New Mexico’s Raton Basin coalbed methane play

Gretchen K. Hoffman and Brian S. Brister, New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, 801 Leroy Place, Socorro, NM 87801

Abstract Bureau of Geology and Mineral Resources. drainage efficiency, and their potential eco- There is also a significant body of data and nomic viability. There are restrictions on The Raton Basin became New Mexico’s literature devoted to the coal resources of the number of wells that can be drilled per newest natural gas-producing region in 1999 the region stored at the bureau’s Coal square mile in coalbed methane develop- when a new pipeline allowed production of Library. For this paper we reviewed this ment. Therefore, data and literature origi- coalbed methane near Vermejo Park, west of Raton. As of May 2003, 256 wells had been public data set with the intent to update nally designed to describe and support drilled and completed, producing more than and summarize what is known about the coal mining can be a valuable resource in 22 billion cubic feet of coalbed methane from coal-bearing formations and their associat- understanding and developing emerging coals in the Upper Cretaceous to Paleocene ed methane production. coalbed methane plays like the Raton Vermejo and Raton Formations. Less than Basin. half of the prospective area as delimited by Basin structure The Raton coal field is defined as the the presence of thermally mature coal has New Mexico portion of the Raton Basin been developed. An extensive geologic data Baltz (1965) provided a thorough descrip- including Upper Cretaceous and Pale- set exists at the New Mexico Bureau of Geol- ocene coal-bearing sequences in the Ver- ogy and Mineral Resources including infor- tion of the Raton structural basin, para- mation from coal mining and coalbed phrased here. The Raton Basin is an elon- mejo and Raton Formations. This field methane production. Study of that data set gate, northerly trending, asymmetric struc- encompasses a highly dissected plateau has resulted in better resolution of basin tural downwarp formed during the region, incised by the Canadian and Ver- structure and coal thickness, extent, and Laramide orogeny (Fig. 1). On its steeply mejo Rivers and their tributaries. The east- quality. In addition, potential for production dipping to overturned western flank lies ern margin of the plateau rises over 1,000 ft from Raton Formation sandstone reservoirs the Sangre de Cristo uplift. To the north are above the surrounding plain, and access to is indicated for a large area where coal beds the Wet Mountains uplift and the Apisha- the coal-bearing units is through canyons are currently being developed. pa arch. The eastern flank dips gently (less created by the drainage systems. The than 3°) westward off of the Sierra Grande rugged terrain is conducive to under- Introduction arch. In New Mexico the post-Laramide ground mining, starting at coal outcrops in Cimarron arch separates the basin into two canyon walls and tunneling inward either New Mexico’s Raton Basin has long been subbasins, the southern of which was in a room-and-pillar configuration or more known for its coal resources. Although coal named the Las Vegas Basin by Darton recently by longwall mining methods. Sur- is not being mined today, a number of sur- (1928). The Upper Cretaceous to Paleocene face mining began in the 1960s and is lim- face and underground mines operated in coal-bearing formations of the Raton Basin ited to areas of lesser relief in the upper the basin during the past century. In 1999 exist only north of the Cimarron arch. Tim- drainages of the Vermejo River. Locations the basin became New Mexico’s newest ing of basin formation is indicated by syn- of historic mining districts are shown in natural gas-producing region. As of May depositional structures in the Late Creta- Figure 3. 2003, 256 wells were actively producing ceous to Paleocene coal-bearing units Lee (1924) outlined the coal resources of methane (CH4, the most abundant compo- (Lorenz et al., 2003) and an unconformity the Raton coal field in New Mexico and nent of natural gas) derived from coal beds that places conglomeratic Paleocene Poi- discussed the early mining districts of the in the Upper Cretaceous Vermejo Forma- son Canyon Formation in angular contact area. Coal was discovered as early as the tion and Upper Cretaceous to Paleocene with older rocks at the basin’s western 1820s (Fig. 4). Coal mining for local domes- Raton Formation. Although there is a large flank. For the New Mexico portion of the tic use began in the 1870s. Beginning in the area underlain by these formations, the basin, a structure-contour map of the top 1890s with the arrival of railroad trans- coalbed methane play covers only a small of the Trinidad Sandstone from outcrop portation, commercial use of the coal part of Colfax County where geologic con- and well data delineates the area of interest included fuel for steam engines, coke for ditions are conducive to methane genera- for coal and coalbed methane (Fig. 2). copper smelters in the Southwest, and tion and storage in the coal beds. eventually fuel for electricity generation. An exploration and pilot development In 1955 Kaiser Steel of Fontana, California, drilling project conducted by Pennzoil in Raton Basin exploration history acquired a 530,000 acre mineral estate from 1989–1991 demonstrated that a coalbed St. Louis Rocky Mountain Pacific (Kaiser Coal mining methane resource existed, but economics Steel, 1976) that was eventually incorporat- and lack of a pipeline prevented the onset In most coalbed methane operations, pro- ed as part of the currently productive of production until 1999. All current duction of water and accompanying deple- coalbed methane area. Following the coalbed methane production operations in tion of pressure is the mechanism that acquisition, Kaiser began an extensive the New Mexico portion of the Raton Basin causes methane gas to desorb from the coal exploration drilling program that deter- are being conducted by El Paso Raton LLC matrix and migrate through the pore sys- mined that the York Canyon region had the in cooperation with the Vermejo Park tem to a producing well. Thus, the pres- greatest potential for development of both Ranch. Both entities have worked closely ence of both methane and water during underground and surface mining. These to make the coalbed methane operation coal mining may be an indicator of coalbed drill hole data are an important addition to today’s model for environmentally respon- methane potential. Mine records also pro- the data derived from coalbed methane sible energy production. vide valuable information on the strati- well records. El Paso Raton LLC has provided the graphic complexity of the coal-bearing for- From 1888 to 2001, 104 million short tons state of New Mexico with an extensive mations. Variability in coal seam thickness of coal were extracted from the Raton coal data set of Raton Basin well logs and cores, and extent are critical parameters in field in New Mexico, which is 7% of the which reside at the New Mexico Subsur- coalbed methane operations for determin- face and Core Libraries at the New Mexico ing the number of wells, their spacing, (Text continued on p. 100)

NoNovember 2003, Volume 25, Number 4 NEW MEXICO GEOLOGY 95 . o c i x e M w e N n i s a e r a g n i c u d o r p - e n a h t e m d e b l a o c e r a . ) d 9 e 7 d 9 u 1 l ( c n o t I e . o w c T i x d e n a M ) 3 w 0 e 0 N 2 ( d s n e a c r o u d o s a r e o R l l o a C r , e n n i i s a M B d n n a o t y a g R o l e o h e t f G o f o s e u r a u e t r a u e f B l o a c r i u x t e c u M r t s w e d N n a m y o g r f o l d o e e v G i r e — 1 d y E g R o l U o G e I F G

96 NEW MEXICO GEOLOGY November 2003, Volume 25, Number 4 . t f 0 0 5 = l a v r e t n i r u o t n o C . a t a d e c a f r u s d n a , e n i m , l l e w m o r f d e t e r p r e t n i e n o t s d n a S d a d i n i r T e h t f o p o t e h t f o p a m r u o t n o c - e r u t c u r t S — 2 E R U G I F

November 2003, Volume 25, Number 4 NEW MEXICO GEOLOGY 97 e r a n w o h s o s l A . n o i t c u d o r p d n a n o i t a r o l p x e s a g d n a l i o r o f d e l l i r d s l l e w d n a d l e i f l a o c n o t a R e h t f o , ) 1 9 9 1 ( e r o m l l i P . m ) o 7 r . f g i d F e ( i f ’ i B d – o B m d , n s a t c ) i 6 r t . s g i i d F ( g ’ n i A – n i A m s c n i o r i o t t c s e i s H s s — o 3 r c E f R o U s e G n I i l F

98 NEW MEXICO GEOLOGY November 2003, Volume 25, Number 4 . . k t ) c 2 n 9 u e r 9 t m 1 t ( y r e b a n p i d e e t m D r n o s o e p r c s r r n a u a o r m t i s e C d R s n ' l a y a r a e l i u w t p a d i k c N M o t d s d n l n a l a a s l g a m r r s u e a b n s i t o t t i M t l P , e y t b g a r r y e o r n t y E n e , e v l l l n l e a o s c s w u y g b R n t o e l r c e e a f b h r t o u e R s v y e o b h b t a o t o t o m t h o h r P f g . u e l w o e p r i b p V i t g — n n t i i f e a e b l m s r i e e l h a w t o o o L C t t - e a r d p n o t u o r r o g o r l e f d d n n u a . , r d s l e e b d i i f a r l , o l f a o o y c o . o r j n n o o o h t i t t t i a d a r e R w i o l e r p p a h r t c p o a n e C , i l t t e t s s t g u u n d h d e s o v k e D o c t o s d n r i p e l s t l i e a a l l h o e a P i r c r f e d g o t n n a i y a s d m y e a t t e i o r t l i v u i r h t o e c c W a p l o . t e g 0 o h n 3 i h 9 n d 1 P i n . . a s m a c n f r , o o o i o t s e c a i o r n l x i e l e p p e x M e O m i t s T w — t e u h — d N 4 g l , i r a E n o o r R c s e U t p w n G p a e I D v F U

November 2003, Volume 25, Number 4 NEW MEXICO GEOLOGY 99 estimated 1.5 billion tons demonstrated most suitable for the historic mines is the maturity. Unfortunately, the Pennzoil pro- resource (Pillmore, 1991). Demonstrated least suitable for current coalbed methane gram suffered from the lack of a pipeline, resources are based on measured (0–0.25 development. low gas prices at that time, and expiration mi) and indicated resources (0.25–0.75 mi) Another lesson learned is that some of the section 29 tax credits in 1991. Infor- from a known point, either drill hole or mines had limited extent because coal bed mation derived from the Pennzoil data set outcrop. Inferred estimates increase the thickness tends to be highly variable over was studied and published in various basin resources to more than 9 billion tons. short distances. Kaiser’s and (later) Pitts- reports by the Gas Research Institute, Active mining was suspended in 2002 due burg & Midway’s extensive exploration notably those of Stevens et al. (1992) and to poor economics. Although rail access is drilling programs yielded successful Tyler et al. (1995). available, the cost of mining coal in the underground and surface-mining opera- By 1994 the first pipeline was built to area cannot compete with Wyoming coal tions targeting thick coals over several transport Raton Basin coalbed methane selling for $5.62/ton (2001). Underground square miles. This suggests that coalbed from the Colorado part of the basin, and a mining has the greatest potential in the methane development in the Raton Basin development boom began, accelerating as Raton coal field; however, the recovery might benefit from an exploratory phase gas prices improved through the late rate for underground operations is less focused on locating areas of thick coal and 1990s. A group of several companies, now than surface mining, making this method perhaps avoiding less-economic blanket- consolidated to El Paso Raton LLC, less economic. The coals in the Vermejo like development of large areas typical in acquired the Pennzoil Vermejo Park miner- and Raton Formations tend to be discon- basins with thicker and more extensive al estate in New Mexico and began to tinuous and relatively thin, requiring the coal beds. define the reserves in 1999 with explorato- mining of multiple seams and further ry stratigraphic test wells, many of which decreasing the economic viability of min- Oil and gas exploration were cored. Commercial coalbed methane ing. More than 150 exploratory wells have been production in the New Mexico part of the There are several important observa- drilled in Colfax County, 74 of which Raton Basin began in October 1999 upon tions to be gleaned from the mining histo- reached the Cretaceous Dakota Sandstone. completion of a pipeline. Subsequent ry of the region. With a few notable excep- Beginning in 1924 most early exploration development has expanded concentrically tions, it appears that most mines operated focused on finding oil because it could be within the areas identified as potential by without methane or water production trucked or shipped by rail to refineries. On Pennzoil’s 1989–1991 exploratory efforts. problems. Some of the early mines near the other hand, natural gas required Blossburg reported problems with ventila- pipelines for transportation. Several larger Coalbed methane-related literature tion such that methane accumulating in companies made brief exploration forays the mines led to explosions and mine clo- into the basin, notably Continental Oil Coalbed methane has been recognized as sures. A gas explosion closed another mine with nine wells in 1954–1955, Pan Ameri- an important and widespread resource in located between Brilliant and Blossburg can with nine wells in 1957–1960 and later the U.S. only since the 1980s. There are a (Lee, 1924). One mine near Blossburg as Amoco with eight wells in 1968–1974, few key papers that describe the condi- reported problems with water, but pumps and Odessa Natural Gas with eight wells tions favorable for coalbed methane were installed and the mine was kept in 1972–1973. These early attempts com- reserves in the Raton Basin. A pioneering open. Lee (1924) reported methane in some monly reported gas shows in the Raton study of coalbed methane potential in the of the Van Houten mines. The under- and Vermejo Formations and oil and gas Raton Basin by Jurich and Adams (1984) ground Cimarron mine was closed because shows in the underlying Trinidad Sand- estimated a total resource of 8–18 trillion of problems related in part to methane in stone through Dakota Sandstone (Baltz, cubic feet of gas (Tcf) for the entire basin. the mine that would have required over- 1965; Woodward, 1984). The overall results Close (1988) updated the earlier work and hauling the ventilation system (Jim suggested that the basin might be analo- included a detailed study of the deposi- O’Hara, 2003 pers. comm.). gous with the Denver–Julesburg (Wood- tional environments, cleat orientation and Dawson had two infamous explosions ward, 1984) or San Juan Basins in terms of fracture patterns, thermal maturity param- that killed a sum of 383 miners, but mine widespread oil and gas in fractured, low- eters, and regional thermal history of the inspector reports and Phelps Dodge permeability formations. However, the basin. Close and Dutcher (1991) estimated records suggest ignition of coal dust rather Raton Basin lacked the pipeline infrastruc- the coalbed methane resource to be 40 bil- than methane was the cause. Other mining ture and moderately porous sandstone lion cubic feet (Bcf) per square mile with an explosions were also attributed to coal reservoirs that made the San Juan Basin so estimated ultimate reserve base of 1 Tcf. dust. An interesting question is, Why were prolific beginning in the late 1950s. The Gas Research Institute (GRI) pub- there not more methane problems reported Pennzoil began exploring the potential lished a coalbed methane assessment of in a basin that would eventually become of its Raton Basin minerals estate in 1981 the Raton Basin (Stevens et al., 1992) that an important coalbed methane basin? The with several noncommercial deeper Creta- summarized reservoir characteristics and answer is in part due to the topography ceous tests and shallow coal tests. By 1989 estimated the mean coalbed methane and hydrology of the region, which place it had assembled a huge 780,000-acre min- resource of the Raton and Vermejo coals at the outcrop of the Raton and Vermejo For- eral estate, purchased in part from Kaiser 10.2 Tcf. New data from wells drilled in the mations in the eastern basin flank well Steel in 1989 (Whitehead, 1991). The suc- basin were incorporated into the GRI above the regional water table. However, cessful coalbed methane development report along with gas desorption measure- the Cimarron mine and successful coalbed boom in the San Juan Basin, coupled with ments and new vitrinite reflectance data, methane production from areas near Ver- section 29 tax credits for development of collected in part from coal cores available mejo Park are along the water-saturated, unconventional gas reservoirs, encouraged at the NMBGMR (Stevens et al., 1992, p. deeper axial portion of the basin. Stevens Pennzoil to evaluate the coalbed methane 41). Flores and Bader (1999) summarized et al. (1992) noted gas contents increase potential around the Vermejo Park area previous studies and future potential of with depth below the potentiometric sur- with approximately 30 wells in 1989–1991, mining and coalbed methane without face (water table measured in wells) rather 22 of which were produced briefly to eval- including a specific resource assessment of than depth from surface. This has negative uate economic viability (Whitehead, 1991). the basin. Johnson and Finn (2001) evaluat- implications for the viability of coalbed Pennzoil had apparently used the older ed the potential for basin-centered gas in methane development attempts in coal Kaiser data set as they focused their coal the Raton Basin in the sandstones in the beds within a few miles of their eastern bed exploratory program on areas where Trinidad, Vermejo, and Raton Formations. outcrop in the Raton Basin. Thus the area the coal was thick and of higher thermal A new Raton Basin characterization project

100 NEW MEXICO GEOLOGY November 2003, Volume 25, Number 4 is underway at the NMBGMR that lying immediately above the Trinidad unit represents prograding conglomeratic includes a GIS-linked digital database. Sandstone.” This sequence of sandstone, lithofacies derived from the Sangre de That data will be available as an open-file siltstone, mudstone, shale, carbonaceous Cristo uplift. report in early 2004. shale, and coal averages approximately Flores (1987) recognized three upward- 350 ft (107 m) thick. The Vermejo Forma- coarsening megacycles in the Vermejo, Coal-related stratigraphy tion represents delta-plain deposits land- Raton, and Poison Canyon Formations. ward of the shoreface, delta-front and bar- The Vermejo Formation to the basal Raton Coal was first reported in the Raton Basin rier-bar sediments of the Trinidad Sand- conglomerate represents the first megacy- region in 1820 by the Long expedition (Pill- stone (Flores, 1987; Pillmore and Flores, cle; the lower coal zone and middle barren more, 1976). Orestes St. John was one of the 1987). The thicker coals are commonly con- sequence in the Raton represent the sec- earliest geologists to look at the coal centrated near the base of the Vermejo For- ond, and the third megacycle consists of resources in the Raton Basin as part of the mation in proximity to the Trinidad upper the upper coal zone of the Raton and the Hayden survey, later assessing the coal shoreface sandstone. Poison Canyon Formation. These megacy- resources for the Maxwell land grant in the In general, the Raton Formation uncon- cles apparently record local Late Creta- 1870s (Pillmore, 1976). Willis T. Lee, formably overlies the Vermejo Formation. ceous to Paleocene tectonic pulses affect- employed by the U.S. Geological Survey, Lee (1917) divided the Raton Formation ing the basin and adjacent uplift. did extensive geologic work in the basin, into the informal basal conglomerate, as reported in his 1917 and 1924 publica- lower coal zone, a sandstone-dominated Coal thickness and continuity tions. Knowlton (1917) investigated the barren series (middle barren sequence fossil flora in the Vermejo and Raton For- herein), and an upper coal zone. The Raton Most of the coalbed methane wells in the mations, helping to define the ages of these Formation basal conglomerate is a 10- to New Mexico part of the Raton Basin pro- formations. Wanek (1963) published a map 30-ft-thick (3- to 9-m-thick) pebble con- duce methane from the Vermejo Formation with text on the coal resources of the glomerate to granule quartzose sandstone with contributions in some wells from the southern Raton coal field. Pillmore began eroded into the Vermejo Formation. Over- Raton Formation. For this study, we exam- mapping several quadrangles in the Raton lying the basal conglomerate, the 100- to ined well logs throughout the area at a field in the 1960s and published a compre- 300-ft-thick (30- to 91-m-thick) lower coal density of one well per square mile where hensive paper (1969) on the coal deposits, zone consists of sandstone, siltstone, mud- available, recording thickness of coal beds drawing on previous work and access to stone, carbonaceous shale, and thin, dis- ≥ 1 ft (0.3 m) thick. Lack of lateral continu- coal data from Kaiser Steel. He defined sig- continuous coal. This sequence represents ity for most of the coals in the Vermejo and nificant coal beds or zones in the Vermejo meandering stream floodplain deposits Raton Formations dictates grouping the and Raton Formations within the coal field that grade upward into braided stream coals together by formation to do any eval- and specified geographical areas where deposits of the overlying middle barren uation of the overall thickness characteris- these coal zones exist. Pillmore and Flores sequence (Flores and Pillmore, 1987; John- tics. Table 1 is a compilation of the publicly (1987) published several papers together, son and Finn, 2001), which varies from 165 available data. These wells are concentrat- separately, and with other co-authors to 600 ft thick (50 to 183 m thick). The mid- ed in the areas northeast and southwest of through the 1980s on the sedimentology of dle barren sequence merges with the Poi- Vermejo Park. The entire Raton Formation the Raton Basin and the location of the Cre- son Canyon Formation to the west (Pill- was not recognized in the open-hole geo- taceous–Tertiary boundary within the more and Flores, 1987). The upper coal physical logs because wells are cased to the lower coal zone of the Raton Formation. zone is a return to finer-grained deposits in 300-ft (91-m) depth to protect shallow See Baltz (1965) for a comprehensive an alluvial plain environment (Flores, ground water. Any coals above this depth summary of the stratigraphy of the region. 1987). Peat swamps developed between are not represented in the data in Table 1. The coal-bearing sequence in the Raton the meandering stream channels. Coal The average and maximum total coal Basin is underlain by the Trinidad Sand- beds are lenticular within the upper coal thickness and number of seams is greater stone. As thick as 130 ft (40 m), it forms a zone but tend to have greater thickness in the Raton Formation. The maximum prominent cliff along the eastern edge of than those in the lower coal zone of the average seam thickness is the only statistic the basin. Hills (1899) described the Raton Formation. that is significantly greater for the Vermejo Trinidad Sandstone in the Raton Basin, The Raton Formation is overlain by and Formation. A tally of individual seams later to be defined by Lee (1917). The intertongues to the west with the Poison from 1 ft (0.3 m) to > 10 ft (3 m) from these upward-coarsening sandstones show bio- Canyon Formation; the contact can be gra- same data indicates 84% of Raton coals are turbation and commonly contain Ophio- dational in parts of the basin. Where the 1–3 ft (0.3–1 m) thick, whereas 73% of Ver- morpha casts (Flores, 1987) suggesting a contact intersects the surface it is mapped mejo coals are in this same thickness range. shallow marine to shoreface depositional as a transitional area (e.g. as mapped by Vermejo coals 5 ft (1.5 m) thick or greater environment. The lower part of the forma- the New Mexico Bureau of Geology and make up about 8% of the data set, and tion has ripple lamination that grades Mineral Resources and others), in part Raton coals 5 ft (1.5 m) thick or greater upward into planar and trough cross-lami- because of vegetative cover, but also the account for 3% of the data set. nation (Flores, 1987), demonstrating an lack of a detailed study of the Poison Vermejo Formation upward increase in depositional energy Canyon Formation. The Poison Canyon and reflecting the overall shallowing and Formation consists of coarse-grained to Because the Vermejo Formation contains regression of the seaway. conglomeratic arkosic sandstones. This some of the thickest coals in the Raton Conformably overlying the Trinidad TABLE 1—Coal thickness and seam properties of Vermejo and Raton Formations. Data from coalbed Sandstone is the coal-bearing Vermejo For- methane and oil and gas geophysical logs. Raton coal picks from logs with 1,400 ft (427 m) of section mation. However, Lee (1917) and Wanek from base of Raton. Vermejo coal picks from logs with base of Raton and top of Trinidad. (1963) recognized transgressive tongues of Total coal thickness Number of seams Average seam thickness the Trinidad Sandstone extending into the ft (m) per well ft (m) Vermejo Formation along the southern margin of the basin. Both noted the gener- Formation Raton Vermejo Raton Vermejo Raton Vermejo al thinning of the Vermejo Formation to the Average 27 (8.2) 17.47 (5.32) 15 7 2 (0.6) 2.5 (0.76) east. Lee (1917, p. 51) defined the Vermejo Maximum 66 (20) 41.50 (12.6) 30 17 3.2 (0.9) 5.5 (1.7) Formation for exposures at Vermejo Park, Minimum 8 (2.4) 4 (1.2) 4 2 1.2 (0.4) 1.5 (0.4) and described it as the “coal measures Well count 59 (18) 133 (40.5)

NoNovember 2003, Volume 25, Number 4 NEW MEXICO GEOLOGY 101 . n o i t c e s o j e m r e V e t e l p m o c h t i w s l l e w f o s g o l l a c i s y h p o e g m o r f d e t e r p r e t n i s s e n k c i h t l a o c t e n n o i t a m r o F o j e m r e V — 5 E R U G I F

102 NEW MEXICO GEOLOGY November 2003, Volume 25, Number 4 Basin, these were the predominant coals Raton section logged). Like the Vermejo that the coalbed methane gas being pro- being mined in the early period of mining coal beds, Raton coals tend to be discontin- duced today was thermally rather than along the eastern edge of the basin. Figure uous or lenticular. We believe that the biologically generated. There is evidence 5 is a map of net Vermejo Formation coal existing well control does not reveal their from fission track studies that approxi- derived from well log interpretation (sum complexity, making contour mapping mately 1 km (0.62 mi) of denudation has of Vermejo coal beds ≥ 1 ft [0.3 m] thick, problematic. In the wells examined, net occurred in the Vermejo Park region since wells with complete section of Vermejo). In Raton coal ranges from 8 to 66 ft (2.4 to 20 the Miocene (Hemmerich, 2001). Miggins the wells examined, net Vermejo coal m) thick. Wells examined that are encom- (2002) conducted an extensive study dat- ranges from 4 to 41.5 ft (1.2 to 12.6 m) sup- passed by the two producing areas average ing the igneous intrusions of the region, porting observations from surface work approximately 24 ft (7 m) net thickness for and he reported ages from 33 to 19.7 Ma, and mining that describe lenticularity of the southwestern area (29 wells) and 29 ft most being clustered around 25 Ma. Like coal beds and associated variability in (9 m) net thickness for the northeastern the Spanish Peaks in Colorado, the struc- individual coal bed thickness. Figure 5 fur- area (30 wells). It is significant to point out tural dome of Vermejo Park is probably a ther illustrates the lenticularity or lack of that many wells do not produce from the result of laccolithic intrusion; wells on the continuity of the coal seams within the upper coal zone, particularly in the south- Vermejo Park structure bottom in igneous Vermejo Formation. Given the current den- western area. Most wells are not complet- rocks at atypically shallow depths relative sity of wells we believe that there is insuf- ed above the 1,000-ft (305-m) depth pre- to wells outside of the dome. Although ficient control to draw meaningful contour sumably to avoid excessive water produc- dikes and sills in the area tend to have a maps. Wells examined that are encom- tion. Figures 6 and 7 show that, like the limited direct effect (contact metamor- passed by the two producing areas average Vermejo Formation, individual coal beds phism) on adjacent rocks, regionally ele- approximately 19 ft (5.8 m) net thickness in the Raton Formation have limited extent vated heat flow and convection of associat- for the southwestern area (62 wells) and 18 and thickness and tend to be concentrated ed fluids (hot ground water) can influence ft (5.5 m) net thickness for the northeastern into zones. a much greater volume of the coal-bearing area (57 wells). Several wells on the map sequences. Thus the combination of both fall outside the producing areas (thus 133 Coal quality maximum paleoburial depth and elevated wells total). heat flow during the Miocene is the likely The Vermejo and Raton Formations con- Figures 6 and 7 are stratigraphic cross cause for relatively high thermal maturity tain low-sulfur, moderate-ash coals of sections based on wells spaced approxi- of coals shallowly buried today. 3 high-volatile A to B bituminous rank. The mately ⁄4 to 1 mi (1.2 to 1.6 km) apart, and quality of the coals within the two forma- they depict coal beds interpreted from geo- tions does not vary significantly (Hoffman, physical logs and those coals that were Related gas sands 1996). However, there are areas within the completed for coalbed methane produc- coal field where Oligocene and younger In their 2001 study, Johnson and Finn con- tion. Coal beds cannot be readily correlat- sills have intruded coal seams, destroying sider the Raton Formation through ed between wells at this well spacing. This the economic potential of the seam. The Trinidad Sandstone in the Raton Basin to degree of stratigraphic complexity high-volatile bituminous rank indicates have basin-centered gas potential where adversely affects the ability to efficiently that these coals have reached the bitu- vitrinite reflectance exceeds 1.1 %Ro. How- drain reservoirs with widely spaced wells ever, all of the gas producing wells have a 1 minization stage (Levine, 1993) when gen- at the current density of ⁄2 mi (0.8 km) eration and entrapment of hydrocarbons lesser %Ro in the two producing areas that spaced wells. Overall, the Vermejo Forma- takes place, vitrinite reflectance (%R —a we have examined, and many of these tion thins eastward, but the number and o method to estimate thermal maturity) show evidence of gas saturation in some thickness of coal beds does not appear to increases to 0.6–1.0, and the moisture con- sandstone beds, most commonly in the change significantly. The Vermejo Forma- tent of the coal decreases. basal part of the Raton Formation. The tion may be important for coalbed Some unpublished %R data are avail- presence of gas in sandstones is suggested methane production over a large area and o able for the Raton Basin in addition to the from well logs where neutron log porosity was an obvious target for past mining. published data. Most of these data are is reduced and density porosity is elevated such that there is a crossover of the two log Raton Formation from surface channel samples, either from outcrops or at mine faces; the remainder curves. Figure 10 is a well log cross section The lower coal zone of the Raton Forma- are from cores. There are 19 samples from through the western part of the northeast- tion has several thin lenticular coals of lit- the Raton Formation and 14 samples from ern coalbed methane production area. The tle importance for mining; however, a the Vermejo Formation. Figure 9 shows the cross section shows all sand beds greater lower-zone coal was mined at Sugarite in deep and surface vitrinite reflectance data than 6 ft (2 m) in thickness and coal beds the eastern part of the coal field. These and the producing areas within the Raton ≥ 1 ft (0.3 m) thick, and indicates which lower-zone coals have been completed in Basin in New Mexico. The data shown sands have the well log gas effect. These 1 many coalbed methane wells. The upper have not been adjusted to any set depth or wells are spaced only ⁄2 mi (0.8 km) apart, coal zone has more economic potential for datum. The data close to the edge of the but similar observations can be made mining and coalbed methane as it tends to basin range from 0.45 to 0.75 %Ro. Given about the continuity of sandstone beds as have some lateral continuity. The York that coal is primarily a gas-prone source for coal beds. Although the sandstone beds Canyon coal bed in the upper coal zone rock and that thermogenic gas generation fall within zones, it is often difficult to cor- averages 5–6 ft (1.5–2 m) thick and was the becomes significant at approximately 0.8 relate individual lenticular fluvial sand- principal bed mined at the York Canyon %Ro, these areas probably have little stone beds between wells. complex. In the Upper York or Left Fork potential for coalbed methane as they are district where the Cimarron underground relatively thermally immature and above Summary of current coalbed mine operated (Fig. 3), there are two coals the water table. The northwest corner of that range in thickness from 3.5 to 11 ft the Raton coal area has the greatest methane operations (1–3.4 m). coalbed methane potential, because %Ro is Coalbed methane wells in the Raton Basin Figure 8 is a map of net Raton Formation greater than 0.8 and much of the coal lies coal from well log interpretation (sum of in New Mexico produce from three statu- below the water table. tory pools: Stubblefield Canyon (Raton– Raton coal beds ≥ 1 ft [0.3 m] thick, wells Coal rank and maturity indicators in the with a minimum of 1,400 ft [427 m] of Raton Basin coal beds strongly suggest (Text continued on p. 108)

NoNovember 2003, Volume 25, Number 4 NEW MEXICO GEOLOGY 103 ” m n o o r i f t l a l r e o f w r e e P h t “ f . l o l t e r a w p h d c e a e g g r o o l f e l d o e . t h n - a o c n i i t e d c p n u o i d e e o r h r t a p f ) r o t f o f p 0 o d t 0 e 5 e t – e h t . g r g s . i a e t ( n n s m e r e u e l b k o r e c a v l l a m e h h w t t a h p h c e t a l D e l . e f o d w e p e v i o h t r t e e n d h i T e s r t . s a n i n a o t m p a u l d o t o h c s c r l i l e f h e e w w r . e e ) h h t t m f k f o o 6 . e 1 p s ( o a i t b e m e h 1 h t t s t i s a i s h l e l t e n h o w c t s u n s d e n e d a e w S t g e d n b a a r d g r i n a n i i c s r l a l T p e e s h W e t t . f a 8 o m d i p n x o a t o r , e 5 p h , p T 3 . A . . s ) m t g u i s t a F a e d n i o c t i s t h s p e p a a w r m ( g ’ i n t o A a – r n t A s w n e o o h h i t t s c s i e n s o n i s o t i s c t o e a r s C m s r s — o o 6 r F c E o j f R e o U m e r n G e i I F V L

104 NEW MEXICO GEOLOGY November 2003, Volume 25, Number 4 - p a c e e S . 8 d n a , 5 , 3 . s g i F n i s p a m n o n w o h s n o i t c e s s s o r c f o e n i L . ) m k 2 . 1 ( i m 4 ⁄ 3 s i s l l e w n e e w t e b g n i c a p s e . t n a o i m t i c x u o r r t s p n p o A c . ) n t s o i a t e c e o s t t s s s e o r w c ( ’ n o B – s t B n n e o i m t c m e o s c s r s o o f r 6 C . — g i 7 F E r R o f U n G o I i t F

November 2003, Volume 25, Number 4 NEW MEXICO GEOLOGY 105 . d e g g o l s a w n o i t a m r o F n o t a R f o e r o m r o ) m 7 2 4 ( t f 0 0 4 , 1 e r e h w y l n o d e d u l c n i s l l e W . s g o l l a c i s y h p o e g m o r f d e t e r p r e t n i s s e n k c i h t l a o c t e n n o i t a m r o F n o t a R — 8 E R U G I F

106 NEW MEXICO GEOLOGY November 2003, Volume 25, Number 4 r o f d e t s u j d a n e e b t o n e v a h t a h t a t a d w a r y l n o e d u l c n i d e t c i p e d s t n i o P . o R . % h 8 t . p 0 e ± d - e i u d l n a i v y r t i u r o u t t n a o c m l y a b m d r e e t s h t e g k g c u o r s s e i c r y t u i o v s i t a c , u ) o d o R r % p ( e e n c a n h a t t e c e l m f e d r e b e l t i a n o i c r t i e l v b f a o b o p r a p f M o — a 9 e r E A R . r U o t G I a c F

November 2003, Volume 25, Number 4 NEW MEXICO GEOLOGY 107 1 FIGURE 10—Cross section that provides a closer spaced view of the west- wells is ⁄2 mi (0.8 km). See caption for Fig. 6 for other comments on cross ern part of cross section A–A’ (Fig. 6). Sandstone beds interpreted to be gas section construction. charged are indicated by red rectangles. Approximate spacing between

Vermejo), Van Bremmer Canyon (Verme- this paper, pool boundaries are artificial gas producers. However, drilling is contin- jo), and Castle Rock Park (Vermejo). The subdivisions. All currently producing uing, and the field is expected to expand formation names that are a part of the offi- pools are located on the Vermejo Park rapidly beyond the producing areas cial pool names do not accurately reflect Ranch in Colfax County. shown on our maps. The ultimate density the formations from which coal beds are To date 256 producing wells have been of wells and the areas developed on the producing in all wells in these pools. For drilled and completed as coalbed methane Vermejo Park Ranch are limited by con-

108 NEW MEXICO GEOLOGY November 2003, Volume 25, Number 4 FIGURE 11—Graph of gas and water production for Colfax County, production, monthly production, and cumulative number of active New Mexico, current through May 2003. Data include cumulative wells versus date. tractual agreement between the mineral surface impacts, and pipeline right-of- coal bed below 1,000 ft (305 m; for many and surface owners in the interest of envi- ways are quickly reclaimed. Water and gas but not all wells), and the coals are stimu- ronmental preservation. Operations are are piped to central facilities where gas is lated by hydraulic fracturing, a procedure coordinated carefully with the Vermejo compressed for pipeline transport and to create and prop open fractures that typ- Park Ranch and the New Mexico Oil Con- water is disposed of by deep saline aquifer ically uses more than 100,000 lb (45,000 kg) servation Division, which has regulatory injection, a manner approved by the New of quartz sand carried by nitrogen and jurisdiction over drilling on privately Mexico Oil Conservation Division. Wells fresh water-based foam. Sandstone beds, owned lands within the state. Drilling and and gas compressors are equipped with even those with gas shows, have been other operations are planned so that they electric motors to minimize noise and mostly avoided to date, perhaps because lessen the impact on other surface activities emissions. of concerns about excess water produc- of the Vermejo Park Ranch. Spacing of In general, the coalbed methane wells tion. However, at least one sandstone test wells is approximately 160 acres per well, are drilled to the top of the Pierre Shale (at is now producing, and others are likely to 1 equating to approximately ⁄2 mi (0.8 km) a depth of approximately 2,200 ft [670 m]). follow. between wells. The footprint of well pads The casing and cementing program is Figure 11 depicts total production of 1 2 is about ⁄2 acre (2,024 m ). Large areas with designed to protect shallow ground water methane and related water for Colfax coalbed methane reserves are left undevel- (to approximately 300 ft [91 m]), yet allow County, New Mexico. As of May 2003 the oped to preserve critical habitat for elk and most of the Raton and Vermejo coal beds to field was producing more than 1 billion bison herds. Wells are rarely noticed when be completed together. Following geo- cubic feet (Bcf) per month. More than 22 driving the main roads on the ranch. Wells, physical logging, steel production casing is Bcf has been produced since inception in roads, pipelines, and other infrastructure run to total depth and then cemented into October 1999. This activity benefits the are located and constructed to minimize place. The casing is then perforated at each economy of Colfax County and the state of

November 2003, Volume 25, Number 4 NEW MEXICO GEOLOGY 109 New Mexico through severance (and Raton Basin, Colorado and New Mexico: Unpub- logical Survey, Professional Paper 101, pp. 9–221. other) taxes and employment. As the play lished Ph.D. dissertation, Southern Illinois Uni- Lee, W. T., 1924, Coal resources of the Raton coal matures it will continue to have a growing versity, 432 pp. fields, Colfax County, New Mexico: U.S. Geolog- Close, J. C., and Dutcher, R. R., 1991, Update on ical Survey, Bulletin 752, 254 pp. economic impact. coalbed methane potential of Raton Basin, Col- Levine, J. R., 1993, Coalification—the evolution of orado and New Mexico: Society of Petroleum coal as a source rock and reservoir rock for oil Conclusion Engineers, SPE20667, 16 pp. and gas; in Law, B. E., and Rice, D.D. (eds.), Darton, N. H., 1928, “Red beds” and associated for- Hydrocarbons from coal: American Association It is too early to predict the life span and mations in New Mexico, with an outline of the of Petroleum Geologists, Studies in Geology 38, geology of the state: U.S. Geological Survey, Bul- pp. 39–77. ultimate recovery of the current coalbed letin 794, 356 pp. Lorenz, J. C., Cooper, S. P., and Keefe, R. G., 2003, methane development efforts in Colfax Flores, R. M., 1987, Sedimentology of Upper Creta- Syn-sedimentary deformation in the central County, New Mexico. The longest-produc- ceous and Tertiary siliciclastics and coals in the Raton Basin, Colorado and New Mexico—a ing wells (since October 1999) have accu- Raton Basin, New Mexico and Colorado; in potential control on sand body orientation (abs.): mulated 0.12 Bcf on average per well to Lucas, S. G., and Hunt, A.P. (eds.), Northeastern American Association of Petroleum Geologists, New Mexico: New Mexico Geological Society, Annual Meeting, Program with Abstracts, May date or an average of approximately 0.5 Bcf Guidebook 38, pp. 255–264. 11–14, 2003, Salt Lake City, Utah, p. A107. per square mile. At present, the developed Flores R. M., and Pillmore, C. L., 1987, Tectonic con- Miggins, D. P., 2002, Chronologic, geochemical, and acreage covers about half of the area where trol on alluvial paleoarchitecture of the Creta- isotopic framework of igneous rocks within the production potential appears to be favor- ceous and Tertiary Raton Basin, Colorado and Raton Basin and adjacent Rio Grande rift, south- able. New Mexico; in Ethridge, F. G., Flores, R. M., and central Colorado and northern New Mexico: Increases in production volume have Harvey, M. D. (eds.), Recent developments in flu- Unpublished M.S. thesis, University of Colorado, vial sedimentology: Society of Economic Paleon- Boulder, 438 pp. been tied closely to stages of development tologist and Mineralogists, Special Publication New Mexico Bureau of Geology and Mineral drilling. Future volume increases will 39, pp. 311–320. Resources, 2003, Geologic map of New Mexico, require some development of private and Flores, R. M., and Bader, L. R., 1999, A summary of 1:500,000: New Mexico Bureau of Geology and public lands not drilled to date. Given the Tertiary coal resources of the Raton Basin, Col- Mineral Resources. geologic complexity of the coal-bearing orado and New Mexico; in 1999 Resource assess- Pillmore, C. L., 1969, Geology and coal deposits of sequences, it seems unlikely that the cur- ment of selected Tertiary coal beds and zones in the Raton coal field, Colfax County, New Mexico: the northern Rocky Mountains and Great Plains Mountain Geologist, v. 6, no 3, pp. 125–142. rent density of wells is the most efficient region: U.S. Geological Survey, Professional Pillmore, C. L., 1976, The York Canyon coal beds; in for reserve recovery. Therefore, reserves Paper 1625-A, chapter SR. Ewing, R. C., and Kues, B. S. (eds.), Vermejo Park, may eventually grow through targeted Hemmerich, M., 2001, Cenozoic denudation of the northeastern New Mexico: New Mexico Geologi- infill drilling of vertical or horizontal Raton Basin and vicinity, northeastern New Mex- cal Society, Guidebook 27, pp. 249–251. wells. It is clear that initial coalbed ico and southeastern Colorado, determined using Pillmore, C. L., 1991, Geology and coal resources of apatite fission-track thermochronology and sonic the Raton coalfield; in Molnia, C. L., Jobin, D. A., methane development in the New Mexico log analysis: Unpublished M.S. independent O’Conner, J. T., and Kottlowski, F. E. (eds.), Coal- portion of the Raton Basin has been suc- study, New Mexico Institute of Mining and Tech- fields of New Mexico—geology and resources: cessful in terms of both technical and eco- nology, 121 pp. U.S. Geological Survey, Bulletin 1972, pp. 45–68. nomic benchmarks and that development Hoffman, G. K., 1996, Coal resources of New Mexi- Pillmore, C. L., and Flores, R. M., 1987, Stratigraphy will continue to expand in the coming co: New Mexico Bureau of Mines and Mineral and depositional environments of the Creta- decade. Resources, Resource Map 20, scale 1:1,000,000, 22 ceous–Tertiary boundary clay and associated pp. rocks, Raton Basin, New Mexico and Colorado; in Hills, R. C., 1899, Description of the Elmoro quad- Fassett, J. E., and Rigby, J. K. (eds.), The Creta- Acknowledgments rangle, Colorado: U.S. Geological Survey, Geo- ceous–Tertiary boundary in the San Juan and logic Atlas, Folio 58, 6 pp. Raton Basins, New Mexico and Colorado: Geo- We thank Roy Johnson of the New Mexico Johnson, R. C., and Finn, T. M., 2001, Potential for a logical Society of America, Special Paper 209, pp. Oil Conservation Division and Amy basin-centered gas accumulation in the Raton 111–130. Basin, Colorado and New Mexico; in Nuccio, V. Stevens, S. H., Lombardi, T. E., Kelso, B. S., and Trivitt-Kracke of the New Mexico Library F., and Dyman, T. S. (eds.), Geologic studies of Coates, J. M., 1992, A geologic assessment of nat- of Subsurface Data for providing well data. basin-centered gas systems: U.S. Geological Sur- ural gas from coal seams in the Raton and Ver- Christopher Haley, Johanna Abney, and vey, Bulletin 2184-B, pp. 1–14. mejo Formations, Raton Basin: Gas Research Matthew Herrin assisted in gathering, Jurich, D., and Adams, M. A., 1984, Geologic Institute, Report GRI-92/0345, 84 pp. compiling, and checking database infor- overview, coal, and coalbed methane resources of Tyler, R., Kaiser, W. R., Scott, A. R., Hamilton, D. S., mation and references. Leo Gabaldon (car- Raton Mesa region—Colorado and New Mexico; and Ambrose, W. A., 1995, Geologic and hydro- in Rightmire, C. T., Eddy, G. E., and Kirr, J. N. logic assessment of natural gas from coal— tography), Nancy Gilson and Jane Love (eds.), Coalbed methane resources of the United Greater Green River, Piceance, Powder River, and (editors) provided graphic and editorial States: American Association of Petroleum Geol- Raton Basins, western United States: The Univer- assistance. Funding for this project is ogists, Studies in Geology 17, pp. 163–184. sity of Texas at Austin, Bureau of Economic Geol- derived from the New Mexico Bureau of Kaiser Steel Corporation, 1976, Underground and ogy, Report of Investigations 228, 217 pp. Geology and Mineral Resources and the surface operations at the York Canyon mine; in Tweto, O., 1979, Geologic map of Colorado: U.S. Carson National Forest. We thank review- Ewing, R. C., and Kues, B. S. (eds.), Vermejo Park, Geological Survey in cooperation with the Col- northeastern New Mexico: New Mexico Geologi- orado Geological Survey, scale 1:500,000. ers Greer Price, James O’Hara, and Scott cal Society, Guidebook 27, pp. 253–255. Wanek, A. A., 1963, Geology and fuel resources of Cooper for their suggestions to improve Knowlton , F. H., 1917, Fossil floras of the Vermejo the southwestern part of the Raton coal field, Col- the manuscript. and Raton formations of Colorado and New fax County, New Mexico: U.S. Geological Survey, Mexico; in Lee, W. T., and Knowlton, F. H. (eds.), Coal Investigation Map 45. Geology and paleontology of Raton Mesa and Whitehead, N. H., 1991, Coal-bed methane in New References other regions in Colorado and New Mexico: U.S. Mexico: New Mexico Geology, v. 13, no. 4, pp. Geological Survey, Professional Paper 101, pp. 82–88. Baltz, E. H., 1965, Stratigraphy and history of Raton 9–221. Woodward, L. A., 1984, Potential for significant oil Basin and notes on San Luis Basin, Colorado– Lee, W. T., 1917, Geology of the Raton Mesa and and gas fracture reservoirs in Cretaceous rocks of New Mexico: American Association of Petrole- other regions in Colorado and New Mexico; in Raton Basin, New Mexico: American Association um Geologists, Bulletin, v. 49, no. 11, pp. Lee, W. T., and Knowlton, F. H. (eds.), Geology Petroleum Geologists, Bulletin, v. 68, no. 5, pp. 2041–2075. and paleontology of Raton Mesa and other 628–636. Close, J. C., 1988, Coal-bed methane potential of the regions in Colorado and New Mexico: U.S. Geo-

110 NEW MEXICO GEOLOGY November 2003, Volume 25, Number 4