a stratigraphically complex, mud-dominated sequence with multiple unconformities 

and large variations in thickness (Houseknecht and Bird, 2004) 

that contains petroleum source and reservoir rocks. Normal 

faulting and formation of sediment-filled grabens and halfgrabens, some containing more than 3 km of fill, occur mainly 

north of the present coastline. Uplift and erosion along the rift 

margin created a regional Lower Cretaceous unconformity 

(fig. 2), considered to be the “breakup” unconformity (Grantz 

and May, 1982). This unconformity, which progressively 

truncates older rocks northward onto the Barrow arch, is partly 

responsible for many of the largest oil accumulations in northern Alaska by providing a hydrocarbon-migration pathway 

for charging multiple, subunconformity reservoirs. Cretaceous 

mudstone overlying the unconformity serves as a seal, creating combination structural-stratigraphic traps under favorable 

circumstances, such as at the Prudhoe Bay oil field.

Cretaceous and Tertiary deposits derived from the 

Brooks Range orogen are assigned to the Brookian sequence. 

These voluminous deposits filled the Colville foreland basin, 

overtopped the rift shoulder (Barrow arch), and built the passive margin that forms the present continental terrace north 

of Alaska. The Brookian sequence consists of a complex 

assemblage of siliciclastic strata that include distal, condensed 

marine mudstone (Hue Shale); relatively deep marine basinal, 

slope, and outer-shelf mudstone and turbidite sandstone 

(Torok, Seabee, and Canning Formations); and shallow-marine 

to coal-bearing nonmarine sandstone, mudstone, and conglomerate (Nanushuk, Tuluvak, Prince Creek, Schrader Bluff, 

and Sagavanirktok Formations). Organic-rich beds of the Hue 

Shale are important oil source rocks, and Brookian mudstones 

may contain gas source rocks. Reservoir rocks consist of 

turbidite and shallow-marine to nonmarine sandstone, and 

known oil and gas accumulations occur in both structural and 

stratigraphic traps within the Brookian sequence. Sediment 

accumulation in the Colville Basin and on the passive margin 

north of the Barrow arch generally progressed from west to 

east during the Cretaceous and Tertiary (Bird and Molenaar, 

1992); an exception to this pattern is a significant Tertiary 

depocenter that was active in the northern Chukchi Sea during 

the early Tertiary (Sherwood and others, 1998). Deposition of 

a thick Brookian sequence provided the overburden necessary 

for thermal maturation of petroleum source rocks in Ellesmerian, Beaufortian, and Brookian strata.

Petroleum Resources

Known (Discovered) Resources in Unitized 

Oil Fields

Approximately 15 billion bbl of oil has been produced 

from the Arctic Alaska Petroleum Province, and about 12 

billion bbl from the Prudhoe Bay oil field (fig. 1; table 1; 

NPRA

ANWR

1002

Area

Colville

River

Kuparuk River

Oooguruk

Nikaitchuq

Milne

 Point

Northstar

Prudhoe Bay

Duck Island

Badami

Point Thomson

Lookout

Spark

Tarn

Meltwater

Alpine

Tabasco

Approximate axis

of Barrow arch

TAPS

0 100 km

0 100 mi

Figure 3. Central Arctic coast of northern Alaska (see fig. 4), showing locations of oil-field units (colored blocks), 

newly announced satellite pools (Lookout and Spark) to the Colville River unit, Trans-Alaska Pipeline System (TAPS), 

and boundaries of Federal land (Arctic National Wildlife Refuge [ANWR] and National Petroleum Reserve in Alaska 

[NPRA]). Data from Alaska Oil and Gas Conservation Commission (2004) and Alaska Division of Oil and Gas (2006).
Petroleum Resources 

Oil field

Cumulative

oil production

(million bbl)

Remaining

oil reserves

(million bbl)

Gas reserves

(billion ft3)

Badami1 4 2 0

Colville River2 185 510 400

Duck Island 466 117 843

Kuparuk River3 2,139 1,401 1,150

Milne Point 236 391 14

Northstar 90 115 450

Prudhoe Bay4 11,990 3,192 24,526

Point 

Thompson5

--- 243 8,000

Other 

undeveloped6

--- 488 ---

NPRA 

undeveloped

--- 255 ---

Total 15,110 6,714 35,383

1

Field was put in warm shut-in in August 2003, and production was 

resumed in 2005.

2

Includes the Alpine oil field and its satellites.

3

Includes the Kuparuk oil field and its satellites.

4

Includes Prudhoe Bay initial producing areas, Prudhoe Bay satellites, 

and the “greater Point McIntyre area.”

5

Undeveloped.

6

Includes the Liberty and other known onshore and offshore accumulations outside NPRA.

Table 1. Cumulative oil production and oil and gas reserves 

for unitized and other oil fields in northern Alaska and adjacent 

offshore areas through 2005.

[All values are totals for unitized oil fields. Cumulative oil production includes 

oil and natural-gas liquids; remaining oil and gas reserves are based on the 

sum of forecasted production from 2006 through 2035. Reserve estimates 

include resources in undeveloped accumulations and do not correlate directly 

with proven reserves reported by field operators. NPRA, National Petroleum 

Reserve in Alaska]

Alaska Division of Oil and Gas, 2006). Virtually all production is from an area along the coast near the Barrow arch and 

centered at Prudhoe Bay (fig. 3). These accumulations are 

estimated to hold remaining reserves of nearly 7 billion bbl of 

oil and more than 35 trillion ft3 of gas (table 1; Alaska Division of Oil and Gas, 2006), including resources in undeveloped accumulations that are not typically reported as “proven 

reserves.” Therefore, the reserve estimates reported herein 

(Alaska Division of Oil and Gas, 2006) are higher than the 

4.4 billion bbl and 8.4 trillion ft3 of proven reserves of oil and 

gas, respectively, reported for the entire State of Alaska by the 

Energy Information Administration (2006a, b).

Oil (including condensate) is marketed through the TransAlaska Pipeline System (fig. 3); however, gas cannot be marketed at present in the absence of a gas pipeline. Most known 

petroleum accumulations are in structural and (or) combination structural-stratigraphic traps related to closure along the 

Barrow arch, which has focused hydrocarbon migration since 

Early Cretaceous time. Thus, reserves are in multiple stratigraphic horizons in most oil-field units (table 2).

Since 1995, several petroleum accumulations in stratigraphic traps have been developed, including (1) incised 

shoreface sandstones in the Beaufortian sequence (Alpine pool 

in the Colville River unit and the newly announced Lookout 

and Spark discoveries in the National Petroleum Reserve in 

Alaska [NPRA]); (2) turbidite sandstones in the Brookian 

sequence (Badami unit; Tarn and Meltwater pools in the Kuparuk River unit; Nanuq pool in the Colville River unit); and (3) 

fluvial-estuarine incised channel sandstones in the Brookian 

sequence (Tabasco pool in the Kuparuk River unit, fig. 3; 

table 2). Although some of these stratigraphic traps occur near 

the axis of the Barrow arch, most are off structure and thus 

provide evidence for future potential petroleum discoveries in 

similar stratigraphic traps.

A large oil, condensate, and natural-gas accumulation occurs 

in the Point Thomson field, about 80 km east of Prudhoe Bay (fig. 

3). Although no production has been reported from this field, the 

Alaska Division of Oil and Gas (2006) has estimated reserves at 

243 million bbl of liquid petroleum and 8 trillion ft3 of gas—the 

largest known hydrocarbon accumulation in onshore Arctic Alaska 

that has not yet been developed and produced.

Two new field units, the Oooguruk and Nikaitchuq, were 

formed in 2003 and 2004, respectively (table 2). Wells in 

both units have tested positive for oil, and additional delineation drilling is ongoing. One former unit, the Kuukpik, which 

was located between the Colville River and Oooguruk units 

(fig. 3), was terminated in 2001 despite positive oil tests from 

multiple wells (table 2).

Other Known (Discovered) Resources

At least 27 oil and gas accumulations are known outside 

the unitized oil fields discussed in the previous subsection (fig. 

4; table 2). Three gas accumulations (A–C, fig. 4) have been 

developed for local use by the community of Barrow near the 

northernmost part of NPRA. The Alaska Division of Oil and 

Gas (2006) has estimated that, collectively, these gas fields 

have produced more than 40 billion ft3 of gas and contain 34 

billion ft3 of gas of proven reserves. The remaining 24 known 

accumulations are undeveloped and include discoveries during 

the initial exploration within Naval Petroleum Reserve No. 4 

(now NPRA) by the U.S. Navy in the 1940s and 1950s, such 

as the Umiat, Fish Creek, and Simpson oil accumulations and 

the Gubik, Meade, Square Lake, and Wolf Creek gas accumulations (fig 4; table 2). Among these discoveries, the Umiat 

ranks as the largest oil accumulation, with an estimated 70 

million bbl recoverable (Molenaar, 1982), and the Gubik as 

the largest gas accumulation, with an estimated 600 billion ft3

recoverable (Kumar and others, 2002). All other petroleum 

accumulations are either poorly defined or considered to be 

subeconomic, and so no estimates of recoverable resources 
 Oil and Gas Resources of the Arctic Alaska Petroleum Province

Accumulation Brookian Beaufortian Ellesmerian

Active producing units

Badami X – – – –

Colville River X X – –

Duck Island – – – – X

Kuparuk River X X – –

Milne Point X X X

Northstar – – – – X

Prudhoe Bay X X X

Former unit terminated in 2001 (no production)

Kuukpik x X – –

Units not yet producing

Oooguruk (formed in 2003) x X – –

Nikaitchuq (formed in 2004) x X X

Point Thompson X X – –

Other developed discoveries

A. East Barrow—gas (Native lands in NPRA) – – X – –

B. South Barrow—gas (Native lands in NPRA) – – X – –

C. Walakpa-Barrow—gas (Native lands in NPRA) – – X – –

Other undeveloped discoveries

1. Burger—gas and condensate (Federal offshore area) – – X – –

2. East Kurupa—gas (Native lands) X – – – –

3. East Umiat—gas (Native lands) X – – – –

4. Fish Creek—oil (NPRA) X – – – –

5. Gubik—gas (Native lands) X – – – –

6. Gwydyr Bay—oil (State onshore-offshore areas) – – X X

7. Hammerhead—oil (Federal offshore area) X – – – –

8. Hemi Springs—oil (State onshore area) – – X – –

9. Kalubik—oil (State offshore area) x X – –

10. Kavik—gas (State onshore area) – – – – X

11. Kemik—gas (State onshore area) – – – – X

12. Kuvlum—oil (Federal offshore area) X – – – –

13. Liberty—oil (Federal offshore area) – – – – X

14. Meade—gas (NPRA) X – – – –

15. Mikkleson—oil (State onshore-offshore areas) X – – – –

16. Mooses Tooth—oil (NPRA) – – X – –

17. Rendezvous—oil (NPRA) – – X – –

18. Sandpiper—gas and condensate (Federal offshore area) – – – – X

19. Sikulik—gas (Native lands in NPRA) – – X – –

20. Simpson—oil (NPRA) X – – – –

21. Square Lake—gas (NPRA) X – – – –

22. Stinson—oil (State offshore area) X – – – –

23. Umiat—oil (NPRA) X – – – –

24. Wolf Creek—gas (NPRA) X – – – –

Table 2. Tectonostratigraphic occurrences of known petroleum accumulations in the Arctic Alaska Petroleum Province.

[Entries are based on stratigraphic position of reservoir. See figure 3 for locations of unitized oil fields, and figure 4 for locations of other developed 

and undeveloped discoveries. Large Xs, proven reserves or tests that indicate producible hydrocarbons; small xs, possible recoverable resources]
Petroleum Resources 

have been made. The geology of many of these accumulations 

was summarized by Kumar and others (2002).

Industry exploration of the Brooks Range foothills (fig. 

1) during the 1960s and 1970s resulted in the discovery of the 

East Kurupa, Kavik, and Kemik gas accumulations, all poorly 

defined in size. Recent estimates suggest recoverable volumes 

of gas ranging from 95 to 172 billion ft3 in the Kavik accumulation (Verma and others, 2006); no estimates have been made 

for the other accumulations.

Exploration in Federal and State offshore areas during the 

1980s and 1990s resulted in the discovery of several petroleum accumulations that have not yet been developed. Those 

accumulations nearest to onshore infrastructure may be the 

most likely targets. The Liberty (also known as the Tern Island) 

accumulation, just southeast of the Duck Island unit (figs. 3, 

4) and estimated to contain 120 million bbl of recoverable oil, 

may be developable by extended-reach drilling from onshore 

(Petroleum News, 2006). Accumulations in both Ellesmerian 

and Beaufortian reservoirs at Gwydyr Bay are estimated at 48 

to 73 million bbl of recoverable oil (Thomas and others, 1993). 

Other oil discoveries for which no estimates of recoverable 

resources are available include the Stinson, Hammerhead, and 

Kuvlum, all north and east of the Point Thomson unit (figs. 3, 

4). The Sandpiper accumulation, just northwest of the Northstar unit (figs. 3, 4), contains oil, condensate, and gas; poorly 

constrained estimates of 93 and 150 million bbl of recoverable 

oil have been reported (Thomas and others, 1993, 1996).

On the Chukchi Shelf (fig. 4), the Burger gas and condensate accumulation is estimated to contain 9.5 trillion ft3

 of gas 

and 489 million bbl of natural gas liquids (Craig and Sherwood, 2004). These estimates are risked, mean volumes for 

the “most likely” trap-fill model used in the analysis.

Total Known (Discovered) Resources

Total known oil and gas resources of the Arctic Alaska 

Petroleum Province (fig. 1) are estimated and summarized 

in table 3. Historical production and estimates of remaining 

reserves are available in the public domain for all producing fields in Arctic Alaska (Alaska Oil and Gas Conservation 

Commission, 2004; Alaska Division of Oil and Gas, 2006); 

however, similar data are not available for inplace oil. For this 

reason, more uncertainty is associated with estimates of inplace 

oil than with those of ultimate recoverable resources (table 3).

The original inplace estimate for reservoirs of the Ellesmerian sequence (fig. 2) in known petroleum accumulations 

is about 30 billion bbl of oil, of which about 15 billion bbl of 

oil and 38 trillion ft3 of gas is recoverable. These strata include 

the main reservoir in the Prudhoe Bay oil field (fig. 1), from 

which approximately 12 billion bbl of oil has already been 

produced (Alaska Division of Oil and Gas, 2006). The high 

recovery factor (>50 percent) reflects the exceptional reservoir 

quality along the Barrow arch of the main siliciclastic units in 

the Ellesmerian sequence, including the Kekiktuk Conglomerate, Ivishak Sandstone, and Sag River Sandstone (fig. 2).

Reservoir

Estimated

volume of

inplace oil

(billion bbl)

Estimated ultimate recoverable

Oil

(billion bbl)

Gas

(trillion ft3)

Brookian 40 3 2

Beaufortian 10 5 12

Ellesmerian 30 15 38

Total 80 23 52

Table 3. Estimated volumes of inplace oil and ultimate 

recoverable oil and gas in known accumulations, listed by 

tectonostratigraphic reservoir unit.

[From Bird (2001), updated with data from Alaska Oil and Gas Conservation 

Commission (2004) and Alaska Division of Oil and Gas (2006)]

The original inplace estimate for reservoirs of the Beaufortian sequence (fig. 2) in known accumulations is about 10 

billion bbl of oil, of which about 5 billion bbl of oil and 12 

trillion ft3 of gas is recoverable. These strata include the main 

reservoirs in the Kuparuk River field, from which approximately 2 billion bbl of oil has already been produced, and 

the main reservoir in the Colville River unit (Alpine pool and 

some satellite pools), which is expected to produce more than 

500 million bbl of oil. A recovery factor of about 50 percent 

reflects a combination of good to excellent reservoir quality, 

the occurrence of light (API gravity, 38–40°) oil in several 

accumulations, and horizontal well-production strategies 

implemented in recently developed accumulations.

The original inplace estimate for reservoirs of the 

Brookian sequence (fig. 2) in known accumulations is about 

40 billion bbl of oil, of which about 3 billion bbl of oil and 2 

trillion ft3 of gas is recoverable. Estimated ultimate recovery 

for oil includes offshore discoveries (for example, the Hammerhead and Kuvlum) yet to be developed. Brookian reservoirs are generally heterogeneous and, when charged with 

lighter oil in stratigraphic traps, such as the Tarn (API gravity, 

37°), recovery factors generally are lower than in Ellesmerian 

and Beaufortian reservoirs. Estimated ultimate recovery for 

gas includes accumulations in the Brooks Range foothills (for 

example, the Gubik) yet to be developed. Huge accumulations 

of heavy (API gravity, 8–22°) oil occur in Brookian reservoirs 

in the Kuparuk River (West Sak and Ugnu pools), Milne Point 

(Schrader Bluff pool), and Prudhoe Bay (Orion pool) units. 

In the Kuparuk River field alone, Werner (1987) reported 

an inplace estimate of 18 to 40 billion bbl for most of these 

heavy-oil accumulations.

Undiscovered Resources

The U.S. Geological Survey (USGS) and the U.S. Minerals Management Service (MMS) have recently reassessed 

undiscovered petroleum resources for most of the Arctic 
 Oil and Gas Resources of the Arctic Alaska Petroleum Province

Arctic National

Wildlife Refuge

National Petroleum

Reserve in Alaska

176° 172° 168° 164° 160° 156° 152° 148° 144° 140° 136°

66°

68°

70°

72°

74°

ANWR 1002 Area

 Oil

 Gas

10.4 (5.7 - 16.0) BBO

 3.8 (0.0 - 10.9) TCF

NPRA

 Oil

 Gas

10.6 (6.7 - 15.0) BBO

61.4 (40.4 - 85.3) TCF

Hope Basin

 Oil

 Gas

0.2 (0.0 - 0.6) BBO

3.8 (0.0 - 15.0) TCF

Chukchi Shelf

 Oil

 Gas

15.4 (2.3 - 40.1) BBO

76.8 (10.3 - 209.5) TCF

Beaufort Shelf

 Oil

 Gas

8.2 (0.4 - 23.2) BBO

27.7 (0.6 - 72.2) TCF

Central North Slope

 Oil

 Gas

4.0 (2.6 - 5.8) BBO

33.3 (23.9 - 44.9) TCF

Arctic Circle

Russia

Canada

0 100 200

KILOMETERS

10

11

22

233 5 21

24

2

14

C

A19

B

1

4

1617

20

18

7 12 13 6

8

9

15

Figure 4. Arctic Alaska Petroleum Province, showing resource estimates (mean and range of 95- to 5-percent-confidence-level 

volumes) of undiscovered oil (in billions of barrels [BBO]) and gas (in trillions of cubic feet [TCF]) for Federal onshore and offshore 

assessment areas. Estimates for onshore areas (National Petroleum Reserve in Alaska [NPRA], central North Slope, and 1002 Area of 

the Arctic National Wildlife Refuge [ANWR]), which include adjacent State offshore area and Native holdings onshore, are from U.S. 

Geological Survey, where “oil” includes crude oil only and “gas” includes nonassociated gas only. Estimates for Federal offshore area 

(Hope Basin, Chukchi Shelf, and Beaufort Shelf) are from the U.S. Minerals Management Service, where “oil” includes both crude 

oil and natural-gas liquids and “gas” includes both nonassociated and associated gas. Red letters and numbers, known (discovered) 

petroleum accumulations outside unitized oil fields, keyed to table 2. Dashed rectangle, area of figure 3. Data from Schuenemeyer 

(1999, 2003), Bird and Houseknecht (2001, 2002), Bird and others (2005), and U.S. Minerals Management Service (2006).

Alaska Petroleum Province; the results are summarized in 

figure 4 and table 4.

Estimated mean volumes of undiscovered oil and gas 

resources for NPRA (fig. 4), including the adjacent State offshore area and Native holdings within NPRA, are 11.99 billion 

bbl of total liquid petroleum (crude oil and natural-gas liquids) 

and 73.03 trillion ft3 of gas (nonassociated and associated) 

(table 4; Bird and Houseknecht, 2002; Schuenemeyer, 2003). 

Subsequent to that study, industry has reported data from new 

discovery wells in the northeastern part of NPRA. The new 

data from Beaufortian reservoirs indicate that the accumulations contain less oil and more gas and condensate than previously estimated, mostly on the basis of hydrocarbon composition in the Alpine accumulation just east of NPRA (fig. 3). If 

these new data are representative of undiscovered Beaufortian 

reservoirs in NPRA, less crude oil and more natural-gas liquids and associated gas may be present (fig. 4; table 4).

USGS-estimated mean volumes of undiscovered oil and 

gas resources for the central North Slope (fig. 4), located east 

of NPRA and west of the Arctic National Wildlife Refuge 
Summary 

Oil and natural-gas liquids

(billion bbl)

Natural gas

(trillion ft3)

Crude

oil

Naturalgas

liquids

Total

liquids

Nonassociated

gas

Associated

gas

Total

gas

Onshore and State offshore areas

NPRA1 10.56 1.43 11.99 61.35 11.68 73.03

Central North Slope2 3.98 0.48 4.46 33.32 4.20 37.52

ANWR, 1002 Area3 10.36 0.19 10.55 3.84 4.76 8.60

Subtotal 24.90 2.10 27.00 98.51 20.64 119.15

Federal offshore area

Chukchi Shelf4 – – – – 15.38 – – – – 76.77

Beaufort Shelf4 – – – – 8.22 – – – – 27.65

Hope Basin4 – – – – 0.15 – – – – 3.77

Subtotal – – – – 23.75 – – – – 108.19

Arctic Alaska Petroleum Province onshore and offshore areas

Total – – – – 50.75 – – – – 227.34

1

Bird and Houseknecht (2002).

2

Bird and others (2005.

3

Bird and Houseknecht (2001).

4

U.S. Minerals Management Service (2006).

Table 4. Estimated mean volumes of undiscovered, technically recoverable petroleum in conventional 

accumulations for areas in the Arctic Alaska Petroleum Province.

[Estimates for onshore and State offshore areas versus Federal offshore area are listed separately because of differences in the 

assessment methods used by the U.S. Geological Survey and U.S. Minerals Management Service. See figure 4 for 95- and 5-percent-confidence-level volumes. ANWR, Arctic National Wildlife Refuge; NPRA, National Petroleum Reserve in Alaska]

(ANWR) and including the adjacent State offshore area, are 

4.46 billion bbl of total liquid petroleum and 37.52 trillion ft3

of gas (table 4; Bird and others, 2005). USGS-estimated mean 

volumes of undiscovered oil and gas resources for the 1002 

Area of ANWR, including the adjacent State offshore area and 

Native holdings on the ANWR coastal plain, are 10.55 billion 

bbl of total liquid petroleum and 8.60 trillion ft3 of gas (table 

4) (Schuenemeyer, 1999; Bird and Houseknecht, 2001).

MMS-estimated mean volumes of undiscovered oil and 

gas resources for the Federal offshore area (fig. 4) are (1) for 

the Chukchi Shelf at water depths less than 100 m, 15.38 billion bbl of total liquid petroleum and 76.77 trillion ft3

 of gas; 

(2) for the Beaufort Shelf at water depths less than 500 m, 8.22 

billion bbl of total liquid petroleum and 27.65 trillion ft3 of 

gas; and (3) for the Hope Basin, 0.15 billion bbl of total liquid 

petroleum and 3.77 trillion ft3 of gas (table 4; U.S. Minerals 

Management Service, 2006).

The total volumes of undiscovered oil and gas resources 

in the Arctic Alaska Petroleum Province can be approximated 

by summing all mean volumes, yielding more than 50 billion 

bbl of total liquid petroleum and more than 227 trillion ft3 of 

gas (table 4). Total estimated mean volumes of undiscovered 

oil and gas resources are approximately equal for both onshore 

and offshore areas. These total estimated mean volumes lack 

the ranges of uncertainty inherent in assessments of undiscovered resources. The mean estimates for each assessment 

area, including oil and gas volumes at the 95- and 5-percentconfidence levels, are listed on figure 4. Ranges of uncertainty 

cannot be aggregated to total resources for the entire Arctic 

Alaska Petroleum Province because of differences in the 

assessment methods used by the USGS and MMS.

Summary

Approximately 15 billion bbl of oil has been 

produced from the Arctic Alaska Petroleum Province, 

and proven reserves are estimated at more than 7 billion 

bbl of oil and 35 trillion ft3 of gas. Most oil production is 
10 Oil and Gas Resources of the Arctic Alaska Petroleum Province

from Ellesmerian reservoirs, consisting of Mississippian 

through Triassic marine carbonate and marine to nonmarine 

siliciclastic deposits that accumulated on the shelf of a 

passive continental margin. Lesser production has been from 

Beaufortian reservoirs, consisting of Jurassic through Early 

Cretaceous marine siliciclastic deposits associated with 

the rift opening of the Canada Basin, and from Brookian 

reservoirs, consisting of Cretaceous through Tertiary marine to 

nonmarine siliciclastic strata deposited as wedges of sediment 

shed from the Brooks Range orogenic belt. Most production 

is from structural and combination structural-stratigraphic 

traps, although several recent oil discoveries are in purely 

stratigraphic traps.

Mean estimates of undiscovered, technically 

recoverable petroleum resources in conventional 

accumulations for the Arctic Alaska Petroleum Province 

indicate that more than 50 billion bbl of liquid petroleum 

(oil and natural-gas liquids) and more than 227 trillion ft3 of 

gas (nonassociated and associated) remains to be discovered, 

distributed approximately equally between the Federal 

offshore area (24 billion bbl of oil and 108 trillion ft3 of gas) 

and combined onshore and State offshore areas (27 billion bbl 

of oil and 119 trillion ft3 of gas).

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Reference citation for this paper: 

Houseknecht, D.W., and Bird, K.J., 2006, Oil and gas resources of the Arctic Alaska 

petroleum province: U.S. Geological Survey Professional Paper 1732-A, 11 p., 

available online at: http: //pubs.usgs.gov/pp/pp1732a/