Central-northern Appalachian coalbed methane flow grows

July 7, 1997
Over the past decade in the U.S., coalbed methane (CBM) has become an increasingly important source of unconventional natural gas. The most significant CBM production occurs in the San Juan basin of Colorado and New Mexico and the Black Warrior basin of Alabama ( Fig. 1 [65359 bytes] ), which collectively in 1995 accounted for about 94% of U.S. CBM production. 1
Paul C. Lyons
U.S. Geological Survey Reston, Va
Over the past decade in the U.S., coalbed methane (CBM) has become an increasingly important source of unconventional natural gas. The most significant CBM production occurs in the San Juan basin of Colorado and New Mexico and the Black Warrior basin of Alabama ( Fig. 1 [65359 bytes]), which collectively in 1995 accounted for about 94% of U.S. CBM production. 1

During the early 1980s to early 1990s, CBM exploration and development was stimulated by the federal Windfall Profit Act of 1980 (Nonconventional Fuels Tax Credit under Sec. 29) for wells drilled between Dec. 31, 1979, and Dec. 31, 1992. Under this act, tax credits, which amounted to as much as almost half of the market value of the gas in 1992, were tied to inflation.

In 1991 with the passage of the Gas and Oil Act in Virginia, clarification of ownership rights spurred development of CBM in Virginia (Table 1 [24643 bytes]). This act states: "When there are conflicting claims to the ownership of coalbed methane gas, the Board, upon application from any claimant, shall enter an order pooling all interest or estates in the coalbed methane drilling unit for the development and operation thereof."

Early CBM production

In the northern Appalachian basin of northern West Virginia, Pennsylvania, Ohio, and Maryland (Fig. 1), CBM has been produced from the Pittsburgh coal bed in commercial quantities since 1932 and 1956 in Big Run and Pine Grove fields, respectively, of Wetzel County, W. Va.2-3 Cumulative unstimulated gas production (until 1982) from about 52 wells in Big Run field was about 2 bcf at typical production rates of about 38 Mcfd.4 CBM production from the Pittsburgh, Clarion, Kittannings, and other Allegheny formation coal beds in the northern Appalachian basin involved eight historic projects (1932-80).5

There are records of three CBM wells in Harlan County, Ky., that produced during 1957-80.6 Historic production (1970-88) for the central Appalachian basin of Virginia, Tennessee, eastern Kentucky, and southern West Virginia (Fig. 1) also has been summarized.5 In Virginia, CBM has been produced in commercial quantities in the Southwest Virginia coalfield since 19887 (Fig. 2 [24136 bytes]).

At the end of 1995, the Black Warrior basin of Alabama, had cumulative CBM production of about 615,652 MMcf.8 In the Cahaba coal field of Alabama (Fig. 1) in the southern Appalachian basin, CBM production began in 1990, 10 years after the beginning of CBM production in the Black Warrior basin (Fig. 2). Cumulative CBM production (1990-95) in the Cahaba coal field was about 2,907 MMcf.8

Recent production

In 1995, CBM production in the U.S. was 973 bcf, of which the Appalachian basin (including the Black Warrior basin 8) accounted for nearly 144 bcf (Table 1). In the central Appalachian basin, low well costs and attractive wellhead gas prices spurred continued CBM development, even without tax support after 1992.

In the northern Appalachian basin, CBM wells are shallow (generally less than 1,000 ft) and generally near an anticlinal structure.3

In 1992, about 272 new CBM wells in Virginia were completed.9 Individual wells at depths up to 2,680 ft were producing as much as 356 Mcf/day. For 1994, the average daily production rate for CBM wells in Virginia was 119.6 Mcfd, and the average price for CBM in Virginia was $2.16 Mcf.9 For 1995, CBM production data for all states in the northern and central Appalachian basin is estimated here at nearly 31.3 bcf (Table 1, Fig. 2).

For 1992-95, 86% to 94% of central and northern Appalachian CBM production came from southwestern Virginia, which reflects a lack of CBM development in Appalachian states with large coal resources such as Pennsylvania, Ohio, and West Virginia. For these years there is a clear increase in the percentage of CBM being produced in the central and northern Appalachian basin as compared with the Warrior basin of Alabama,8 ranging from 7% of the total Appalachian CBM production in 1992 to 22% in 1995 (Table 1, Fig. 2).

This trend indicates the increasing importance of central Appalachian CBM, especially Virginia CBM. Production of CBM in Virginia comes mainly from Nora (Dickenson and Russell counties) and Oakwood (Buchanan County) fields. As of April 1996, 708 CBM wells were producing in Virginia.9 The principal producers are Equitable Resources Exploration (EREX), Pocahontas Gas Partnership, OXY USA, Consol Inc., and Island Creek Coal Co. In 1995, CBM production represented 61% of Virginia's natural gas production.7

In northern West Virginia for 1992-94, there is a record of production from seven CBM wells in Monongalia County, all producing from the Pittsburgh coal bed and averaging 36 Mcfd for 1994.10 The Pittsburgh wells in Wetzel County have been abandoned. Gob gas from the Pittsburgh coal mines was produced in both West Virginia and Pennsylvania through converted pre-mine ventilation wells.11 Gob wells produce gas from the collapsed overburden at underground coal mines that use the longwall mining technique.

There was no CBM production in Tennessee, Ohio, and Maryland for 1992-94. At present, there are no plans for CBM development in Tennessee and Maryland. There was one CBM well (Equitable KF1300 test well) producing in eastern Kentucky for this period, but production data for this well (estimated here at 90 Mcfd, Table 1) are not available.6

Gas composition

In Virginia, coalbed gas contains an average of 96.6% methane and has an average gross calorific value of about 990 BTU/cu ft. 5 There is as much as 2% CO2 and 4% heavier gases (mainly ethane) in coalbed gas in Virginia. 12 In Greene County, Pa., coalbed gas contains 94% methane with a similar gross calorific value of 979 BTU/scf as reported from a CBM well; the remaining 6% consists of ethane, propane, butane, pentane, nitrogen, and carbon dioxide. 12-14

Undiscovered potential

The greatest potential for undiscovered CBM in the central and northern Appalachian basin is in West Virginia, Pennsylvania (including the Anthracite region), Ohio, and Virginia (including the Valley coal fields). Estimated in-place CBM resources in the central (5.0 tcf) and northern (61.0 tcf) Appalachian basin total 66.0 tcf,12-14 as compared with an estimated 2 tcf for the Cahaba and 20 tcf for the Black Warrior basin in the southern Appalachian basin. The amounts of technically recoverable CBM resources in these areas12 are shown (Table 2 [10617 bytes]).

The greatest potential for CBM development in the central Appalachian basin is in the Lower Pennsylvanian Pocahontas coal beds, which have total gas values as much as 660 cf/ton, and New River coal beds of Virginia and southern West Virginia.15 In the northern Appalachian basin, the largest CBM potential is in Middle Pennsylvanian Allegheny formation coal beds (which have total gas values as much as 252 cf/ton) and Upper Pennsylvanian Pittsburgh, Redstone, Sewickley, and Waynesburg coal beds of West Virginia and Pennsylvania.16

In southeastern West Virginia, 10 new CBM wells were permitted in Wyoming, Raleigh, and McDowell counties in 1995 and another 10 new CBM permits were issued in 1996.17 These wells will be producing mainly from the Pocahontas No. 3 and No. 4 coal beds.

In Virginia, the principal known CBM reservoirs are the Lower Pennsylvanian Pocahontas formation and Lee formation coal beds at depths of 500-3,000 ft.1 The target coal beds for CBM in the central Appalachian basin are dominantly low volatile bituminous coal.5

Natural fractures in coal (cleats) are the principal conduits for the transfer of methane from coal reservoirs. In the central and northern Appalachian basin, face and butt cleats are perpendicular and parallel, respectively, to fold axes.18 The permeabilities vary from 5-27 md for the Pocahontas No. 3 coal bed in the central Appalachian as compared to much lower permeabilities of 0.25-0.64 md for the Mahoning and Lower Kittanning coal beds in the northern Appalachian basin.6 In the Anthracite region of eastern Pennsylvania, Law19 reported that cleat systems are absent or poorly developed and mineral-filled, and this will undoubtedly be a major factor in preventing CBM development in some parts of that region.

In Pennsylvania, an estimated 30 new CBM wells were expected to be drilled in 1996-97 by BTI Energy, Canton Oil & Gas Co., Belden & Blake, Equitable Resources, LAHD Energy, Jesmar Energy, CNG Producing, and the M.L. Minter Family.20

New E&D areas

In southern West Virginia, there is substantial potential for CBM development from the Pocahontas coal beds. The average gas content in Wyoming and Raleigh counties, W. Va., is 385 and 322 cf/ton,21 respectively, which indicates a high potential for CBM development. The number of new CBM wells in these counties has been increasing over the last few years, which reflects the beginning of important new CBM development in this part of the central Appalachian basin.

There is unknown CBM potential in southeastern Kentucky. The coal is mainly of high volatile A bituminous rank and has gas content of as much as 127 cf/ton at depths of 650-800 ft in Clay County.21 However, there is insufficient gas-test information in many areas of southeastern Kentucky and, thus, more CBM gas tests are necessary to determine CBM potential.

In the Cumberland plateau of Tennessee, there are deep coal beds that may have CBM potential.22-23 The thicker coal beds, which are generally 3.5-4.5 ft thick, are the Windrock, Joyner, Poplar Creek, Wilder, and Sewanee coal beds. These coals are of high volatile A and B bituminous rank.

Ohio has a fair potential for CBM development from Allegheny coal beds underneath Monongahela and Dunkard strata,24 immediately west of the Ohio River. Total thickness of Allegheny coals of high volatile A/B biutminous rank is as much as 18 ft in places.

The CBM potential of the Anthracite region of Pennsylvania has not been determined. Two core holes were drilled in the mid-1970s,25 and desorption data are available.26 Very high gas contents of 602-692 cf/ton are known for the Peach Mountain coal bed in Schuylkill County at a depth of 685 ft.21 There are also other data21 showing very low CBM contents for the Orchard coal bed (6-29 cf/ton) in the same county. The Tunnel coal bed also has high total gas contents (448-586 cf/ton).21 These data suggest a possibility for CBM development in some parts of this region where permeability and structural controls are favorable.

Maryland has no gas-content measurements available, but its CBM resources need to be determined. The Georges Creek coal field of Maryland holds the greatest CBM potential for Maryland coal fields because of its thick coals of low volatile bituminous rank and thick sedimentary cover, as much as about 2,000 ft locally.

Conclusions

Except in Alabama and Virginia, CBM is mainly an undeveloped natural gas resource in the Appalachian basin. In 1995, as shown in Table 1 and Fig. 2, nearly 144 bcf of CBM was produced in the Appalachian basin (including the Black Warrior basin) at a value of about $260 million. 27

During 1992-95, CBM production in the central and northern Appalachian basin quadupled to nearly 31.3 bcf/year (Table 1, Fig. 2) at a value of over $55 mil- lion,27which represents only about 0.2% of the estimated technically recoverable CBM resource.12

Legal matters of CBM ownership and environmental problems such as water disposal will be important issues to resolve in the various Appalachian states. "The Energy Policy Act of 1992 requires the Interior Secretary to administer a federal program to regulate coalbed methane in states where..." ownership disputes have impeded development.28 These states in 1995 included Kentucky, Pennsylvania, and Tennessee; Ohio was recently removed from the list of affected states.

The abatement of me- thane, a well-known greenhouse gas, from coal beds and coal mines due to CBM production may also have a beneficial affect on coal-mine safety.

CBM development in the Appalachian states could also reduce U.S. dependence on high-sulfur coal and will provide what many people consider a clean source of fossil fuel. It is also likely the demand for gas in the Northeast will increase, and cost-effective CBM recoverability technology could keep CBM competitive with conventional gas prices.29 Further details on Appalachian CBM are given in Lyons.30

Acknowledgments

Thanks to: The staff of the various corporations, operators, state geological surveys, and oil and gas boards for contributing information to this report; E.D. Attanasi, U.S. Geological Survey, for providing information on wellhead values used in the preparation of this report; and A.K. Markowski, Pennsylvania Topographic and Geologic Survey, for reviewing this article.

References

1. Stevens, S.H., Kuuskraa, J.A., and Schraufnagel, R.A., Technology spurs growth of U.S. coalbed methane, OGJ, Jan. 1, 1996, pp. 56-63.

2. Repine, T.E., Jr., Coalbed methane-A new West Virginia industry?, Mountain State Geology, Spring, 1990, pp. 6-7.

3. Patchen, D.G., Schwietering, J.F., Avary, K.L., and Repine, T.E., Coalbed gas production, Big Run and Pine Grove fields, Wetzel County, W. Va., West Virginia Geological and Economic Survey Publication C-44, 1991, 33 p.

4. Hunt, A.M. and Steele, D.J., Coalbed methane development in the northern and central Appalachian basins-past, present, and future, in Proceedings, 1991 Coalbed methane Symposium: University of Alabama, Tuscaloosa, 1991, pp. 127-141.

5. Hunt, A.M., and Steele, D.J., Coalbed methane development in the Appalachian basin: Quarterly Review of Methane from Coal Seams Technology 1, No. 4, July, 1991, pp. 10-19.

6. B.C. Nuttall, Kentucky Geological Survey, personal comm., April 1996.

7. Nolde, J.E., Coalbed methane in Virginia, Virginia Minerals, Vol. 41, No. 1, February 1995, pp. 1-7.

8. J.C. Pashin, Alabama Geological Survey, personal comm., April-May, 1996.

9. Jack Nolde, Virginia Division of Mineral Reseources, personal comm., March-June, 1996.

10. Avary, K.L., West Virginia Geological and Economic Survey, personal comm., April, 1996.

11. Bruner, K.R., Oldham, A.V., Repine, T.E., Markowski, A.K., and Harper, J.A., Geological aspects of coalbed methane in the northern Appalachian coal basin, southwestern Pennsylvania and north-central West Virginia, Topical Report (August 1990-August 1993), Gas Research Institute, Chicago, Ill., 1995, 72 p.

12. Rice, D.D., Geologic framework and description of coal-bed gas plays, in Gautier, D.L., Dolton, G.L., Takahashi, K.I., and Varnes, K.L., eds., National Assessment of U.S. Oil and Gas Resources: Results, methodology, and supporting data, U.S. Geological Survey Digital Data Series DDS-30, 1995, 103 p., maps.

13. Markowski, A.K., Reconnaissance of gas contents and geological aspects of the coalbed methane resources in Pennsylvania, Pennsylvania Topographic and Geologic Survey, 4th ser., Open-File Report 95-09, 1995, 16 p.

14. West Virginia Geological and Economic Survey and Pennsylvania Topographic and Geologic Survey, Geological aspects of coalbed methane occurrence in the Northern Appalachian Coal Basin: Gas Research Institute Contract No. 5091-214-2261, 1993, 86 p.

15. Kelafant, J.R., and Boyer, C.M., A geologic assessment of natural gas from coal seams in the central Appalachian basin, Gas Research Institute, 1988, 66 p.

16. Adams, M.A., Eddy, G.E., Hewitt, J.L., Kirr, J.N., and Rightmire, C.T., Geological overview, coal resources, and potential methane recovery from coalbeds of the Northern Appalachian Coal Basin-Pennsylvania, Ohio, Maryland, West Virginia, and Kentucky, in Rightmire, C.T., Eddy, G.E., and Kirr, J.N., eds., Coalbed methane resources of the U.S., AAPG Studies in Geology No. 17, 1984, pp. 15-71.

17. Avary, K.L., West Virginia Geological and Economic Survey, personal comm., April 1996.

18. McCulloch, C.M., Deul, M., and Jeran, P.W., Cleat in bituminous coalbeds, U.S. Bureau of Mines, Report of Investigations 7910, 1974, 23 p.

19. Law, B.E., The relationship between coal rank and cleat spacing: Implications for the prediction of permeability in coal, Proceedings of the 1993 International Coalbed Methane Symposium, The University of Alabama, Tuscaloosa, May 17-21, 1993, pp. 435-441.

20. A.K. Markowski, Pennsylvania Topographic and Geologic Survey, personal comm., April-June, 1996.

21. Diamond, W.P., LaScola, J.C., and Hyman, D.M., Results of direct-method determination of the gas content of U.S. coalbeds, U.S. Bureau of Mines Information Circular 9067, 1986, 95 p.

22. Wilson, C.W., Jr., Jewell, J.W., and Luther, E.T., Pennsylvanian geology of the Cumberland Plateau, Tennessee Department of Conservation, Division of Geology, Folio, 1956, 21 p.

23. Luther, E.T., The coal industry of Tennessee, Tennessee Department of Conservation and Commerce, Division of Geology, Information Circular No. 10, 1960, 58 p.

24. Couchot, M.L., Crowell, D.L., Van Horn, R.G., and Struble, R.A., Investigation of the deep coal resources of portions of Belmont, Guernsey, Monroe, Noble, and Washington Counties, Ohio, Ohio Department of Natural Resources, Report of Investigations No. 116, 1980, 49 p.

25. J.R. Levine, Consulting geologist, Tuscaloosa, Alabama, personal comm., April, 1996.

26. Diamond, W.P., and Levine, J.R., Direct method determination of the gas content of coal, procedures and results, U.S. Bureau of Mines Report of Investigation 8515, 1981, 36 p.

27. Data for West Virginia, Pennsylvania, and Kentucky from U.S. Department of Energy, Natural Gas Annual 1995, November 1996, p. 17; data for Virginia from Jack Nolde, Virginia Division of Mineral Resources.

28. Petroleum Information Corp., Ohio removed from list of affected coalbed methane states: Appalachian Basin Report, Section, Vol. 34, No. 8,. 1995, p. 11.

29. Steele, D.J., Coalbed methane technology development in the Appalachian basin, Quarterly Review of Methane from Coal Seams Technology, Vol. 7, No. 4, July, 1990, p. 23.

30. Lyons, P.C., Coalbed methane potential in the Appalachian states of Pennsylvania, West Virginia, Maryland, Ohio, Virginia, Kentucky, and Tennessee-An overview, U.S. Geological Survey, Open-File Report 96-735, 1996, 58 p., 8 figs.

31. Tully, J., Coal fields of the conterminous United States, U.S. Geological Survey, Open-File Report No. 96-92, 1996, scale 1:5,000,000.

Publication

The Geological Interpretation of Well Logs, Second Edition, by Malcolm Rider, published by Gulf Publishing Co., Box 2608, Houston, Tex. 77001. 280 p., $65 plus shipping.

The principal open hole logging tools are considered from theory to data acquisition and interpretations, and new versions of old tools are included.

The book has a geological emphasis that makes it ideal for the geologist or sedimentologist using logs or anyone in industry or academia who requires an understanding of the basics of logs and recent advances in technology.

Jurassic Reef Play: East Texas Basin, by Scott Montgomery, published by Petroleum Information/Dwights LLC, 1675 Broadway, Suite 700, Denver, Colo. 80202. 82 p., $58.

This geological overview of the hot East Texas gas play concludes that drilling for the Upper Jurassic reef reservoirs remains at an early stage.

Expansion of the reef play will have immediate implications for exploration in North Louisiana and Mississippi.

The Author

Paul C. Lyons is a research geologist with the U.S. Geological Survey. His current assignment is Appalachian coalbed methane. He has been the senior editor of eight volumes of scientific papers and is on the International Journal of Coal Geology editorial board. He received a PhD in geology from Boston University.

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