Potential for a Basin-Centered Gas

Accumulation in the Raton Basin, 

Colorado and New Mexico

By Ronald C. Johnson and Thomas M. Finn

U.S. Geological Survey Bulletin 2184-B

U.S. Department of the Interior

U.S. Geological Survey

Geologic Studies of Basin-Centered Gas Systems

Edited by Vito F. Nuccio and Thaddeus S. Dyman

This work funded by the U.S. Department of Energy, National 

Energy Technology Laboratory, Morgantown, W. Va., under 

contracts DE-AT26-98FT40031 and DE-AT26-98FT40032, and by the 

U.S. Geological Survey Central Region Energy Resources Team
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

Any use of trade, product, or fi rm names in this publication

is for descriptive purposes only and does not

imply endorsement by the U.S. Government

This publication is only available online at:

http://geology.cr.usgs.gov/pub/bulletins/b2184-b/

Posted online June 2001, version 1.0
III

Contents

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

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

Thermal Maturity and Coal Rank in the Raton Basin.............................................................................. 5

Coal-Bed Methane in the Raton Basin...................................................................................................... 5

Geology of Basin-Centered Gas Accumulations..................................................................................... 7

Evidence for a Basin-Centered Gas Accumulation in the Raton Basin............................................... 9

Discussion...................................................................................................................................................... 9

References Cited ........................................................................................................................................ 12

Figures

 1. Generalized geologic map of the Raton Basin, Colorado and New Mexico ...................... 2

 2. Generalized stratigraphic column for the Colorado portion of the Raton Basin................ 3

 3. Generalized stratigraphic column for Cretaceous and Tertiary rocks 

in the Raton Basin......................................................................................................................... 4

 4. East-west stratigraphic cross section across the southern part of the 

Raton Basin showing vertical and lateral variations in Upper Cretaceous 

and Paleocene rocks ................................................................................................................... 5

 5. Coal rank map at the base of the Vermejo Formation, Raton Basin..................................... 6

 6. Map showing areas of current coal-bed methane production in the 

Raton Basin.................................................................................................................................... 8

 7. Approximate depths to the top of the Trinidad Sandstone .................................................. 11

Table

 1. List of wells in the Raton Basin that tested gas of had gas shows in 

sandstones of Upper Cretaceous and Paleocene age ........................................................ 10
Abstract

The Raton Basin appears to contain a signifi cant continuous or basin-centered gas accumulation in sandstones of the 

Upper Cretaceous Trinidad Sandstone and Vermejo Formation 

and Upper Cretaceous and Paleocene Raton Formation. The 

accumulation is underpressured and occurs at comparatively 

shallow (<3,500 ft) depths. The sandstones are interbedded 

with coal beds that are currently being developed for coal-bed 

methane, and the coals are the likely source for gas found in 

the sandstones. Based on analogs with other Rocky Mountain 

basins, relatively water-free production should occur where 

levels of thermal maturity in the coals exceed a vitrinite refl ectance value of 1.1 percent. This level of thermal maturity 

occurs over much of the central part of the Raton Basin. 

Because of the shallow depths, some of the accumulation has 

probably been degraded by surface water invasion.

Introduction

The Raton Basin covers an area of about 4,000 mi2

in southeastern Colorado and northeastern New Mexico. The 

basin is bounded on the west by the Sangre de Cristo Mountains, on the north by the Wet Mountains, on the southeast by 

the Sierra Grande arch, on the east by the Las Animas arch, 

and on the northeast by the Apishapa arch (fi g. 1). The basin 

is highly asymmetrical, with the deep basin axis just east of the 

Sangre de Cristos. The east fl ank of the basin is gently tilted 

toward the west at from 1° to 5°, whereas steep dips and thrust 

faults occur along the west fl ank adjacent to the Sangre de 

Cristo Mountains. The Raton Basin is in the southeastern part 

of the area that was affected by the Laramide orogeny (Late 

Cretaceous through Eocene) in the central Rocky Mountain 

region. The Basin contains a thick stratigraphic section of 

Devonian through Plio-Pleistocene-age rocks (fi g. 2). 

Evidence for a basin-centered or continuous gas accumulation of some sort in the Raton Basin has been presented by 

many authors (Dolly and Meissner, 1977; Broadhead, 1982, 

1991; Rose and others, 1986; and Woodward, 1987). The 

reservoir units considered by these authors most likely to 

contain a basin-centered gas accumulation include the Upper 

Cretaceous Trinidad Sandstone and Vermejo Formation, Upper 

Cretaceous and Paleocene Raton Formation, and the Paleocene 

Poison Canyon Formation (fi g. 3). In addition, minor amounts 

of hydrocarbons have been produced on structures at shallow 

depths (< 3,000 ft) from fractured reservoirs in the Cretaceous 

Niobrara, Carlile, and Greenhorn Formations, and the Cretaceous Pierre Shale in the Raton Basin since 1892. Production 

from these units in the Denver Basin to the north is considered 

unconventional because of low pressures and low matrix permeabilities (see Denver Basin discussion in Gautier and others, 

1995). It is possible that unconventional or basin-centered 

accumulations could occur in these fractured Cretaceous units 

at greater depths in the Raton Basin. This possibility has not 

been addressed by previous workers and is beyond the scope 

of this paper. The purpose of this report is to summarize 

the evidence for a basin-centered gas accumulation in the 

Trinidad Sandstone, Vermejo Formation, and Raton Formation 

presented by previous authors and to reexamine this evidence 

in light of new understandings about how basin-centered accumulations are created and destroyed.

The marginal-marine Trinidad Sandstone conformably 

overlies the Pierre Shale throughout the basin and was deposited along an eastward-prograding shoreline during the fi nal 

retreat of the Cretaceous Seaway from northern New Mexico 

and southern Colorado. The Trinidad Sandstone was deposited 

in shallow marine, shoreface, and deltaic environments (Pillmore and Maberry, 1976; Billingsley, 1977). It varies from 0 

to more than 300 ft thick (Rose and others, 1986, fi g. 7) and is 

truncated by the Poison Canyon Formation in the northernmost 

part of the basin.

The Upper Cretaceous Vermejo Formation conformably 

overlies the Trinidad Sandstone. The Vermejo Formation varies 

from 0 to 380 ft thick and is also truncated by the Poison 

Canyon Formation in the northernmost part of the basin. The 

Potential for a Basin-Centered Gas 

Accumulation in the Raton Basin, 

Colorado and New Mexico

By Ronald C. Johnson1 and Thomas M. Finn1

1

 U.S. Geological Survey, Denver, Colo.

1
Figure 1. Generalized geologic map of the Raton Basin, Colorado and New Mexico. From Flores and Bader (1999).

105 ̊ Alluvium, slopewash, and landslide material

Basalt flows

Cuchara Formation

Huerfano Formation

Middle Tertiary intrusives

Trinidad Sandstone andPierre Shale undivided

Pierre Shale/Niobrara undivide

Poison Canyon Formation

Precambrian rock undivided

Raton Formation

Vermejo Formation

Colorado

New Mexic

C

M

Raton Basin boundary

Apishapa arch

Sierra Grande arch Las Animas

Sangre de Cristo Mountains

Basin axis

arch

0 15 Miles0 20 Kilometers

Raton

Walsenburg

Stonewall
RECENT

PLEISTOCENE

PLIOCENE

MIOCENE

OLIGOCENE (?)

EOCENE

PALEOCENE

CRETACEOUS

JURASSIC

TRIASSIC

PERMIAN

PENNSYLVANIAN

DEVONIAN

MISSISSIPPIAN

PRE-CAMBRIAN

ERA

AGE

STRATIGRAPHIC

FORMATIONS

LITHOLOGY

THICKNESS

OIL AND

GAS SHOWS

POTENTIAL

SOURCE ROCKS

EXTENT OF

INTRUSION

CENOZOIC MESOZOIC PALEOZOIC

ALLUVIUM, DUNES,

LANDSLIDES, SOIL ZONES

OGALLALA FM

DEVILS HOLE FM

VOLCANIC INTRUSIONS,

PLUGS, DIKES, SILLS

INTRUDES ENTIRE SECTION

FARASITA FM

HUERFANO FM

CUCHARA FM

POISON CANYON FM

RATON FM

VERMEJO FM

TRINIDAD SS

PIERRE SH

SMOKY HILL MARL

FT HAYES LS

NIOBRARA

BENTON

CARLILE SH

GREENHORN LS

GRANEROS SH

DOCKUM GROUP

DAKOTA SS PURGATOIRE FM

MORRISON

ENTRADA WANAKAH

YESO FM

SANGRE DE

CRISTO FM

MAGDALENA GROUP

TERERRO FM

ESPIRTU SANTO FM

MAFIC GNEISS

METAQUARTZITE GROUP

GRANITE & GRANITE GNEISS

0 - 200'

200 - 500'

0 - 1500'

0 - 1200'

0 - 2000'

0 - 5000'

0 - 2500'

0 - 2075'

0 - 360'

0 - 255'

1300 - 2900'

900'

0 - 55'

BERNAL FM SAN ANDRESS LS GLORIETA SS

165 -225'

20 - 70'

175 - 400'

140 -200'

100 -150'

150 - 400'

30 - 100'

40 - 100'

0 - 1200'

0 - 125'

10 - 20'

0 -200'

200 - 400'

700 - 5300'

4000 - 5000'

40 - 50'

25'

7000' ?

5000' ?

4000' ?

RATON COAL

(GAS)

VERMEJO COAL

(GAS)

NIOBRARA

(OIL)

GRANEROS

(OIL)

?

INTRUSIVES MIOCENE

SHALLOW

GAS

OBJECTIVE

SECTION

Figure 2. Generalized stratigraphic column for the Colorado portion of the Raton Basin. From Dolly and Meissner (1977).

Potential for a Basin-Centered Gas Accumulation in the Raton Basin, Colorado and New Mexico 3
Vermejo was deposited in fl uvial channel, overbank-levee, crevasse splay, fl ood-plain lake, low-lying and raised mire environments (Strum, 1985; Flores, 1987; Flores and Pillmore, 

1987). Total coal in the Vermejo Formation ranges to more 

than 30 ft (Tyler and others, 1995).

The Upper Cretaceous through Paleocene Raton Formation unconformably overlies the Vermejo Formation throughout much of the basin and ranges from 0 to 2,100 ft thick. 

It is divided into a basal conglomeratic interval, a lower coalrich interval, a sandstone-rich interval, and an upper coal-rich 

interval (fi g. 4). The Cretaceous-Tertiary boundary is conformable in the Raton Basin and occurs near the top of the lower 

coal-rich interval in the Raton Formation (Tschudy and others, 

1984; Pillmore and Flores, 1984). The basal conglomerate unit 

is as much as 50 ft thick and consists of interbedded pebble 

conglomerate and quartzose sandstone (Pillmore and Flores, 

1987). The lower coal-rich zone varies from 100 to 250 

ft thick, and the upper coal-rich zone varies from about 

600 to 1,100 ft thick. Both are composed of interbedded sandstone, siltstone, mudstone, carbonaceous shale, and coal. The 

coaly intervals include lenticular channel sandstones and thin, 

comparatively persistent, crevasse-splay sandstones. Total net 

thickness of coal in the Raton Formation ranges from less than 

20 ft to more than 140 ft (Tyler and others, 1995). The sanddominated interval separates the two coal-rich zones and varies 

from 180 to 600 ft thick. Sandstones are coarsest in the 

sand-dominated interval. Estimates of total coal in both the 

Vermejo and Raton Formations vary from 1.5 to 4.8 billion 

short tons (Read and others, 1950; Wanek, 1963); however, 

more recently, Amuedo and Bryson (1977) estimated 5 billion 

short tons in the Vermejo Formation alone.

The Poison Canyon Formation varies from 0 to about 

2,500 ft thick and conformably overlies and intertongues with 

the Raton Formation (Johnson and Wood, 1956; Flores, 1987). 

The formation consists of interbedded coarse-grained conglomeratic sandstone, mudstone, and siltstone (Hills, 1888; 

Johnson and others, 1966) and becomes fi ner grained toward 

the east in the basin. The Poison Canyon contains little coal 

or carbonaceous shale.

The Raton Basin was extensively intruded by dikes, sills, 

laccoliths, and stocks in middle to late Tertiary time. A major 

intrusive center of Oligocene and Miocene age (26 to 22 Ma), 

Figure 3. Generalized stratigraphic column for Cretaceous and Tertiary rocks in the Raton Basin. From Flores and Bader (1999), modifi ed from 

Pillmore (1969), Pillmore and Flores (1987), and Flores (1987). TERTIARY PALEOCENE MESOZOIC UPPER CRETACEOUS

AGE LITHOLOGY FORMATION NAME

POISON CANYON

FORMATION 

VERMEJO

FORMATION 

RATON

FORMATION 

TRINIDAD SANDSTONE

PIERRE SHALE

APPROX.

THICKNESS

IN FEET

500+

1800-1900

0(?)–2,100

0–380

0–300

K/T boundary

GENERAL DESCRIPTION

SANDSTONE–Coarse to conglomeratic beds 13–50 feet 

thick. Interbeds of soft, yellow-weathering clayey 

sandstone. Thickens to the west at expense of 

underlying Raton Formation

SANDSTONE--Fine to medium grained; contains casts of 

Ophiomorpha

SHALE--Silty in upper 300 ft. Grades upward to finegrained sandstone. Contains limestone concretions

SANDSTONE–Fine to medium grained with mudstone, 

carbonaceous shale, and extensive, thick coal beds. 

Local sills

Formation intertongues with Poison Canyon Formation 

to the west

UPPER COAL ZONE–Very fine grained sandstone, 

siltstone, and mudstone with carbonaceous shale 

and thick coal beds

BARREN SERIES–Mostly very fine to fine-grained 

sandstone with minor mudstone, siltstone, with 

carbonaceous shale and thin coal beds

LOWER COAL ZONE–Same as upper coal zone; coal 

beds mostly thin and discontinuous. Conglomeratic 

sandstone at base; locally absent

{

{

{

4 Geologic Studies of Basin-Centered Gas Systems
thought to represent the roots of breached volcanoes (Steven, 

1975), occurs in the northern part of the basin (fi g. 1). Two of 

these breached intrusions form East and West Spanish Peaks 

which tower over the basin at elevations of 12,683 ft and 

13,724 ft, respectively. Dikes and sills related to this intrusive 

center occur throughout the northern part of the basin. Sills 

related to this intrusive center have intruded coal beds and 

destroyed tremendous quantities of coal in this area (Carter, 

1956).

Thermal Maturity and Coal Rank 

in the Raton Basin

Thermal maturity at the base of the Vermejo Formation 

varies from a vitrinite refl ectance of 0.57 percent around the 

margins of the northern part of the basin to 1.58 percent along 

the Purgatoire River in the central part of the basin (fi g. 5). 

Coal ranks of anthracite or greater occur locally near intrusions (Jurich and Adams, 1984). The unusually high coal ranks 

along the Purgatoire River are unusual in that they do not 

occur near the major intrusions found farther to the north in the 

basin. Wells drilled near the river have, however, encountered 

some sills (ARI, Inc., 1991) that may have played a role in 

elevating coal ranks. Merry and Larsen (1982) suggested that 

the high coal ranks may be due to a combination of deep 

burial during the Pliocene and proximity to intrusions. Tyler 

and others (1991) suggested that hot waters ascending to an 

ancestral Purgatoire River may account for the high values 

near the river. 

Coal-Bed Methane in the Raton Basin

It has long been known that coals in the Raton Basin 

contain large amounts of methane. Nearly all coal mines in 

the basin encountered some gas. Jurich and Adams (1984) 

reported that 2 million cubic feet of methane per day 

(MMCFD) was being ventilated from just three mines in the 

INDEX MAP

COLORADO

NEW

MEXICO

0

0 50 Kilometers

50 Miles

COLO.

N.MEX.

SANGRE DE CRISTO MOUNTA NI S

Poison

Canyon

Formation

Coal Sandstone

West East

Siltstone and mudstone Measured section Cross section 

VERMEJO FORMATION

PIERRE SHALE

Coarsening-upward

megacycle

Coarsening-upward Basal Raton megacycle conglomerate

TRINIDAD SANDSTONE

Sandstone-dominated

interval

Lower Coal Zone

RATON

FORMATION

Upper Coal Zone

Coarsening-upward

megacycle

0

300

Feet

N

w

E

Explanation

Figure 4. East-west stratigraphic cross section across the southern part of the Raton Basin showing vertical and lateral variations in Upper 

Cretaceous and Paleocene rocks. From Flores (1987), Flores and Bader (1999).

Potential for a Basin-Centered Gas Accumulation in the Raton Basin, Colorado and New Mexico 5
Huerfano River

River

Cucharas

Apishapa

River

Purgatoire

River

Vermejo

River

Eagle

Nest

Lake

0 15 Miles

0 20 Km

Low-volatile bituminous

Medium-volatile bituminous

High-volatile A bituminous

High-volatile B bituminous

High-volatile C bituminous

Tertiary intrusive rocks

ARI Inc. (1991)

Close (1988)

EXPLANATION

Syncline

COLORADO

NEW

MEXICO

R 72 W R 68 W R 70 W R 66 W R 64 W R 62 W R 60 W

T

25

S

T

27

S

T

29

S

T

31

S

T

33

S

T35S

T32N

T

30

N

T

28

N

T26N

R 16 E R 18 E R 20 E R 22 E R 24 E R 26 E

N37°

0.7 0.8

0.9

1.0

1.2

1.1

1.3

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.7

W105°

SAGUACHE

ALAMOSA

COSTILLA

PUEBLO

HUERFANO

LAS ANIMAS

COLORADO

TAOS NEW MEXICO COLFAX

Stonewall Trinidad

Raton

Walsenburg

Trinidad SandstonePierre Shale contact

Cimarron

North

Pontilo

Creek

Figure 5. Coal rank map at the base of the Vermejo Formation, Raton Basin. Variations in vitrinite refl ectance (percent Ro) are also 

shown. Adapted from Tyler and others (1995).

6 Geologic Studies of Basin-Centered Gas Systems
west-central part of the basin. Reported gas contents for coal 

in the Vermejo Formation vary from 115 to 492 ft3/short 

ton (3.6–15.5 cm3/g), whereas coals in the Raton Formation 

contain from 23 to 193 ft3/short ton (0.72–6.07 cm3/g) (Tyler 

and others, 1995). In 1998, there were about 85 coal-bed methane wells in the Raton Basin producing about 17.5 MMCFD 

(Johnson and Flores, 1998). By February 2000, the number 

of wells had increased to 459. Wells are completed mainly in 

the Vermejo Formation. Production thus far is concentrated in 

a 25- by 15-mile northeast-trending area near the Purgatoire 

River, west of Trinidad, Colo., in an area where coal ranks are 

unusually high (fi g. 6). Coal-bed methane exploration began in 

the Raton Basin by Amoco in 1980 at their Cottontail Pass unit 

(fi g. 6). The best wells in Amoco’s unit yielded more than 590 

thousand cubic feet of gas per day (MCFD). Maximum depth 

for coal-bed methane wells in the basin is about 2,400 ft in the 

northwest part of Amoco’s Cottontail Pass unit.

Geology of Basin-Centered 

Gas Accumulations

Extensive basin-centered or continuous gas accumulations have been identifi ed in many Rocky Mountain basins that 

formed during the Laramide orogeny (Late Cretaceous through 

Eocene). Reservoirs within basin-centered gas accumulations 

typically have low permeabilities (in situ permeability to gas of 

0.1 millidarcy or less) and are commonly referred to as tight 

gas reservoirs (Spencer, 1989). These accumulations differ 

from conventional gas accumulations in that they (1) cut across 

stratigraphic units, (2) commonly occur structurally down dip 

from more permeable water-fi lled reservoirs, (3) have no obvious structural and stratigraphic trapping mechanism, and (4) 

are almost always either overpressured or underpressured. The 

abnormal pressures of these reservoirs indicate that water in 

hydrodynamic equilibrium with outcrop is not the pressuring 

agent. Instead, hydrocarbons within the tight reservoirs are 

thought to provide the pressuring mechanism (Spencer, 1987). 

Masters (1979) was one of the fi rst to study these unique 

accumulations, which occur downdip from more permeable, 

water-wet rocks. Masters (1979) proposed that gases generated 

in the deep, thermally mature areas of sedimentary basins with 

low-permeability rocks are inhibited from migrating upward 

and out of the basin by a capillary seal. Masters (1979) pointed 

out that low-permeability rocks (<1 mD), with 40 percent 

water saturation, are only three-tenths as permeable to gas 

as they are to water, and, at 65 percent water saturation, the 

rock is almost completely impervious to the fl ow of gas. The 

concepts for the development of basin-centered gas accumulations in the Rocky Mountains have been further refi ned by a 

number of workers such as Jiao and Surdam (1993), Meissner 

(1980, 1981, 1984), McPeek (1981), Law (1984), Law and 

others (1979, 1989), Law and Dickinson (1985), MacGowan 

and others (1993), Spencer and Law (1981), Spencer (1985, 

1987), and Yin and Surdam (1993). In general, the conceptual 

models suggest that overpressuring, which is commonly 

encountered in these basin-centered accumulations, is the 

result of volumetric increases during gas generation in source 

rocks that are interbedded with sandstone reservoir rocks. Law 

(1984) suggested that migration distances from source rock 

to reservoir rock in the basin-centered gas accumulation of 

the Greater Green River Basin of Wyoming, Colorado, and 

Utah are generally less than a few hundred feet. Much of the 

water that originally fi lled pore spaces in potential reservoirs 

is driven out by hydrocarbons (Law and Dickinson, 1985). 

According to Law and Dickinson (1985), the capillary seal is 

activated as gas replaces water in the pore space, and hence 

the basin-centered gas accumulations seal themselves as they 

form. These seals are so effi cient that they may be able to 

maintain abnormally high pressures for tens of millions of 

years after gas generation has ceased (MacGowan and others, 

1993).

Many basin-centered gas accumulations in Rocky Mountain basins are partially to totally underpressured, and it is 

believed that all of these underpressured areas were overpressured at some time in the past (Meissner, 1978; Law and 

Dickinson, 1985). Moreover, it is believed that a previous 

period of overpressuring would have been necessary to drive 

much of the water out of the system. A change from overpressured to underpressured conditions can occur as a result of 

cooling related to uplift and erosion or to a decrease in thermal 

gradient (Meissner, 1978; Law and Dickinson, 1985). Most 

of the cooling in Rocky Mountain basins has occurred within 

the last 10 m.y. as the onset of major regional uplift initiated 

a period of rapid downcutting throughout the region. For a 

summary of the evidence for late Cenozoic uplift in the Rocky 

Mountain region, see Keefer (1970) and Larson and others 

(1975). Overpressured areas became underpressured during 

cooling as gas contracted and the rate of gas generation 

decreased (Meissner, 1978; Law and Dickinson, 1985). Surface water enters the basin-centered accumulation through 

newly created permeability pathways created as pore throats 

and fractures dilate. According to Meissner (1978) this contraction may ultimately result in a “dead” basin where the 

basin-centered accumulation has been completely dissipated. 

Many Rocky Mountain basin-centered gas accumulations have 

underpressured zones surrounding an overpressured central 

core indicating that this process has only partially run to completion. The underpressured zone will grade outward into a 

predominantly water-bearing zone that is in pressure equilibrium with the local hydrodynamic regime. Any gas present 

in this water-bearing zone will be trapped in conventional 

reservoirs on anticlinal structures or in stratigraphic pinchouts.

Levels of thermal maturity defi ne areas where potential 

source rocks have generated gas at some time in the past and 

are commonly used as an indirect method of defi ning the limits 

of a basin-centered gas accumulation. Masters (1984, p. 27, 

fi g. 25), in a study of the basin-centered gas accumulation in 

the deep basin of Alberta, indicated that a vitrinite refl ectance 

Potential for a Basin-Centered Gas Accumulation in the Raton Basin, Colorado and New Mexico 7
0 15 Miles

0 20 Km

COLORADO

NEW

MEXICO

R 72 W R 68 W R 70 W R 66 W R 64 W R 62 W R 60 W

T

25

S

T

27

S

T

29

S

T

31

S

T

33

S

T35S

T32N

T

30

N

T

28

N

T26N

R 16 E R 18 E R 20 E R 22 E R 24 E R 26 E

N37°

Producing area

Potential producing area

Syncline

EXPLANATION

Amoco Cottontail

Pass unit

Evergreen Spanish

Peak unit

C.I.S. exploration

project

Lorencito

Stroud Apache Canyon area

Canyon area

Thrust fault

W105°

SAGUACHE

ALAMOSA

COSTILLA

PUEBLO

HUERFANO

LAS ANIMAS

COLORADO

TAOS NEW MEXICO COLFAX

Stonewall Trinidad

Raton

Walsenburg

Trinidad SandstonePierre Shale contact

Cimarron

Raton

Basin

synclonal

axis

Raton

Basin synclinal

axis

Figure 6. Map showing areas of current coal-bed methane production in the Raton Basin. Adapted from Hemborg (1996).

8 Geologic Studies of Basin-Centered Gas Systems
(Rm) of 1.0 percent corresponds approximately to the limit of 

the accumulation. In the Piceance Basin of western Colorado, 

Johnson and others (1987) used a vitrinite refl ectance (Rm) 

of 1.1 percent to defi ne the limits of the basin-centered gas 

accumulation. Rm values of from 0.73 to 1.1 percent were 

used to defi ne a transition zone containing both tight reservoirs 

and reservoirs with conventional permeabilities. Johnson and 

others (1996, 1999) used these same thermal maturity limits to 

help defi ne the basin-centered gas accumulation in the Wind 

River Basin of Wyoming and the Bighorn Basin of Wyoming 

and Montana. In the Greater Green River Basin of Wyoming, 

Colorado, and Utah, Law and others (1989) used an Rm of 

0.80 percent to defi ne the top of overpressuring in that basincentered gas accumulation. 

Evidence for a Basin-Centered Gas 

Accumulation in the Raton Basin

Evidence for gas at shallow depths in uppermost Cretaceous and Paleocene strata in the Raton Basin has been 

documented by Dolly and Meissner (1977), Broadhead (1982, 

1991), Rose and others (1986), and Woodward (1987) and 

is summarized in table 1. According to Dolly and Meissner 

(1977, p. 259) “...gas fl ows encountered during the drilling 

and testing of exploratory and shallow water wells are of 

a nearly universal nature in sandstones, coals, and fracture 

zones present in Poison Canyon, Raton, Vermejo, and Trinidad 

formations.” Dolly and Meissner (1977) describe sandstones in 

these formations as “tight, clay-fi lled” and similar to productive Cretaceous and Tertiary sandstones in many other Rocky 

Mountain basins. They cite one well, the Filon no. 1 Golden 

Cycle in sec. 11, T. 29 S., R. 67 W. that tested 30 MCF of gas 

from a zone at 1,630 to 1,760 ft in the lower part of the Raton 

Formation. An unusually low fl uid pressure gradient of 0.25 

psi/ft was noted by Dolly and Meissner (1977, p. 268) in the 

tested interval from this well indicating signifi cant underpressuring. They noted that this pressure gradient corresponds to 

a potentiometric head of approximately 780 ft below the well 

site. Initial production testing, after fracturing with nitrogen 

foam and KCl-inhibited water, indicated a fl ow rate of 75 

MCFPD and 1,500 barrels of water per day (BWPD). After 

2 months, the well stabilized at about 72 MCFPD and 100 

BWPD. It is unclear how much of the initial water production 

was “frac” water. Although Dolly and Meissner (1977, fi g. 13) 

clearly believed that discrete gas-water contacts existed in the 

productive lenticular sandstones, the presence of underpressured gas in tight reservoirs is characteristic of many basincentered gas accumulations in the Rocky Mountain region. 

Underpressuring indicates that the reservoirs are isolated from 

the regional ground-water regime.

More recently, Rose and others (1986) used variations 

in resistivity logs to try to delineate the gas-saturated basincentered accumulation in just the Trinidad Sandstone in the 

northern part of the basin. The Trinidad is a marginal marine 

“blanket-like” sandstone that persists throughout the Raton 

Basin. This contrasts with the much more lenticular fl uvial 

sandstones found in the nonmarine parts of the Upper Cretaceous and Paleocene section in the basin. Rose and others 

(1986) suggested that an analog to the Trinidad Sandstone 

may be the highly gas productive Upper Cretaceous marginalmarine Pictured Cliffs Sandstone in the San Juan Basin to 

the west. The Pictured Cliffs Sandstone produces gas from 

stratigraphic traps formed by stratigraphic step-ups toward the 

northeast (Meissner, 1984).

Regional underpressuring at shallow depths in the Raton 

Basin has been documented by several workers (Howard, 

1982; Geldon, 1990; Close and Dutcher, 1990; Tyler and 

others, 1995). A potentiometric surface map of the VermejoRaton aquifer constructed by Stevens and others (1992) and 

published by Tyler and others (1995, p. 170) indicates that 

underpressured conditions exist in the main coal-bearing intervals throughout most of the basin. Tyler and others (1995, 

p. 169–170) state that the pressure regime in the basin is 

poorly understood but list some of the possible causes for this 

underpressuring. They noted that low pressures indicate that 

the rocks are isolated from topographically high recharge areas 

along the west margin of the basin and suggest that low permeability in the sandstones and coal beds may limit hydrologic 

connection. 

Discussion

It has long been suspected that a signifi cant basin-centered type gas accumulation is present in Upper Cretaceous 

and Paleocene sandstones in the Raton Basin. Few attempts 

have been made to develop these resources because of the lack 

of gas pipelines out of the basin. Success with the current coalbed methane exploration in the basin will eventually alleviate 

this pipeline problem and should lead to new attempts to 

develop these sandstone gas resources. Gas resources found in 

coal beds and in adjacent sandstone reservoirs are developed 

concurrently in many Rocky Mountain basins.

It is suggested here that the widespread gas shows and 

abnormally low pressures encountered in the Vermejo and 

Raton Formations indicate a basin-centered gas accumulation 

developed in these units. Using analogs from other Rocky 

Mountain basins, intervals where thermal maturities of source 

rocks are greater than an Rm of 1.1 percent were probably 

once overpressured and largely gas saturated. At lower levels 

of thermal maturity, both gas-charged and water-wet sandstones were probably present. The big unanswered question 

in the Raton Basin is how much of the original accumulation is 

still intact? Present-day depths to the top of the Trinidad Sandstone are less than 3,500 ft throughout most of the basin (fi g. 

7) except in the immediate vicinity of the Spanish Peaks where 

it is deeper than 9,000 ft. The widespread reports of underpressured gas-saturated sandstones at shallow depths suggests that 

Potential for a Basin-Centered Gas Accumulation in the Raton Basin, Colorado and New Mexico 9
a largely intact basin-centered gas accumulation still exists in 

the Trinidad Sandstone, Vermejo Formation, and Raton Formation.

Gas from coal beds and gas from sandstones are typically 

developed together in Rocky Mountain basins. The San Juan 

Basin of New Mexico and Colorado has by far the most successful coal-bed methane production in the United States. Yet 

the original exploration targets were not the coal beds but the 

adjacent sandstones, which were typically gas charged (Dugan 

and Williams, 1988). Only after gas wells started experiencing 

increases in rates of production did operators begin to suspect 

that adjacent coal beds were contributing signifi cantly to production. At Grand Valley fi eld in the Piceance Basin of western 

Colorado, lenticular fl uvial sandstones interbedded with coals 

of the Cameo-Fairfi eld coal zone have become the principal 

exploration target in the fi eld, although both coals and sandstones were originally targeted (Reinecke and others, 1991). 

Sandstones adjacent to the thick lower Tertiary coal beds in 

the Powder River Basin of Wyoming and Montana are typically gas charged (Hobbs, 1978) and are increasingly becoming targets for exploration. Gas from coal beds and adjacent 

sandstones are typically comingled in the Upper Cretaceous 

Table 1. List of wells in the Raton Basin that tested gas of had gas shows in sandstones of Upper Cretaceous and Paleocene age. 

[Data compiled from Dolly and Meissner (1977), Broadhead (1982, 1991), Rose and others (1986), and Woodward (1987). TKr, Raton Formation; Kv, Vermejo 

Formation; Kt, Trinidad Sandstone; Kp, Pierre Shale] 

 Operator Well Location Remarks Source 

Colorado 

Filon Expl............... 1 Bohlman .............. 28S-67W-4 ............... No DST’s. Gas shows from TKr, Kv. ........ Dolly and Meissner (1977) 

Kimbark Oper. ....... 1 Dog Spr. .............. 28S-68W-16 ............. Rec. gas from DST from 

 Kt & Kp.................................................. Rose and others (1986) 

Pan Amer. Pet......... M-1 State................ 29S-66W-33 ............. DST gas show fromTKr. ........................... Dolly and Meissner (1977) 

Pan Amer. Pet......... 1 Dick Realty.......... 29S-67W-3 ............... Rec. gas from DST from 

 TKr & Kv. .............................................. Dolly and Meissner (1977) 

Pan Amer. Pet......... 1 Rohr..................... 29S-67W-9 ............... Rec. gas from DST from 

 TKr & Kv. .............................................. Dolly and Meissner (1977) 

Filon Expl............... 1 Golden Cycle....... 29S-67W-11 ............. Rec. gas from DST from 

 TKr. Gas show in Tpc. .......................... Dolly and Meissner (1977) 

Clark & Perkins...... 1 Goemmer............. 29S-67W-11 ............. Rec. gas from DST from 

 TKr (?).................................................... Dolly and Meissner (1977) 

HBB Inc. ................ 22-7 Goemmer........ 30S-68W-7 ............... Shut-in gas well. Perfs. 

 4898–5100, Kt &Kp. .............................. Completion card. 

Filon Expl............... 1 Zele's Hope.......... 31S-65W-31 ............. Gas shows during drilling.......................... Dolly and Meissner (1977) 

HBB Inc. ................ 1 Schultz................. 31S-67W-27 ............. Rec. gas from Kt........................................ Rose and others (1986) 

Wood, et al. ............ 1 State..................... 32S-67W-36 ............. Shut-in gas well. Prod. 

 zone; 1935-2135, Kv. ............................. Completion card. 

New Mexico 

Odessa Nat. Corp.... 4-X W.S. Ranch ..... 29N-18E-12.............. Gas show in Kp. ........................................ Completion card. 

Amer. Fuels............ 1 W.S. Ranch.......... 29N-19E-6................ Gas shows in Kp........................................ Woodward (1987) 

Odessa Nat. Corp.... 3 W.S. Ranch.......... 29N-19E-24.............. Gas shows in Kp........................................ Woodward (1987) 

Odessa Nat. Corp.... 1 W.S. Ranch.......... 30N-18E-16.............. Gas shows in Kv & TKr. ........................... Woodward (1987) 

Amer. Fuels Corp. .. 3 W.S. Ranch.......... 30N-18E-22.............. Gas shows in Kp........................................ Woodward (1987) 

Odessa Nat. Corp.... 5 W.S. Ranch.......... 30N-18E-22.............. Gas shows in Kp & Kt............................... Completion card. 

Odessa Nat. Corp.... 2 Vermejo............... 30N-19E-16.............. Gas shows in Kp........................................ Woodward (1987) 

Odessa Nat. Corp.... 2 W.S. Ranch.......... 30N-20E-30.............. Gas shows in Kp........................................ Woodward (1987) 

Continental Oil ....... 1 St. Louis .............. 30N-22E-13.............. Gas shows in Kp........................................ Completion card. 

Penzoil Co. ............. 2 Vermejo............... 31N-17E-1................ Shut- in gas well. Prod. 

 zone, Kp, 691 MCFD. ............................ Completion card. 

Penzoil Co. ............. 1 Vermejo Ranch.... 31N-17E-34.............. Gas show in Kt. ......................................... Broadhead (1982) 

Penzoil Co. ............. 311 M Castle Rock . 31N-18E-31.............. Extensive oil shows 

 in TKr & Kv. .......................................... Broadhead (1991) 

Continental Oil ....... 2 St. Louis .............. 31N-21E-26.............. Oil in fractures in Kp................................. Woodward (1987) 

Pan Amer. Pet......... 1 Kaiser Steel ......... 31N-22E-31.............. Gas show in Kt. ......................................... Completion card. 

10 Geologic Studies of Basin-Centered Gas Systems
0 15 Miles

0 20 Km

COLORADO

NEW

MEXICO

R 72 W R 68 W R 70 W R 66 W R 64 W R 62 W R 60 W

T

25

S

T

27

S

T

29

S

T

31

S

T

33

S

T35S

T32N

T

30

N

T

28

N

T26N

R 16 E R 18 E R 20 E R 22 E R 24 E R 26 E

N37°

W105°

SAGUACHE

ALAMOSA

COSTILLA

PUEBLO

HUERFANO

LAS ANIMAS

COLORADO

TAOS NEW MEXICO COLFAX

Stonewall Trinidad

Raton

Walsenburg

Trinidad SandstonePierre Shale contact

Cimarron

Huerfano River

River

Cucharas

Apishapa

River

Purgatoire

River

Vermejo

River

North

Pontilo

Creek

Eagle

Nest

Lake

Lynn

Canadian

River

La Veta

Casa Grande

West Spanish

Peak

East Spanish

Peak

45

40

35

45

25

35

15

5

30

25

20

15

10

5

20

15

10

5

25

20

15

5

10

Figure 7. Approximate depths (in hundreds of feet) to the top of the Trinidad Sandstone. Map constructed by overlaying the structure 

contour map of the top of the Trinidad Sandstone (Tyler and others, 1995, fi g. 113) on State topographic maps for Colorado and New 

Mexico.

Potential for a Basin-Centered Gas Accumulation in the Raton Basin, Colorado and New Mexico 11
Ferron Sandstone Member of the Mancos Shale in the Wasatch 

Plateau of central Utah. 

Within a few years, the Raton Basin may well evolve into 

both a coal-bed methane play and a basin-centered sandstone 

gas play. At present, there appears to be no identifi ed production in the Raton Basin from sandstones within the basincentered accumulation, and it is diffi cult to assess how successful this play will be. A more comprehensive study of this 

potential gas resource should be made once reliable information is available concerning sandstone-production characteristics in the basin. 

References Cited

Amuedo, C.L., and Bryson, R.S., 1977, Trinidad-Raton Basins: A model 

coal resource evaluation program, in Murray, D.K., ed., Geology 

of Rocky Mountain Coal: Proceedings of the 1976 Symposium, 

Colorado Geological Survey, p. 45–60.

ARI, Inc., 1991, Geologic assessment of natural gas from coal seams 

in the Raton Basin: Geologic peer review prepared for the Gas 

Research Institute, 93 p. 

Billingsley, L.T., 1977, Stratigraphy of the Trinidad Sandstone and 

associated formations Walsenburg area, Colorado, in Veal, H.K., 

ed., Exploration Frontiers of the Central and Southern Rockies: 

Rocky Mountain Association of Geologists Guidebook, p. 235–246.

Broadhead, R.F., 1982, Oil and gas discovery wells drilled in New 

Mexico in 1981: New Mexico Geology, v. 4, no. 2, p. 17–19.

Broadhead, R.F., 1991, Oil and gas discovery wells drilled in New 

Mexico in 1990: New Mexico Geology, v. 13, no. 4, p. 75–81.

Carter, D.A., 1956, Coal deposits of the Raton Basin, in McGinnis, 

C.J., ed., Geology of the Raton Basin, Colorado: Rocky Mountain 

Association of Geologists Guidebook, p. 89–92.

Close, J.C., 1988, Coalbed methane potential of the Raton Basin, 

Colorado and New Mexico: Southern Illinois University, Department 

of Geology Ph.D. thesis, 432 p.

Close, J.C., and Dutcher, R.R., 1990, Update on coalbed methane 

potential of Raton Basin, Colorado and New Mexico: Society 

of Petroleum Engineers, Proceedings, 65th Technical Conference, 

SPE Paper 20667, p. 497–512.

Dolly, E.D., and Meissner, F.F., 1977, Geology and gas exploration 

potential, Upper Cretaceous and lower Tertiary strata, northern 

Raton Basin, Colorado, in Veal, H.K., ed., Exploration Frontiers of 

the Central and Southern Rockies: Rocky Mountain Association of 

Geologists Guidebook, p. 247–270.

Dugan, T.A., and Williams, B.L., 1988, History of gas produced 

from coal seams in the San Juan Basin, in Fassett, J.E., ed., 

Geology and coalbed methane resources of the northern San Juan 

Basin, Colorado and New Mexico: Rocky Mountain Association of 

Geologists Guidebook, p. 1–9.

Flores, R.M., 1987, Sedimentology of Upper Cretaceous and Tertiary 

siliciclastics and coals in the Raton Basin, New Mexico and 

Colorado, in Lucas, S.G., and Hunt, A.P., eds., Northeastern 

New Mexico: New Mexico Geological Society 38th Annual Field 

Conference, p. 255–264.

Flores, R.M., and Bader, L.R., 1999, A summary of Tertiary coal 

resources of the Raton Basin, Colorado and New Mexico, chap. SR 

of Fort Union Coal Assessment Team, 1999 Resource Assessment 

of Selected Tertiary Coal Beds and Zones in the Northern 

Rocky Mountains and Great Plains Region: U.S. Geological Survey 

Professional Paper 1625-A [available only on CD-ROM].

Flores, R.M., and Pillmore, C.L., 1987, Tectonic control on alluvial 

paleoarchitecture of the Cretaceous and Tertiary Raton Basin, 

Colorado and New Mexico, in Ethridge, F.G., Flores, R.M., and 

Harvey, M.D., eds., Recent developments in Fluvial Sedimentology: 

Society of Economic Paleontologists and Mineralogists Special 

Publication 39, p. 311–321.

Gautier, D.L., Dolton, G.L., Takahashi, K.I., and Varnes, K.L., 1995, 

National assessment of Unites States oil and gas resources—

Results, methodology, and supporting data: U.S. Geological Survey 

Digital Data Series DDS-30, release 2, [CD-ROM].

Geldon, A.L., 1990, Ground-water hydrology of the central Raton Basin, 

Colorado and New Mexico: U.S. Geological Survey Water Supply 

Paper 2288, 81 p.

Hemborg, H.T., 1996, Raton Basin coalbed methane production picking 

up in Colorado: Oil and Gas Journal, Nov. 11, 1996, p. 101–102.

Hills, R.C., 1888, The recently discovered Tertiary beds of the Huerfano 

River Basin, Colorado: Colorado Scientifi c Society, Proceedings, v. 

3, p. 148–164.

Hobbs, R.G., 1978, Methane occurrences, hazards, and potential 

resources—Recluse geologic analysis area, northern Campbell 

County, Wyoming: U.S. Geological Survey Open-File Report 78-401, 

20 p.

Howard, W.B., 1982, The hydrogeology of the Raton Basin, southcentral Colorado: Indiana University M.S. thesis, 95 p.

Jiao, Z.S., and Surdam, R.C., 1993, Low-permeability rocks, capillary 

seals, and pressure compartment boundaries in the Cretaceous 

section of the Powder River Basin, in Stroock, B., and Andrew, 

S., eds., Wyoming Geological Association Jubilee Anniversary Field 

Conference Guidebook, p. 297–310. 

Johnson, R.B., and Wood, H.H., Jr., 1956, Stratigraphy of Upper 

Cretaceous and Tertiary rocks of Raton Basin, Colorado and New 

Mexico: American Association of Petroleum Geologists Bulletin, v. 

40, p. 707–721.

Johnson, R.B., Dixon, G.H., and Wanek, A.A., 1966, Late Cretaceous 

and Tertiary stratigraphy of the Raton Basin of New Mexico and 

Colorado, in Northrop, S.A., and Read, C.B., eds., Guidebook of 

Taos-Raton-Spanish Peaks Country, New Mexico and Colorado: 

New Mexico Geological Society 17th Field Conference, p. 88–98.

Johnson, R.C., Crovelli, R.A., Spencer, C.W., and Mast, R.F., 1987, An 

assessment of gas resources in low-permeability sandstones of the 

Upper Cretaceous Mesaverde Group, Piceance Basin, Colorado: 

U.S. Geological Survey Open-File Report 87-357, 165 p.

Johnson, R.C., Finn, T.M., Crovelli, R.A., and Balay, R.H., 1996, An 

assessment of in-place gas resources in low-permeability Upper 

12 Geologic Studies of Basin-Centered Gas Systems
Cretaceous and lower Tertiary sandstone reservoirs, Wind River 

Basin, Wyoming: U.S. Geological Survey Open-File Report 96-264, 

67 p.

Johnson, R.C., and Flores, R.M., 1998, Developmental geology of 

coalbed methane from shallow to deep in Rocky Mountain basins 

and in Cook Inlet–Matanuska Basin, Alaska, U.S.A. and Canada: 

International Journal of Coal Geology 35, p. 241–282.

Johnson, R.C., Crovelli, R.A., Lowell, B.G., and Finn, T.M., 1999, An 

assessment of in-place gas resources in the low-permeability 

basin-centered gas accumulation of the Bighorn Basin, Wyoming 

and Montana: U.S. Geological Survey Open-File Report 99-315-A, 

123 p.

Jurich, D., and Adams, M.A., 1984, Geologic overview, coal and 

coalbed methane resources of Raton Mesa region, Colorado and 

new Mexico, in Rightmire, C.T., Eddy, G.E., and Kirr, J.N., eds., 

Coalbed Methane Resources of the United States: American 

Association of Petroleum Geologists Studies in Geology Series 17, 

p. 163–184.

Keefer, W.R., 1970, Structural geology of the Wind River Basin, 

Wyoming: U.S. Geological Survey Professional Paper 495-D, 35 p.

Larson, E.E., Ozima, M., and Bradley, W.C., 1975, Late Cenozoic 

basin volcanism in northwestern Colorado and its implications 

concerning tectonism and the origins of the Colorado River 

system, in Curtis, B.F., ed., Cenozoic History of the Southern Rocky 

Mountains: Geological Society of America Memoir 144, p. 155–178.

Law, B.E., 1984, Relationships of source-rock, thermal maturity, 

and overpressuring to gas generation and occurrence in lowpermeability Upper Cretaceous and lower Tertiary rocks, Greater 

Green River Basin, Wyoming, Colorado, and Utah, in Woodward, J., 

Meissner, F.F., and Clayton, J.L., eds., Hydrocarbon Source Rocks of 

the Greater Rocky Mountain Region: Denver, Colo., Rocky Mountain 

Association of Geologists, p. 469–490.

Law, B.E., and Dickinson, W.W., 1985, Conceptual model for the origin 

of abnormally pressured gas accumulations in low-permeability 

reservoirs: American Association of Petroleum Geologists Bulletin, 

v. 69, no. 8, p. 1295–1304.

Law, B.E., Spencer, C.W., and Bostick, N.H., 1979, Preliminary results 

of organic maturation, temperature, and pressure studies in 

the Pacifi c Creek area, Sublette County, Wyoming, in 5th DOE 

Symposium on Enhanced Oil and Gas Recovery and Improved 

Drilling Methods, Proceedings, v. 3 [Gas and Drilling]: Tulsa, Okla., 

Petroleum Publishing Co., p. 1–13.

Law, B.E., Spencer, C.W., Charpentier, R.R., Crovelli, R.A., Mast, 

R.F., Dolton, G.L., and Wandrey, C.J., 1989, Estimates of 

gas resources in overpressured low-permeability Cretaceous 

and Tertiary sandstone reservoirs, Greater Green River Basin, 

Wyoming, Colorado, and Utah, in Eisert, J.L., ed; Gas Resources of 

Wyoming: Wyoming Geological Association 14th Field Conference 

Guidebook, p. 39–61.

MacGowan, D.B., Garcia-Gonzalez, M., Britton, D.R., and Surdam, 

R.C., 1993, Timing of hydrocarbon generation, organic-inorganic 

diagenesis, and the formation of abnormally pressured gas 

compartments in the Cretaceous of the Greater Green River 

Basin: A geochemical model, in Stroock, B., and Andrew, S., eds., 

Wyoming Geological Association Guidebook, Jubilee Anniversary 

Field Conference, p. 325–348.

Masters, J.A., 1979, Deep basin gas trap western Canada: American 

Association of Petroleum Geologists Bulletin, v. 63, no. 2, p. 

151–181.

Masters, J.A., 1984, Lower Cretaceous oil and gas in western Canada, 

in Masters, J.A. ed., Elmworth Case Study of a Deep Basin Gas 

Field: American Association of Petroleum Geologists Memoir 38, p. 

1–33.

McPeek, L.A., 1981, Eastern Green River Basin—A developing giant 

gas supply from deep, overpressured Upper Cretaceous sandstone: 

American Association of Petroleum Geologists Bulletin, v. 65, p. 

1078–1098.

Meissner, F.F., 1978, Patterns of source-rock maturity in non-marine 

source rocks of some typical western interior basins in non-marine 

Tertiary and Upper Cretaceous source rocks and the occurrences 

of oil and gas in the west-central U.S.: Rocky Mountain Association 

of Geologists Continuing Education Course Notes.

Meissner, F.F., 1980, Examples of abnormal fl uid pressure produced 

by hydrocarbon generation: American Association of Petroleum 

Geologists Bulletin, v. 65, p. 749.

Meissner, F.F., 1981, Abnormal pressures produced by hydrocarbon 

generation and maturation and their relation to processes of 

migration and accumulation: American Association of Petroleum 

Geologists Bulletin, v. 65, p. 2467. 

Meissner, F.F., 1984, Cretaceous and lower Tertiary coals as sources 

for gas accumulations in the Rocky Mountain area, in Woodward, 

Jane, Meissner, F.F., and Clayton, J.L., eds., Hydrocarbon Source 

Rocks of the Greater Rocky Mountain Region: Rocky Mountain 

Association of Geologists, p. 401–431.

Merry, R.D., and Larsen, V.E., 1982, Geologic investigation of the 

methane potential of western U.S. coalbeds: Final report prepared 

for the Gas Research Institute under contract no. CE-807083, 155 p.

Pillmore, C.L., 1969, Geology and coal deposits of the Raton coal fi eld, 

Colfax County, New Mexico: Mountain Geologist, v. 6, p. 125–142.

Pillmore, C.L., and Maberry, J.O., 1976, Depositional environments and 

trace fossils of the Trinidad Sandstone, southern Raton Basin, New 

Mexico, in Ewing, R.C., and Kues, B.S., eds., Guidebook to Vermejo 

Park Northeastern New Mexico: New Mexico Geological Society 

27th Field Conference, p. 191–195.

Pillmore, C.E., and Flores, R.M., 1984, Field Guide and discussion 

of coal deposits, depositional environments and the CretaceousTertiary boundary, southern Raton Basin, in Lintz, J., Jr., ed., 

Western Geological Excursions: Geological Society of America 

Annual Meeting Guidebook, v. 3, p. 1–51.

Pillmore, C.E., and Flores, R.M., 1987, Stratigraphy and depositional 

environments of the Cretaceous-Tertiary boundary clay and 

associated rocks, Raton Basin, New Mexico and Colorado, in

Fassett, J.E., and Rigby, J.K., Jr., eds., The Cretaceous-Tertiary 

Boundary in the San Juan and Raton Basins, New Mexico and 

Colorado: Geological Society of America Special Paper 209, p. 

111–130.

Potential for a Basin-Centered Gas Accumulation in the Raton Basin, Colorado and New Mexico 13
Read, C.B., Duffney, R.T., Wood, G.H., Jr., and Zapp, A.D., 1950, Coal 

resources of New Mexico: U.S. Geological Survey Circular 89, 24 p.

Reinecke, K.M., Rice, D.D., and Johnson, R.C., 1991, Characteristics 

and development of fl uvial sandstone and coalbed reservoirs of 

Upper Cretaceous Mesaverde Group, Grand Valley fi eld, Garfi eld 

County, Colorado, in Schwochow, S.D., Murray, D.K., and Fahy, M.F., 

eds., Coalbed Methane of Western North America: Rocky Mountain 

Association of Geologists 1991 Guidebook, p. 209–225.

Rose, P.R., Everett, J.R., and Merin, I.S., 1986, Potential basin-centered 

gas accumulation in Cretaceous Trinidad Sandstone, Raton Basin, 

Colorado, in Spencer, C.W., and Mast, R.F., eds., Geology of Tight 

Gas Reservoirs: American Association of Petroleum Geologists 

Studies in Geology Series 24, p. 111–128.

Spencer, C.W., 1985, Geologic aspects of tight gas reservoirs in the 

Rocky Mountain region: Journal of Petroleum Technology, July, p. 

1308–1314.

Spencer, C.W., 1987, Hydrocarbon generation as a mechanism 

for overpressuring in the Rocky Mountain region: American 

Association of Petroleum Geologists Bulletin, v. 71, p. 368–388.

Spencer, C.W., 1989, Review of characteristics of low-permeability 

gas reservoirs in Western United States: American Association of 

Petroleum Geologists Bulletin, v. 73, no. 5, p. 613–629.

Spencer, C.W., and Law, B.E., 1981, Overpressured, low-permeability 

gas reservoirs in Green River, Washakie, and Great Divide Basins, 

southwestern Wyoming [abs.]: American Association of Petroleum 

Geologists Bulletin, v. 65, p. 569.

Stevens, S.H., Lombardi, T.E., Kelso, B.S., and Coates, J.M., 1992, 

A geological assessment of natural gas from coal seams in the 

Raton and Vermejo Formations, Raton Basin: Advanced Resources 

International, Inc., [topical report prepared for the Gas Research 

Institute under contract no. 5091-214-2316, GRI 92/0345], 84 p.

Steven, T.A., 1975, Middle Tertiary volcanic fi eld in the southern Rocky 

Mountains, in Curtis, B.F., ed., Cenozoic History of the Southern 

Rocky Mountains: Geological Society of America Memoir 144, p. 

75–94.

Strum, S., 1985, Lithofacies and depositional environments of the 

Raton Formation (Upper Cretaceous–Paleocene) of northeastern 

New Mexico: North Carolina State University M.S. thesis, 81 p.

Tschudy, R.H., Pillmore, C.L., Orth, C.J., Gilmore, J.S., and Knight, 

J.D., 1984, Disruptions of the terrestrial plant ecosystem at the 

Cretaceous-Tertiary boundary, Western Interior: Science, v. 225, 

no. 4666, p. 1030–1034.

Tyler, R., Ambrose, W.A., Scott, A.R., and Kaiser, W.R., 1991, Coalbed 

methane potential of the Greater Green River, Piceance, Powder 

River and Raton Basins: University of Texas at Austin, Bureau of 

Economic Geology, [topical report prepared for the Gas Research 

Institute under contract no. 5087-214-1544, GRI-91/0315], 244 p.

Tyler, R., Kaiser, W.R., Scott, A.R., Hamilton, D.S., and Ambrose, W.A., 

1995, Geologic and hydrologic assessment of natural gas from coal: 

Greater Green River, Piceance, Powder River, and Raton Basins, 

Western United States: Austin, Tex., Bureau of Economic Geology, 

Report of Investigations 228, 219 p.

Wanek, A.A., 1963, Geology and fuel resources of the southwestern 

part of Raton coal fi eld, Colfax County, New Mexico: U.S. 

Geological Survey Coal Investigations Map C-45.

Woodward, L.A., 1987, Oil and gas potential of the Raton Basin, New 

Mexico, in Lucas, S.G., and Hunt, A.P., eds., Northeastern New 

Mexico: New Mexico Geological Society Guidebook, p. 331–338.

Yin, P., and Surdam, R., 1993, Diagenesis and overpressuring in 

the Almond Sandstone, Mesaverde Group, in Stroock, B., and 

Andrew, S., eds., Wyoming Geological Association Guidebook, 

Jubilee Anniversary Field Conference, p. 349–357.

Manuscript approved for publication May 21, 2001

Published in the Central Region, Denver, Colorado

Editing, page layout, photocomposition—Richard W. Scott, Jr.

Cover design—Carol A. Quesenberry

Graphics by the authors

14 Geologic Studies of Basin-Centered Gas Systems