Chapter 1

Executive Summary—Petroleum 

Systems and Geologic Assessment of 

Undiscovered Hydrocarbon Resources 

of the Western Oregon and Washington 

Province

By Michael E. Brownfield, Ronald R. Charpentier, Troy A. Cook, 

Timothy R. Klett, Richard M. Pollastro, and Christopher J. Schenk

Chapter 1 of 4

Geologic Assessment of Undiscovered Hydrocarbon Resources 

of the Western Oregon and Washington Province 

By U.S. Geological Survey Western Oregon and Washington Province Assessment Team

U.S. Geological Survey Digital Data Series DDS–69–X

U.S. Department of the Interior

U.S. Geological Survey

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U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2011

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Suggested citation:

Brownfield, M.E., Charpentier, R.R., Cook, T.A., Klett, T.R., Pollastro, R.M., and Schenk, C.J., 2011,

Executive Summary—Petroleum systems and geologic assessment of undiscovered hydrocarbon resources of the 

Western Oregon and Washington Province: U.S. Geological Survey Digital Data Series DDS–69–X, chap. 1, 4 p.
iii

Contents

Introduction.....................................................................................................................................................1

Resource Summary .......................................................................................................................................1

For Additional Information............................................................................................................................3

Western Oregon and Washington Province Assessment Team ...........................................................3

References Cited............................................................................................................................................3

Figures

1. Map showing the Western Oregon and Washington Province located in western 

Oregon and Washington..............................................................................................................2

2. Photograph showing outcrop of part of the deltaic lower member of the 

middle Eocene Coaledo Formation at Shore Acres State Park, near Coos Bay, 

Oregon ............................................................................................................................................4

3. Photograph showing upper Eocene turbidite sandstones along the 

northwest shore of the Olympic Peninsula, northwestern Washington .............................4

Table

1. Western Oregon and Washington Province assessment results.........................................3
Introduction

The U.S. Geological Survey (USGS) recently completed 

an assessment of the undiscovered, technically recoverable 

oil and gas resources of the Western Oregon and Washington 

Province (fig. 1) (Brownfield and others, 2008). The province 

includes all of Oregon and Washington north of the Klamath Mountains and west of the crest of the Cascade Range, 

and extends offshore to the 3-mi limit of State waters on the 

west and to the International Boundary in the Straits of Juan 

de Fuca and Canada on the north. It measures about 450 mi 

north–south and 50 to 160 mi east–west, encompassing more 

than 51,000 mi2

 (fig. 1).

The assessment of the Western Oregon and Washington 

Province is geology based and used the total petroleum system 

(TPS) concept. The geologic elements of a TPS include 

hydrocarbon source rocks (source rock maturation and hydrocarbon generation and migration), reservoir rocks (quality and 

distribution), and traps for hydrocarbon accumulation. Using 

these geologic criteria, two conventional and one unconventional (continuous) total petroleum systems were defined, with 

one assessment unit (AU) in each TPS: (1) the CretaceousTertiary Composite TPS and the Western Oregon and Washington Conventional Gas AU, (2) the Tertiary Marine TPS and 

the Tertiary-Marine Gas AU, and (3) the Tertiary Coalbed Gas 

TPS and the Eocene Coalbed Gas AU, in which a cell-based 

methodology was used to estimate coalbed-gas resources.

The province (fig. 1) occupies a complex geologic setting 

along the northwest continental margin of North America. 

Some 5,000 ft to more than 23,000 ft of Paleogene volcanic 

rocks, marine mudstone and arkosic and lithic sandstone, 

and nonmarine arkosic and lithic sandstone, mudstone, 

Using a geology-based assessment methodology, the U.S. Geological Survey estimated mean volumes of 2.2 trillion cubic 

feet (TCF) of undiscovered natural gas and 15 million barrels of oil (MMBO) in the Western Oregon and Washington 

Province. More than 67 percent, or 1.5 TCF, of the undiscovered natural gas is continuous accumulations of coalbed gas in 

Tertiary coals in western Oregon and Washington.

Executive Summary—Petroleum Systems and Geologic 

Assessment of Undiscovered Hydrocarbon Resources of 

the Western Oregon and Washington Province

By Michael E. Brownfield, Ronald R. Charpentier, Troy A. Cook, Timothy R. Klett, Richard M. Pollastro, and 

Christopher J. Schenk

carbonaceous shale, and coal are present in western Oregon 

and Washington; these rocks include potentially mature source 

rocks and reservoir rocks.

Before 1979, the only oil and gas production was in the 

Washington part of the province. Small amounts of gas were 

produced from the Paleogene Chuckanut Formation below 

Quaternary gravels near Bellingham (fig. 1), and about 12,000 

barrels of oil and associated gas were produced near Grays 

Harbor from 1957 to 1961 (fig. 1) from the upper Oligocene 

to middle Miocene Hoh Formation (McFarland, 1983). Currently, the only hydrocarbon production within the province 

is from the Mist gas field discovered in May 1979 in northwestern Oregon (fig. 1). The Mist field has produced about 65 

billion cubic feet of gas (BCFG) through 2008 from reservoirs 

in the upper part of the Eocene Cowlitz Formation.

Resource Summary

The USGS assessed both undiscovered technically 

recoverable conventional oil and gas and continuous (unconventional) coalbed gas in the Western Oregon and Washington 

Province (table 1), resulting in an estimated total mean of 2.2 

trillion cubic feet of gas (TCFG) and a mean of 15 million barrels of oil (MMBO). More than 67 percent of the total mean 

gas (1.5 TCFG) is contained within the hypothetical Eocene 

Coalbed Gas AU, which encompasses an area of more than 11 

million acres. In this continuous AU, the Eocene coals, such 

as the coal-bearing Eocene Coaledo Formation (fig. 2), serve 

as both the source rock and reservoir. Mean volumes were 

estimated at 454 BCFG for the Western Oregon-Washington 

Conventional Gas AU and 15 MMBO of conventional oil and 
2 Executive Summary—Petroleum Systems and Geologic Assessment of Undiscovered Hydrocarbon Resources

Figure 1. Map showing the Western Oregon and Washington Province located in 

western Oregon and Washington; boundary is shown in red. Cretaceous-Tertiary 

Composite Total Petroleum System (TPS) is shown in orange. Tertiary Coalbed 

Gas TPS is shown in dark blue. Tertiary Marine TPS shown in dark green. Eastern 

Oregon and Washington Province boundary is shown in yellow (Brownfield and 

others, 2006; Brownfield, 2008). Location of the Coos Bay coal field shown as a 

solid brown oval and the Mist gas field shown as a solid red circle.

WASHINGTON

OREGON

NEVADA

MT

IDAHO

CALIFORNIA

CANADA

Yakima

Spokane

Richland

Portland

Eugene

Columbia River

Pacific

 Ocean

Potholes 

 Reservoir

Banks 

Lake

Coeur 

d'Alene 

Lake

Lake 

Pend 

Oreille

Malheur 

Lake

Crater 

 Lake

Mist

gas field

§ ̈¦5

§ ̈¦84

§ ̈¦84

§ ̈¦82

§ ̈¦90

§ ̈¦90

P a c i f i c 

O c e a n

WA

OR

NV

MT

ID

CA

CANADA

Location map

125° 123° 121° 119° 117° 115°

42°

44°

46°

48°

50°

Coos 

Bay

Coos 

Bay

coal

field

Seattle

Bellingham

Olympic

Peninsula

Strait of 

Juan de Fuca

Grays Aberdeen

Harbor

§ ̈¦5

American

Quasar

Hickey 9–12

0 60 KILOMETERS

0 60 MILES
References Cited 3

Total Petroleum System (TPS) 

and Assessment Unit (AU)

Field 

Type

Total Undiscovered Resources

Oil (MMBO) Gas (BCFG) NGL (MMBNGL)

F95 F50 F5 Mean F95 F50 F5 Mean F95 F50 F5 Mean

Cretaceous-Tertiary Composite TPS

Western Oregon and Washington

Conventional Gas AU

Oil 0 0 0 0 0 0 0 0 0 0 0 0

Gas 79 403 1,000 454 0 1 2 1

Tertiary Marine TPS

Tertiary Marine Gas AU

Oil 2 9 45 15 3 14 70 22 0 1 4 1

Gas 34 195 646 249 1 5 17 6

Total Conventional Resources 2 9 45 15 116 612 1,716 725 1 7 23 8

Tertiary Coalbed Gas TPS

Eocene Coalbed Gas AU CBG 0 0 0 0 565 1,307 3,024 1,489 0 0 0 0

Total Continuous Resources 0 7020 0 0 565 1,307 3,024 1,489 0 0 0 0

Total Undiscovered 

Oil and Gas Resources 2 9 45 15 681 1,919 4,740 2,214 1 7 23 8

Continuous 

Resources

Conventional 

Resources

Table 1. Western Oregon and Washington Province assessment results.

[MMBO, million barrels of oil; BCFG, billion cubic feet of gas; MMBNGL, million barrels of natural gas liquids. Results shown are fully

risked estimates. For gas accumulations, all liquids are included as the NGL (natural gas liquids). Undiscovered gas resources are the sum 

of nonassociated and associated gas. F95 represents a 95 percent chance of at least the amount tabulated; other fractiles are defined similarly. 

TPS, total petroleum system; AU, assessment unit; CBG, coalbed gas. Gray shading indicates not applicable]

249 BCFG for the Tertiary Marine AU, which contains Paleogene turbidite rocks (fig 3). In this AU there are numerous gas 

and oil seeps; potential source rocks are marine shales, and the 

reservoir rocks are arkosic and lithic turbidite sandstones.

For Additional Information

Supporting geologic studies of TPS and AU, and reports 

on the methodology used in the Western Oregon and Washington Province assessment are in other chapters within this 

publication. Assessment results are also available at the USGS 

Central Energy Team website, http://energy.cr.usgs.gov/oilgas/

noga/.

Western Oregon and Washington 

Province Assessment Team

Michael E. Brownfield (mbrownfield@usgs.gov), Ronald 

R. Charpentier, Troy A. Cook, Timothy R. Klett, Richard M. 

Pollastro, and Christopher J. Schenk.

References Cited

Brownfield, M.E., Tennyson, M.E., Ahlbrandt, T.S., 

Charpentier, R.R., Cook, T.A., Klett, T.R., Pollastro, R.M., 

and Schenk, C.J., 2006, Assessment of undiscovered gas 

resources of the Eastern Oregon and Washington Province, 

2006: U.S. Geological Survey Fact Sheet 2006–3091, 2 p.

Brownfield, M.E., 2008, Chapter 2–Cretaceous-Tertiary 

Composite Total Petroleum System and geologic assessment of undiscovered gas resources of the Eastern Oregon 

and Washington Province, of chap. 2, U.S. Geological 

Survey Eastern Oregon and Washington Assessment Team, 

Geologic assessment of undiscovered gas resources of the 

Eastern Oregon and Washington Province: U.S. Geological 

Survey Digital Data Series DDS–69–O, 43 p.

McFarland, C.R., 1983, Oil and gas exploration in 

Washington, 1900–1982: Washington Division of Geology 

and Earth Resources Information Circular 75, 119 p.

Table 1. Western Oregon and Washington Province assessment results.
4 Executive Summary—Petroleum Systems and Geologic Assessment of Undiscovered Hydrocarbon Resources

Figure 2. Outcrop of part of 

the deltaic lower member of the 

middle Eocene Coaledo Formation 

at Shore Acres State Park, near 

Coos Bay, Oregon (fig. 1). Strata 

are dipping eastward toward the 

trough of the South Slough syncline 

in the Coos Bay coal field (fig. 1).

Figure 3. Upper Eocene turbidite 

sandstones along the northwest 

shore of the Olympic Peninsula, 

northwestern Washington. Cape 

Flattery in the distance. Turbidite 

units are potential reservoirs within 

the Tertiary Marine Total Petroleum 

System and the Tertiary Marine Gas 

Assessment Unit.

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