Bureau of Mines Report of Investigations/l977 

Geology and Methane Content 

of the Upper Freeport Coalbed 

in Fayette County, Pa. 

UNITED STATES DEPARTMENT OF THE INTERIOR 
UNITED STATES DEPARTMENT OF THE INTERIOR 

Cecil D. Andrus, Secretary 

BUREAU OF MINES 
This publication has been cataloged as follows: 

Steidl, Peter F 

Geology and methane content of the Upper Freeport coalbed 

in Fayette County, Pa. / by Peter F. Steidl. [Washington] : 

Bureau of Mines, 1977. 

17 p. t ill., maps, diagrams ; 26 cm. (Report of investigations - 

Bureau of Mines ; 8226) 

Bibliography: p. 15- 16. 

1. Coal - Geology - Pennsylvania - Fayette County, 2. Methane. 

3. Mine gases. I. United States, Bureau of Mines. 11. Title. 

111. Series: United States. Bureau of Mines. Report of investigations - Bureau of Mines ; 8226. 

TN23.U7 no.8226 622.06173 

U.S. Dept. of the Int. Library 
CONTENTS 

Page 

Abstract ................................................................ Introduction ......................................................... Acknowledgments ...................................................... Previous work ........................................................... Stratigraphy ......................................................... Structure ...... ....................................................... Overburden .............................................................. Joint and cleat data ...... ........................................... Coal thickness and methane resources .................................... Methane content ......................................................... Summary and conclusions .................................................. References .............................................................. Appendix.--Average of coal cleat trends for individual quadrangles in 

the study area ...................................................... 

ILLUSTRATIONS 

Location of data points ............................................ Generalized stratigraphic column of the Upper Freeport coalbed and 

adjacent strata ................................................. Fence diagram of the 50 feet of strata above the Upper Freeport 

coalbed ......................................................... Structure map drawn on the base of the Upper Freeport coalbed with 

structure northwest of Chestnut Ridge anticline projected down 

from structure for the Pittsburgh coalbed ......o............ . Isopach of overburden thickness above the Upper Freeport coalbed ... Cleat spacing in specimen of Upper Freeport coal ................... Rose diagrams of coal cleat and rock joint measurements in Fayette 

County. Pa .................................................... Diagram of the face and butt cleat trends in each quadrangle ....... Isopach of the Upper Freeport coalbed .............................. Graph of depth versus gas content for Pittsburgh coal cores ........ Graph of fixed carbon versus gas content of coal cores from 

several coalbeds ................................................. 
GEOLOGY AND METHANE CONTENT OF THE UPPER FREEPORT 

COALBED IN FAYETTE COUNTY, PA, 

by 

Peter Fa Steidl ' 

ABSTRACT 

As part of the Bureau of Mines methane control program, the Upper Freeport coalbed was studied in Fayette County, Pa., where this coalbed lies about 

650 feet below the Pittsburgh coalbed and contains the largest remaining 

reserves of any coalbed in the county. Coal and overburden isopachs, structure and joint pattern maps, and a fence diagram were prepared using data from 

gas and oil exploration logs and coal outcrops. These maps will aid in determining the need and/or feasibility of degasifying the Upper Freeport coalbed 

in the study area. Much of the coalbed in this area is under 600 to 1,400 

feet of overburden. By correlation with data from the Pittsburgh coalbed, the 

gas content at depths of this order is estimated to be between 140 to 300 cf/ 

ton of coal, for a total of 190 to 400 billion cubic feet of methane in this 

coalbed in Fayette County. 

INTRODUCTION 

The Upper Freeport coalbed has been mined in Fayette County since about 

1840, with the most active mining occurring from about 1900 to about 1945. 

Strip mines continue to operate in this coalbed in the eastern part of the 

county, but there are no longer any active underground mines although much 

coal is still minable. 

The free swelling index and agglutinating values of the Upper Freeport 

coal are within the normal range for coking coals. High ash and sulfur content of this coal and the difficulty in cleaning it to levels acceptable for 

coking will limit its use for metallurgical purposes () Blending may be 

necessary since analyses indicate a sulfur content greater than 1.5 pct. 

The present study was undertaken as part of the Bureau of Mines methane 

control program and provides data on methane content, cleat orientation, and 

other characteristics of this coalbed where much coal is still present. Over 

370 data points, including gas and oil wells, coal exploration holes, and outcrop exposures were used in preparing the maps (fig. 1). 

'~eolo~ist, Pittsburgh Mining and Safety Research Center, Bureau of Mines, 

Pittsburgh, Pa. 

a~nderlined numbers in parentheses represent items in the list of references 

preceding the appendix. 
FIGURE 1. - Location of data points. 

The author thanks S. M. Linger, W. C. Doran, J. G. Tilton, and 

J. C. Patton of the Equitable Gas Co.; E. Campbell, P. Garrett, and 

T. K. Reeves of the Peoples Natural Gas Co.; R. H. Hoffman 11, M. A. Sholes, 

and L. Heyman of the Pennsylvania Geological Survey; and S . E . Cortis and 

T . Alexander of the Pennsylvania Bureau of Subsurface Subsidence for supplying 

data. Thanks are also extended to H. E. Steinman of the Jones & Laughlin 

Steel Corp. ; and W. E . Edmunds of the Pennsylvania Geological Survey for 

supplying data and reviewing the manuscript. 
PREVIOUS WORK 

There have been few previous investigations of the Upper Freeport coalbed 

in Fayette County. Past reports contain analyses and give carbonizing properties of the coal, as well as isopach and struccure maps for parts of the 

county. Some coal thicknesses and outcrop descriptions from early reports 

provided useful data (L, 3-4, 13, l5). Hickok and Moyer (7) published a 

geologic map with coalbed outcrop lines for Fayette countyin 1938. The 

structure map was drawn on the base of the Pittsburgh coalbed for the part of 

the county northwest of Chestnut Ridge and on the base of the Upper Freeport 

coalbed for the remainder of the county. 

It has been estimated that the recoverable coal from this coalbed was 

1,029 million tons in Fayette County in 1928 (12). This estimate was based 

on the assumption that the coalbed has a uniform thickness of 42 inches in 

townships along the Monongahela River. However, since its thickness is variable, a conservative 50 pct was used for the estimate of recoverable coal 

which does not include any part of the coalbed less than 18 inches thick. 

Subsequently this estimate was revised to 1,150 million tons (7). According 

to Dowd (z), the Upper Freeport coalbed contained the largest reserves of any 

coalbed in the county, but ~owd's estimate, which does not include inferred 

coal, was much lower than ~ickok's (1). Dowd's figure of 127 million tons was 

based on reserves in beds 28inchesor more thick and a 52.9 pct recovery. 

Hickok and Moyer reported that the Upper Freeport coalbed is fairly persistent in Fayette County and is cut out in some places and replaced by sandstone. Their study found the coalbed to range from 2 to 9 feet thick, with 

persistent clay partings. Unusual thicknesses of up to 16 feet, including 

sizable partings, were also observed. 

A study by Koppe (2) of the Upper Freeport in adjacent parts of Allegheny, Butler, Armstrong, and Westmoreland Counties found basal partings in 

structurally low areas. He reports that "ancient topographic highs (areas of 

no partings) occupy positions relative to present anticlines suggesting that 

the paleotopography was controlled by the same structures observable today." 

STRATIGRAPHY 

The Upper Freeport coalbed occurs at the top of the Allegheny Group, 

about 650 feet below the Pittsburgh coalbed. Seven relatively thin and often 

discontinuous coalbeds (fig. 2) which may occur in 200 feet of stratigraphic 

section in the Allegheny and Conemaugh Groups make correlation difficult. One 

of the most useful aids in correlating these coalbeds is their depth below the 

Pittsburgh coalbed. Another aid in correlation is the Freeport limestone 

which sometimes occurs beneath the Upper Freeport coalbed underclay. The 

Mahoning (Dunkard) sandstone is usually present above as shown in the fence 

diagram (fig. 3). Two coalbeds occur within 55 feet of the Upper Freeport 

coalbed, the Mahoning coalbed above and the Lower Freeport below, neither of 

whichis usually as thick or persistent as the Upper Freeport. 
- - 

LEGEND 

~cO~I Limestone Sandstone Shale 

FIGURE 2. - Generalized stratigraphic column of the Upper Freeport coalbed and adiacent 

strata. 

Due to the presence of an irregular surface beneath the Upper Freeport 

coalbed, there are areas where the peat was eroded or was not deposited. 

Evidence of this can be found along Chestnut Ridge where the lower Mahoning 

(Big Dunkard) sandstone cuts out some or all of the Upper Freeport coalbed 

(1). On some higher areas, plant remains were washed away to low areas or 

decayed before peat formed and therefore no coal is present. 
0 

0 

w4 6 k~lmters 

Horizontal scale Pa. - - - - - - 

W. Va. i .A Md. 

FIGURE 3. - Fence diagraril of the 50 feet of strata above the Upper Freeport coalbed. 

STRUCTURE 

A structure map was drawn using the bottom of the Upper Freeport for the 

datum base (fig. 4).3 Much of the structure was taken from a previous map (7) 

drawn on the base of the Pittsburgh coalbed for the part of the county north= 

west of Chestnut Ridge and on the base of the Upper Freeport coalbed for the 

remainder of Fayette County. The approximate structure for the Upper Freeport 

was derived by subtracting 650 feet from the elevation of the Pittsburgh coalbed. Other changes were made wherever additional data showed the need for 

them. 

The major structures present from east to west are Laurel Hill antic line , Ligonier syncline , Chestnut Ridge a n t i c l i n e , Uniontown sync line , Fayette anticline, Lambert syncline, Brownsville anticline, and Port Royal 

syncline. All these structures trend northeast-southwest and affect the 

3~he coal isopach, overburden isopach, and structure map are available from 

the author at scales of 1:24000 (1 inch equals 2,000 feet) and 1:96000. 
FIGURE 4. - Structure map drawn on the base of the Upper Freeport coalbed with structure 

northwest of Chestnut Ridge anticline proiected down from structure for the 

Pittsburgh coalbed. 

elevation and presence of coalbeds in the area. On Chestnut Ridge and Laurel 

Hill anticlines there are places where the Upper Freeport coalbed outcrops and 

large areas where it has been eroded. 

Structural relief of the Upper Freeport coalbed in the study area is over 

2,800 feet; the highest part (more than 2,600 feet above sea level) is located 

along the eastern flank of the Chestnut Ridge anticline, and the lowest part 

(more than 200 feet below sea level) is located in the Lambert syncline. 

There is moderate dip throughout most of the area with the beds varying from 

flat lying to dipping 23" (a slope about 2,200 feet per mile) on the western 

flank of the Chestnut Ridge anticline. 

coal. important in laying out the 

mine, spacing vertical boreholes, and orienting horizontal holes drilled underground. Data were collected from 23 quadrangles and plotted on rose diagrams (fig. 7). For 8 of 

the quadrangles located totally or partially within the study area, an average 

of more than 16 locations were used, with an average of more than 8 measurements taken at each location. All but four quadrangles had locations where 

readings were taken from coalbeds. 

In figure 8 distinct trends, corresponding to face and butt cleat directions, are apparent for readings taken in coal. The face cleat and systematic 

(primary) rock joints in the study area generally trend N 72" W. Nearly 

perpendicular totheseare the butt cleat and the nonsystematic (secondary) 

joints which trend N 21° E. The face cleat direction is parallel to the 

direction of the principal compressive stress that produced the present structure and perpendicular to the fold axes. The butt cleat is parallel to the 

structural axes of the Allegheny Front. 
FIGURE 7. - Rose diagrams of coal cleat and rock ioint measurements in Fayette County, Pa, 
0 5 I0 miles 

0 5 10 15 kilometers 

LEGEND 

I f Key Map 

Butt cleat 

b - 1 

1 L6 

I 

Fayette City 

26 

A 

70 I 

New Salem 

22 

4 

72 I 

-.,I 

Smithfield 

0- 

2P 

I 7 1 h1 

Lake Lynn 

I 

\ 

26\-w 

A 

7 1 

\I 

Dawson 

25 

fi 

74 -' 

Uniontown 

',8 

68 v1 

Brownfield 

0- 

Pa. 

W. Va. -m 

I 

SCALE 

3t, 

70 .--3 - 

-California # 

0 w 

l4 32 

'>"A 4' 

( Carmichaels fl 

( :4 

72 ->' 

\ Masontown 

-0 

PI 

I 72 \' 

Morgantown N 

I 

Face cleat 

P 

/'27 4 

71 -2 

Connellsville 

23 

A 

73 I 

-.I' 

South Connellsville 

20 

A 

68 I 

-.,I 

Fort Necessity 

lo---- 

FIGURE 8. - Diagram of the face and b u t t c l e a t trends in each quadrangle. 

COAL THICKNESS AND METHANE RESOURCES 

7 1 

Friendsville 

2? \ 

I 

70 I 

-4 I 

Bruceton Mills 

Where present, the Upper Freeport coalbed usually ranges from 2 to 8 feet 

thick. Commonly the coalbed occurs in two benches with a 6-inch parting. The 

top and bottom benches average 25 and 21 inches thick, respectively. The shale 

parting rarely attains a thickness greater than 2 feet, but where it does only 

Donegal 

18 

Brandonville 

7 I 

seven /springs 

/ 

A 

7-I 

I 

I 

Mill Run Kingwood 

74 I 

Ohiopyle , 

-lS 

1 81:A2~ 

Confluence 

Md. 

00 -- 
FIGURE 9. - lsopach of 
one bench is usually of minable thickness. Occasionally, there is a middle 

bench up to 3 feet thick or an upper split of the seam averaging 30 inches. 

In order to calculate the total volume of methane in this part of the 

Upper Freeport coalbed, it was necessary to estimate the total coal in place. 

The area of each interval was measured from topographic maps. Multiplying 

this figure times the average coal thickness for the interval (2 feet for the 

0- to 4-foot interval and so on) gives the volume of coal. Dividing the volume in cubic feet by 24.6 gives the number of short tons, assuming the specific gravity of this coal to be 1.3 (81.3 lb/cu ft). An equation for this 

follows : 

average interval thickness X interval area, Tons of coal = 24.6 cu ft/ton 

An estimate of 1,340 million tons of coal in place was made by using over 

370 data points. In some areas there are insufficient data to draw isopach 

lines (fig. 9). There are, however, sufficient data points surrounding the 

area to assume an average thickness of 2 feet or more. Due to the highly variable thickness of the Upper Freeport coalbed in the study area, a conservative 

thickness of 2 feet was used to estimate the coal in place in these areas. 

Assuming methane content to be 140 to 300 cubic feet per ton of coal, there is 

190 to 400 billion cubic feet of methane in the Upper Freeport coalbed in 

Fayette County. 

METHANE CONTENT 

The amount of methane adsorbed on the coal microstructure depends on 

several factors: temperature, pressure, overburden thickness, and rank. 

Coalbed pressure is the fluid pressure of the bed. At most it is equal to the 

hydrostatic pressure, which has a gradient of about 0.43 psi per foot of water 

column. Bureau research has shown that for each additional 100 feet of overburden, an increase of about 0.8 cu cm of methane per gram of coal (25.6 cu 

ft/ton) can be expected in the Pittsburgh coalbed (fig. 10). This correlates 

well with tests done on the Upper Freeport coalbed which has a gas content per 

volume of coal similar to the Pittsburgh coalbed. 

In some coalbeds, the increase in gas content with the increase in depth 

is due partly to the decrease in volatile matter. However, pressure and 

temperature associated with past tectonic activity have had a much greater 

effect on the coal rank in the study area than present overburden thickness. 

The increased yield of methane is associated with the decrease in hydrogen 

content, which begins in the bituminous coal range (14). Higher rank coals 

have a structure which can adsorb more of the metha; produced during 

coalification. 

The relationship of gas content to fixed carbon content is shown on 

figure 11 (11). In Fayette County the Upper Freeport coal, which varies 

between 63 and 75 pct fixed carbon in DAF (dry ash free) samples, is expected 

to have a gas content between 3 and 10 cu cm/g, with some variation due to 

depth. In the study area this coal averages 68.5 pct fixed carbon from 
10 I I 1 I I I I I I 

KEY I - Pittsburgh coal - 

A Upper Freeport coal 

- 

- 0, 

m' 

o E 6- - 

- 

- 

- 

- 

0 

- 

*He 

/' 

1 I I 1 1 I I 1 

0 , 400 800 1,200 

OVERBURDEN, ft 

FIGURE 10, - Graph of depth versus gas content for 

Pittsburgh coal cores, 

GAS CONTENT, cm3/g 

FIGURE 11. - Graph of fixed carbon versus gas content 

of coal cores from several coalbeds, 

adapted from previous publication (11); 

published analyses (2, 6-7) 

and should average about 6.1 

cu cm of methanelg of coal. 

This is only 13 pct higher 

than the value determined by 

the direct desorption method 

for three Greene County core 

samples (8,s). Results 

from these tests are plotted 

on the graph of data from 

the Pittsburgh coalbed 

(fig. 10). The average depth 

of these three sampleswas 962 

feet, and the average gas 

content was 5.3 cu cm/g. 

A reason for this anomaly 

could be a reduction in 

overburden pressure due to 

mining of the overlying 

Pittsburgh coalbed, thus 

establishing new equilibrium 

conditions . The lower 

hydrostatic pressures could 1 

cause gas to desorb from the 

Upper Freeport coalbed. New 

points have been plotted for 1 

the Upper Freeport coalbed 1 

by subtracting the over- I 

burden above the mined 

Pittsburgh coalbed to 

reflect the assumed equilibrium depths (A', - - B', and c', 

fig. 10). 

An important but 

unknown factor is the length 

of time necessary for gas to 

desorb from a coalbed under 

such conditions and a new 

equilibrium to be established. Points A 'and B ' plot 

closely to on $e 

graph for the Pittsburgh 

coalbed, however, point C' 

does not. This point could 

be in£ luenced by the overlying virgin Pittsburgh coalbed to the west and southwest, and point C_ may indeed 

be the true depth equilibrium for this core sample. 
SUMMARY AND CONCLUSIONS 

The Upper Freeport coalbed in Fayette County contains 190 to 400 billion 

cubic feet of methane based on an estimate of the total coal in place. The 

methane content is assumed to be 140 to 300 cubic feet per ton of coal. The 

total coal in place was determined by using 370 data points. The variable 

thickness of the coalbed in this area will require careful property evaluation 

and mine planning . 

The structural elevation ranges from 200 feet below to 2,600 feet above 

sea level, and overburden thickness ranges from 0 to over 1,400 feet. The 

face cleat trends N 72" W, and the butt cleat trends N 21" E. 

Degasification in advance of mining may be advisable for parts of the 

coalbed with more than 200 cu ft of methane per ton of coal in place. Gas 

contents of this order can be expected where the Upper Freeport is under 

more than 800 feet of overburden, mostly in the western part of the county. 

Due to the variable nature of the Upper Freeport coalbed in this area, a 

core hole spacing of 2,000 feet or less may be necessary to accurately determine reserves and low coal areas. 
REFERENCES 

Ashley, G. H. The Coal Fields of Pennsylvania. Pa. Geol. Survey. 

Bull. M-6, 4th Series, Pt. 1, 1928, 241 pp. 

. Anaylses of Pennsylvania Bituminous Coals. BuMines Tech. 

Paper 590, 1939, 503 pp. 

Campbell, M. R. Description of the Masontown and Uniontown Quadrangles, 

Pa. U.S. Geol. Survey Geol. Atlas Folio 82, 1902, 21 pp. 

. Description of the Brownsville and Connellsville Quadrangles , Pa. U.S. Geol. Survey Geol. Atlas Folio 94, 1902, 19 pp. 

Dowdy J. J., L. A. Turnbull, A. L. Toenges, R. F. Abernethy, and 

D. A. Reynolds. Estimate of Known Recoverable Reserves of Coking Coal 

in Fayette County, Pa. BuMines RI 4807, 1951, 19 pp. 

Fieldner, A. C., J. D. Davis, W. A. Selvig, D. A. Reynolds, R. E. Brewer, 

G. C. Sprunk, and C. R. Holrnes. Carbonizing Properties and 

Petrographic Composition of Upper Freeport Coal From Morgantown 

District Monongalia County, W. Va., and of Lower Freeport Coal From 

Eastern Indiana County Near Carnbria County, Pa. BuMines Tech. 

Paper 621, 1941, 77 pp. 

Hickok, W. Om, IVY and F. T. Moyer. Geology and Mineral Resources of 

Fayette County, Pa. Pa. Geol. Survey Bull. C-26, 1940, 530 pp. 

Kissell, F. N., C. M. McCulloch, and C. H. Elder. The Direct Method of 

Determining Methane Content of Coalbeds for Ventilation Design. 

BuMines RI 7767, 1973, 17 pp. 

Koppe, E. F. Some Geological Factors Affecting the Upper Freeport Coal 

and Its Quality. Trans. AIME, v. 217, 1960, pp. 185-189. 

McCulloch, C. M., J. R. Levine, F. N. Kissell, and M. Deul. Measuring 

the Methane Content of Bituminous Coalbeds. BuMines RI 8043, 1975, 

22 PP 

McCulloch , C . M. , and W . P. Diamond. Inexpensive Method Helps Predict 

Me thane Content of Coalbeds. Coal Age , June 1976, pp . 102-106. 

Reese, J. F., and J. D. Sisler. Bituminous Coal Fields of Pennsylvania 

Coal Resources. Pa. Geol. Survey Bull. M-6, Pt. 111, 1928, 153 pp. 

~isler, J. D. Bituminous Coal Fields of Pa. Pa. Geol. Survey Bull. 

M-6 Pt. 11, 1975, 511 pp. 

Stach, E . , D. Chandra, M. T Mackowsky, G. H. Taylor, M. Teichmcller , and R. ~eichmcller. tach's Textbook of Coal Petrology. ~ebrider 

Borntraeger , Berlin-Stutgart , Germany, 1975, 428 pp. 
15. Stevenson, J. J. The Geology of the Fayette-Westmoreland District, 

Part I. Eastern Allegheny, Western Fayette , and Westmoreland Counties. 

Pa. Geol. Survey, v. KK, 438 pp. 

16. Wolfson, D. E., and C. Ortuglio. Carbonizing Properties of Coals From 

Fayette , Greene, and Washington Counties, Pa. BuMines RI 7131, 1968, 

14 PP* 
APPENDIX. --AVERAGE OF C CAL CLEAT TRENDS FOR INDIVIDUAL 

QUADWNGLES IN THE STUDY AREA 

Quadrangle 

Brownfield. .......................... California... ......................... Carmichaels.... ....................... Confluence. ........................... Connellsville ......................... Dawson........... ..................... Donegal ............................... Fayette City .......................... Fort Necessity ........................ Friendsville... ....................... Lake Lynn ............................. Masontm....... ...................... Mill Run.............................. 

Morgantown North... ................... New Salem ............................. Ohiopyle .............................. Smithfield......... ................... South Connellsville.. ................. Uniontown............................. 

l~ide peak. 

"Double peak. 

Face c1-eat peak 

, 68 W 

Butt cleat peak 

18 E 

30 E 

14 E, 32 E2 

25 E 

27 E 

26 E 

22 E 

16 E2 

20 E 

18 E, 28 E2 

20 E 

24 E 

18 E 

15 ~l 

26 E 

18 E 

22 E 

23 E 

25 EI