A Preliminary Assessment of in Place Coalbed

8/14/2019 A Preliminary Assessment of in Place Coalbed

1/22

.International Journal of Coal Geology 38 1998 115136

A preliminary assessment of in place coalbedmethane resources in the Virginia portion of the

central Appalachian Basin

Jack E. Nolde)

, David SpearsVirginia Diision of Mineral Resources, P.O. Box 3667, Charlottesille, VA 22903, USA

Received 2 May 1997; accepted 1 July 1998

Abstract

In the central Appalachian basin, Virginia leads in coalbed methane drilling and production,

even though it only contains a small fraction of the total coal resources and basin area. In 1992,

coalbed methane surpassed conventional and shale gas as Virginias largest source of natural gas.By the end of 1996 there were 814 wells producing coalbed methane in Virginia. Average daily

3.production per well in 1996 was 114 Mcf 3.2 Mm . Cumulative production of coalbed methane 3.from 1988 through 1996 is 121,542,188 Mcf 3,445,073 Mm . Factors influencing this trend

include the presence of abundant coal in place including coal remaining in ground after mining,

sufficient overburden, high gas-content coal beds, high gas permeability, existing pipeline

infrastructure, and legislative clarification of uncertain coalbed gas ownership. Development of

coalbed methane in Virginia began in late 1988. Production is from coal beds in the southwestern

Virginia coalfield, a structurally distinct area along the southeastern margin of the central

Appalachian basin. Ten coal beds within the Lower Pennsylvanian Pocahontas and Lee Forma-

tions and the Lower Pennsylvanian portion of the Norton Formation have been targeted for

production of coalbed methane. Estimated coal in place for these coal beds is about 14.9 billion3 3 . 3short tons. Estimated gas contents of the coal beds range from 256 ft 7.9 m rt to 698 ft rton

3 . 21.5 m rt . These data yield an estimated in-place coalbed methane resource of 6.7 Tcf 0.183.Tm for Virginia. The U.S. Geological Survey reported the in-place coalbed methane resource for

3. 3.the entire central Appalachian basin to be 5 Tcf 0.13 Tm , with 3.07 Tcf 0.08 Tm technically 3.recoverable. An estimated in-place coalbed methane of 6.7 Tcf 0.18 Tm is more compatible

with 3.07 Tcf of technically recoverable coalbed methane for the central Appalachian basin.

q 1998 Elsevier Science B.V. All rights reserved.

Keywords: Central Appalachian Basin; coalbed methane resources; Virginia

)

Corresponding author. Tel.: q1-804-293-5121; Fax: q1-804-293-2239

0166-5162r98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved. .P I I : S 0 1 6 6 - 5 1 6 2 9 8 0 0 0 3 5 - 4


2/22

( )J.E. Nolde, D. Spearsr International Journal of Coal Geology 38 1998 115136116

1. Introduction

.The central Appalachian basin, as defined by Adams et al. 1982 covers an area of2 2 .nearly 23,000 mile 59,500 km in Virginia, West Virginia, Kentucky, and Tennessee.

.The Virginia portion Fig. 1 , known as the southwestern Virginia coalfield, lies at the

southeastern margin of the basin, where the basin is bounded by the southern Ap-palachian thrust belt. The southwestern Virginia coalfield covers an area of approxi-

2 2 .mately 1520 mile 3,937 km , only 7% of the total central Appalachian basin area.

Nevertheless, Virginia contains about 96% of this part of the basins producing coalbed

methane wells. In the southwestern Virginia coalfield, coal and coalbed methane are .produced in Buchanan, Dickenson, Russell, and Wise Counties Fig. 2 . .At least 57 minable coal beds occur in southwestern Virginia Nolde, 1994 . Of these,

10 of the deeper coal beds are currently the targets for coalbed methane development. .These coal beds are, in ascending stratigraphic order Fig. 3 , Pocahontas No. 3,

Pocahontas No. 6, Pocahontas No. 9, Lower Horsepen, Fire Creek, War Creek, MiddleHorsepen, Upper Horsepen, Greasy Creek, and Upper Seaboard. Estimated coal re-

sources for these coal beds amounts to 14.9 billion short tons.

The release of methane gas in coal beds is a serious safety hazard to underground

miners. Since 1884, underground mine accidents related to methane gas have occasion-

Fig. 1. Index map showing location of study area with respect to part of the northern and southern Appalachian . .basin stipple and the central Appalachian basin heavy stipple .


3/22

( )J.E. Nolde, D. Spearsr International Journal of Coal Geology 38 1998 115136 117

.Fig. 2. Map showing coalbed methane pools hachured and major structural features in the southwestern

Virginia coalfield.

ally killed or injured miners and interfered with coal mining in southwestern Virginia. In

that year, an explosion in an underground mine near the Town of Pocahontas killed 114 .miners Harnsberger, 1919 . Modern mine safety practices, including ventilation of

methane gas, have reduced the risk, but have not eliminated accidents. As recently as

1994, an explosion attributed to methane gas occurred in a mine in south-central

Buchanan County.In southwestern Virginia, natural gas has been produced from Devonian and Missis-

.sippian rocks since 1948 Huddle et al., 1956 . Coalbed methane production in the .overlying Pennsylvanian rocks began in 1988 Nolde, 1995 . Cumulative coalbed

methane production in Virginia for 1988 through 1996 is 121,542,188 Mcf 3,445,0733. .Mm Table 1 . Current calculations of coal in place and gas content data suggest that

3.there is 6.7 Tcf 0.18 Tm of in-place coalbed methane resources in Virginia.

This paper presents a overview of our present knowledge of the coalbed methane

resources of southwestern Virginia. After first outlining the history of development and

production and the methodology used to determine the methane resource, the strati-graphic setting of the resource is outlined. The subsurface distribution and significance

of the ten coal beds is outlined. Conclusions are drawn as to why Virginia dominatescoalbed methane production in the central and northern Appalachian basin see Lyons,

.1997 .

1.1. Methodology

Data for the present study are from published geologic maps and approximately 900coalbed methane wells and coal-exploration holes. As part of a continuing study of the

subsurface geology of the southwestern Virginia coalfield, coal distribution and thick-

ness maps were compiled for each of the ten coal beds that are targets for coalbed


4/22

Fig. 3. Generalized NWSE stratigraphic cross-section across the central portion if the southwestern Virginia coalfie.lithic arenite .


5/22


Table 1 .Coalbed methane production statistics thousand cubic feet, Mcf for Virginia, 1988 to 1996

Year Number of Annual gas Average monthly Average daily Cumulative

gas wells production gas production gas production gas production . . . .Mcf Mcf Mcf Mcf

1988 2 11,856 494 16 11,8561989 10 181,526 1513 50 193,382

1990 39 799,569 1708 56 992,951

1991 85 1,142,651 1120 37 2,135,602

1992 277 6,641,852 1998 66 8,777,454

1993 465 19,923,463 3570 117 28,700,917

1994 492 28,331,817 4799 158 57,032,734

1995 681 30,355,870 3715 122 87,388,604

1996 814 34,153,584 3496 114 121,542,188

methane development. The following procedure was used to estimate coal volumes.

Coal bed distribution and isopach maps were generated using Dynamic Graphics .Interactive Surface Modeling ISM software. The isopach interval was set at 14 in.

.Overburden maps with a contour interval of 500 ft 152 m were overlain onto the coal

distribution and isopach maps to eliminate from tonnage calculations areas under less . .than 500 ft 152 m of cover Table 2 and areas with coal less than 14 in. thickness. A

.minimum depth of 500 ft 152 m is generally required for coal to contain any .appreciable amount of gas in place Kelafant and Boyer, 1988; Rice, 1995 . Polygons

delineating the various thickness and overburden categories were constructed. The endproduct was a map color-coded so that polygons for each category could be distin-

guished. The area, in acres, was digitized for each polygon using the US Geological . .Surveys GSDIG program Selner and Taylor, 1992 . Coal tonnages Table 2 were then

calculated by multiplying the number of acres by the median thickness of the coal bed .and the factor 1800 short tons per acre-foot 13,238 trha m . Only the Pocahontas No. 3

coal bed has been mined and its mined-out area was subtracted from the estimate for

coal in place.

Gas-content data for 65 coal samples from the central Appalachian basin were .

published by Diamond and Levine 1981 . Sixty-one of these coal samples are of lowvolatile bituminous rank, and the remaining four samples are of medium volatile

bituminous rank. The desorption values for the 61 low volatile bituminous coal samples .Fig. 4 were used to determine the linear regression equation representing the change in

gas content with depth:

gas content ft3rton s152q0.2=depth ft . .

This equation was used to estimate gas contents for the target coal beds, which aresummarized in Table 3. Estimated gas contents range from about 256 cu ft per ton 7.9

3 . 3 3 .m rt to as much as 698 ft rton 21.5 m rt .

The following formula was used to calculate the in-place coalbed methane resource:

Gas resourcess coal density = median coal thickness . .

= gas content = area . .


6/22


Table 2 .Estimated coal resources million short tons for target coalbed methane beds

.Coal bed and Overburden category ft Mined or Estimated

thickness lost in coal5001000 10001500 15002000 20002500 )2500 .category in. mining resource

Pocahontas No. 31428 0.00 50.45 10.93 46.01 5.52 0.00 112.91

2842 42.57 56.94 171.91 30.45 0.52 0.00 302.39

)42 0.00 32.28 1,377.57 79.77 0.00y 0.21 1,489.41

Total 42.57 139.67 1,560.41 156.23 6.04 0.00 1,904.71

Pocahontas No. 6

1428 0.00 49.15 35.67 150.10 18.02 0.00 252.94

2842 40.93 54.73 165.27 29.27 5.00 0.00 295.20

)42 0.00 26.65 1,137.47 65.87 0.00 0.00 1,229.99

Total 40.93 130.53 1,338.41 245.24 23.02 0.00 1,778.13

Pocahontas No. 9

1428 53.24 283.39 217.25 6.88 0.00 0.00 560.76

2842 48.67 111.24 168.74 0.00 0.00 0.00 328.65

)42 0.00 66.67 0.00 0.00 0.00 0.00 66.67

Total 101.91 461.30 385.99 6.88 0.00 0.00 956.08

Lower Horsepen

1428 88.20 318.63 367.58 70.80 0.00 0.00 845.21

2842 59.64 135.75 249.95 206.54 0.00 0.00 651.88

)42 0.00 29.65 118.29 92.48 0.00 0.00 240.42

Total 147.84 484.03 735.82 369.82 0.00 0.00 1,737.51

Fire Creek

1428 10.19 211.46 58.19 26.28 0.00 0.00 306.12

2842 42.70 207.53 158.37 157.76 0.00 0.00 566.36

)42 11.14 41.02 70.89 105.58 0.00 0.00 228.63

Total 64.03 460.01 287.45 289.62 0.00 0.00 1,101.11

War Creek

1428 17.58 364.63 100.35 45.32 0.00 0.00 527.88

2842 56.14 331.52 216.65 183.72 0.00 0.00 788.03

)42 79.46 150.87 260.76 388.31 0.00 0.00 879.40

Total 153.18 847.02 577.76 617.35 0.00 0.00 2,195.31

Middle Horsepen

1428 130.96 545.09 89.23 0.00 0.00 0.00 765.28

2842 111.14 399.96 101.15 14.74 0.00 0.00 626.99

)42 0.00 26.62 0.00 0.00 0.00 0.00 26.62

Total 242.10 971.67 190.38 14.74 0.00 0.00 1,418.89

Upper Horsepen

1428 0.00 522.09 263.25 0.00 0.00 0.00 785.34

2842 59.99 236.40 86.13 0.00 0.00 0.00 382.52

)

42 0.00 73.01 18.86 0.00 0.00 0.00 91.87Total 59.99 831.50 368.24 0.00 0.00 0.00 1,259.73


7/22


.Table 2 continued

.Coal bed and Overburden category ft Mined or Estimated

thickness lost in coal5001000 10001500 15002000 20002500 )2500 .category in. mining resource

Greasy Creek

1428 640.95 398.78 40.56 0.00 0.00 0.00 1080.292842 0.00 143.36 61.96 0.00 0.00 0.00 205.32

)42 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Total 640.95 542.14 102.52 0.00 0.00 0.00 1285.61

Upper Seaboard

1428 700.10 398.78 40.56 0.00 0.00 0.00 1139.44

2842 0.00 130.32 56.33 0.00 0.00 0.00 186.65

)42 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Total 700.10 529.10 96.89 0.00 0.00 0.00 1,326.09

Grand Total 2193.60 5396.97 5643.87 1699.88 29.06y 0.21 14,963.17

.The gas resource estimates are in units of trillion cubic feet Tcf . All calculated

values are resources or in-place gas, rather than reserves or recoverable gas. In-place

coal estimates and gas contents were used to determine the coalbed methane resources

for the 10 target coal beds.

2. Structural setting

The southwestern Virginia coalfield lies along the southeastern margin of the central .Appalachian basin Fig. 1 . The coalfield is partly within the Cumberland overthrust

block, a large thrust sheet that extends from southwestern West Virginia, through

.Fig. 4. Gas content vs. depth for central Appalachian basin coal beds data from Diamond and Levine, 1981 .


8/22


Table 3 .Estimated coalbed methane resources trillion cubic feet, Tcf for target coal beds by overburden category,

0.12 Tcf gas has been produced from 1988 to 1996

.Coal bed and thickness Overburden category ft Estimated gas . .category inches resource Tcf 5001000 10001500 15002000 20002500 )2500

Pocahontas No. 31428 0.00 0.02 0.01 0.03 0.01 0.07

2842 0.01 0.02 0.09 0.02 0.00 0.14

)42 0.00 0.01 0.69 0.05 0.00 0.75

total 0.01 0.05 0.79 0.10 0.01 0.96

Pocahontas No. 6

1428 0.00 0.02 0.02 0.09 0.01 0.14

2842 0.01 0.02 0.08 0.02 0.01 0.14

)42 0.00 0.01 0.57 0.04 0.00 0.62

total 0.01 0.05 0.67 0.15 0.02 0.90

Pocahontas No. 9

1428 0.02 0.11 0.11 0.01 0.00 0.25

2842 0.02 0.04 0.09 0.00 0.00 0.15

)42 0.00 0.03 0.00 0.00 0.00 0.03

total 0.04 0.18 0.20 0.01 0.00 0.43

Lower Horsepen

1428 0.03 0.13 0.18 0.04 0.00 0.38

2842 0.02 0.05 0.13 0.12 0.00 0.32

)42 0.00 0.01 0.06 0.06 0.00 0.13

total 0.05 0.19 0.37 0.22 0.00 0.83

Fire Creek

1428 0.01 0.09 0.03 0.02 0.00 0.15

2842 0.01 0.08 0.08 0.10 0.00 0.27

)42 0.01 0.02 0.04 0.10 0.00 0.17

total 0.03 0.19 0.15 0.22 0.00 0.59

War Creek

1428 0.01 0.15 0.05 0.03 0.00 0.24

2842 0.02 0.13 0.11 0.11 0.00 0.37

)42 0.02 0.06 0.13 0.23 0.00 0.44

total 0.05 0.34 0.29 0.37 0.00 1.05

Middle Horsepen

1428 0.04 0.22 0.04 0.00 0.00 0.30

2842 0.03 0.16 0.05 0.01 0.00 0.25

)42 0.00 0.01 0.00 0.00 0.00 0.01

total 0.07 0.39 0.09 0.01 0.00 0.56

Upper Horsepen

1428 0.00 0.21 0.13 0.00 0.00 0.34

2842 0.02 0.09 0.04 0.00 0.00 0.15

)42 0.00 0.03 0.01 0.00 0.00 0.04total 0.02 0.33 0.18 0.00 0.00 0.53


9/22


.Table 3 continued

.Coal bed and thickness Overburden category ft Estimated gas . .category inches resource Tcf 5001000 10001500 15002000 20002500 )2500

Greasy Creek

1428 0.19 0.16 0.02 0.00 0.00 0.37

2842 0.00 0.06 0.03 0.00 0.00 0.09)42 0.00 0.00 0.00 0.00 0.00 0.00

total 0.19 0.22 0.05 0.00 0.00 0.46

Upper Seaboard

1428 0.21 0.16 0.02 0.00 0.00 0.39

2842 0.00 0.05 0.03 0.00 0.00 0.08

)42 0.00 0.00 0.00 0.00 0.00 0.00

total 0.21 0.21 0.05 0.00 0.00 0.47

Grand Total 0.68 2.15 2.84 1.08 0.03 6.78

.southwestern Virginia, and into Kentucky and Tennessee Henika, 1994 . The coalfield

is bounded on the southeast by closely spaced faults of the southern Appalachian thrustbelt. This belt consists of the Hunter Valley, St. Paul, and Richlands thrust faults Fig.

.2 . To the northwest, the Cumberland overthrust block is bounded by the Pine Mountain

fault, a low-angle thrust fault that extends beneath part of the coalfield. The Cumberland

thrust sheet is complicated by a number of internal structures, which include transverse .faults and gentle folds Henika, 1994 . All of these structures are interpreted to have

been formed during the late Paleozoic Alleghany orogeny. Local structure does not

appear to influence coalbed methane production, except to the extent that syndeposi-

tional structures may have influenced the accumulation of coal.

3. Stratigraphic and tectonic overview

Paleozoic strata of the central Appalachian basin are related to the tectonic evolution

of the Paleozoic continental margin. The first phase started during late Precambrian

time, when rifting of Grenville-age crust resulted in the formation of a marginal ocean.Near the edge of the continent, a thick sequence of siliciclastic sediments was deposited.

Overlaying these basal siliciclastic rocks is a thick carbonate shelf deposit of Cambrian

and Ordovician age. This passive margin became active at the start of the Middle

Ordovician creating a foreland basin. This basin was filled with black muds and

turbidites. The lowering of source areas slowed siliciclastic input and a carbonate shelf

and bank was re-established. Carbonate deposition, with some quartzose sand and chert

formation, lasted until Late Devonian time. These sediments were covered by black

muds and turbidites of the Chattanooga Shale, during the Acadian orogeny. The upper

part of the sequence is the Price delta of Late Mississippian age, comprising the Priceand Maccrady Formations. This clastic sequence became inundated and a carbonate

shelf developed creating the muds forming the Late Mississippian Greenbrier Limestone.

As carbonate deposition slowed, red, green, gray muds, and sand of latest Mississippian


10/22


age were deposited, composing the Bluefield, Hinton, and Bluestone Formations. In

southwest Virginia, deep gas production comes from the Devonian and Mississippian .formations. These formations range in thickness from about 3400 ft 1036 m along the

.Kentucky and Virginia Boundary to as much as 5000 ft 1524 m in the northeastern

part of the coalfield. The Mississippian strata were in turn covered by a coal-bearing

clastic wedge during Early Pennsylvanian time, that resulted from Alleghany continentalcollision.

.These Lower Pennsylvanian rocks in the southwestern Virginia coalfield Fig. 3 , .range in thickness from 800 ft 244 m in the northeastern part of the coalfield to as

. .much as 5150 ft 1570 m in the southwestern part Nolde, 1994 . They have been

mapped as the Pocahontas and Lee Formations, and lower part of the Norton Formation.

The Pocahontas Formation contains coal beds in sequences of sandstone, siltstone,

and shale. The sandstones are medium to light gray, fine grained, micaceous and

feldspathic. The siltstones and shales are medium to dark gray, carbonaceous, and

contain abundant plant material. Major coal beds are the Pocahontas Nos. 3 and 6. ThePocahontas No. 3 coal bed is the thickest and most economically valuable coal in

Virginia. The strata between the base of the formation and the Pocahontas No. 3 coal .bed are as much as 225 ft 69 m thick and thin northwestward to where they were

eroded during deposition of the lower quartz arenite member of the Lee Formation.

Pocahontas-equivalent strata above the No. 3 coal bed intertongue with the lower quartz .arenite. These strata range from 300 to 500 ft 91 to 152 m in thick.

Strata between the base of the Pocahontas No. 8 coal bed and the Upper Seaboard

coal bed consist of laterally equivalent rocks assigned to the Lee Formation and the

lower part of the Norton Formation. The Lee Formation contains quartz arenites which .grade laterally to the southeast into lithic arenites in the Norton Formation Fig. 3 .

Principal coal beds in the Lee Formation are, in ascending order, Pocahontas No. 9,

Lower Horsepen, Fire Creek, War Creek, Middle Horsepen, Upper Horsepen, Greasy .Creek, and Upper Seaboard. This interval of strata averages 700 ft 213 m in thickness.

4. Target coal beds

The stratigraphy and distribution of the ten target coal beds are discussed briefly in

the following sections. Figs. 514 show the approximate area of distribution of these

coal beds, and Table 2 summarizes the estimated tonnage of coal in place. A preliminary

estimate of total gas in place in southwestern Virginia for the ten target coal beds is 6.7 3.Tcf 0.18 Tm . The top three coal beds with coalbed methane resources are Pocahontas

.No. 3, Lower Horsepen, and War Creek Table 3 . Coalbed methane distribution within .each of the various overburden intervals Table 4 indicates that 91% of the total gas in

.the coal bed occurs at depths from 1000 to 2500 ft 304 to 762 m . This interval also

.contains approximately 85% of the total coal in place Table 2 . As part of the 1995National Assessment of United States Oil and Gas Resources performed by the US

.Geological Survey, Rice 1995 reported the total in place coalbed methane resource for 3. 3.the central Appalachian basin to be 5 Tcf 0.13 Tm with 3.07 Tcf 0.08 Tm


11/22


Fig. 5. Map showing approximate extent of the Pocahontas No. 3 coal bed, beneath more than 500 ft of

overburden.

technically recoverable. Our data suggest that the U.S. Geological Survey in-place

coalbed methane resources for the central Appalachian basin should be revised upward.

4.1. Pocahontas No. 3 coal bed

.The Pocahontas No. 3 coal bed underlies about 367,500 acres 148,700 ha in the .southwestern Virginia coalfield Fig. 5 . The coal occurs primarily in the southeastern

.portion of the coalfield. The No. 3 coal bed lies from 1385 to 2587 ft 422 to 790 m


overburden.


12/22



overburden.

below drainage throughout most of the area. The Pocahontas No. 3 is about 225 ft 69.m above the Bluestone Formation in the southeastern part of the coalfield. The coal

. .bed, including partings, ranges from less than 1.0 ft 0.3 m to as much as 7.6 ft 2.3 m .

thick. The average thickness of the No. 3 coal bed is 3.4 ft 1 m . The No. 3 coal bed .thins to the northwest Fig. 5 , and is eventually truncated by an unconformity below the

lower quartz arenite member of the Lee Formation.

Fig. 8. Map showing approximate extent of the Lower Horsepen coal bed, beneath more than 500 ft of

overburden.


13/22


Fig. 9. Map showing approximate extent of the Fire Creek coal bed, beneath more than 500 ft of overburden.

The total estimated original volume of the Pocahontas No. 3 is 1.90 billion short tons.

Of this amount, 0.21 billion short tons has been mined and lost in mining. This yields an

estimate for the volume of coal of 1.69 billion short tons.


.The Pocahontas No. 6 coal bed covers an area of about 355,800 acres 143,900 ha in . .the southwestern Virginia coalfield Fig. 6 . The No. 6 coal bed lies about 200 ft 61 m

above the Pocahontas No. 3 coal bed and is limited to the southeastern parts of the

coalfield area. The interval between the Pocahontas No. 3 to No. 6 coal beds gradually

Fig. 10. Map showing approximate extent of the War Creek coal bed, beneath more than 500 ft of overburden.


14/22


Fig. 11. Map showing approximate extent of the Middle Horsepen coal bed, beneath more than 500 ft of

overburden.

.decreases westward to about 130 ft 40 m . Average thickness of the No. 6 coal bed is .1.4 ft 0.4 m . Northwestward, the No. 6 coal is replaced by the lower quartz arenite of

the Lee Formation. This yields an estimate for coal in place of 1.78 billion short tons.


.In southwestern Virginia, the Pocahontas No. 9 coal bed Fig. 7 covers an area of .about 383,400 acres 155,000 ha . In this area, the Pocahontas No. 9 coal bed lies 445 ft

.135 m above the Pocahontas No. 3 coal bed. Where the Pocahontas No. 6 coal is

Fig. 12. Map showing approximate extent of the Upper Horsepen coal bed, beneath more than 500 ft of

overburden.


15/22


Fig. 13. Map showing approximate extent of the Greasy Creek coal bed, beneath more than 500 ft of

overburden.

.absent, the Pocahontas No. 9 occurs about 70 ft 21 m above the lower quartz arenite

member of the Lee Formation. The average thickness of the Pocahontas No. 9 is 1.3 ft . .0.4 m . This yields an estimate for coal in place as 0.96 billion short tons Table 2 .

4.4. Lower Horsepen coal bed

.In southwestern Virginia, the Lower Horsepen coal bed Fig. 8 covers an area of . .about 567,900 acres 230,000 ha . The coal bed is about 300 ft 91 m above the top of

.the lower quartz arenite member of the Lee Formation and about 50 ft 15 m above the

Fig. 14. Map showing approximate extent of the Upper Seaboard coal bed, beneath more than 500 ft of

overburden.


16/22


Table 4 .Estimated coalbed methane resources trillion cubic feet, Tcf by overburden category, 0.12 Tcf of gas has

been produced from 1988 to 1996

Overburden Coal density Median coal Gas content Area Estimated gas3 3 . . . . . .category ft lbrft thickness ft ft rton acres resource Tcf

5001000 2000 2.01 302 559,569 0.6810001500 2000 1.91 402 1,399,958 2.15

15002000 2000 2.81 502 1,007,422 2.84

20002500 2000 2.65 602 338,289 1.08

)2500 2000 1.77 652 12,964 0.03

Total 6.78

Pocahontas No. 9 coal bed. The average thickness of the Lower Horsepen is 1.8 ft 0.55.m . This yields an estimate for coal in place of 1.74 billion short tons.

4.5. Fire Creek coal bed

.In southwestern Virginia, the Fire Creek coal bed Fig. 9 covers an area of about .367,900 acres 148,900 ha . The Fire Creek coal bed is limited to the southern part of

.the coalfield, where it lies 30 to 60 ft 9 to 18 m above the Lower Horsepen. In the

northeast part of the coalfield a sandstone occupies the Fire Creek coal interval.

The Fire Creek coal commonly consists of two splits, separated by as much as 15 ft .4.5 m of siltstone. The coal bed is well developed in the central part of the area where

.thicknesses of more than 3.5 ft 1.1 m are present. The coal has an average thickness of .2.3 ft 0.7 m . This yields an estimate for coal in place of 1.10 billion short tons.

4.6. War Creek coal bed

.In southwestern Virginia, the War Creek coal bed Fig. 10 covers an area of about . 588,300 acres 238,000 ha . In the coalfield area the War Creek is 600 to 700 ft 183 to

.213 m above the Pocahontas No. 3 coal bed.

The interval between the lower and middle quartz arenite members thins to the

. .northwest from about 400 ft 122 m to 100 ft 30 m and the War Creek lies near themiddle of that sequence. The War Creek coal bed is eventually replaced by the

northwestward-thickening and coalescing lower and middle quartz arenite members of

the Lee Formation.

Although the bed is rather extensive in areal distribution, the coal is not particularly

thick in the central and southern part of the coalfield. The War Creek coal bed has an .average thickness of 2.2 ft 0.7 m . This yields an estimate for coal in place of 2.19

billion short tons.

4.7. Middle Horsepen coal bed

.In southwestern Virginia, the Middle Horsepen coal bed Fig. 11 covers an area of . about 475,200 acres 207,500 ha . In the area, the Middle Horsepen is 110 to 120 ft 33


17/22


18/22


.coal has an average thickness of 1.6 ft 0.5 m . This yields an estimate for coal in place

of 1.33 billion short tons.

5. History of coalbed methane development

In 1973, TWM Petroleum entered into an agreement for the lease of oil and gas rights

on acreage owned by Island Creek Coal, a subsidiary of Occidental Petroleum. The

agreement was for drilling vertical ventilation holes into the deep mines in the

Pocahontas No. 3 coal bed in Buchanan County. The agreement expired in 1975. In

1978, Occidental Petroleum, working with the US Department of Energy, developed a

method for recovering methane from horizontal boreholes in the Virginia Pocahontas

No. 5 mine. Also, in 1978, the Clinchfield Coal began working with the US Department

of Energy on a project at the McClure No. 1 mine in Dickenson County. They drilledfive vertical boreholes to test the possibility of producing methane gas from the Jawbonecoal bed. Desorption tests on two cores indicated a gas content of 280 cu ft per ton 8.7

3 .m rt . They also studied the effect of borehole spacing on gas drainage rates. The .project ended in 1980 and Clinchfield Coal Pittston Coal Group was convinced that

there was potential for coalbed methane production in the Nora gas field. The Pittston .Coal Group began working with Equitable Resources Energy EREX to develop the

resource. .EREX began drilling for coalbed methane in 1988 Fig. 15; Table 5 . They completed

two wells during 1988. EREX completed the 1 Squire Smith on September 9, 1988 andthe 101 Jessee Wampler on October 11, 1988. In 1989, EREX drilled 11 wells. In 1990,

EREX drilled 42 coalbed methane wells. Also during 1990, Consolidation Coal drilled 7

wells, OXY, USA drilled 18 wells, and Island Creek Coal and Pocahontas Gas .Partnership PGP drilled one well each. With the extension of the federal Tax Credit

during 1990 to December 31, 1992, coalbed methane drilling increased to 118 wells in

Fig. 15. Number of coalbed methane wells and vertical ventilation holes drilled per year.


19/22


20/22


Fig. 16. Production curves of monthly gas production from 1 Squire Smith and 101 Jessee Wampler coalbed

methane wells.

wells completed in 1988, the 1 Squire Smith and 101 Jessee Wampler are shown in Fig.16. Data are for the first 99 months of production. Cumulative production from the two

3.wells, for October through December, was 11,856 Mcf 336 Mm . Development

Fig. 17. Annual and cumulative coalbed methane production for Virginia, 1988 to 1996.


21/22


.rapidly extended to the northeast, west, and southeast during 1991 and 1992 Fig. 2 .

Annual production and cumulative production curves are compiled in Table 1 and

shown in Fig. 17. Table 1 also shows average production per month and average daily

production per well. Total coalbed methane production during 1996 was 34,153,584 Mcf 3.968,072 Mm . Cumulative coalbed methane production for 1988 through 1996 is

3.121,542,188 Mcf 3,445,073 Mm .The major operators in Virginia are Equitable Resources Energy Company 288

. . wells , Pocahontas Gas Partnership 258 wells , and Consolidation Coal Company 202

. .wells Table 4 . Minor coalbed methane operators are Island Creek Coal Company,

Ratliff Gas Company, and Virginia Gas Company.

6. Effect of regulations on coalbed methane development

The federal Windfall Profit Act of 1980 Nonconventional Fuels Tax Credit under.Section 29 spurred exploration and development of coalbed methane for wells drilled

between December 31, 1979, and December 31, 1992.

Several legal issues in the past have influenced coalbed methane development. The

principal issue was concerning coalbed gas ownership. If a land owner holds the surface

and mineral rights, there is no question that he also owns the coalbed methane resource.

However, in Virginia it is common that mineral rights are severed from the surface

owner, and the coal owner severed from the oil and gas rights. Potential claimants are

the coal owner, coal lessee, oil and gas owner, the oil and gas lessee, and the surface

owner. The ownership issue was complicated in Virginia by the 1977 Migratory GasAct, which gave the surface owner certain rights to migratory gases. If coalbed methane

is considered a migratory gas, the law gives ownership to the surface owner. It has been

argued that coalbed methane is a non-migratory gas, provided the gas stays in the coal

bed and produced by a well in that coal bed. It also has been argued that the law was

unconstitutional because it can take or transfer property rights from the coal owner or oil

and gas lessee to the surface owner without compensation.

Part of the ownership question was resolved when the 1990 Virginia General

Assembly repealed the 1977 Act. Besides repealing the Migratory Gas Act, the General

Assembly passed legislation allowing development and production, and forced poolingof interests with proceeds held in escrow while ownership rights are being resolved.

7. Conclusions

Virginia leads in the drilling and production of coalbed methane in the central and

northern Appalachian basin. Geologic and economic factors for this lead include the

presence of abundant coal resources, sufficient overburden, high gas-content coal beds,

existing pipeline infrastructure, and legislative clarification of uncertain gas ownership.Ten coal beds are targets for methane production. Estimated coal in place for these coal

beds is about 14.9 billion short tons. Estimated in place coalbed methane resource in 3.Virginia is 6.7 Tcf 0.18 Tm .


22/22


Acknowledgements

We would like to thank Gene Rader and Ian Duncan of the Virginia Division of

Mineral Resources and Ken Englund, Robert Milici, and Paul Lyons of the US

Geological Survey for comments and critical reviews. The authors accept sole responsi-

bility for information and interpretations in this paper.

References

Adams, M.A., Hewitt, J.L., Malone, R.D., 1982. Coalbed methane potential of the Appalachians. Society of

Petroleum Engineers and U.S. Department of Energy Proceedings, Pittsburgh, pp. 125134.

Diamond, W.P., Levine, J.R., 1981. Direct method determination of the gas content of coal: procedures and

results. US Bureau of Mines Rept. Inv. 8515, 36 pp.

Harnsberger, T.K., 1919. The geology and coal resources of the coal-bearing portion of Tazewell County.

Virginia Geological Survey Bulletin 19, 195 pp.Henika, W.S., 1994. Internal Structure of the coal-bearing portion of the Cumberland Overthrust Block in

southwestern Virginia and adjoining areas. Geology and Mineral Resources of the southwest Virginia

coalfield. Virginia Division of Mineral Resources Publication 131, pp. 100120.

Huddle, J.W., Jacobsen, E.F., Williamson, A.D., 1956. Oil and gas wells drilled in southwestern Virginia

before 1950. U.S. Geological Survey Bulletin 1027L, 502573.

Kelafant, J.R., Boyer, C.M., 1988. A geological assessment of natural gas from coal seams in the central

Appalachian basin. Topical Report GRI 88r0302, Gas Research Institute, 66 pp.

Lyons, P.C., 1997, Central-northern Appalachian coalbed methane flow grows. Oil and Gas Journal. July 7,

1997, pp. 7679.

Nolde, J.E., 1994. Devonian to Pennsylvanian stratigraphy and coal beds of the Appalachian plateaus province.

Geology and Mineral Resources of the southwest Virginia coalfield. Virginia Division of Mineral

Resources Publication 131, pp. 185.

Nolde, J.E., 1995. Coalbed methane in Virginia. Virginia Minerals 41, 17.

Rice, D.D., 1995. Geologic framework and description of coal-bed gas plays. In: Gautier, D.L., Dolton, G.L., .Takahashi, K.I., Varnes, K.L. Eds. , National Assessment of US Oil and Gas Resources: Results,

methodology, and supporting data, US Geological Survey Digital Data Series DDS-30, 103 pp., maps.

Selner, G.I., Taylor, R.B., 1992. GSMAP, GSMEDIT, GSMUTIL, GSPOST, GSDIG, and other programs,

Version 8, for the IBM PC and compatible microcomputers, to assist workers in the earth sciences. US

Geological Survey Open File Report 92-217, 217 pp.

A Preliminary Assessment of in Place Coalbed

Documents