By J. P. Ulery and G. M. Molinda 

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

William P. Clark, Secretary 

BUREAU OF MINES 

Robert C. Horton, Director 
Library of Congress Cataloging in Publication Data: 

Ulery, J, P, (James P,) 

Infl~lence of overlying strata on rncth~uie emissions in a northern 

Vl'est Virginia coal mine. 

(Report of investigations ; 8875)) 

Hibliography : p. 12- 14. 

Supt. of 1)ocs. no.: 1 28.23:8879. 

1. rnilics ,111ci ~nini~!g-R'est Vi~~i~~in-Siifet Int.ilsures. 2. 

(:oal bc.J me thane drilinage-Vl'est Virginia. . Sandstone-U.'c.st \'ir- . . glnla. I. \!olinda, (;. 31. (C;rc,gory \I.). 11. 'l'itle. Ill. Series: Reporr of invc.stigatio~~s (United States. I3ure;lu of '\lines) ; 8879. 

'I'N23,U-13 [TN29.5] 622s[fi22'.81 84-800029 

. 
CONTENTS 

Page 

Abstract ....................................................................... Introduction ................................................................... Acknowledgments ................................................................ Stratigraphy ................................................................... Structure ...................................................................... Methane occurrence and emission ................................................ Discussion ..................................................................... Conclusions .................................................................... References ..................................................................... 

ILLUSTRATIONS 

1 . Location of study area ..................................................... 2 . Generalized stratigraphic section of Pittsburgh Formation in study area .... 3 . Structural contour map drawn on base Pittsburgh Coalbed .................... 4 . Percentage of sandstone in the Lower Member of the Pittsburgh Formation .... 5 . Isopach of rider coal interval above the Pittsburgh Coalbed ................ 6 . Cross-sectional view of typical clay vein .................................. 7 . Panel diagram of eastern portion of study area ............................. 
UNIT OF MEASURE ABBREVIATIONS USED IN THIS REPORT 

cm centimeter mi mile 

cm3 /g cubic centimeter per gram m3 /d cubic meter per day 

ft3/d cubic foot per day MM~ t3/d million cubic feet per day 

f t3/t cubic foot per ton f t foot 

h hour in inch 

/ 

m meter minute of arc 
INFLUENCE OF OVERLYING STRATA ON METHANE EMISSIONS 

IN A NORTHERN WEST VIRGINIA COAL MINE 

By J. P. Ulery and G. Me Molinda 

ABSTRACT 

Since 1970, abnormally high methane emissions have been observed in 

eastern sections of the Federal No. 2 Mine operating in the Pittsburgh 

Coalbed in northern West Virginia. The nature and volume of these 

emissions indicate a source other than the coalbed. An investigation 

was undertaken to delineate probable methane sources. Gas well information and stratigraphic correlation of corehole data indicates that a 

sandstone directly above the main coalbed is an additional source of 

methane emissions. The sandstone body appears to be an ancient stream 

channel, infilled with fine-grained sand and organic matter. Coalification of the organic matter produced methane as a byproduct. Additional methane presumably migrated into the sandstone unit from the 

subjacent coalbeds. The methane became trapped in the porous clastic 

unit by the surrounding impermeable strata. Mine development near this 

unit creates a significant pressure gradient, triggering abnormal methane emissions into the mine along naturally occurring fractures. Predevelopment methane drainage of the sandstone could be accomplished by 

completing vertical boreholes along its trend. 

' Geologist. 

Pittsburgh Research Center, Bureau of Mines, Pittsburgh, PA. 
1-  -  -    - - - - I 

I West Virginia e6G I MONONGALIA COUNTY 

I 

I M 8: %G I Blacksville I 

I 

I4 

East bleeders 

-- - -52 ' Mon -36.1 

l 

Mlne property line' 

5;1 

LEGEND 

i:lGob area 

l Data polnt 

7.5'quadrangle 

@ Gas well 

FIGURE 1. - Location of study area. 
a tunnel-boring machine; now most are of this investigation is to assess the 

driven by continuous-mining machines. geologic factors influencing abnormally 

high methane emissions associated with 

The Federal No. 2 Mine has been the the East bleeders development, the sinksite of several Bureau of Mines investi- ing of Shriver Run shaft and a tunnelgations relating to methane occurrence boring project. 

and emissions (10-11, -- - 35). The purpose 

ACKNOWLEDGMENTS 

The authors gratefully acknowledge the to acknowledge Albert Sainato, mining 

cooperation of Federal No. 2 Mine per- engineering technician of the Pittsburgh 

sonnel and Eastern Associated Coal Corp., Research Center, for his contribution 

especially Frank Peduti, electrical engi- to the drilling and emission data in 

neer, and Gary McHenry, division acci- the section on methane occurrence and 

dent investigator. The authurs also wish emission. 

STRATIGRAPHY 

The minable coalbeds of southwestern 

Pennsylvania and northern West Virginia 

belong to the Pennsylvanian System deposited approximately 280 to 310 million 

years ago. The Pittsburgh Coalbed is the 

basal unit of the Monongahela Group deposited during the late Pennsylvanian. 

The Monongahela Group contains the Pittsburgh, Redstone, Sewickley, and Uniontown 

Coalbeds and exhibits cyclical accumulations of sediments in fluvial and lacustrine environments (4, 7-8,16, 21). - --- - 

The Monongahela Group is subdivided 

into the Pittsburgh and Uniontown Formations (2). The Pittsburgh Formation ex- - tends from the base of the Pittsburgh 

Coalbed to the base of the Uniontown 

Coalbed and ranges from 275 to 350 ft (84 

to 107 m) in thickness across the study 

area. The Pittsburgh Formation is further subdivided into the following five 

members, in ascending order: Lower, Redstone, Fishpot, Sewickley, and Upper. 

This investigation is primarily concerned 

with the lower three members (fig. 2). 

In the study area, the Lower Member is 

25 to 45 ft (8 to 14 m) thick, and includes the interval from the base of the 

Pittsburgh Coalbed to the base of the 

Redstone Coalbed. Above the Pittsburgh 

Coalbed lies the rider coalbed interval, 

a 1.5- to 8-ft (5 to 25 m) sequence of 

soft, gray, clay shales and brittle, 

dark, carbonaceous shales interbedded 

with up to five coalbeds. The rider 

coalbeds vary in thickness from 2 to 29 

in (5 to 75 cm); the thicker coalbeds 

tending to be bony and impure. Overlying 

the rider coalbed interval and extending 

upward to the Redstone Coalbed is a medium to dark gray limy shale that grades 

laterally and vertically into gray, shaly 

limestone and fine-grained nonmarine 

limestone. In portions of the study 

area, the limestone-shale facies gives 

way to fine-grained sandstone and sandy 

shale. 

The Redstone Member ranges from 25 to 

35 ft (8 to 11 m) in thickness and extends from the base of the Redstone Coalbed horizon to the base of the Fishpot 

Coalbed horizon. The Redstone Coalbed 

ranges from 0 to 22 in (0 to 56 cm) 

thick. It is often overlain by a soft 

clay shale 1 to 5 ft (0.3 to 1.5 m) thick 

and occasionally by a dark siltstone of 

similar thickness. The remaining thickness is composed primarily of hard, gray, 

fine-grained, nonmarine limestone, grading laterally into gray shaly limestone 

and calcareous shale. 

The Fishpot Member is 20 to 30 ft thick 

and extends to the base of the Sewickley 

Coalbed. The Fishpot Coalbed ranges from 

0 to 12 in (0 to 30 cm) in thickness and 

is fairly persistent across the study 

area. Overlying the Fishpot Coalbed horizon is usually 1 to 5 ft (0.3 to 1.5 m) 
Pittsburgh Goalbed 

FIGURE 2. - Generalized stratigraphic section of Pittsburgh Formation in study area. 

of gray shale or clay shale. Above this 

shale, in much of the study area, is a 

coarser clastic sequence of gray sandy 

shale and minor fine-grained sandstone 3 

to 25 ft (1.0 to 8.0 m) thick. Above the 

unit is 1 to 4 ft (0.3 to 1.0 m) of clay 

shale or dark, carbonaceous shale that 

directly underlies the Sewickley Coalbed. 

Where the sandy shale-sandstone sequence 

is absent, gray fine-grained limestone or 

limy shale is present. 

Above the Fishpot Member is the Sewickley Coalbed, persistent throughout the 

study area. The Sewickley Coalbed ranges 

from 3 to 5 ft (1.0 to 1.5 m) in thickness and is usually overlain by a massive 

sandstone up to 50 ft (15 m) thick. 

STRUCTURE 

The Federal No. 2 Mine property lies in Just northeast of the mine property are 

the Pittsburgh Plateau section of the Ap- the southern terminations of two major 

palachian Plateau physiographic province. structural features, the Belle Vernon 

The Pittsburgh Plateau section is charac- anticline and the Whitely syncline (30: - 

terized by broad open folds generally - 31). The mine property itself lies aptrending northeast-southwest with little proximately midway between the axes of 

or no faulting present. the Mooresville anticline to the east and 
L-J' 

FIGURE 3. - Structural contour map drawn on base Pittsburgh Coalbed. 
METHANE OCCURRENCE AND EMISSION 

Methane occurrence in the coalbeds of 

the Pittsburgh Formation in southwestern 

Pennsylvania and northern West Virginia 

has been documented through Bureau of 

Mines direct-method testing. Gas content 

of these coalbeds is significant, with 

the Pittsburgh Coalbed having values 

ranging from 89.6 to 265.6 ft3/t or 2.8 

to 8.3 cm3Ig (5). - 

As previously stated, the Federal NO. 2 

Mine has been the site of a number of Bureau of Mines studies dealing with the 

emission, drainage, and utilization of 

coalbed methane. One study of particular 

interest demonstrated that methane emissions into mine workings are influenced 

by the presence of nearby oil and gas 

wells (21). This influence was also 

noted in later methane drainage work (10- - 

- 11). 

This study was undertaken as a consequence of abnormally high methane emissions observed on the eastern side of the 

mine. Abnormal methane emissions were 

first encountered during driving of the 

East bleeders section (fig. 1) in 1970- 

71. Before full development, the section 

was sealed off and a vertical drainage 

hole was drilled ffom the surface. Accurate records of the ventilated gas were 

not kept; however, emissions have been 

sufficient to prevent mine personnel from 

reopening the section. 

In 1978, Shriver Run shaft was sunk 

along Shriver Run just west of Daybrook, 

WV. The shaft was located approximately 

6,000 f t (1,830 m) from the mine workings 

and was to be connected by a tunnel bored 

from 1 North Mains (fig. 1). Methane 

emission problems first occurred while 

the shaft was being sunk. When the shaft 

bottom was approximately 50 ft (15 m) 

above the Pittsburgh Coalbed, abnormal methane flows were encountered. To 

alleviate this problem, about 14 holes 

were drilled radially downward and outward from the shaft bottom to within 5 

ft (1.5 m) of the Pittsburgh Coalbed. 

Gas from these holes was piped to an 8-in 

(20-cm) vertical pipe and vented at the 

surface. Approximately 2 years after the 

shaft was sunk, the vertical drainage 

pipe had a gas flow of 370,000 ft 3/d and 

had produced an estimated 270 M.Plft3/d of 

gas (2). Since then these holes have 

produced gas continuously, although at 

present the flow rate is negligible. 

Further methane emission problems developed during drivage of the 6,000-ft 

(1,830-m) tunnel to intercept the shaf t . When the tunnel boring machine penetrated 

a clastic dike3 about 125 ft (38 m) from 

the shaft bottom, methane emission problems developed that could not be controlled by ventilation alone. In an 

attempt to decrease emissions into the 

tunnel, nine horizontal degasification 

holes were drilled from the tunnel and 

shaft into the main coalbed or one of 

the rider coalbeds. The final three 

holes were drilled at a low angle upward 

through the rider coalbeds, into the 

clay vein and associated fracture system. 

These holes showed abnormally high methane flows (220,000 ft 3/d or 67,056 m3/d) 

(33) and significantly lowered emissions, 

anowing tunnel drivage to continue to 

Shriver Run shaft. 

3~he term "clastic dike" is the proper 

scientific terminology for approximately 

vertical, tabular, sediment-infilled discontinuities in coalbeds; however, "clay 

vein" is so firmly established in coal 

mine terminology that it will be used instead of clastic dike throughout this report. Clay veins usually extend into the 

mine roof and are commonly associated 

with warped, fractured and slickensided 

roof strata (9, 14). - - 
Pennsylvania GREENE 

- COUNTY - - - - -- -- - - -- -- - - -- - - - - -- I 

West Virginia MONONGALIA COUNTY 1 

I I 

I I 

I I 

I 

LEGEND I 

Data point I 

m=- I 0.20 pct I 

> 20 5 40 pct I 

I m>40=60pct 1 

[I1111> 60s 80 PC' I 

I 

+ ZS'quadrangle I 

I 

I 

I Z I 

1 

I 

I 

I 

0 4,000 8,000 I 

IIII] 

I 

I Scale, ft I 

I 

Mine property l~ne 

a 

Contour ~nrerval, 20 pet I I 

I 

I 

----------- J 

FIGURE 4. - Percentage of sandstone in the Lower Member of the Pittsburgh Formation. 
FIGURE 5. - lsopach of rider coal interval above the Pittsburgh Coalbed. 

in a lower energy environment; therefore, 

the rider coalbeds were not eroded. The 

location of this sandstone unit corresponds with Pittsburgh sandstone mapped 

on a more regional scale (16, - 32). 

The presence of the sandstone was not 

detected in underground reconnaissance as 

present workings are still 1,000 to 2,000 

ft (305 to 610 m) from the approximate 

edge of this unit. Some indirect evidence indicating the presence of the 

sandstone channel was observed, however. 

First, clay vein occurrence is more frequent in the southeastern portion of the 

mine. A number of workers have noted increased clay vein and fracture frequency 

associated with the margins - of sandstone 

channels (18, 20, 22, 24, 34). Clay 

veins at ~ederalNo. 2 Mine are very infrequent in western portions of the mine 

workings; they are most frequent in the 

southeastern corner. The southeastern 

corner (2 South Mains area, figure 1) is 

the area of present workings closest to 

the mapped channel. A clay vein was also 

encountered extremely close to the sandstone unit at the site of the methane 

emission problem during the tunnel-boring 

project. 

Observed clay veins were generally Uto V-shaped and cut out 2 to 6 ft (0.6 

to 1.8 m) of coal laterally and 1 to 4 ft 

(0.3 to 1.0 m) of coal vertically. Most 

of the clay veins observed had a thin 

stringer of clay or a fracture extending nearly to the floor. Roof expressions of the clay veins were apparent 

as 3- to 5-ft (1.0- to 1.5-m) wide zones 

of irregularly fractured top containing 

subrounded limestone blocks that form 

hummocky, "pillowlike" structures. In 

cross section, the clay veins were composed of numerous large, subrounded to 

subangular blocks of light to medium 
sons. First, no methane problems were 

encountered cutting the main bench during 

the tunnel-boring project. Methane problems did occur, however, 50 ft (15 m) 

above the coalbed during sinking of 

Shriver Run shaft, and in the tunnel when 

LEGEND 

Gray limestone ~nclusoons Bone partlng 

Coal wlth cleat Cloy veln rnatrux; dark gray to black. 

Sllckensided planes silly Shole to Shole 

FIGURE 6. - Cross-sectional view oftypical clay vein. 

normal methane emissions: a shallow, 

conventional gas reservior,4 or migration 

of gas from existing oil and gas wells. 

The positive effect of oil and gas wells 

on methane emissions into mine workings 

was documented by the Bureau more than 10 

years ago (35). The magnitude of the 

methane emission problem in the eastern 

area was apparent even then. In that Bureau report, the East bleeders section, 

driven parallel to face cleat, showed the 

highest methane concentration and emission rate of any individual section in 

the mine (35, figure 2). Other Bureau of 

Mines research has shown that horizontal 

degasification holes and mine entries 

oriented parallel to the face cleat show 

minimum gas flows, while those oriented 

perpendicular to the face cleat show maximum flows (23). The East bleeders section is an anomaly to this rule because 

it shows significantly higher methane 

4~he gas is trapped stratigraphically 

and/or structurally in porous sandstones 

or limestones. 
I 

I 

,Property line 

0 

- 

1000 2.000 

Scale. 11 

0 Sandy shole 

- * - - 7 ::' Llrney shale ,+- A 

FIGURE 7. - Panel diagram of eastern portion of study area. 
strata, and its location with respect to 

mine workings. 

Gas production from shallow horizons in 

the Pennsylvanian coal-bearing strata of 

northern West Virginia is not unknown. A 

1937 report (28) characterizing the physical and chemical properties of West Virginia natural gases included several Samples of coalbed-associated gas. Most of 

these samples were taken from wells producing in the Pittsburgh Coalbed horizon 

along a northeast-southwest trending line 

in eastern Wetzel County, about 15 mi 

west of the present study area. In a report on oil and gas in Monongalia Cotinty 

(12), the author states that "...a little 

has probably been produced from the 

Pittsburgh coal in the western part of 

Monongalia County." He also notes that 

other Pennsylvanian sands in this area 

"...produced gas from widely scattered 

rather small wells and groups of wells... 

examining well records at the West Virginia Geological and Economic Survey. 

Three wells targeted for deeper horizons 

(fig. 1) located along the north-south 

sandstone trend, produced significant 

initial gas flows from the Pittsburgh 

Coalbed horizon. Well Mon-351 completed 

to about 75 ft (22.9 m) below the Pittsburgh Coalbed showed an initial open-flow 

potential of 21,000 ft3/d (6,400 m3/d), 

which was sustained for 8 h before being 

plugged. The specific production horizon 

was not identified on the well record; 

however, 31 ft (9.5 m) of sandstone was 

logged above the Pittsburgh Coalbed. 

Well Mon-377 was completed to about 50 ft 

(15 m) below the Pittsburgh Coalbed. 

Again, the specific producing horizon was 

not identified; but an initial open-flow 

potential of 20,000 f t3/d (6,096 m3/d) 

was sustained for 10 h before cementing. 

Well Mon-363 was drilled to about 45 ft 

(14 m) below the Pittsburgh Coalbed. The 

since about 1925, however, many wells driller's log indicates a gas "show" from 

have been drilled for gas production from a "soft shale" immediately above the 

these sands, with a moderate degree of coalbed. Initial open-flow potential was 

success." Several other areas showing noted at 17,000 ft3/d (5,182 m3/d) ; final 

production from Pennsylvanian strata have open flow before cementing was 12,000 

also been noted (3). - ft3/d (3,658 m3/d). The length of time 

the well was open was not noted. 

Further evidence for a conventional 

shallow gas reservoir was obtained by 

CONCLUSIONS 

Evidence indicates that abnormal methane flows associated with the tunnelboring project, sinking Shriver Run shaft 

and East bleeders development are probably due to the presence of a shallow gas 

reservoir trending north-south along the 

eastern border of the Federal No. 2 Mine 

property. Significant gas production 

from the more shallow coal-bearing strata 

of northern West Virginia has been documented (3, 12-13, 15, 28) ----- 

The reservoir rock is a sandstone apparently grading upward and laterally 

into a sandy shale. Isopaching of corehole data shows that the configuration 

of this unit is that of a distributary 

channel with a finer grained, westwardextending lobe, possibly representing a 

crevasse splay (29). - The channel was 

probably partially infilled with fine 

sand and organic debris as it eroded into 

the rider coalbed sequence. Later, finer 

sediments, along with additional organic 

matter, may have been washed in during 

flooding of the Redstone peat (coal) 

swamp. 

Deep burial and tectonic activity followed, transforming the organic matter 

accumulated in peat swamps into coal. 

Coalification of the organic matter in 

the sandstone produced methane as a byproduct. Gas formed from organic matter 

in the westward-oriented lobe migrated up 

dip into the main channel system. Some 

methane formed during coalification of 

the subjacent coalbeds and may also have 

migrated into the sandstone. The gas 

was stratigraphically trapped in the 
sandstone by the impermeable limy shales often causing the fractures to open, aland fine-grained limestones surrounding lowing gas migration into mine workings 

it. as the channel is approached. 

Clay veins and fractured, slickensided The most feasible premining methane 

roof have been observed in mine workings drainage system would utilize vertical 

nearest the channel. Presumably, these boreholes and/or shaft degasification 

formed as a result of differential com- techniques (10-11). -- Previous Bureau of 

paction and stratal readjustments due to Mines research has shown that these deoverburden and tectonic stresses in the gasification procedures can reduce methless competent shales adjacent to the ane emissions and provide a safer work 

sandstone unit (17-19, -- - 22). Mining near environment. 

these features redistributes stresses, 

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-1-U.S. GPO: 1984-705-02Oi5030