Report of Investigations 91 95 

Geologic Factors Influencing the Gas 

Content of Coalbeds in Southwestern 

Pennsylvania 

By James P. Ulery 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Donald Paul Hodel, Secretary 

BUREAU OF MINES 

T S Ary, Director 
Library of Congress Cataloging in Publication Data: 

Ulery, J. P. (James P.). 

Geologic factors influencing the gas content of coalbeds in southwestern 

Pennsylvania. 

(Report of investigations; 9195) 

Bibliography: p. 19-20. 

Supt. of Docs. no.: I 28.23:9195. 

1. Coalbed methane-Pennsylvania. 2. Coal-Geology-Pennsylvania. I. Title. 

11. Series: Report of investigations (United States. Bureau of Mines); 9195. 

TN23.U43 [TN844.6] 622 s [622'.334] 88-600119 
CONTENTS 

Page 

Abstract ........................................................................... Introduction ........................................................................ Acknowledgments .................................................................... Coal petrography and the maceral concept ................................................. Coalification and rank ................................................................. Coalification and methane generation ..................................................... Retention and emission of coalbed methane ................................................ Studyarea ......................................................................... Relation of coalbed gas content to petrographic and geologic factors .............................. Paleogeothermal gradient and former depth of burial .......................................... Conclusions ........................................................................ References ......................................................................... Appendix . Results of petrographic and chemical analyses ...................................... 

ILLUSTRATIONS 

1 . Common macerals and their possible origin ............................................. 2 . ASTM rank classification ........................................................... 3 . Mapofstudyarea ................................................................ 4 . Stratigraphic column of Monongahela and Dunkard Groups ................................. 5 . Stratigraphic section penetrated by Westmoreland County, PA. corehole ........................ 6 . Structural contour map of study area on base of Pittsburgh Coalbed ........................... 7 . Ternary plot of maceral composition of sampled coalbeds ................................... 8 . Vitrinite percent versus total. desorbed. and residual gas contents ............................. 9 . Vitrinite reflectance versus total gas content ............................................. 10 . Depth of cover versus total gas content ................................................ 11 . Isoreflectance map of Lower Waynesburg Coalbed ........................................ 12 . Structural cross section of Upper and Lower Waynesburg Coalbeds ............................ 13 . Panel diagram of Uniontown and Upper and Lower Waynesburg Coalbeds ...................... 14 . Modified Karweil nomogram ........................................................ 15 . Vitrinite reflectance versus depth below Fish Creek Coalbed horizon ........................... 16 . Estimated paleotemperature at top and bottom of 1-km-thick sedimentary section ................. 17 . Estimated maximum paleotemperature of Pittsburgh Coalbed ................................ 18 . Estimated former depth of burial of Pittsburgh Coalbed .................................... A- 1 . Relationship between inertinite and desorbed. residual, and total gas contents .................... A - 2 . Relationship between exinite and desorbed, residual, and total gas contents ...................... 

TABLES 

1 . Gas content and vitrinite reflectance data for Upper and Lower Waynesburg Coalbeds in 

figure12 ...................................................................... 2 . Gas content and vitrinite reflectance data for Upper and Lower Waynesburg Coalbeds in 

figure13 ...................................................................... A- 1 . Maceral composition and gas content data .............................................. A-2 . Chemicaldata ................................................................... 
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 

Btu/lb British thermal unit per pound min minute 

"C degree Celsius m .y. million years 

cm3/g cubic centimeter per gram Pm micrometer 

"C/km degree Celsius per kilometer Pet percent 

ft foot pct/ft percent per foot 

in inch pct/km percent per kilometer 

km kilometer 
GEOLOGIC FACTORS INFLUENCING THE GAS CONTENT 

OF COALBEDS IN SOUTHWESTERN PENNSYLVANIA 

By James P. uleryl 

ABSTRACT 

A Bureau of Mines geologic study of Pennsylvanian and Permian coalbeds in southwestern 

Pennsylvania was undertaken to determine the effects of coalbed geology and petrology on in situ 

coalbed gas contents. Data were obtained from 18 coreholes from parts of four 7.5 ' quadrangles in 

southwestern Washington and northwestern Greene Counties, and from a single corehole in Westmoreland County. 

A total of 88 samples from 24 coalbeds were collected for direct-method testing to determine gas 

content. The samples were also analyzed for petrographic composition, chemical composition, and 

vitrinite reflectance values. Corehole information was used to generate isopach maps and geologic cross 

sections useful in data interpretation. 

Results of the investigation show that coalbed gas content is related to vitrinite reflectance, but not 

to petrographic composition. Gas contents are also influenced by other geologic factors such as roof 

rock lithology and competency, and location with respect to local fold structure. 

INTRODUCTION 

Because of the hazards associated with methane emissions and ignitions in underground coal mines, 

the Bureau of Mines conducts fundamental research regarding the occurrence, emission, and drainage 

of coalbed methane. Previous studies have demonstrated the feasibility of degassing virgin reserves and 

producing commercial-quality methane gas from horizontal or vertical boreholes. By using the directmethod to determine coalbed gas contents, geologic studies have established that methane content is 

related primarily to the rank of the coalbed and its depth (27, 30): The direct-method developed by 

the Bureau measures gas released from a coal sample sealed in an airtight container. All gas contents 

in this study were determined by this direct-method, which is presented in more detail by Kissell (27). 

The objective of this report is to provide an overview of coalification, coal petrography and the 

maceral concept, and to review theories regarding gas generation and storage by coalbeds. More importantly, this report will assess the effects of variations in petrographic composition, rank, and local 

geology on the gas contents of coalbeds from the Dunkard Basin in southwestern Pennsylvania. The 

report concentrates on a relatively small area in the basin to minimize the effects of regional variations 

on former depth and duration of burial, and paleogeothermal gradient. Subsequent reports will address 

variation in gas contents with petrographic features across a wider range of rank and geothermal 

conditions. 

'~eologist, Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 

2~talic numbers in parentheses refer to items in the list of references preceding the appendix at the end of this report. 
ACKNOWLEDGMENTS 

The author gratefully acknowledges the invaluable samples, cooperation in sample collecting and logging, 

assistance of Donald G. Puglio, project geologist, of work on correlation of the Permian coalbeds, and 

Consolidation Coal Co., Northern Appalachian Exploration innumerable helpful discussions and suggestions 

Div., Library, PA, for securing permission to collect the throughout the preparation of this report. 

COAL PETROGRAPHY AND THE MACERAL CONCEPT 

Coal petrography refers to the macroscopic and 

microscopic characterization and description of coal or 

coal fragments on the basis of one or more physical 

criteria such as reflectance, morphology, luster, or color. 

Characterization on the macroscopic scale includes the 

thickness, abundance, and luster of various coal bands, and 

includes a description of interbedded noncoal layers such 

as bone, pyrite, shale, or other rock types. Petrographic 

analysis on a microscopic scale is accomplished either by 

viewing coal thin sections in transmitted light or by viewing 

coal fragments on a polished pellet with reflected light. 

Currently most petrographic analyses are accomplished by 

reflected light techniques. 

Pioneering work in the field of coal petrography was 

done in the United States by Reinhardt Thiessen (50-51), 

and in England by Marie Stopes (44-45). Because they 

were using two different methods of analysis (Thiessen, 

transmitted light; Stopes, reflected light), the classification 

systems developed by each investigator varied considerably. 

Most modern classification systems stem from the 

Stopes system, and recognize three main groups of 

microscopic components or macerals. Macerals are the 

fundamental components of coal, roughly analogous to 

minerals in rocks (45). Macerals, however, are not 

crystalline and are classified on the basis of reflectance, 

morphology, origin, or mode of preservation (42). 

The three maceral groups recognized are vitrinite, 

inertinite, and exinite (or liptinite). These three groups 

may be further subdivided into individual macerals, 

submacerals, and maceral varieties, the only limitations 

being the degree of alteration and the needs of the 

researcher. Figure 1 lists the important macerals of the 

three groups and gives brief descriptions of each. 

Vitrinite occurs most frequently and accordingly is the 

most important maceral group found in bituminous coals. 

Most vitrinite originates from the trunks, branches, stems, 

leaves, and roots of various flora that existed in ancient 

coal forming swamps (50-51). In lower rank coals the vitrinite macerals, telinite and collinite, are often found in 

close association (42). Telinite refers to preserved cell 

wall material, whereas collinite refers to a structureless 

gel-like maceral often found filling the aforementioned 

cell structures. As rank progresses, cell structure is 

obliterated and the two macerals are referred to simply as 

vitrinite. 

Figure 1.-Common macerals and their possible origin. 

Maceral group 

V~trlnl te 

Exln~ te

lner t ~n~te 

Maceral 

Tel~n~ t e 

Col l~n~ te 

Spor~n~te 

Cu trn~te 

Reslnlte 

Algln~ te 

B~tum~nlte 

- 

Exudatln~te 

Fluorln~te 

Seml fus~n~te 

Fus~n~ te 

M~cr~n~te 

Macr~n~te 

Sclerotln~te 

Or I~I n 

Pr~mar~ly roots, bark and woody materlal 

Also twlgs, leaves 

Formed from gels of humlc mater~als 

excreted from plant mater~al 

Spore and pollen cell wal Is 

Wax11 ke coatlng of leaves and stems 

Numerous mater~al ~nclud~ng prlmary resins, 

fats, and 011s 

Algae 

Probably related to decompos~t Ion of algae, 

faunal plankton and bacter~a 

"~econdar y" reslnlte formed dur~ng 

coal~f~cat~on, ve~nlets 

"~econdar~" reslnlte probably formed from 

plant 011s dur~ng coal~f~cat~on, massive 

Formed from or v~tr~n~t~c mater~al from one 

or more processes act~ng before and /or 

durlng coal~frca t Ion 

Formed by degradat~on and devolat~l~zat~on 

of cell wall and exlnlt~c mater~al 

Fus~n~t~zed coll~n~t~c (gel) mater~al 

Fungol remalns In younger coals, fusln~t~zed 

cell secret Ions (res~ns) In older coals 

Medium 

br~ght 

Least brlght 

med~um to 

dark gray 

usually 

black 

Bright 

to 

very bright 

Appearance 

Preserved woody remalns w~t h 

cell structure 

Occurs lnf~l l~ng cell structure and as 

macerated mater~al ln attr~tal coal 

ldentlfled by morpholog~cal character~st~cs 

- - - - - - - - - - - - - - 

Usually very dark, occas~onally rn~staken for 

m~neral matter or fracture 

Dlstlnct organlc orlgln seen by f luorescence 

ldent~fled by morpholog~cal character~st~cs 

Occurs as bands or lenses usually wlth a we1 l 

developed pore system 

Occurs as rounded gra~ns,usually -Z I fim in 

dlameter In groundmass 

Usually structureless, more or less amorphous 

non granular groundmass; occas~onal ly 

lsolated part~cles 

ldentlf~ed by rnorpholog~cal character~st~cs, usually somewhat rounded w~th pore structure 
Two other important vitrinite macerals are telocollinite 

and desmocollinite, also known as vitrinite A and B, 

respectively (7,42). Generally concentrated in attrital coal 

layers, desmocollinite (vitrinite B) has a lower reflectance 

and higher hydrogen content than telocollinite (vitrinite A), 

which is usually found in nonattrital coal layers. 

Consequently attrital coal or bands within coal may be 

important in assessing gas generation potential. 

Important macerals of the inertinite group, so named 

for their relatively inert behavior in the coking process, 

include fusinite, semifusinite, and micrinite. Fusinite is a 

charcoal-like substance usually formed by rapid charring 

and alteration of cell wall material (vitrinite) prior to, or 

shortly after, incorporation into the enclosing sediment. 

This charring may be a result of paleo-forest fires (42), 

and an abundance of this maceral may indicate relatively 

dry conditions. Semifusinite is a less altered maceral and 

represents material intermediate between vitrinite and 

fusinite. 

Micrinite is an atypical inertinite maceral because it 

generally does react during the coking process. The 

genesis of micrinite remains controversial and several 

modes of origin have been proposed. One school of 

thought suggests that micrinite originates from physical 

degradation and metamorphism of cell wall material (39, 

41). Another suggests a subaqueous formation via 

chemical-biological agents during the peat stage (38, 52). 

A third hypothesis contends micrinite originates during 

coalification through metamorphism of exinite macerals 

(48-49). 

The exinite group macerals, which may be very 

important in methane generation, are derived primarily 

from spores, cuticles, resins, waxes, fats, and oils present 

in the original plant material. The exinite macerals are 

relatively rich in hydrogen and volatile matter and readily 

react during coalification. Another feature of exinite 

macerals is their fluorescence when irradiated with 

ultraviolet light. Fluorescence microscopy has led to the 

discovery of some previously unrecognized exinite 

macerals, fluorinite, exudatinite, and bituminite (48). 

Exudatinite may be significant because it represents a 

mobile "secondary" maceral generated during the coalification process, and its formation is likely concurrent with 

oil generation in source rocks of the same region (49). 

Therefore exudatinite in coals suggests that certain primary 

exinite macerals have volatilized releasing significant 

methane. 

Fluorescence tends to decrease with increasing coalification, concomitant with the gradual disappearance of 

the exinite macerals (48-49). Significant alteration of 

original exinitic material begins to occur in the upper highvolatile rank and by low-volatile rank exinite have virtually 

disappeared (42). The alteration of exinite may be partially responsible for the higher gas contents found in 

medium- and low-volatile rank coals. 

COALlFlCATlON AND RANK 

The importance of the coalification process on gas 

formation and maceral associations necessitates a brief 

discussion. The coalification process is the gradual, 

progressive alteration (metamorphism) of plant material to 

peat, lignite, bituminous, and higher rank coals (42). 

Coalification is achieved through the interaction of 

temperature, time, and pressure (12, 36, 41-42, 60-61). 

Coals form in low-lying swampy areas in which subsidence and sedimentation occur simultaneously. The 

continued subsidence of these areas results in thick 

accumulations of sediments and deep burial. Temperature 

and pressure increase proportionately with burial causing 

physicochemical reactions resulting in coalification. One 

would expect, then, that at any given location the rank of 

coal material should increase with depth. This premise 

has been substantiated in numerous borehole profiles and 

is known as Hilt's law (42). 

The relative importance of the coalification variables - temperaturetime, and pressure - isubject to various 

interpretations. Most researchers agree that temperature 

has a very significant influence on coalification as indicated 

by rank studies adjacent to igneous intrusives (4,42). The 

effects of intrusive bodies on coalification are generally 

localized, whereas regional coalification results from heat 

associated with an area's geothermal gradient and the heat 

conductivity of the enclosing strata. High geothermal 

gradients however, may be associated with very large, 

deep-seated intrusive bodies. Changes in temperature 

during coalification occur then in three primary ways: 

(1) at a constant geothermal gradient, temperature 

increases as depth of burial increases; (2) changes in 

geothermal gradient due to mantle processes or large, 

deep-seated plutonic intrusives; and (3) localized 

temperature increase adjacent to smaller igneous intrusions (dikes, sills). 

The effect of time on coalification has been discussed 

by Bostick (3-4) and Stach (42), and is a significant factor 

in this process. For example, if two coalbeds were subjected to similar temperatures, the one subjected for the 

longest time (geological) should attain a higher rank. 

The effect of pressure on coalification has been 

extensively discussed and remains controversial. White 

(58-61) in his pioneering work on the carbon-ratio theory, 

related the degree of coalification to the occurrence of oil 

and gas, and concluded that tectonic pressure was important in promoting coalification. This view has lost 

acceptability because recent experiments have suggested 

that static pressure inhibits chemical coalification reactions 

(9, 36, 42-43), possibly because the removal of gas and 

other volatiles becomes more difficult. 
Various systems have been proposed to classlfy coals 

according to their rank or degree of metamorphism. Early 

classification systems were often based on volatile matter, 

fmed carbon, calorific value, caking or coking power, and 

agglomerating properties. Because these parameters can 

be determined by fairly simple procedures, and have close 

relations to important uses of coal, classification systems 

based on them have found great acceptability and are used 

today. 

As coal research progressed, the need for a classification system applicable to scientific research as well as 

enhanced coal technologies was needed. It soon became 

obvious that comparative rank studies should be made on 

the basis of vitrinite only, since this tends to exclude the 

influence of the heterogeneity of most coals. Vitrinite is 

used because it is the most abundant and readily isolated 

maceral found in coal. Comprehensive, comparative studies of all rank parameters show th~t certain parameters are 

more applicable to particular ranks of coal, while no single 

parameter is relevant throughout the rank series. 

Measurement of vitrinite reflectance has become increasingly popular as a means of determining coal rank by 

photometrically measuring the amount of light reflected 

from the maceral vitrinite. Numerous studies relating 

reflectance to other rank parameters have been completed 

and are summarized by McCartney (29) and Stach (42). 

Mean-maximum vitrinite reflectance was used in this 

study and is a commonly used petrographic technique for 

rank determination in the United States. According to 

American Society for Testing and Materials (ASTM) 

standards, it is determined on 100 vitrinite points 

statistically distributed over the whole surface of the 

polished specimen. For each point, the stage is rotated 

through 360" and the maximum reflectance intensity 

recorded. During reflectance measurement, care must be 

taken to exclude any influence from relief or 

inhomogeneities (e.g., scratches, fine cracks, or minute 

mineral inclusions). The maximum reflectance readings 

are usually plotted on a histogram, and the values averaged 

to determine mean-maximum reflectance. Internationally, 

mean-random reflectance, determined on nonrotated 

vitrinite particles is commonly used. Figure 2 compares 

ASTM rank with various rank parameters including 

random and maximum reflectance and shows their ranges 

of applicability. 

Figure 2.-ASTM rank classification; its relation to various ranking parameters and the range of appikrbility of these parameters. 

Sub- \ 

Medium 2 Lignite 5 Peat 

'I 

Semi- High volatile Anthra- Low 

Vitrinite reflectance 

(max in oil), % 

Volatilematter(dry 

ash free) daf, O/O 

Fixed carbon 

daf, % 

Bed moisture 

Calorific value, 

(btu/lb) 

Range of applicability 

of various rank 

parameters 

Rank (ASTM) biturn~nous volatile 

I ' I ' I I '1'1' 1 I I I I - 

2 1.8 1.6 1.4 1.2 1.0 0!8 0.6 0.5 0.4 0.3 0.2 

' 1 1' 1' 1 '1 1 ' 1' 1 '1 '1' 1' 1' 1' 1' 1 '1 '1 

4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 64 68 

I 1 I I I 

9 1 87 77 71 60 

I 1 I I 

8-10 25 35 75 

1 I I I I 

15,500 15,500 12,600 9,900 7200 

Volatile matter (daf) ----- 

Fixed carbon ( daf) ---------- 

Reflectance of vitrinite ------ - 

Moisture Bed moisture - 

anthracite 

bituminous 

Calorific value (daf ) 

volatile 

$ bit:r$"l 2 bituminous cite A I B I c ;& B I C 
COALlFlCATlON AND METHANE GENERATION 

The occurrence of explosive gases or firedamp in coal 

mines has long been known in areas where bituminous 

coals are worked (11, 17, 24, 34, 37, 57). The origin of 

these gases was once the subject of debate concerning 

whether or not they were generated in situ or migrated 

into the coalbed from adjacent strata (11,37). Today most 

researchers agree that the majority of the gases were 

generated within the coalbed during the coalification 

process (17,25,34,57). Some methane gas found in lowrank coals (lignites) was probably generated by biogenetic 

processes (26). 

Formation of methane as well as carbon dioxide and 

water during the coaMcation process was hypothesized by 

White (58-60) and later by Kim (25), Patteisky (34), and 

Selden (38). In a review of European firedamp drainage, 

Venter (57) also concluded that most firedamp was 

probably generated from the organic matter during the 

coalification process. Hargraves (17), in studying outburst 

phenomena in Australian mines, also concluded that the 

methane contained in coal is a byproduct of coalification 

and attempted to estimate the volumes of methane, carbon 

dioxide, and water released during progressive 

coalification. 

More recently, the work of Juntgen (21) and others (6, 

15, 18,22-23,32,40) has provided conclusive evidence for 

the generation of coalbed gases as byproducts of the coalification process. The work of Juntgen (21) is particularly 

significant because a fundamental parallelism between 

coalification and pyrolysis is established. If one accepts 

this premise, there can be little doubt as to the in situ 

origin of coalbed gas. During pyrolysis (heating in an 

oxygen deficient atmosphere) coal releases H,O, CO,, N,, 

H, CH,, and heavier hydrocarbons, then tar; the coal 

eventually becomes coke. If the heating rate is decreased, 

tar formation likewise decreases, eventually to essentially 

zero, while production of methane and other volatiles increases. Using these observations, Juntgen (21) estimated 

that the volume of methane generated by the time a coal 

reached low-volatile bituminous rank was far in excess of 

the storage capacity of the coal. 

Kroger (28) studied the behavior of the individual 

macerals during pyrolysis and demonstrated that exinite 

macerals generate the most volatile matter (water, hydrocarbon, and other gases) and inertinite macerals release 

the least. Similarly, if other coalification variables are 

equal (temperature, time, and pressure), one might expect 

exinite-rich coals to generate more methane than normal 

coals. 

Finally, the work of Creedy (10) is noteworthy for the 

refinement in measurement of occluded gases in coal. 

Creedy's work on the relationship between petrographic 

characteristics and coalbed gas contents established that 

for bituminous coals, gas content generally increases 

proportionately with rank as determined by vitrinite 

reflectance. It was also concluded that gas emission rates 

increased in coal samples with higher fusinite contents. 

RETENTION AND EMISSION OF COALBED METHANE 

Most methane and other gases are retained in coal by 

the process of adsorption (24, 33, 37, 57). Adsorption 

occurs when natural intermolecular attractions between the 

coal and gas molecules bond the gases to the walls of 

naturally occurring pores and fissures in coal. The packing 

together of the adsorbed gas molecules on the large 

internal surface area provided by pores and fissures 

enables large amounts of gas to be retained in a small 

volume of coal. Free gas also occurs in the fissure and 

pore systems and is believed to be in equilibrium with the 

gas in the adsorbed phase (42). 

If the coalbed is capped by an impermeable layer, free 

gas in the fissure-pore network is also in equilibrium with 

the hydrostatic pressure of the surrounding strata. However, if the coalbed is capped by permeable strata, free 

gas will percolate upward, escaping from the coalbed. This 

loss of free gas destroys the equilibrium between free and 

adsorbed gas, allowing desorption to begin. 

Desorption is the opposite of adsorption and occurs 

when the free gas pressure in fracture-pore system is 

lowered causing a disequilibrium between the free and 

adsorbed gas phases. Pressure changes in the free gas 

occur either by gradual percolation upward through 

permeable strata, or lateral migration through the coal 

caused by a pressure differential (16). Both of these 

processes require an interconnected fissure (fracture) 

system. This fissure system is known as cleat and occurs 

in most coalbeds of the United States. 

According to Cervik (8), mass transport of gas through 

the fracture system is governed by Darcy's law, the driving 

force being a pressure gradient. Mass transport through 

the micropore system is governed by Fick's law of diffusion, where concentration gradient is the driving force. 
Key Dlon 

Figure 3.-Map of study area. 
Lo 

Vertical scale, f t 

Washington A Coalbed 

Washington Coalbed (group) 

Little Washington Coalbed 

Waynesburg "B" Coalbed 

Waynesburg "A'] coal bed 

Way nesburg Coal beds 

Uniontown Coal bed 

Sewickley Coalbed 

Pittsburgh Coalbed 

rtigraphic column of Monongahela and Dunkard Groups. 
- 

1 Upper Freeport Coalbed Ezzl 

=Upper Kittanning 

Coalbeds 

Mahoning Coal bed 

n 

Middle Kittanning .-%r , . 

Coal bed ........... 

Clarion Coalbed 

Brookvi lle Coal bed 

m 

.- 

ver l ILUI 

Bottom of hole scale, L, 

I Mercer Coalbed \ln-ain-l 

Limestone 

Shale and clays1 

Siltstone 

Sandstone 

Sandstone or 

siltstone streaks 

Coal 

Figure 5.-Stratigraphic section penetrated by Westmoreland County, PA, corehok. 
This report deals primarily with the rocks of the 

Pennsylvanian Monongahela Group and the Late Pennsylvanian-Permian Dunkard Group (2) of southwestern 

Pennsylvania. It also includes data from the Conernaugh, 

Allegheny, and Pottsville Groups of Westmoreland County. 

A generalized stratigraphic column of the Monongahela 

and Dunkard Groups in the main study area is shown in 

figure 4. A stratigraphic column of the lithologies 

penetrated in the Westmoreland County corehole is shown 

in figure 5. 

Structurally the main study area is characterized by 

broad open folds whose flanks seldom dip more than 1" 

or 2". Little or no faulting is associated with these 

features. Flexure occurred as a result of northwesterly 

directed compressive forces that were active during the 

Allegheny orogeny in the late Paleozoic (31). These forces 

ultimately culminated in large-scale regional uplift of the 

area. 

Major structural features of the main study area are the 

Nineveh syncline, the Washington anticline, and the 

southern terminus of the Finney syncline. These structures 

are shown on a structural contour map (fig. 6) drawn on 

the base of the Pittsburgh Coalbed. 

The Nineveh syncline is one of the more prominent 

structures of the Pittsburgh Plateaus physiographic 

province, extending more than 60 miles in a northeasterly 

direction across northern West Virginia and southwestern 

Pennsylvania. This syncline approximates the axis of the 

Dunkard Basin and is one of the deepest troughs in the 

region. In two areas along the syncline, just south of the 

study area, the Pittsburgh Coalbed is just 100 ft above sea 

level (43), its lowest point in the Dunkard Basin. Within 

the study area, the Pittsburgh Coalbed ranges from about 

200 to 400 ft above sea level along this syncline. 

LEGEND 

Contour interval. 100 ft 0 - 1 

Stole, mile Town or city 

A- A' Cross section. 

Waynesburg Coalbed 

Figure 6.-Structural contour map of study area on base of Pittsburgh Coalbed. 
West of the axis of the Nineveh syncline, the strata rise of the crest of the Washington anticline, dips are much 

fairly rapidly and uniformly towards the axis of the Wash- gentler, sloping northwestward to the weakly expressed 

ington anticline, also a prominent structural feature. West terminus of the Finney syncline. 

RELATION OF COALBED GAS CONTENT TO PETROGRAPHIC 

AND GEOLOGIC FACTORS 

A number of researchers have related the methane content of coalbeds to various geologic factors associated with 

coal formation and occurrence (10, 15, 17, 21, 26, 34). 

Previous work by the Bureau has established that gas content is chiefly a function of depth of cover and rank (11, 

25, 27, 30, 37). Other workers (10, 53, 55) have noted 

similar relationships and detailed work is beginning to look 

more closely at the relationship between gas content and 

petrography. 

A total of 88 samples were collected for gas content and 

petrographic analyses. Plotting of petrographic composition on ternary diagrams revealed that 92 pct of the 

samples fell within the area shaded in figure 7 as would 

most U.S. bituminous coals. The coals typically contained 

75 to 90 pct vitrinite (by volume), 5 to 20 pct inertinite, 

and about 5 pct exinite. Most of the samples (78) were 

from the Pittsburgh through Nineveh Coalbeds (fig. 4), 

however, 10 samples from the Mercer through the Ames 

Coalbeds (fig. 5) were sampled from the Westmoreland 

County corehole. 

In hand specimen, most samples would best be described as hard, blocky coals with mostly thin to medium 

bands of interbedded bright and dull coal. Most coalbeds 

had several distinct bone layers 1/4- to 1-in thick, as well 

as abundant pyrite streaks and lenses. Thin, 1/16- to 

1/8-in fusain bands were occasionally noted. 

Vitrinite 

100 pct 

LEGEND 

lnertinite 

100 pct 

88 total samples 92 pct of samples 

Outliers 

Sewickley Coalbed 

2 Waynesburg "B" Coalbed 

3 Upper Waynesburg Coalbed 

4,5 Lower Waynesburg Coalbed 

Exinite 

A A A 100 pct 

Figure 7.-Ternary plot of maceral composition of sampled coalbeds. 
Figure 8.-Vitrinite percent versus total, desorbed, and residual gas contents. 

100 

90 

80@ 

70 

60 

50 

1 I I I I I 1 I I 0 - 0 

- 0 0 o8 Bo - 80000 

- O' O 00.&8&5~8~ Ja v0 0 0 

0 

0 

oOOP~ 00 - 0 0 O 0 

00 0 0 - 0 

- 0 

0 

- 

- 

- 0 - cb - - 

I I I I I I I I I 

0 I 2 3 4 5 6 7 8 9 10 

DESORBED GAS, 

100- 

90 4- 

0 

a 

; 80- 

lz 

5 F 70- 

5 

60 

50, 

I I I 1 1 I 

- 0 0 - 

- '80 ~o~~~~ o O o - O 0 - 8$80i80 0~800~ o 0 - 8 o 0 ""8" 0 Q0 0 0 -0 

- 0 0 O 0 

O 8 0 - 0 

- - 0 0 - 

I I I I I I 

0 0.5 1 .O 1.5 2 .O 2.5 3.0 3.5 4.0 

RESIDUAL GAS, cm3/g 

100 I I 1 I I 1 I I I 

0 - 0 - 

90 - 0 - 0 0 

- 0 O oO 

- 00 0 Oo 0 

0 

70 - 0 

0 

4 

- 0 

60 - - 0 0 - - 

50. I I I I I I I I I 

1 2 3 4 5 6 7 8 9 10 11 

TOTAL GAS, crn3/g 
Individual maceral compositions of samples from each 

coalbed were plotted graphically along with gas contents, 

(fig. 8). Additional graphs are given in the appendix No 

correlation was found between desorbed, residual, or total 

gas content, and maceral composition. Complete data on 

maceral composition, chemical analysis and gas contents 

are also given in the appendix. 

A better correlation appears to exist between gas 

content and vitrinite reflectance. Reflectance is used 

extensively in oil and gas exploration to determine the 

thermal maturity of potential source rocks (4,6, 15,22-23, 

40). The degree of thermal maturity of the organic source 

material indicates the types and relative amounts of 

hydrocarbons that may be found in nearby reservoir rock. 

Figure 9 depicts vitrinite reflectance plotted against gas 

content; the data set was analyzed by a computerized 

statistical program to determine the best fit function. Best 

fit was obtained with a linear regression that had a 

multiple correlation coefficient (R2) of 0.73. Figure 10 

depicts overburden versus gas content. This data set was 

also analyzed statistically and the best fit function was 

found to be a second degree polynomial with an R2 value 

0.31. Clearly, as a parameter for estimating gas content, 

vitrinite reflectance appears more useful than depth of 

cover. 

0.7 0.8 0.9 1 .O 

VlTRlNlTE REFLECTANCE MEAN-MAXIMUM, pet 

Figure 9.-Vitrinite reflectance versus total gas content. 

200 400 600 800 1,000 1,200 

DEPTH OF OVERBURDEN, ft 

Figure 10.-Depth of cover versus total gas content 
LEGEND 

Town or city O Data points with meon-maximum -- 7.5' top0 raphic 

ref lectance percent of vitrinite quadrang?e boundary 

I 

Ou 

Scale, mile 

Figure 1 1 .-lsoreflectance map of Lower Waynesburg Coalbed. 
TABLE 1. - Gas content and vltrinite reflectance data for Upper and Lower Waynesburg Coalbeds in flgure 12 

Map key Waynesburg Coalbed Gas, cm3/g Mean-maximum vitrinite Roof lithology (caprock) 

Desorbed Residual Total reflectance, pct 

UW1 ... Umer . . ......... 1.9 1.8 3.7 0.75 Hard shale. 

LWlA ... Lower ......... 2.3 1.2 3.5 

LW1B.. . .. .do ......... 2.8 1.5 4.3 

UW2 ... Upper ......... 2.6 2.1 4.7 

LW2A ... Lower ......... 2.7 1.9 4.6 

.. .do ......... Upper ......... Lower ......... Upper ......... Lower ......... Upper ......... Lower ......... .. .do ......... Upper ......... Lower ......... 

Claystone parting. 

Do. 

Hard shale. 

Claystone and shale parting. 

Do. 

Broken shale. 

Claystone parting. 

Shale. 

Shale parting. 

Hard shale. 

Claystone parting. 

Do. 

Hard shale. 

Broken shale and claystone 

parting. 

UW ... Upper ......... 3.8 2.5 6.3 .75 Hard shale. 

LWA ... Lower ......... 4.0 1.5 5.5 .80 Broken claystone parting. 

LWB ... .. .do ......... 3.6 2.5 6.1 -79 Do. 

ND Not determined. 

CROSS SECTION A-A' 

LI ! 

Scale, ft 

Figure 12.-Structural cross section of Upper and Lower Waynesburg Coalbeds showing gas contents. 
OShole 

=Shale w~th sandstone streaks 

C Sondslme 

L~rnestone 

LW I 2 Drill holelocat~on 

/ 

/ 

/ 

/ 

/ Horizmtal 

Scale, ft 

Figure 13.-Panel diagram of Uniontown and Upper and Lower Waynesburg Coalbeds. 
The effects of structural position on reflectance values 

and gas contents is illustrated by table 1 and figure 12, 

which is a cross section of the Upper and Lower Waynesburg Coalbeds. This diagram shows that where the coalbeds are overlain by shale, gas content and vitrinite 

reflectance increase towards the synclinal axis except where 

the coalbeds are overlain by incompetent fractured strata. 

This difference in gas content may result from increased 

gas generation by the higher reflectance coals due to 

greater temperature and former depth of burial. The difference may be further influenced by the increased fracturing and destressing of the strata towards anticlinal 

crests. Figure 12 also illustrates that reflectance and 

structural position may be more influential on gas content 

than depth of cover (overburden). 

Roof lithologies may also influence gas contents as 

shown in table 2 and figure 13. Core samples of Waynesburg Coalbed overlain by massive channel-phase sandstone 

(Waynesburg sandstone) show distinctly lower gas contents 

and reflectance values than do samples overlain by thick 

shale. The lower gas content then, may be due to gas 

migration into the porous sandstone and/or lower gas 

generation as indicated by lower reflectance. Significant 

gas emission from a sandstone overlying the Pittsburgh 

Coalbed in northern West Virginia (54) may support the 

migration theory. On the other hand, the sandstone may 

have in effect acted as a heatsink, its better thermal 

conductivity than shale allowing it to draw geothermal heat 

away from the coalbed, causing a lower degree of coalification (reflectance) (5, 42). Another possibility is that 

paleocurrent action, in scouring the channel where the 

sandstone was later deposited, may have resulted in increased maceration and oxidation forming desmocollinite 

or vitrinite B, the lower reflectance vitrinite noted by 

Brown (7). 

PALEOGEOTHERMAL GRADIENT AND FORMER DEPTH OF BURIAL 

Vitrinite reflectance gradients were used in conjunction 

with a version of Karweil's coalification nomogram [as 

modified by Bostick (3)] to estimate former maximum 

depth of burial and paleogeothermal gradient influencing 

coalification of the organic material in the sedimentary 

sequence of the northern Dunkard Basin. In the modified 

Karweil nomogram (fig. 14), the coalification temperature 

can be estimated from vitrinite reflectance data if the 

length of time (geologic) the organic matter was near 

maximum depth of burial can be reasonably estimated. 

By looking at the overall stratigraphic (vertical) 

variation in vitrinite reflectance values, one may calculate 

the reflectance gradient in terms of percent reflectance 

change per unit distance (vertical). The reflectance 

gradient can then be converted to a temperature gradient 

using the modified Karweil nomogram. By comparing the 

paleotemperature gradients responsible for coalification in 

different sedimentary basins or within a single basin, one 

may begin to explain the differences in overall gas content 

of similar coal-bearing sequences. 

I I I I, 111 Ill, 

0.1 0.5 I 5 10 

MAXIMUM REFLECTANCE, pct 

Figure 14.-Modified Kanweil nomogram. 

The coalbeds of the main study area were grouped 

stratigraphically and their average reflectances calculated 

and plotted versus depth, using average stratigraphic 

intervals for the study area. Average mean-maximum vitrinite reflectance values were determined for 11 coalbeds 

ranging from the Pittsburgh Coalbed upward to the Ten 

Mile Coalbed, a stratigraphic interval of about 750 ft. The 

Fish Creek Coalbed horizon, averaging 60 ft above the 

Ten Mile Coalbed, was used as a horizontal datum. The 

vitrinite reflectance gradient was calculated to be 0.288 pct 

per 1,000 ft (55) (fig. 15). Figure 15 also shows the number of samples for each coalbed and the range of reflectance values for that horizon. The circled anomalous 

reflectance values are those mentioned previously beneath 

thick Waynesburg Sandstone. The reflectance gradient of 

the coalbeds sampled from the Westmoreland County 

borehole shows a similar reflectance gradient of 0.295 pct 

per 1,000 ft (53), implying the gradient may be similar for 

the Pennsylvanian-Permian section throughout southwestern Pennsylvania. 

In order to utilize the modified Karweil nomogram, the 

effective heating time or the length of geologic time that 

the sediments were within 15" C of their maximum 

temperature must be estimated. Essentially, this would 

also be the approximate length of geologic time that the 

sedimentary section remained at or near maximum depth 

of burial. For the coalbeds of the Dunkard Basin, this has 

been estimated to be 25 to 50 m.y. (20). Based on 

estimated paleotemperatures using 25, 35, and 50 m.y. 

effective heating times, it seems likely that the coalbeds 

investigated spent about 35 to 50 m.y. at or near their 

maximum depth of burial. Shorter times yield higher 

paleotemperatures that seem unlikely based on deeper oilproducing zones; longer times are probably inappropriate 

based on 250 m.y. before present timing of the Allegheny 

orogeny (56). The entire section studied (Pittsburgh to 
1 1 

- - 

- - 

- 

- 

0 - 

H Range of reflection * 

- 3 No. of samples 

Average reflectance 

o Anomalous reflectance values - (still used in averages) 

- 

- Reflectance gradient: 0.288 pct per 1,000 ft 

I 

VlTRlNlTE REFLECTANCE. MEAN-MAXIMUM, pct 

Figure 15.-Vitrinite reflectance versus depth below Fish Creek 

Coalbed horizon. 

Ten Mile Coalbeds) underwent the same effective heating 

time as evidenced by the continuous sedimentary record 

remaining above the Ten Mile Coalbed (minimum 600 ft). 

This indicates that subsidence was relatively continuous 

and the study section did not reach maximum depth of 

burial until welI after deposition of the Ten Mile Coalbed. 

Therefore, the length of time each studied coalbed was at 

maximum depth of burial would be the same. 

Because most geothermal gradients are expressed in 

metric terms (degree Celsius per kilometer) it would be 

convenient to work with reflectance gradients expressed 

in similar units. The measured reflectance gradient for 

about 800 ft of section above the Pittsburgh Coalbed was 

found to be 0.288 pct per 1,000 ft in Washington and 

Greene Counties. A similar gradient of 0.295 pct per 

1,000 ft was found for a 1,100-ft section below the Pittsburgh Coalbed in Westmoreland County. This represents 

a measured reflectance gradient averaging 0.29 pct per 

1,000 ft for about 1,900 ft or nearly 213 km of sediment 

above and below the Pittsburgh Coalbed. Therefore extrapolating this gradient to a full kilometer does not seem 

unreasonable. This average reflectance gradient (0.29 pct 

per 1,000 ft) converts to a reflectance gradient of 0.95 

pct/km that was used in calculating the paleogeothermal 

gradients. 

To calculate the paleogeothermal gradient, a lower 

reflectance value of 0.6 pct was chosen for the Fish Creek 

Coalbed horizon. This value seems reasonable based on 

0 

0.1 0.5 I 5 10 

MAXIMUM REFLECTANCE, pct 

Figure 16.-Estimated paleotemperature at top and bottom of 

1 -km-thick sedimentary section. 

the average reflectance of the Ten Mile Coalbed and the 

presence of a continuous section above it. Adding the 

reflectance change for a kilometer of intervening sediment 

yields an upper reflectance value of 1.55 pct. By inserting 

these values into the Karweil nomogram, using 50 m.y. 

effective heating time, paleotemperature of 72" C is estimated for 0.6 pct reflectance and a paleotemperature of 

140" C is estimated for a reflectance of 1.55 pct (fig. 16). 

The difference in temperature then corresponds to the 

paleogeothermal gradient of 68" C/km, which is significantly higher than the 30" C/km paleogradient estimated 

by Hower (20). If shorter effective heating (burial) times 

are used (i.e., 25 and 35 m.y.), paleogeothermal gradients 

of up to 90" C/km are implied. 

Substantiating this estimate is difficult. Thermal 

gradients measured in modern sedimentary basins are typically lower, on the order of 20" to 40" C/km (15,22-23), 

however, significantly higher gradients are not uncommon 

(42). Assuming the Earth has been steadily cooling since 

its origin, the overall geothermal heat flow would obviously 

have been greater 300 m.y.; however, it is unlikely that this 

alone would account for such a high gradient. Possibly this 

ancient, higher, background heat flow coupled with heat 

loss from a thermal event associated with the Appalachian 

orogeny produced the higher thermal gradient. 

Projection of the reflectance gradient to deeper 

horizons seems to correlate well with the limited published 

data on the thermal maturity of these horizons. For 

example, projecting the reflectance gradient from the 

0.6 pct average for the Fish Creek Coalbed horizon to the 

base of the Mississippian System (about 0.8 km lower) 

yields a projected reflectance of 1.36 pct for this horizon. 

The conodont color alteration index (CAI) for the Mississippian rocks of the study area is between 1.5 and 2.0 (13). 

This approximates a vitrinite reflectance of 0.85 to 1.3 pct 

(13), so the 1.36-pct projection is slightly high, but not 

unreasonable. Projecting the reflectance gradient farther 

down section to the base of the Devonian (about 2 km 

below the Pittsburgh Coalbed) yields an estimated 

reflectance of 2.7 pct. Measured mean-maximum vitrinite 
3 00 I Ill I I Ill I I 11 I 1111 

I Surface, 20" C 

~e~ih of 

burial 

MAXIMUM REFLECTANCE. pet Pittspiu: palbed, 

Figure 17.-Estimated maximum paleotemperature of Pittsburgh 

Coal bed. 

reflectance values of 2.4 and 2.6 pct have been recorded 

for Lower Devonian rocks in southwestern Pe~sylvania 

and northern West Virginia (46), indicating that the 

calculated reflectance gradient may likely extend from the 

Permian through Devonian Systems in southwestern 

Pe~sylvania. 

Once the estimate of the paleogeothermal gradient has 

been established, estimating former maximum depths of 

burial becomes relatively simple. For example, typical 

vitrinite reflectance of the Pittsburgh Coalbed in the study 

area is 0.80 pct. Using this value with the Karweil 

nomogram and assuming 50 m.y. effective heating time, a 

100" C maximum paleotemperature is suggested for the 

Pittsburgh Coalbed (fig. 17). Assuming a surface 

temperature of 20" C, the difference from the paleosurface to the Pittsburgh Coalbed is 80" C (fig. 18). If 

the paleogeothermal gradient was 67" C/km, then simple 

If thermal gradient = 68' C/ km, 

then depth of burial = 1.2 km 

Figure 18.-Estimated former depth of burial of Pittsburgh 

Coalbed. 

arithmetic indicates the former maximum depth of burial 

of the Pittsburgh Coalbed to be 1.2 km. 

This estimated former maximum depth of burial agrees 

well with the estimates of McKee (31), who calculated a 

1.5-km burial for the Pittsburgh Coalbed based on an average volatile matter content It also agrees well with the 

implied depth of burial suggested by Farrington's (14) estimates as to the original thickness of the Permian strata. 

The 1.2-km estimate is, however, significantly lower than 

the former depth of burial suggested by Hower (20), a 3.5- 

to 4.0-km burial for Allegheny Group coalbeds. 

CONCLUSIONS 

This report represents a Bureau of Mines preliminary 

investigation on the effects of petrographic characteristics 

on gas generation, storage, and emission by coalbeds. 

Further studies will attempt to carry the findings of this 

study into coalbeds of differing ranks and geologic settings. 

The following are the conclusions resulting from this 

investigation: 

1. Review of pertinent literature shows that a relationship exists between the coamcation process and 

hydrocarbon generation in coalbeds. 

2. No correlation was found between methane content 

and petrographic composition of coalbeds. 

3. A preliminary correlation was found in high-volatile 

rank coals between vitrinite reflectance and gas content. 

This correlation may also be valid for higher rank coals. 

4. The primary vitrinite reflectance-gas content relationship may be influenced by such geologic factors as integrity and composition of the roof rock and position with 

respect to regional anticlinal and synclinal structures. 

5. The coal-bearing sequence of the northern Dunkard 

Basin was subject to a calculated paleogeothermal gradient 

of 65" to 75" C/km. The Pittsburgh Coalbed was 

probably formerly buried under about 1.2 (this report) to 

1.5 km (31) of overburden. 
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APPENDIX A.- RESULTSOF PETROGRAPHIC AND CHEMICAL ANALYSES 

TABLE A.1 . . Maceral composition and gas content data 

Sample Gas. cm3/a (MMF) Mean-max Total Total Total 

Coalbed depth. County Desorbed Residual Total reflectance. vitrinite. exinite. inertinite. 

ft 

Lower Waynesburg 305 Greene ..... 0.7 

Upper Washington 227 Washington . . 3 

Fish Creek ...... 213 Greene ..... . 3 

Ten Mile ........ 447 .. .do ...... . 3 

Do ........... 181 .. .do ...... . 2 

Upper Waynesburg 278 Washington . . 2 

Uniontown ...... 341 .. .do ...... . 1 

Lower Waynesburg 306 Greene ..... 1.0 

Do ........... 619 ... do ...... . 3 

Waynesburg A ... 165 Washington . . 7 

Upper Waynesburg 695 Greene ..... . 1 

Lower Waynesburg 472 Washington . . 6 

Washington A .... 247 .. .do ...... . 7 

Ten Mile ........ 265 Greene ..... 1.2 

Washington ..... 551 ... do ...... 1.3 

Do ........... 138 Washington . 2.0 

Lower Waynesburg 603 .. .do ...... 1.4 

Washington A .... 506 Greene ..... . 4 

Pittsburgh Rider . . Washington . 1.4 

Upper Waynesburg 881 Greene ..... . 5 

Do ........... 601 Washington . 1.7 

Lower Waynesburg 282 .. .do ...... 2.2 

Pittsburgh ...... 339 ... do ...... 1.8 

Pittsburgh Rider . . 715 .. .do ...... . 7 

Waynesburg B ... 164 ... do ...... 2.0 

Upper Waynesburg 469 .. .do ...... 2.1 

Lower Waynesburg 441 .. .do ...... 2.4 

Pittsburgh ...... 338 .. .do ...... 1.8 

Pittsburgh Rider . . 540 ... do ...... 2.2 

Sewickley ....... 509 Greene ..... . 9 

Upper Waynesburg 394 Washington . 1.9 

Fishpot ........ 510 Greene ..... 1.4 

Lower Waynesburg 882 .. .do ...... . 8 

Uniontown ...... 951 .. .do ...... 2.4 

Pittsburgh ...... 340 Washington . 1.9 

Waynesburg ..... 599 Greene ..... . 4 

Lower Waynesburg 698 .. .do ...... 2.5 

Do ........... 823 ... do ...... 1.7 

Sewickley ....... 539 Washington . 1.8 

Lower Waynesburg 601 Greene ..... 1.9 

Washington ..... 558 ... do ...... 2.0 

Lower Waynesburg 475 Washington . 2.4 

Uniontown ...... 416 .. .do ...... . 1 

Upper Waynesburg 820 Greene ..... 2.0 

Uniontown ...... 666 Washington . 2.3 

Do ........... 537 ... do ...... 2.7 

Pittsburgh ...... 660 ... do ...... 2.1 

See explanatory note at end of table . 

Dct 

0.60 

-63 

. 70 

. 66 

-64 

. 73 

. 71 

. 72 

-77 

. 73 

. 73 

. 67 

-73 

-62 

-74 

. 71 

. 72 

-64 

. 70 

. 66 

. 74 

. 7 1 

. 73 

. 78 

. 69 

. 72 

. 76 

. 76 

. 6 1 

. 73 

. 75 

. 67 

. 72 

. 77 

-72 

-69 

-72 

-75 

. 83 

-79 

. 76 

-74 

. 72 

. 77 

. 69 

. 71 

-83 

Dct 

5.5 

3.3 

3.0 

2.8 

2.9 

1.8 

3.0 

3.2 

5.5 

1.8 

10.0 

18.4 

2.6 

2.4 

6.9 

5.6 

3.3 

2.7 

2.4 

4.6 

1.7 

2.9 

4.5 

-8 

3.1 

3.3 

11.8 

4.8 

3.0 

2.0 

3.2 

2.4 

3.3 

2.0 

3.1 

11.5 

2.3 

3.6 

9.1 

2.9 

4.0 

6.6 

3.1 

3.5 

2.1 

2.2 

8.9 

Dct 

15.6 

23.5 

13.9 

13.2 

12.4 

17.4 

16.3 

6.4 

9.3 

14.5 

14.5 

24.7 

10.1 

9.8 

17.3 

9.8 

7.5 

12.1 

11.8 

8.1 

12.0 

12.6 

10.6 

10.3 

10.9 

12.2 

14.4 

10.5 

12.1 

2.0 

9.9 

14.8 

9.6 

17.0 

11.0 

31.3 

12.6 

7.1 

9.5 

6.3 

14.2 

6.7 

16.9 

8.5 

17.1 

17.9 

20.4 

Sample 

No . 

1467 

1472 

1588 

1509 

1561 

1585 

1587 

1468 

1580 

1 584 

1539 

1 527 

1534 

1589 

1538 

1459 

1505 

1537 

1749 

1521 

1504 

1586 

1722 

1183 

1460 

1525 

1543 

1721 

1754 

1642 

1450 

1470 

1522 

1523 

1723 

1566 

1540 

1560 

1550 

1568 

1591 

1 529 

1549 

1558 

1506 

1530 

1175 
TABLE A.1 . . Maceral composition and gas content data-Continued 

- . - - 

Sample 

Coalbed depth, 

ft 

Lower Waynesburg 399 

Waynesburg B ... 752 

Upper Waynesburg 596 

Uniontown ...... 512 

Sewickle y ....... 639 

Uniontown ...... 762 

Pittsburgh ...... 524 

Waynesburg A ... 556 

Pittsburgh ...... 556 

Uniontown ...... 67 1 

Pittsburgh Rider . . 517 

Lower Waynesburg 274 

Do ........... 275 

Pittsburgh ...... 523 

Upper Waynesburg 270 

Lower Waynesburg 600 

Sewickley ....... 792 

Pittsburgh ...... 52 1 

Upper Bakerstown 440 

Uniontown ...... 465 

Pittsburgh Rider . . 518 

Pittsburgh ...... 665 

Upper Waynesburg 61 5 

Clarion ......... 957 

Pittsburgh ...... 71 8 

Do ........... 520 

Lower Waynesburg 699 

Sewickley ....... 660 

Pittsburgh ...... 720 

Do ........... 793 

Do ........... 661 

Do ........... 663 

Do ........... 630 

Uniontown ...... 340 

Pittsburgh ...... 717 

Lower Waynesburg 700 

Upper Waynesburg 696 

Pittsburgh Rider . . 79 1 

Mercer ......... 1. 042 

Brush Creek ..... 627 

Middle Kittanning . 866 

Brookville ....... 994 

Mahoning ...... 674 

Upper Freeport ... 728 

Upper Kittanning . 786 

Do ........... 806 

MMF Mineral matter free . 

-- - .- - 

Gas, cm31g (MMF) 

County Desorbed Residual Total 

Washington . Greene ..... .. .do ...... Washington . .. .do ...... Greene ..... Washington . Greene ..... Washington . Greene ..... Washington . .. .do ...... .. .do ...... .. .do ...... .. .do ...... Greene ..... .. .do ...... Washington . Westmoreland 

Washington . .. .do ...... .. .do ...... Greene ..... Westmoreland 

Washington . .. .do ...... Greene ..... Washington . .. .do ...... .. .do ...... .. .do ...... .. .do ...... .. .do ...... .. .do ...... .. .do ...... Greene ..... .. .do ...... Washington . Westmoreland 

.. .do ...... .. .do ...... .. .do ...... .. .do ...... .. .do ...... .. .do ...... .. .do ...... 

Mean-max 

reflectance. 

Dct 

0.72 

. 80 

. 77 

. 71 

. 81 

. 69 

-83 

. 75 

. 7 1 . 69 

. 75 

-77 

-78 

. 82 

. 75 

. 79 

. 78 

. 79 

. 82 

. 70 

-77 

-82 

-76 

-84 

-79 

-77 

. 80 

. 83 

. 84 

. 86 

-87 

. 83 

. 87 

. 74 

. 8 1 . 79 

. 75 

. 82 

. 97 

. 91 

1.04 

1.03 

. 94 

1.00 

-97 

1.09 

Total 

vitrinite. 

pct 

80.1 

89.7 

86.4 

79.3 

86.5 

75.3 

85.5 

88.7 

74.1 

80.6 

88.4 

86.7 

86.0 

86.9 

88.0 

91.1 

87.0 

85.3 

84.9 

76.5 

90.6 

84.5 

85.4 

89.7 

81.3 

83.8 

78.9 

88.9 

88.3 

67.9 

77.7 

74.7 

84.8 

78.8 

82.8 

87.5 

85.5 

85.0 

66.7 

80.8 

80.7 

84.3 

94.5 

90.0 

61.8 

85.7 

Total 

exinite. 

pct 

6.1 

3.3 

2.5 

2.2 

5.5 

3.7 

3.4 

3.2 

8.6 

1.1 

1.1 

4.2 

4.0 

3.4 

3.2 

4.1 

4.5 

1.5 

1.2 

1.2 

. 9 

4.2 

2.6 

. 4 

1.8 

3.1 

8.1 

4.2 

2.4 

9.6 

3.8 

4.9 

3.7 

2.7 

4.7 

5.6 

4.6 

4.3 

1.9 

. 2 

2.2 

2.5 

1.2 

1.6 

2.7 

1.5 

Total 

inertinite. 

pct 

13.8 

7.0 

11.1 

18.5 

8.0 

21 . 0 

11.1 

8.1 

17.3 

18.3 

10.5 

9.1 

10.0 

9.7 

8.8 

4.8 

4.5 

13.2 

13.9 

22.3 

8.5 

11.3 

12.0 

9.9 

16.9 

13.1 

13.0 

6.9 

9.3 

22.5 

18.5 

20.4 

11.5 

18.5 

12.5 

6.9 

9.9 

10.7 

31.3 

19.0 

17.1 

13.2 

4.3 

8.4 

35.5 

12.8 

Sample 

No . 

1451 

1520 

1565 

1544 

1545 

1541 

1133 

1578 

1752 

1569 

1128 

1462 

1463 

1132 

1461 

1567 

1573 

1131 

171 5 

1453 

1129 

1178 

1579 

1765 

1185 

1130 

1593 

1531 

1186 

1171 

1176 

1 in 

1158 

1464 

1184 

1594 

1592 

1170 

1768 

1731 

1744 

1767 

1732 

1741 

1742 

1743 
TABLE A.2 . . Chemical data 

Total gas. 

Coalbed 

Upper Washington .......... Lower Waynesburg .......... Fish Creek ................ Ten Mile .................. Do ..................... Upper Waynesburg ......... Uniontown ................ Lower Waynesburg .......... Do ..................... Waynesburg A ............. Upper Waynesburg ......... Ten Mile .................. Lower Waynesburg .......... Washington A .............. Washington ............... Do ..................... Pittsburgh Rider ............ Washington A .............. Lower Waynesburg .......... Upper Waynesburg ......... Do ..................... Lower Waynesburg .......... Pittsburgh ................ Waynesburg B ............. Pittsburgh Rider ............ Sewickley ................. Pittsburgh Rider ............ Lower Waynesburg .......... Upper Waynesburg ......... Pittsburgh ................ Waynesburg ............... Lower Waynesburg .......... Upper Waynesburg ......... 3.7 

Fishpot .................. 3.7 

Uniontown ................ Pittsburgh ................ Lower Waynesburg .......... Do ..................... Sewickley ................. Washington ............... Lower Waynesburg .......... Do ..................... Upper Waynesburg ......... Uniontown ................ Do ..................... Do ..................... Do ..................... 

Ash Sulfur Fixed Fixed 

(AR) (AR) carbon carbon 

(DMMF) 

52.0 

Volatile Volatile 

matter matter 

(AR) (DMMF) 

27.2 48.0 

Apparent 

rank 

NAp 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV- A 

HV- A 

HV-A 

HV-A 

HV-A 

HV- A 

HV-A 

HV-A 

HV-A 

HV-A 

HV- A 

HV- A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV- A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV- A 

HV-A 

HV-A 

HV-A 

HV-A 

HV-A 

HV- A 

HV- A 

HV- A 

HV-A 

Sample 

No . 

- . 

See explanatory notes at end of table . 
TABLE A.2 . . Chemical data- Continued 

Total gas. Ash Sulfur Fixed 

Coalbed C,& lg (AR) (AR) arbon 

l R lAR1 

Lower Waynesburg .......... 4.3 19.1 3.75 48.6 

Pittsburgh ................ 4.3 5.3 1.40 55.4 

Upper Waynesburg ......... 4.3 21.6 5.77 45.6 

Waynesburg B ............. 4.3 20.7 1.52 48.7 

Uniontown ................ 4.4 16.6 4.10 49.0 

Sewickley ................. 4.4 13.0 3.69 52.7 

Uniontown ................ 4.5 30.4 4.27 38.6 

Pittsburgh ................ 4.5 6.7 3.24 57.5 

Do ..................... 4.5 11.8 3.00 51.4 

Waynesburg A ............. 4.5 25.2 4.91 43.6 

Lower Waynesburg .......... 4.6 25.0 5.67 43.7 

Pittsburgh Rider ............ 4.6 27.4 3.60 39.5 

Lower Waynesburg .......... 4.6 19.5 4.90 46.4 

Do ..................... 4.7 19.8 4.34 45.2 

Pittsburgh ................ 4.7 6.7 2.50 S.3 

Sewickley ................. 4.7 25.3 4.02 41.5 

Upper Waynesburg ......... 4.7 18.9 4.64 48.5 

Pittsburgh ................ 4.8 8.9 2.40 53.2 

Lower Bakerstown .......... 5.0 24.4 4.37 49.0 

Uniontown ................ 5.1 26.4 3.07 44.7 

Clarion ................... 5.2 22.8 5.51 47.2 

Pittsburgh Rider ............ 5.2 16.5 4.70 48.0 

Pittsburgh ................ 5.2 8.9 3.00 54.9 

Upper Waynesburg ......... 5.2 20.0 5.14 46.9 

Pittsburgh ................ 5.3 9.6 1.90 53.8 

Do ..................... 5.5 6.4 4.60 52.7 

Lower Waynesburg .......... 5.5 20.0 4.77 46.9 

Sewickley ................. 5.6 13.6 2.90 50.4 

Pittsburgh ................ 5.6 9.2 2.50 55.1 

Do ..................... 5.8 4.2 1.60 56.2 

Do ..................... 5.8 12.7 2.10 51.9 

Do ..................... 5.8 3.7 1.00 60.0 

Do ..................... 6.0 5.9 0.90 58.7 

Uniontown ................ 6.0 28.9 3.47 42.2 

Pittsburgh ................ 6.1 5.9 2.30 55.4 

Lower Waynesburg .......... 6.1 17.6 3.70 49.1 

Upper Waynesburg ......... 6.3 20.4 6.14 46.9 

Pittsburgh Rider ............ 7.1 16.8 4.50 49.3 

Mercer ................... 7.2 24.2 4.87 53.7 

Brush Creek ............... 8.1 37.6 2.17 39.4 

Middle Kittanning ........... 8.2 14.4 4.23 60.8 

Brookville ................. 8.3 16.5 3.16 60.2 

Mahoning ................ 9.4 15.2 4.20 58.4 

Upper Freeport ............. 10.2 8.1 3.17 60.7 

Upper Kittanning ........... 10.3 27.4 6.45 50.0 

Do ..................... 10.6 19.7 2.12 56.1 

AR As received . MV Medium volatile bituminous . DMMF Dry mineral matter free . MMF Mineral matter free . HV-A High volatile A bituminous . NAp Not applicable . 

Fixed Volatile Volatile Apparent Sample 

carbon matter matter rank No . JDMMR (ARI (DMMR 

61.5 30.9 38.5 HV-A 1451 

HV- A 

HV- A 

HV-A 

HV- A 

HV- A 

HV-A 

HV- A 

HV- A 

HV-A 

HV- A 

HV- A 

HV- A 

HV- A 

HV- A 

HV-A 

HV-A 

HV- A 

HV-A 

HV- A 

MV 

HV-A 

HV-A 

HV-A 

HV-A 

HV- A 

HV-A 

HV-A 

HV-A 

HV- A 

HV- A 

HV- A 

HV- A 

HV- A 

HV-A 

HV-A 

HV-A 

HV-A 

MV 

HV-A 

MV 

MV 

MV 

HV-A 

MV 

MV 
Figure A-1 .-Relationship between inertinite and desorbed, residual, and total gas contents. 

40 

30- 

20 

10-0 

I I I I I I I I I 

- - 

O 0 - 

- oO - 00 

- 8 0 - 0 0 oO OgO 0 

f8 0 - 9 :Q0@0 0@O 0 

B 0 OO@ 00#0 0 0 

0 

- om 0 O ooo 00 0 - 0 0 - 

4 I I I 1 I I I I 

0 I 2 3 4 5 6 7 8 9 10 

DESORBED GAS, cm3/g 

40 

g 30- 

w" 5 20- 

E 

- 10- 

I I I I 1 I I 

- 0 - 

0 - 

- 0 - 0 0 

o o o 8 - 0 0O00 o 8 o 8' O 

BOO0 0° O - 

OOo 8 o 0~~058~ iEg80 00 - 

o O8 8 8 O - 0 

0 0 - 

I I 1 I I I 

0 0.5 1 .O 1.5 2 .O 2.5 3 .O 3.5 4.0 

RESIDUAL GAS, cm3/g 

40b 

30 

20 

10- 

I I I I I I I 1 I 

- - 

- - 

- 

0 

- 

0 0 

- cP 0 d 

o 88 o go 

D Oo O 

O0 0 oO 0 

- 

0 0 0 

0 - 0 - 0 

I 0 1 I I I I I 

0 I 2 3 4 5 6 7 8 9 10 

A 

TOTAL GAS, cm3/g 
DESORBED GAS, cm3/g 

0.5 I .O 1.5 2 .O 2.5 3 .O 3.5 4.0 

RESIDUAL GAS, cm3/q 

TOTAL GAS, cm3/g 

Figure A-2.-Relationship between exinite and desorbed, residual, and total gas contents. 

* U.S. GOVERNMENT PRINTING OFFICE: 611-012/00,004 

1NT.-BU.OF MINES,PGH.,PA. 28791