Assessment of the Coal-Bed Gas Total Petroleum System 

in the Cook Inlet-Susitna Region, 

South-Central Alaska

Assessment of the Coal-Bed Gas Total Petroleum System 

in the Cook Inlet-Susitna Region, 

South-Central Alaska

Scientific Investigations Report 2012–5145

U.S. Department of the Interior

U.S. Geological Survey
Cover photo. View to the southwest across intertidal sand flat along theTurnagain Arm 

of the Cook Inlet with Kenai-Chugach Mountains in background. Sand flat is located 

near Girdwood, Alaska, on northern shore of Turnagain Arm, and distance to mountains 

on southern shore is approximately 7 kilometers (4.3 miles).
Assessment of the Coal-Bed Gas Total Petroleum 

System in the Cook Inlet-Susitna Region, 

South-Central Alaska

By William A. Rouse and David W. Houseknecht

Scientific Investigations Report 2012–5145

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

For more information on the USGS—the Federal source for science about the Earth, its natural and living 

resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1–888–ASK–USGS.

For an overview of USGS information products, including maps, imagery, and publications, 

visit http://www.usgs.gov/pubprod

To order this and other USGS information products, visit http://store.usgs.gov

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the 

U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials 

as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.

Suggested citation:

Rouse, W.A., and Houseknecht, D.W., 2012, Assessment of the Coal-Bed Gas Total Petroleum System in the Cook 

Inlet-Susitna region, south-central Alaska: U.S. Geological Survey Scientific Investigations Report 2012–5145, 19 p.
iii

Contents

Abstract...........................................................................................................................................................1

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

Structural and Tectonic Setting...................................................................................................................2

Stratigraphic Framework..............................................................................................................................2

Lower Tertiary Rocks............................................................................................................................2

Upper Tertiary Kenai Group.................................................................................................................8

Methodology...................................................................................................................................................8

Total Petroleum System..............................................................................................................................12

 Source and Reservoir Rock .............................................................................................................12

Maturation............................................................................................................................................12

Reservoir Rock ....................................................................................................................................15

Assessment Data Input and Results.........................................................................................................15

Summary........................................................................................................................................................17

References Cited .........................................................................................................................................17

Figures

1. Location of the Cook Inlet Coal-Bed Gas Total Petroleum System (TPS), 

major bounding faults, anticlines, and vertical and near-vertical well 

locations within the Cook Inlet-Susitna region, south-central Alaska................................3

2. Tectonic and volcanic settings of the Cook Inlet basin..........................................................4

3. Cross section of the eastern Aleutian Arc, from Mount Spurr to the 

Border Ranges fault, Alaska .......................................................................................................5

4. Tertiary correlation chart for the Cook Inlet-Susitna region.................................................6

5. Depositional model of the Kenai Group in the Cook Inlet basin ...........................................7

6. Well log response of coal and borehole washout intervals in the 

Starichkof State Unit 1 well.........................................................................................................9

7. Cumulative thickness of coal (in feet) as inferred from records of wells 

between 1,000 and 6,000 feet deep in the Cook Inlet basin.................................................10

8. Location of wells with thick coal deposits between depths of 

1,000 and 6,000 feet in the Cook Inlet basin............................................................................11

9. Structure contour map of the top of the Mesozoic basement, Cook Inlet basin .............13

10. Outcrop and well vitrinite reflectance values within the Coal-Bed Gas 

Total Petroleum System (TPS) in the Cook Inlet-Susitna region.........................................14

Tables

1. Assessment data input for the Cook Inlet Coal-Bed Gas Assessment Unit .....................16

2. Summary of results for risked, undiscovered, technically recoverable 

contiguous gas resources for the Cook Inlet Coal-Bed Gas Assessment Unit................16
iv

Conversion Factors

Multiply By To obtain

Length

meter (m) 3.281 foot (ft) 

meter (m) 1.094 yard (yd)

kilometer (km) 0.6214 mile (mi) 

mile (mi) 1.609 kilometer (km) 

Area

acre 0.004047 square kilometer (km2

) 

Volume

cubic centimeter (cm3

 or cc) 0.06102 cubic inch (in3) 

cubic foot (ft3

) 28.32 cubic decimeter (dm3) 

cubic foot (ft3

) 0.02832 cubic meter (m3) 

Mass/weight

gram (g) 0.03527 ounce, avoirdupois (oz avdp)

ton 0.9072 megagram (Mg) or metric ton (t)

The isotope ratio of carbon-13 to carbon-12 relative to the Pee Dee Belemnite (PDB), in per mil, 

is notated as δ13C.
Assessment of the Coal-Bed Gas Total Petroleum System 

in the Cook Inlet-Susitna Region, South-Central Alaska

By William A. Rouse and David W. Houseknecht

Abstract

The Cook Inlet-Susitna region of south-central Alaska 

contains large quantities of gas-bearing coal of Tertiary age. 

The U.S. Geological Survey in 2011 completed an assessment of undiscovered, technically recoverable coal-bed gas 

resources underlying the Cook Inlet-Susitna region based on 

the total petroleum system (TPS) concept. The Cook Inlet 

Coal-Bed Gas TPS covers about 9,600,000 acres and comprises the Cook Inlet basin, Matanuska Valley, and Susitna 

lowland. The TPS contains one assessment unit (AU) that 

was evaluated for coal-bed gas resources between 1,000 and 

6,000 feet in depth over an area of about 8,500,000 acres. 

Coal beds, which serve as both the source and reservoir 

for natural gas in the AU, were deposited during Paleocene–

Pliocene time in mires associated with a large trunk-tributary 

fluvial system. Thickness of individual coal beds ranges from 

a few inches to more than 50 feet, with cumulative coal thickness of more than 800 feet in the western part of the basin. 

Coal rank ranges from lignite to subbituminous, with vitrinite 

reflectance values less than 0.6 percent throughout much of 

the AU.

The AU is considered hypothetical because only a few 

wells in the Matanuska Valley have tested the coal-bed reservoirs, so the use of analog coal-bed gas production data was 

necessary for this assessment. In order to estimate reserves 

that might be added in the next 30 years, coal beds of the 

Upper Fort Union Formation in the Powder River Basin 

of Wyoming and Montana were selected as the production 

analog for Tertiary coal beds in the Cook Inlet-Susitna region. 

Upper Fort Union coal beds have similar rank (lignite 

to subbituminous), range of thickness, and coal-quality 

characteristics as coal beds of the Tertiary Kenai Group. 

By use of this analog, the mean total estimate of undiscovered coal-bed gas in the Tertiary Coal-Bed Gas AU is 

4.674 trillion cubic feet (TCF) of gas.

Introduction

The U.S. Geological Survey (USGS) in 2011 completed 

an assessment of undiscovered, technically recoverable, 

conventional and unconventional oil and gas resources in the 

Cook Inlet-Susitna region of south-central Alaska. The assessment is based on the total petroleum system (TPS) concept 

(Schmoker, 2005) and includes four assessment units (AU). 

Results of the complete assessment were reported by Stanley 

and others (2011). The purpose of this report is to provide a 

synthesis of the geology of the Cook Inlet-Susitna region and 

to present input parameters and results of the Cook Inlet CoalBed Gas TPS resource assessment.

Coal was first discovered in Alaska at Port Graham on 

the Kenai Peninsula by Russian explorers in 1786, although 

it was undoubtedly used by native Alaskans earlier (Merritt 

and Hawley, 1986). The Russian-American Company opened 

the first documented coal mine in Alaska in 1855 at this site, 

exporting 88 tons of coal to California in its first year (Davis,

1981; Merritt and Hawley, 1986). Since then, as much as 

12 billion short tons of coal have been discovered in the Cook 

Inlet-Susitna region, with estimates of undiscovered or hypothetical coal resources at 1,600 billion short tons (Hopkins, 

1951, cited in Flores and others, 2003; Barnes and Cobb, 

1959; Barnes, 1967; Renshaw, 1983; Merritt and Belowich, 

1984; Merritt and Hawley, 1986; Affolter and Stricker, 1987). 

Production of gas from conventional sandstone and conglomerate reservoirs began in 1958, and more than 7.8 trillion 

cubic feet (TCF) have been produced (Alaska Department of 

Natural Resources, Division of Oil and Gas, 2009). As much 

as 93 percent of the natural gas discovered to date may have 

been sourced from coal interbedded with the conventional 

sandstone and conglomerate reservoirs (Claypool and others, 

1980). Geochemical evidence suggests that most of the coalbed-sourced gas in Cook Inlet conventional accumulations is 

biogenic rather than thermogenic, because biogenic gas gener-
2 Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna Region, South-Central Alaska

ated from coal beds is isotopically light (δ13C range of –63 to 

–56 per mil) and chemically dry (C1/C1–5 > 0.99; Claypool and 

others, 1980). 

The large amount of coal in the Cook Inlet-Susitna 

region, coupled with moderate to good gas content, suggests 

the potential for a large untapped coal-bed gas resource. 

Although no official estimates of coal-bed gas resources in 

the Cook Inlet-Susitna region have been published previously 

by the USGS, a total gas-in-place resource of 245 TCF was 

estimated by Montgomery and Barker (2003). 

Structural and Tectonic Setting

The Cook Inlet basin is a northeast-southwest trending 

fore-arc basin flanked by the Aleutian volcanic arc to the 

northwest and Chugach-Kenai accretionary complex to the 

southeast and bounded by active high-angle reverse fault 

zones (fig. 1). The Castle Mountain and Bruin Bay fault zones 

make up the northern and northwestern boundaries, separating 

the uplifted volcanic arc complex from the basin. The southeastern boundary is defined by the Border Ranges fault, which 

separates the basin from the Chugach terrane. 

Basin accommodation for more than 25,000 feet (ft) of 

Tertiary nonmarine strata is attributed to early Tertiary deformation and increased tectonism associated with the subduction 

of the Kula plate and spreading center in the Early Eocene 

(fig. 2) (Byrne, 1979, cited in Swenson, 1997; Pavlis, 1982). 

Tertiary strata are thickest in the basin center and thin towards 

the basin margins (fig. 3). Rapid subsidence and deposition 

of nonmarine sand, organic matter, and silt continued until 

the end of the Pliocene, when the latest phase of tectonism 

deformed the basin margins. 

Numerous fault-cored folds related to this latest phase 

of tectonism are present in the Cook Inlet, with fold axes that 

are generally subparallel to the margins of the basin and trend 

northeast-southwest (Plafker and others, 1994). These folds 

are generally asymmetric and doubly plunging, with opposing 

sense of vergence, and are thought to be developed by righttranspressional deformation on oblique-slip faults extending 

downward into Mesozoic basement (Nokleberg and others, 

1994; Haeussler and others, 2000). Right-transpressional 

deformation of the Cook Inlet likely is driven by a combination of subduction of the Pacific plate and lateral escape of the 

fore arc to the southwest resulting from the collision of the 

Yakutat block to the east of the basin (Haeussler and others, 

2000). Much of the exploration and production activity in the 

Cook Inlet basin to date has focused on the fault-cored folds. 

The Susitna lowland (fig. 1) is considered the northern extension of the Cook Inlet basin, located between the 

Talkeetna Mountains to the east and the Alaska Range to the 

north and west (Miller and Dobrovolny, 1959; Smith, 1995). 

The Susitna arch, a partially buried ridge of granitic rocks near 

the Castle Mountain fault zone, separates the shallower and 

younger Susitna lowland from the Cook Inlet basin 

(Kelly, 1963; Smith, 1995). 

The Matanuska Valley is considered the northeastern 

arm of the Cook Inlet basin, forming a structural trough 

8 to 16 kilometers (km) wide and 80 km long that narrows 

to the northeast (Merritt and Belowich, 1984). The valley is 

between the Talkeetna Mountains to the north and Chugach 

Mountains to the south. The Castle Mountain fault to the 

north and an unnamed fault zone to the south separate Tertiary 

and Cretaceous rocks of the Matanuska Valley from older 

and more highly deformed metamorphic and intrusive rocks 

of the mountains (Barnes and Payne, 1956). Deformation of 

coal-bearing rocks and abundance of igneous dikes and sills 

increase eastward, resulting in coals that are strongly folded 

and faulted and of higher rank compared to coals of the Cook 

Inlet and Susitna lowland (Merritt and Belowich, 1984; 

Stricker, 1991). 

Stratigraphic Framework

Tertiary nonmarine, coal-bearing basin fill unconformably overlies deeply buried, mostly marine Mesozoic rocks 

(fig. 4). Six regional, time-transgressive units were defined 

on the basis of “type” well logs by Calderwood and Fackler 

(1972). These units are thought to contain laterally equivalent 

facies related to a dynamic nonmarine depositional system 

(Swenson, 1997). The coarsest facies (conglomerates and 

sandstones) were deposited near the source by an alluvial fan 

system that drained the basin margins, while a distal axialfluvial system in the center of the basin reworked the alluvial 

fan deposits (Flores and others, 2004) (fig. 5). Coal deposits 

accumulated in mires related to this large fluvial drainage 

system. 

Lower Tertiary Rocks

Lower Tertiary rocks in the Cook Inlet-Susitna region 

include the Paleocene–Eocene Chickaloon Formation and 

Eocene Wishbone Formation. The Chickaloon Formation 

is present in the northeastern part of the basin and crops 

out in the Matanuska Valley. This formation consists of a 

3,300- to 4,900-ft-thick sequence of mudstone, siltstone, and 

sandstone, with minor conglomerate and coal (Triplehorn 

and others, 1984; Flores and Stricker, 1993). Sandstone beds 

are erosionally based and range from lenticular to tabular in 

geometry. As many as 12 coal beds have been reported in the 

Chickaloon Formation. Coal beds are lenticular and vary in 

thickness within 300 ft laterally. Individual coal beds average 

less than 3 ft in thickness, but a coal bed more than 15 ft thick 

has been reported in the Chickaloon mine (Wahrhaftig and 

others, 1994). Coal rank increases from west to east within 

the Matanuska Valley, from high-volatile subbituminous to 

semianthracite. This increase in rank is attributed to heating 

of the coal by the abundant igneous dikes and sills within the 

Chickaloon Formation in the eastern Matanuska Valley 

(Merritt, 1985; Stricker, 1991; Wahrhaftig and others, 1994). 
Stratigraphic Framework 3

Figure 1. Location of the Cook Inlet Coal-Bed Gas Total Petroleum System (TPS), major bounding faults, anticlines, and vertical and 

near-vertical well locations within the Cook Inlet-Susitna region, south-central Alaska. The Coal-Bed Gas Assessment Unit (AU) excludes 

an area in the center of the Cook Inlet basin where the principal coal-bearing units are deeper than 6,000 feet and are unlikely to be 

productive of gas. An area (not shown) around the outer perimeter of the AU where the principal coal-bearing units are shallower than 

1,000 feet also is excluded from the assessment.

154° 153° 152° 151° 150° 149° 148°

62°

61°

60°

62°

61°

60°

154° 153° 152° 151° 150° 149°

TPS boundary

Area excluded from 

 assessment

Major bounding faults

Anticlines

EXPLANATION

Vertical and 

 near-vertical well 

 locations

Coastline

CASTLE MOUNTAIN FAULT

BRUIN BAY FAULT

BORDER RANGES FAULT

SUSITNA

LOWLAND

MATANUSKA

VALLEY

COOK INLET BASIN

Alaska

Range

Aleutian

Range

Talkeetna

Mountains

Chugach

Mountains

0 5 10 20 30 40 MILES

0 2010 4030 50 KILOMETERS

ALASKA

Map area
OCEANIC LITHOSPHERE ASTHENOSPHERE 

ACCRETIONARY COMPLEX FORE-ARC BASIN THRUST FAULT (COOK INLET BASIN) CONTINENTAL LITHOSPHERE MAGMATIC ARC NORTH 

Figure 2. Tectonic and volcanic settings of the Cook Inlet basin (Flores and others, 2004; modified from Swenson, 1997).
Shell

Cottonwood 1

Arco

Middle River

Strat. 1

Arco

Middle River

State

Unit 1

Union

Trading Bay1A

Union

Grayling Unit 1A

Pan Am

North

Redoubt

Shoal St.

Shell MGS

ST-1

Standard-Rich

SCU 41-4

Standard-Rich

Swan Lake

Unit 34-27

BEND IN

SECTION

BEND IN

SECTION

BEND IN

SECTION

BEND IN

SECTION

Jg

Jg ?

Jg ?

Jtk

Jtk Jtk Jtk Jtk

Jtk

Jtk Jtk

Jtk

Tks

Tks

Tks

Jt

Jt

Jt

Jt

Jnc

Jnc

Jnc

Kk

Kk

Tkt

Tkt Tkt Tkt

Tkb

Jtk

Tkt Tkt

Tw

Tw

Tw

Tw

Tkb

Tks

Jt Jt Jnc

Kk

Tw Kk

Jnc

T Pzs R

U D

U D

B B’

B B’C 

C

COOK INLET COOK INLET

Swanson River

Oilfield

Trading Bay Oilfield

MacArthur

River Oilfield

Middle

Ground

Shoal

Oilfield

Trading Bay Oilfield

BRUIN BAY

FAULT ZONE BRUIN BAY FAULT ZONE 

BRUIN BAY

FAULT ZONE

Qs

Qs

Qs

Qs

N

N

Tks

Tkb

Tkt

Tw

Kk

KJm

Jnc

Jt

Jtk

Jg

^Pzs

Sterling Formation (Pliocene and Miocene)Beluga Formation (Miocene)Tyonek Formation and Hemlock Conglomerate (Miocene and Oligocene)

West Foreland Formation (Eocene and Paleocene)Kaguyak Formation (Upper Cretaceous)

McHugh Complex (Cretaceous and (or) Upper JurasChinitna and Naknek Formations (Upper Jurassic)Tuxedni Group (Middle Jurassic)Talkeetna Formation (Lower Jurassic)Granitic rocks (Lower and Middle Jurassic)

Schist and (?) associated ultramafic rocks (Triassic 

Kenai Group (Pliocene, Miocene, and Oligocene)

Qs Quartenary sediments

EXPLANATION

Figure 3. Cross section of the eastern Aleutian Arc, from Mount Spurr to the Border Ranges fault, Alaska (modified from Plafker and others, 1982).
6 Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna Region, South-Central Alaska

Time

(Ma) Period/Epoch

10

20

30

40

50

60

Paleogene Neogene

Quartenary

Pliocene

Miocene

Oligocene

Eocene

Paleocene

Kenai Group

Cook

Inlet Basin

Matanuska

Valley

Susitna

Lowland

Tertiary

Wishbone 

Formation

West Foreland

Formation

Arkose

Ridge 

Formation

Hemlock

Conglomerate

Bell Island

Sandstone

(informal)*

Tsadaka

Formation*

Tyonek

Formation

Tyonek (?)

Formation

Tyonek

Formation

Beluga

Formation

Chickaloon 

Formation

Sterling

Formation

Sterling (?)

Formation

Sterling (?)

Formation

Unnamed Unnamed Unnamed

* Not considered part of Kenai Group

Figure 4. Tertiary correlation chart for the Cook Inlet-Susitna region (modified from Wahrhaftig and others, 1994; formations in 

Susitna lowland from Reed and Nelson, 1980). See Swenson (1997) for interpretation of interfingering relations in Tertiary Strata. 

(Ma, million years before present.) 
Stratigraphic Framework 7

EXPLANATION

Sandstone

Conglomerate

Mudstone and siltstone

Coal and carbonaceous shale

Mires

Normal fault

Meandering and 

anastomosed streams

Ancestral Aleutian-Alaskan Rang

e

Ancestral

Kenai-Chugach

Mountains

Alluvial fan

Figure 5. Depositional model of the Kenai Group in the Cook Inlet basin (Flores and others, 2004; modified from Hayes and others, 1976).

The Chickaloon Formation unconformably overlies the Lower 

and Upper Cretaceous Matanuska Formation, which consists 

of marine sandstone and shale (Barnes and Payne, 1956; 

Grantz and Jones, 1960) and is overlain unconformably by the 

Eocene Wishbone Formation.

The Wishbone Formation consists of 3,000 ft of thick, 

massive conglomerate and sandstone containing clasts that 

indicate a provenance in the Talkeetna Mountains to the north. 

The formation is restricted to the Matanuska Valley and is 

unconformably overlain by flat-lying Tertiary basalt at the east 

end of the Matanuska coal field. The Wishbone Formation 

correlates with the West Foreland Formation in the Cook Inlet 

basin (Wahrhaftig and others, 1994; Flores and others, 2004). 

The West Foreland Formation consists of 2,000 ft of 

tuffaceous claystone, sandstone, and conglomerate, with a few 

thin coals. The formation underlies most of the lower Cook 

Inlet basin southwest of the mouth of the Susitna River and 

much of the lowland area of the northwestern Kenai Peninsula 

(Hartman and others, 1971).

The Wishbone and West Foreland Formations are 

overlain by the Oligocene–Pliocene Kenai Group, though 

the nature of the contact has been the subject of debate. 

C.E. Kirschner (1989, written commun.; cited in Wahrhaftig 

and others, 1994), following the assignment of the West 

Foreland Formation as the basal unit of the Kenai Group by 

Calderwood and Fackler (1972), regarded the West Foreland 

Formation as conformable and probably continuous with the 

rest of the Kenai Group in the subsurface of the Cook Inlet 

basin. Kirschner suggested that an unconformity between the 

West Foreland Formation and parts of the Tyonek Formation 

observed along the margins of the Cook Inlet basin is spatially 

restricted to the margins of the basin; however, Magoon and 

others (1976) regarded the unconformity as regional, because 

sections of the West Foreland Formation that have been dated 

are 20 million years older than rocks of the Kenai Group. 

The USGS has adopted the interpretation of Magoon and 

others (1976) (Wahrhaftig and others, 1994). 
8 Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna Region, South-Central Alaska

Upper Tertiary Kenai Group

The Kenai Group comprises four formations: the Oligocene 

Hemlock Conglomerate, Oligocene–Middle Miocene Tyonek 

Formation, Upper Miocene Beluga Formation, and Upper 

Miocene–Pliocene Sterling Formation (Dall and Harris, 1892; 

Parkinson, 1962; Calderwood and Fackler, 1972). Most coal 

shallower than 6,000 ft in the Cook Inlet-Susitna region is in 

the Kenai Group (Montgomery and Barker, 2003).

The Oligocene Hemlock Conglomerate consists of pebble 

to boulder conglomerate containing clasts of quartz; chert; 

metamorphic, volcanic, and plutonic rock fragments; a few 

thin coal beds; and many siltstone beds. This formation, along 

with the temporally equivalent Bell Island Sandstone and 

Tsadaka Formation in the Matanuska Valley, forms a sheet 

deposit that ranges from 655 to 2,772 ft in thickness (Wolfe 

and Tanai, 1980; Magoon and Egbert, 1986). Sandstone 

reservoirs within the formation average 17 percent porosity 

and 80 millidarcy (md) permeability and represent the main 

producing horizon for oil in the offshore Cook Inlet (Magoon 

and Anders, 1990; Magoon, 1994). 

The overlying Tyonek, Beluga, and Sterling Formations 

make up a thick sequence of alluvial sandstone, conglomerate, 

siltstone, mudstone, carbonaceous shale, and coal, with most 

of the coal in the Tyonek and Beluga Formations (Wahrhaftig 

and others, 1994). Sandstone beds are fine to coarse grained, 

thick, erosive based, crossbedded, and vertically stacked. 

Individual coal beds range in thickness from a few inches to 

more than 50 ft. Coal rank ranges from lignite in the Sterling 

Formation to subbituminous in the Tyonek Formation. Subsurface correlation of coal beds from well to well is difficult for 

distances of more than a mile, suggesting considerable lenticularity of the coal beds and intervening sedimentary rocks. 

In outcrop, however, individual coal beds have been traced for 

as far as 6.2 miles (Barnes, 1966; Ramsey, 1981). 

Methodology

Interpretation of geophysical logs from 153 oil and gas 

exploration wells in the Cook Inlet-Susitna region was used 

to delineate coal-bed thickness and stratigraphic distribution 

in the subsurface (fig. 1). This study was limited to wells for 

which Log ASCII Standard (LAS) files were available. Only 

vertical and near-vertical wells (<500 meters (m) horizontally between surface and bottom-hole locations) with both 

gamma-ray and bulk density logs were included. Wells that 

met these criteria were only in the Cook Inlet basin, excluding 

the Matanuska Valley and Susitna lowland.

Coal beds are readily identified in geophysical logs 

because of their unique physical properties, including low natural radioactivity and low density. Coal generally exhibits low 

radioactivity on gamma-ray logs compared to other lithologies 

in a coal-bearing sequence. Sandstone, however, may have 

similar gamma-ray values, making identification of coal beds 

based solely on gamma-ray logs difficult and requiring the use 

of a supplemental log. 

Coal density averages between 0.7 and 1.8 grams per 

cubic centimeter (g/cc) (Wood and others, 1983), significantly 

less than associated lithologies. This density contrast is easily 

recognized on bulk density logs, where coal exhibits low-density spikes (fig. 6). Whereas the bulk density log is capable of 

identifying thin coal beds, similar density spikes are recorded 

where the borehole diameter is enlarged as a result of washout. 

Caliper logs, which measure the diameter of a borehole, can be 

used to identify areas where low-density measurements may 

be false (fig. 6). 

Net coal-bed thickness between depths of 1,000 and 

6,000 ft was quantified as a mapping parameter (fig. 7); explanation for this depth interval is provided below. Coal beds 

were defined as having bulk density values less than 2 g/cc. 

Digital logs were analyzed by using an automated routine to 

calculate the thickness of strata with a bulk density less than 

2 g/cc between depths of 1,000 ft and 6,000 ft. These results 

include borehole washout intervals. Wells that were characterized by intervals of false low density due to borehole washout 

were removed from net coal thickness calculations in order 

to prevent overestimates. Nevertheless, logs for most wells 

likely contain some false low-density values, resulting in 

overestimates of net coal thickness. Conversely, the lack of a 

bulk density log curve for any part of the 1,000- to 6,000-ft 

depth interval results in an underestimate of net coal thickness. 

Therefore, net coal thickness derived from log analysis is used 

as a general parameter to delineate sweet spots of coal-bed gas 

potential. 

In addition to net coal thickness in the 1,000- to 6,000-ft 

depth interval, individual thick coal deposits were used to 

further delineate sweet spots of coal-bed gas potential 

(fig. 8). Individual thick coal deposits are defined as at least 

25 ft of coal within a 100-ft interval of section. Wells that 

were removed from net coal thickness calculations because 

of borehole washout were manually checked to determine the 

presence and stratigraphic position of thick coal deposits. 
Methodology 9

0.00 150 0.00 20.0 2.00 3.00

1100

1200

1300

1400

1500

PENNZOIL CO INC

STARICHKOF STATE UN 1

50831200010000 Washout interval Washout interval

Log depth

(feet)

Bulk density

(RHOB)

Caliper

(CALI) Gamma ray

(GR)

Figure 6. Well log response of coal and borehole washout 

intervals in the Starichkof State Unit 1 well. Coal beds (black) 

are identified by both low gamma-ray values (GR, red) and 

low-density response on the bulk density log curve (RHOB, 

green). Borehole washout intervals are identified on the 

caliper log (CALI, black). False low-density measurements 

associated with borehole washout intervals are highlighted 

on the bulk density log curve in yellow. 
10 Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna Region, South-Central Alaska

154° 153° 152° 151° 150° 149° 148°

62°

61°

60°

62°

61°

60°

154° 153° 152° 151° 150° 149°

200

200

200

200

200

400

400

400

200

600

600

800

600

400

400

200

200

400

400

400

0 5 10 20 30 40 MILES

0 2010 4030 50 KILOMETERS

Figure 7. Cumulative thickness of coal (in feet) as inferred from records of wells between 1,000 and 6,000 feet deep in 

the Cook Inlet basin.
Methodology 11

154° 153° 152° 151° 150° 149° 148°

62°

61°

60°

62°

61°

60°

154° 153° 152° 151° 150° 149°

TPS boundary

Area excluded from 

 assessment

Major bounding faults

Anticlines

EXPLANATION

Vertical and near-vertical 

 well locations

Coastline

CASTLE MOUNTAIN FAULT

BRUIN BAY FAULT

BORDER RANGES FAULT

MATANUSKA

VALLEY

COOK INLET BASIN

SUSITNA

LOWLANDS

Alaska

Range

Aleutian

Range

Talkeetna

Mountains

Chugach

Mountains

0 5 10 20 30 40 MILES

0 2010 4030 50 KILOMETERS

Wells with thick coal

 deposits

Figure 8. Location of wells with thick coal deposits between depths of 1,000 and 6,000 feet in the Cook Inlet basin. 

Thick coal deposits (green dots) are defined as at least 25 feet of coal within a 100-foot interval of section. 
12 Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna Region, South-Central Alaska

Total Petroleum System

Assessment of undiscovered, technically recoverable 

coal-bed gas resources of the Cook Inlet-Susitna region is 

based on the TPS concept (Schmoker, 2005). A TPS consists 

of all genetically related petroleum generated by a pod or 

closely related pods of mature source rocks. The Coal-Bed 

Gas TPS in the Cook Inlet-Susitna region comprises the Paleocene–Lower Eocene Chickaloon, Oligocene–Middle Miocene 

Tyonek, Upper Miocene Beluga, and Upper Miocene–Pliocene 

Sterling Formations, encompassing an area of about 9,600,000 

acres. The TPS is divided into homogeneous subunits called 

assessment units, or AUs. Owing to similarities in lithology 

and abrupt lateral facies changes in the Chickaloon, Tyonek, 

Beluga, and Sterling Formations, it is difficult to determine 

precise and consistent stratigraphic contacts. Therefore, the 

TPS contains one continuous gas AU in Tertiary coal-bearing 

strata at depths between 1,000 and 6,000 ft. Coal beds generally lose permeability below 6,000 ft, and production levels 

are correspondingly uneconomic (McKee and others, 1986); 

at depths shallower than 1,000 ft, reservoir pressure in coals 

is assumed to be too low.

 An area of approximately 1,100,000 acres within 

the central part of the Cook Inlet basin was excluded from 

the assessment because most coal deposits lie deeper than 

6,000 ft (figs. 1 and 8). Owing to a paucity of well penetrations and limited seismic coverage, the area excluded from 

assessment was based mostly on the Mesozoic basement 

structure contour map (Shellenbaum and others, 2010) (fig. 9).

The area excluded from the assessment roughly outlines that 

area of the basin where depth to basement is greater than 

15,000 ft. The few wells within the zone excluded from the 

assessment contained no individual thick coal deposits.

An additional area along the perimeter of the AU also 

was excluded from assessment because coal deposits are likely 

to be shallower than 1,000 ft. A paucity of well data made 

it difficult to constrain this area, resulting in uncertainty in 

the assessment data input for the total assessment area (see 

“Assessment Data Input and Results”). 

 Source and Reservoir Rock

Coal beds within the TPS are the source of gas for both 

the coal and the conventional accumulations in sandstone 

reservoirs. Individual coal beds range from a few inches to 

more than 50 ft in thickness. Coal beds laterally merge, split, 

and pinch out as influenced by the intervening fluvial-channel 

sandstones. The net coal-thickness isopach shows that the 

thickest accumulations of coal between 1,000 and 6,000 ft in 

depth are along the west shore of the Cook Inlet. Broad areas 

contain more than 400 ft of net coal, with more than 800 ft 

locally (fig. 7). Net coal thickness decreases eastward over 

a 5- to 10-mile distance, and much of the basin contains less 

than 200 ft of net coal (fig. 7). At least one thick coal deposit 

between 1,000 and 6,000 ft depth is found in most of the area 

of the AU (fig. 8).

Maturation

Thermal maturity of the Cook Inlet-Susitna region was 

characterized by using published vitrinite reflectance (VR) 

data from 251 well and outcrop locations (fig. 10). VR in 

outcrops and the shallow subsurface ranges mostly from 

0.18 to 4.18 percent, with values greater than 0.6 percent in 

the southwestern and northeastern parts of the basin. High 

reflectance values in the northeastern Matanuska Valley are 

attributed to tectonic deformation and magmatism along the 

Aleutian volcanic arc (Flores and others, 2003). The central 

part of the Cook Inlet basin and Susitna lowland maintains 

reflectance values of less than 0.6 percent, likely a function 

of low thermal conductivity related to the rapid rate of subsidence and sedimentation in these areas (Flores and others, 

2004). Johnsson and others (1993) determined a similar basinwide variation in thermal maturity from VR at 30 offshore and 

onshore wells in the Cook Inlet basin. 

VR indicates that most coal beds in the Kenai Group 

are thermally immature (<0.6 percent reflectance (Ro

)), 

owing to the very low VR gradient with depth (Johnsson 

and others, 1993). These thermally immature coals range 

from lignite to subbituminous and are the lowest ranks 

from which commercial gas is produced in the United 

States (Flores, 2004). 

Claypool and others (1980) identified two types of natural 

gas occurrences in the Cook Inlet basin separated both stratigraphically and compositionally from each other, suggesting 

different origins:

• Gas produced from reservoirs sourced from coal beds is 

both isotopically light (δ13C range of –63 to –56 per mil) 

and chemically dry (C1/C1–5 > 0.99; Claypool and 

others, 1980). Claypool and others (1980) favored a 

biogenic origin for gas associated with Tertiary coal 

beds on the basis of low thermal maturity and isotopically light and chemically dry gas composition. 

• VR of coals in the Chickaloon and lower Tyonek 

Formations in the Matanuska Valley is greater than 

0.6 percent Ro, indicating a more mature thermal 

history. These thermally mature coals range from bituminous to semianthracite in rank. Gas recovered from 

lower Tyonek Formation coals in the Matanuska Valley is 

isotopically heavier (δ13C range of –48.9 to –44.0 per mil) 

than shallow gas of the central and southern Cook Inlet. 

Given the high-temperature history and heavier gas 

composition, thermogenic gas is likely in coals in the 

Matanuska Valley (Smith, 1995, cited in Montgomery 

and Barker, 2003; Seamount and others, 1997; Barker 

and others, 2001). 
Total Petroleum System 13

154° 153° 152° 151° 150° 149° 148°

62°

61°

60°

62°

61°

60°

154° 153° 152° 151° 150° 149°

0 5 10 20 30 40 MILES

0 2010 4030 50 KILOMETERS

EXPLANATION

TPS Boundary

Isopach line

Contour interval 

is 2,000 feet.

Coastline

Elevation (feet)

< -24,000

-24,000 to -22,000 

-22,000 to -20,000

-20,000 to -18,000

-18,000 to -16,000

-16,000 to -14,000

-14,000 to -12,000

-12,000 to -10,000

-10,000 to -8,000

-8,000 to -6,000

-6,000 to -4,000

-4,000 to -2,000

> -2,000

Figure 9. Structure contour map of the top of the Mesozoic basement, Cook Inlet basin (modified from Shellenbaum and 

others, 2010).
14 Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna Region, South-Central Alaska

154° 153° 152° 151° 150° 149° 148°

62°

61°

60°

62°

61°

60°

154° 153° 152° 151° 150° 149°

TPS boundary

Area excluded from 

 assessment

Major bounding faults

Anticlines

EXPLANATION

Vitrinite reflectance

Coastline

CASTLE MOUNTAIN FAULT

BRUIN BAY FAULT

BORDER RANGES FAULT

SUSITNA

LOWLANDS

MATANUSKA

VALLEY

COOK INLET BASIN

Alaska

Range

Aleutian

Range

Talkeetna

Mountains

Chugach

Mountains

0 5 10 20 30 40 MILES

0 2010 4030 50 KILOMETERS

< 0.6% Ro

0.6% < Ro < 1.0%

> 1.0% Ro

Figure 10. Outcrop and well vitrinite reflectance values within the Coal-Bed Gas Total Petroleum System (TPS) in the 

Cook Inlet-Susitna region. Vitrinite reflectances from well data are limited to the shallowest data at each well. 
Assessment Data Input and Results 15

Reservoir Rock

Coal beds are inferred to serve as both source and 

reservoir rocks in the Cook Inlet Coal-Bed Gas AU. 

Coal-bed gas is produced in place and is adsorbed to coal 

surfaces along fractures, cleats, and pores (Flores, 2004). 

The amount of gas that coal can store is a function of coal 

rank, temperature, and pressure (Flores, 2004). Higher rank 

and pressure generally increase storage capacity, whereas 

higher temperature decreases storage capacity. Average gas 

content from canister desorption measurements on subbituminous coal in the central and southern Cook Inlet basin is 

60 standard cubic feet per ton (scf/ton), whereas higher rank 

bituminous coal of the Matanuska Valley has an average gas 

content of 230 scf/ton (Barker and others, 2001). 

Assessment Data Input and Results

The basic input data used for the assessment of Tertiary 

coal-bed gas in the Cook Inlet-Susitna region are listed in 

table 1. The AU is considered hypothetical because no production has been established from Tertiary coal-bed reservoirs, 

so the use of coal-bed gas analogs from the 48 contiguous 

States was necessary for this assessment. Coal beds of the 

Upper Fort Union Formation in the Powder River Basin of 

Wyoming and Montana were selected as a baseline production 

analog for Tertiary coal beds in the Cook Inlet-Susitna region. 

Upper Fort Union coal beds have the same rank (lignite to 

subbituminous) and similar coal-quality characteristics to coal 

beds of the Tertiary Kenai Group (Flores, 2004). Although 

coals of higher rank and greater gas storage capacity have 

been documented in the northeastern Matanuska Valley, they 

were not considered separately because (1) they are thought 

to be spatially limited to an area along the northeastern part 

of the Castle Mountain fault, (2) the subsurface extent of the 

higher rank coals is poorly constrained, and (3) their reservoir 

properties are thought to be influenced by strain related to the 

Castle Mountain fault and contact metamorphism by igneous 

dikes and sills (Barnes, 1962; Merritt, 1985; Stricker, 1991; 

Wahrhaftig and others, 1994). 

The Tertiary Coal-Bed Gas AU is considered to have 

a minimum estimated ultimate recovery (EUR) per cell of 

0.02 billion cubic feet of gas (BCFG) in this assessment. 

The assessment area contains an estimated minimum of 

8,000,000 acres, mode of 8,500,000 acres, and maximum 

of 9,000,000 acres because of uncertainties in geologic map 

boundaries (table 1). The drainage area of untested cells 

having potential for additions to reserves is estimated at a 

minimum of 40 acres, a mode of 80 acres, and a maximum 

of 140 acres (table 1), values similar to those estimated for 

the Upper Fort Union Formation AU (Flores, 2004). All of 

the AU area is untested (table 1). The fraction of total AU 

area that has potential for additions to reserves in the next 

30 years is estimated at a minimum of 0.5 percent, a mode of 

6 percent, and a maximum of 63 percent (table 1). The mode 

percentage is based on the area of thick coal accumulation 

between 1,000 and 6,000 ft in depth near the western shore 

of the Cook Inlet relative to the total AU area. The minimum 

and maximum percentages reflect considerable uncertainty 

that stems from the absence of subsurface penetrations that 

meet the assessment criteria in more than 30 percent of the 

assessment unit (Susitna lowland and Matanuska Valley). 

The total recovery per cell for untested cells having potential 

for addition to reserves in the next 30 years was estimated at a 

minimum of 0.02 BCFG, a median of 0.16 BCFG, and a maximum of 1.5 BCFG (table 1). Using these inputs, the USGS 

estimates the total undiscovered coal-bed gas resources in 

the Cook Inlet-Susitna region as follows: 1,581 BCFG at F95, 

3,989 BCFG at F50, and 10,069 BCFG at F5; the mean estimate 

is 4,674 BCFG (table 2). 
16 Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna Region, South-Central Alaska

Table 1. Assessment data input for the Cook Inlet Coal-Bed Gas Assessment Unit.

NUMBER OF UNTESTED CELLS WITH POTENTIAL FOR ADDITIONS TO RESERVES

1. Total assessment-unit area (acres): (uncertainty of a fixed value)

calculated mean 8,500,000 minimum 8,000,000 mode 8,500,000 maximum 9,000,000

2. Area per cell of untested cells having potential for additions to reserves (acres): (values are inherently variable)

calculated mean 87 minimum 40 mode 80 maximum 140

uncertainty of 

mean: minimum 40 maximum 120

3. Percentage of total assessment-unit area that is untested (percent): (uncertainty of a fixed value)

calculated mean 100 minimum 100 mode 100 maximum 100

4. Percentage of untested assessment-unit area that has potential for additions to reserves (percent):

(a necessary criterion is that total recovery per cell ≥ minimum; uncertainty of a fixed value)

calculated mean 23 minimum 0.5 mode 6 maximum 63

TOTAL RECOVERY PER CELL

Total recovery per cell for untested cells having potential for additions to reserves:

(values, in billion cubic feet of gas, are inherently variable)

calculated mean 0.206 minimum 0.02 median 0.16 maximum 1.5

Table 2. Summary of results for risked, undiscovered, technically recoverable contiguous 

gas resources for the Cook Inlet Coal-Bed Gas Assessment Unit. 

[BCFG, billion cubic feet of gas. 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]

Assessment unit name Total undiscovered gas resources (BCFG)

F95 F50 F5 Mean

Cook Inlet Coal-Bed Gas 1,581 3,989 10,069 4,674
References Cited 17

Summary

The Cook Inlet Coal-Bed Gas Total Petroleum System 

(TPS) of south-central Alaska comprises coal-bearing 

Tertiary strata of the Cook Inlet basin, Matanuska Valley, and 

Susitna lowland. The TPS contains one hypothetical assessment unit (AU) that was evaluated for coal-bed gas resources 

between 1,000 and 6,000 ft in depth over an area of about 

8,500,000 acres. Coal beds, which range in thickness from a 

few inches to more than 50 ft, were deposited in mires associated with a large trunk-tributary fluvial system. Gas associated with the lignite to subbituminous coal in the AU is likely 

biogenic in origin. Potential for addition to reserves in the next 

30 years is greatest along the western part of the Cook Inlet 

basin, where cumulative coal thickness exceeds 800 ft. Using 

coal beds of the Upper Fort Union Formation in the Powder 

River Basin of Wyoming and Montana as a baseline production 

analog, the USGS estimates the total undiscovered coal-bed gas 

resources in the Cook Inlet Coal-Bed Gas AU as follows: 

1,581 BCFG at F95, 3,989 BCFG at F50, and 10,069 BCFG at F5

; 

the mean estimate is 4,674 BCFG (table 2). 

References Cited 

Affolter, R.H., and Stricker, G.D., 1987, Offshore Alaska coal, 

in Scholl, D.W., Grantz, Arthur, and Vedder, J.G., eds., 

Geology and resource potential of the continental margin of 

western North America and adjacent ocean basins—Beaufort Sea to Baja California: Houston, Tex., Circum-Pacific 

Council for Energy and Mineral Resources, Earth Science 

Series, v. 6, p. 639–647.

Alaska Department of Natural Resources, Division of Oil 

and Gas, 2009, Historical and projected oil and gas 

consumption: p. 26.

Barker, C.E., Dallegge, T.A., and Seamount, D.C., 2001, 

Ongoing coalbed desorption studies, Cook Inlet Basin, 

Alaska [abs.], in Dallegge, T.A., comp., Guide to the 

petroleum, geology, and shallow gas potential of the Kenai 

Peninsula, Alaska: 2001 Petroleum Technology Transfer 

Council, Alaska Department of Natural Resources and 

U.S. Geological Survey Alaska Coalbed and Shallow Gas 

Resources Workshop, Field Trip Guidebook, p. 40–55.

Barnes, F.F., 1962, Variation in rank of Tertiary coals in 

the Cook Inlet basin, Alaska: U.S. Geological Survey 

Professional Paper 450–C, p. C14–C16.

Barnes, F.F., 1966, Geology and coal resources of the BelugaYentna region, Alaska: U.S. Geological Survey Bulletin 

1202–C, p. C1–C34, pls. 1–7.

Barnes, F.F., 1967, Coal resources of Alaska: U.S. Geological 

Survey Bulletin 1242–B, p. B1–B36, pl. 1.

Barnes, F.F., and Cobb, E.H., 1959, Geology and coal 

resources of the Homer district, Kenai coal field, Alaska: 

U.S. Geological Survey Bulletin 1058–F, p. 217–258, 

pls. 17–28.

Barnes, F.F., and Payne, T.G., 1956, The Wishbone Hill district, Matanuska coal field, Alaska: U.S. Geological Survey 

Bulletin 1016, 88 p., 20 pl.

Byrne, Tim, 1979, Late Paleocene demise of the Kula-Pacific 

spreading center: Geology, v. 7, p. 341–344.

Calderwood, K.W., and Fackler, W.C., 1972, Proposed stratigraphic nomenclature for Kenai Group, Cook Inlet Basin, 

Alaska: American Association of Petroleum Geologists 

Bulletin, v. 56, p. 739–754.

Claypool, G.E., Threlkeld, C.N., and Magoon, L.B., 1980, 

Biogenic and thermogenic origins of natural gas in Cook 

Inlet basin, Alaska: American Association of Petroleum 

Geologists Bulletin, v. 64, no. 8, p. 1131–1139.

Dall, W.H., and Harris, G.D., 1892, Correlation papers—

Neocene: U.S. Geological Survey Bulletin 84, 349 p.

Davis, T.N., 1981, Alaska’s Coal, article #492, June 26, 1981: 

Geophysical Institute, University of Alaska Fairbanks.

Flores, R.M., 2004, Coalbed methane in the Powder River 

Basin, Wyoming and Montana—An assessment of the 

Tertiary–Upper Cretaceous Coalbed Methane Total Petroleum System, in Total Petroleum System and assessment of 

coalbed gas in the Powder River Basin Province, Wyoming 

and Montana: U.S. Geological Survey Digital Data Series 

DDS–69–C, chap. 2, 56 p.

Flores, R.M., and Stricker, G.D., 1993, Early Cenozoic depositional systems, Wishbone Hill District, Matanuska coal 

field, Alaska, in Dusel-Bacon, Cynthia, and Till, A.B., eds, 

Geologic studies in Alaska by the Geological Survey, 1992: 

U.S. Geological Survey Bulletin 2068, p. 101–117.

Flores, R.M., Stricker, G.D., and Kinney, S.A., 2003, 

Alaska coal resources and coalbed methane potential: 

U.S. Geological Survey Bulletin 2198, 4 p.

Flores, R.M., Stricker, G.D., and Kinney, S.A., 2004, Alaska 

coal geology, resources, and coalbed methane potential: 

U.S. Geological Survey Digital Data Series DDS–77, 

version 1.0 (2004) 140 p. [CD-ROM]. 

(Also available at http://pubs.usgs.gov/dds/2004/77/.)

Grantz, Arthur, and Jones, D.L., 1960, Stratigraphy and age 

of the Matanuska Formation: U.S. Geological Survey 

Professional Paper 400–B, p. B347–B350.
18 Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna Region, South-Central Alaska

Haeussler, P.J., Bruhn, R.L., and Pratt, T.L., 2000, Potential 

seismic hazards and tectonics of the upper Cook Inlet basin, 

Alaska, based on analysis of Pliocene and younger deformation: Geological Society of America Bulletin, v. 112, no. 9, 

p. 1414–1429.

Hartman, D.C., Pessel, G.H., and McGee, D.L., 1971, 

Preliminary report on stratigraphy of the Kenai group, 

upper Cook Inlet, Alaska: Alaska Division of Geological & 

Geophysical Surveys Special Report 5, 4 p., 10 pl.

Hopkins, D.M., 1951, Lignite deposits near Broad Pass 

Station, Alaska: U.S. Geological Survey Bulletin 963–E, 

p. 187–191, pl. 26.

Hayes, J.B., Harms, J.C., and Wilson, T., 1976, Contrasts 

between braided and meandering stream deposits, Beluga 

and Sterling Formations (Tertiary), Cook Inlet, Alaska, in

Miller, T.P., ed., Recent and ancient sedimentary environments in Alaska—Proceedings, Alaska Geological Society 

Symposium, April 2–4, 1975, Anchorage: Alaska Geological Society, p. J1–J27.

Johnsson, M.J., Howell, D.G., and Bird, K.J., 1993, Thermal 

maturity patterns in Alaska—Implications for tectonic evolution and hydrocarbon potential: American Association of 

Petroleum Geologists Bulletin, v. 77, p. 1874–1903.

Kelly, T.E., 1963, Geology and hydrocarbons in Cook Inlet 

basin, Alaska, in Childs, O.E., and Beebe, B.W., eds., 

Backbone of the Americas—A symposium: American Association of Petroleum Geologists Memoir 2, p. 278–296.

Magoon, L.B., 1994, Tuxedni-Hemlock(!) petroleum system 

in Cook Inlet, Alaska, U.S.A., in Magoon, L.B., and Dow, 

W.G., eds., The petroleum system—From source to trap: 

American Association of Petroleum Geologists Memoir 60, 

p. 359–370.

Magoon, L.B., Adkison, W.L., and Egbert, R.M., 1976, Map 

showing geology, wildcat wells, Tertiary plant fossil localities, K-Ar age dates, and petroleum operations, Cook Inlet 

area, Alaska: U.S. Geological Survey Miscellaneous Investigations Series Map I–1019, 3 sheets, scale 1:250,000.

Magoon, L.B., and Anders, D.E., 1990, Oil-source rock 

correlation using carbon isotope data and biological marker 

compounds, Cook Inlet, Alaska peninsula, Alaska: 

American Association of Petroleum Geologists Bulletin, 

v. 74, p. 711. 

Magoon, L.B., and Egbert, R.M., 1986, Framework geology 

and sandstone composition, in Magoon, L.G., ed., Geologic 

studies of the Lower Cook Inlet COST No. 1 Well, Alaska 

outer continental shelf: U.S. Geological Survey Bulletin 

1596, p. 65–90.

McKee, C.R., Bumb, A.C., Way, S.C., Koenig, R.A., 

Reverand, J.M., and Brandenburg, C.F., 1986, Using 

permeability-vs-depth correlations to assess the potential for 

producing gas from coal seams: Methane From Coal-Seams 

Technology, v. 4, p. 15–26.

Merritt, R.D., 1985, Review of coking phenomena in relation to an occurrence of prismatically fractured natural 

coke from the Castle Mountain mine, Matanuska coal 

field, Alaska: International Journal of Coal Geology, v. 4, 

p. 281–298.

Merritt, R.D., and Belowich, M.A., 1984, Coal geology and 

resources of the Matanuska Valley, Alaska: Alaska Division 

of Geological & Geophysical Surveys Report of Investigations 84–24, 64 p., 3 pl.

Merritt, R.D., and Hawley, C.C., comps., 1986, Map of Alaska’s coal resources: Fairbanks, Alaska Division of Geological & Geophysical Surveys, scale 1:2,500,000.

Miller, R.D., and Dobrovolny, Ernest, 1959, Surficial geology 

of Anchorage and vicinity, Alaska: U.S. Geological Survey 

Bulletin 1093, 128 p.

Montgomery, S.L., and Barker, C.E., 2003, Coalbed methane, 

Cook Inlet, south-central Alaska—A potential giant gas 

resource: American Association of Petroleum Geologists 

Bulletin, v. 87, no. 1, p. 1–13.

Nokelberg, W.J., Plafker, George, and Wilson, F.H., 1994, 

Geology of south-central Alaska, in Plafker, G., and Berg, 

H.C., eds., The geology of North America—The geology of 

Alaska: Boulder, Colo., Geological Society of America, v. 

G–1, p. 311–366.

Parkinson, L.J., 1962, One field, one giant—The story of 

the Swanson River: Oil and Gas Journal, v. 60, no. 13, 

p. 180–183.

Plafker, George, Bruns, T.R., Winkler, G.R., and Tysdal, R.G., 

1982, Cross section of the eastern Aleutian arc, from Mount 

Spurr to the Aleutian trench near Middleton Island, Alaska: 

Geological Society of America, Map and Chart Series, 

MC–28P, scale 1:1,000,000.

Plafker, George, Moore, J.C., and Winkler, G.R., 1994, 

Geology of the southern Alaska margin, in Plafker, George, 

and Berg, H.C., eds., The geology of North America—The 

geology of Alaska: Boulder, Colo., Geological Society of 

America, v. G–1, p. 389–449.

Pavlis, T.L., 1982, Origin and age of the Border Ranges 

fault of southern Alaska and its bearing on the Late Mesozoic tectonic evolution of Alaska: Tectonics, v. 1, no. 4, 

p. 343–368.
References Cited 19

Ramsey, J.P., 1981, Geology-coal resources and mining plan 

for the Chuitna Coal ’80 (Conference proceedings, University of Alaska, Fairbanks, October 21–23, 1980): University 

of Alaska, Mineral Industries Research Laboratory Report 

50, p. 111–121. 

Reed, B.L., and Nelson, S.W., 1980, Geologic map of the 

Talkeetna quadrangle, Alaska: U.S. Geological Survey 

Miscellaneous Investigations Series Map I–1174, scale 

1:250,000, 15 p.

Renshaw, D.E., 1983, Matanuska-Susitna Borough—Summary 

of mineral resources: Palmer, Alaska, Mapmakers, report 

prepared under grant from State of Alaska Division of Geological & Geophysical Surveys, p. 40–41.

Schmoker, J.W., 2005, U.S. Geological Survey assessment 

concepts for continuous petroleum accumulations, in 

Petroleum systems and geologic assessment of oil and gas 

in the southwestern Wyoming Province, Wyoming, Colorado, and Utah: U.S. Geological Survey Digital Data Series 

DDS–69–D, chap. 13, 7 p.

Seamount D.T., Cross, R., and Buck, G., 1997, Geologic and 

engineering report to accompany application for approval 

for unitization of the Pioneer Unit, State of Alaska, December 10, 1997: Alaska Department of Natural Resources, 

Division of Oil and Gas, 47 p.

Shellenbaum, D.P., Gregersen, L.J., and Delaney, P.R., 2010, 

Top Mesozoic unconformity depth map of the Cook Inlet 

Basin, Alaska: Fairbanks, Alaska Division of Geological 

& Geophysical Surveys, Report of Investigations 2010–2, 

1 sheet, scale 1:500,000.

Smith, T.N., 1995, Coalbed methane potential for Alaska 

and drilling results for the upper Cook Inlet Basin, in

Proceedings, Intergas, May 15–19, 1995, Tuscaloosa, 

Ala., University of Alabama: p. 1–21.

Stanley, R.G., Charpentier, R.R., Cook, T.A., Houseknecht, 

D.W., Klett, T.R., Lewis, K.A., Lillis, P.G., Nelson, P.H., 

Phillips, J.D., Pollastro, R.M., Potter, C.J., Rouse, W.A., 

Saltus, R.W., Schenk, C.J., Shah, A.K., and Valin, Z.C., 

2011, Assessment of undiscovered oil and gas resources 

of the Cook Inlet region, south-central Alaska, 2011: 

U.S. Geological Survey Fact Sheet 2011–3068, 2 p.

Stricker, G.D., 1991, Economic Alaskan coal deposits, 

in Gluskoter, H.J., Rice, D.D., and Taylor, R.B., eds., 

Economic geology, U.S.: Geological Society of America, 

The Geology of North America, v. P–2, p. 591–602.

Swenson, R.F., 1997, Introduction to Tertiary tectonics and 

sedimentation in the Cook Inlet Basin, in Karl-Vaughn, 

N.R., and Ryherd, T.J., eds., Guide to the geology of the 

Kenai Peninsula, Alaska: Geological Society of Alaska, 

p. 18–27.

Triplehorn, D.M., Turner, D.L., and Naeser, C.W., 1984, 

Radiometric age of the Chickaloon Formation of south-central Alaska—Location of the Paleocene-Eocene boundary: 

Geological Society of America Bulletin, v. 95, p. 740–742.

Wahrhaftig, C., Bartsch-Winkler, S., and Stricker, G.D., 1994, 

Coal in Alaska, in Plafker, George, and Berg, H.C., eds., 

The geology of North America—The geology of Alaska: 

Boulder, Colo., Geological Society of America, v. G–1, 

p. 937–978.

Wolfe, J.A., and Tanai, Toshimasa, 1980, The Miocene 

Seldovia Point flora from the Kenai Group, Alaska: 

U.S. Geological Survey Professional Paper 1105, 52 p., 

25 pl.

Wood, G.H., Jr., Kehn, T.M., Carter, M.D., and Culbertson, 

W.C., 1983, Coal resource classification system of the 

U.S. Geological Survey: U.S. Geological Survey Circular 891, 

65 p.


Rouse and Houseknecht—Assessment of the Coal-Bed Gas Total Petroleum System in the Cook Inlet-Susitna Region, Alaska—Scientific Investigations Report 2012-5145