of Mines/hdustry Technology Transfer Seminar, 

Morgantown, W. Va., May 30-31,1973 

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

Rogers C. B. Morton, Secretary 

BUREAU OF MINES 

John D. Morgan, Jr., Acting Director 
This publication has been cataloged as follows: 

U.S. Bureau of Mines 

Methane control in eastern U.S. coal mines. Proceedings 

of the symposium of the Bureau of Mines/Industry Technology Transfer Seminar, Morgantown, W. Va., May 30-3 1, 1973. 

[~ashin~t on] U.S. Bureau of Mines [ 19731 

96 p. illus., tables. (U.S. Bureau of Mines, Information circular 8621) 

Includes bibliography, 

1, Coal mines and mining-U,S.-Cong, 2, Methane-Congresses. 

I. U.S, Bureau of Mines. 11. Title. (Series) 

TN23 .U71 no. 8621 622.06173 

U.S. Dept. of the Int, Library 

b 
CONTENTS 

Page 

Abstract ................................................................. 1 

Introduction ............................................................. 1 

Acknowledgments .......................................................... 2 

Welcome. by R . W . Van Dolah .............................................. 3 

Opening Remarks. by J . J . Yancik ......................................... 4 

Methane Control in U.S. Coal Mines-- An Overview, by M . G . Zabetakis ...... 9 

Methane in Coal, by F . N . Kissell ........................................ 18 

Degasification Through Vertical Shafts, by H . H . Fields .................. 25 

The Use of Isolated Coal Panels in the Pittsburgh Coalbed, by C . Findlay, 

S . Krickovic, and J . E . Carpetta ....................................... 39 

Control of Methane by Water Infusion, by J . Cervik and A . Cetinbas ....... 46 

Degasification of a Coal Seam-- Longwall Gob Area, by P . A . Ferguson ...... 58 

Gob Degasification Research-- A Case History, by J . G . Davis and 

S . Krickovic ........................................................... 62 

Degasification Through Vertical Boreholes, by M . Deul and C . H . Elder .... 73 

Panel discussion; panelists: J . Ashcraft, R . Dalzell, J . G . Davis, 

P . A . Ferguson, W . Laird, James Micheal, J . J . Yancik, and 

M . G . Zabetakis, moderator ............................................. 82 

Questions submitted after the seminar .................................... 91 

Registration list ........................................................ 93 

METHANE CONTROL IN EASTERN U.S. COAL MINES 

Proceedings of the Symposium of the Bureau of Mines/lndustry Technology 

Transfer Seminar, Morgantown, W. Va., May 30-31, 1973 

by 

Staff-Mining Research 

ABSTRACT 

Research workers from the Bureau of Mines and industry met with other 

government and industry representatives at the Mont Chateau Lodge, Morgantown, 

W. Va., on May 30-31, 1973, to discuss the current status of methane control 

in eastern U.S. coal mines. The opening remarks, the eight technical presentations, and the discussions of the members of a government-industry panel are 

published here for the benefit of those concerned with the control of methane 

in coal mines. In addition, an introduction has been added to present the 

background of work in this field. 

INTRODUCTION 

The Bureau of Mines has been concerned with the control of methane in 

U. S. coal mines since it was established in 1910. The initial study1 of this 

problem was actually begun in 1907 under the immediate supervision of 

Dr. J. A. Holmes, who subsequently became the first director of the Bureau of 

Mines. This study summarized the work of others in Europe and America as well 

as that of Darton in the laboratory and the flexed beds in the anthracite 

fields of Pennsylvania and in the nearby horizontal beds in Illinois. Briefly, 

Darton noted ". . . some of the causes of the variations in the character, 

amount, and pressure of such (explosive) gases are still unknown." Nevertheless, he concluded that the gas in coal is possibly ". . . locked in some 

loose chemical combination, dissolved as salt dissolves in water, or condensed 

as in porous charcoal, but undoubtedly it fills the pores and crevices in 

which it is condensed . . . ; further, "The pressure of water in the strata 

overlying coal beds is probably a factor of some importance in gas pressure 

. . ." He found that an average of about 1,500 cubic feet of methane were 

released per ton of anthracite mined in the Wilkes-Barre, Pa., area, but that 

quantities in excess of twice this figure were encountered. By contrast, he 

found that the deep mines in Illinois yielded 50 to 260 cubic feet per ton. 

After reviewing the European data, he concluded that, "The extension of boreholes horizontally in the coal bed or from the surface above is a promising 

expedient, but in most cases it does not draw much gas from solid coal because 

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

IDarton, N. H. Occurrence of Explosive Gases in Coal Mines. BuMines Bull. 72, 

1915, 248 pp. 
the surface exposed is too small and gas travels through the coal too slowly 

to affect a wide area." From his study of Pennsylvania mines he noted, "The 

mine operators have to use great precaution to insure complete ventilation in . 11 11 all working chambers of the mines . . ., . . . in the northern basin . . . the volume of air for ventilation is equal to about 341,000 cubic feet for 

every ton of coal mined." This is in excess of 12 tons of air per ton of coal, 

which is a large quantity of air even by today's standards, although some 

gassy mines now use twice this amount. 

Others considered this problem in subsequent years, but little experimental work was conducted here until after World War 11. Approximately 20 

years ago, spindle? published the first of a series of papers on methane control, and Venter and stassen3 prepared their report at the request of the 

Bureau of Mines on the drainage and utilization of firedamp in Europe. ~eul~ 

subsequently presented a survey paper in 1964 and proposed a systematic program that was undertaken by the Bureau and a number of cooperating coal companies. The results of the initial phase of this program were presented at a 

special meeting in Pittsburgh, Pa., on May 8, 1969. The present seminar 

should give an up-to-date account of the work being done in eastern U.S. coal 

mines and reiterate that many procedures are available for use in controlling 

methane before and after mining begins. The seminar itself is one in a series 

devoted to various aspects of mine safety and was sponsored by the Bureau of 

Mines Mining Technology Transfer group; arrangements for the seminar were made 

by Messrs. William Schmidt, Thomas J. Crocker, Donald E. Ralston, Milford L. 

Skow, and Michael G. Zabetakis. 

ACKNOWLEDGMENTS 

The Office of the Assistant Director--Mining and the Technology Transfer 

Group wish to express their appreciation to the speakers and the many people 

who helped with the seminar, especially to Dr. M. G. Zabetakis, then of the 

Pittsburgh Mining and Safety Research Center, now with the Mining Enforcement 

and Safety Administration, for arranging the program and proceedings and to 

Thomas J. Crocker, Spokane Mining Research Center, for making the necessary 

arrangements for the seminar. 

ZSpindler, G. R. Degasification of Coal Beds. Coal Mine Modernization, 1953, 

pp. 206-220. 

3 Venter, J., and P. Stassen. Drainage and Utilization of Firedamp. BuMines 

IC 7670, 1953, 22 pp. 

4~eul, M. Methane Drainage From Coalbeds: A Program of Applied Research. 

Proc. 60th Meeting, Rocky Mountain Coal Min. Inst., June 30-July 1, 1964, 

Vail, Colo., 1964, pp. 54-60. 
WELCOME 

by 

R. W. Van Dolah 1 

I would like to welcome each of you to our first methane control seminar 

in the Technology Transfer Series. In the past, I have taken this opportunity 

to review the functions of the Pittsburgh Mining and Safety Research Center. 

But because we have a rather full schedule today I will instead extend an 

invitation to each of you to visit us in Pittsburgh and Bruceton, Pa., where 

we can show you firsthand what we are doing not only in the area of methane 

control and ventilation, but also in other areas of interest to the mining 

community. 

We trust you will find today's program of interest and invite you to join 

us on the field trip scheduled as part of tomorrow's activities. You will be 

given more information on these trips later today. Without further ado, let 

me introduce our first speaker, who really needs no introduction, Dr. Yancik, 

Acting Assistant Director--Mining. Dr. Yancik will discuss the Bureau's program on methane control. 

IResearch Director, Pittsburgh Mining and Safety Research Center, Bureau of 

Mines, Department of the Interior, Pittsburgh, Pa. 
OPENING REMARKS 

by 

J. J. Yancikl 

I would like to welcome you here this morning to what we expect will be 

an interesting and very informative Technology Transfer Seminar on Methane 

Control in Eastern U.S. Coal Mines. While today's emphasis is on the technical presentations, we do hope that you will be able to accompany our researchers to the field tomorrow where you can see firsthand some of the technology 

discussed today. The purpose of this seminar is to provide the coal mining 

industry with detailed information about recently developed techniques, equipment, and instruments for degasifying or otherwise controlling gas in a coalbed. Techniques that you will hear described include degasifica tion through 

vertical boreholes and shafts, isolation of panels, and water infusion. Also, 

degasification of caved areas through boreholes will be described. 

Methane has been a problem in U.S. coal mines almost as long as underground mining has existed. The hazards associated with concentrations of 

methane are well known to all of us. An ignition of an accumulation of methane can result in a devastating explosion particularly when associated with 

coal mine dust. Coal miners and operators alike go to great pains and expense 

to maintain methane levels within safe limits in an attempt to eliminate the 

possibility of a coal mine disaster. 

A recent survey made by the Bureau of Mines and published in IC 8558 

titled "Methane Emission From U.S. Coal Mines," points out that some U.S. coalbeds contain as much as 10 ft3 of methane per cubic foot of coal. A gassy 

mine producing 5,000 tpd of coal may liberate 5 million cfd of methane; 

several mines in the United States liberate in excess of 10 million cfd of 

methane. Regulations require methane to be diluted and carried safely outside 

in ventilating air and necessitate safeguards against sparks that could cause 

a gas ignition. 

The record of disasters that have resulted from methane emission in underground coal mines i s a l l too familiar in our minds. In fact, a series of 

methane explosions in 1907 in essence brought about the creation of the U.S. 

Bureau of Mines in 1910. The immediate effort has been directed toward preventing disas terous explosions through the promotion of safe mining practices, 

lActing Assistant Director--Mining, Bureau of Mines, U.S. Department of the 

Interior, Washington, D.C. 
approved mining equipment, and adequate ventilation; engineers, scientists, 

and coal miners have long sought methods of totally eliminating the problem. 

But the problem has not been simple. It is true that fatalities resulting 

from methane explosions have been greatly reduced, yet the fundamental probblem still persists. 

Figure 1 reflects the improvements made through the efforts of those 

involved in the industry to control explosions resulting from methane ignitions. The trend in fatalities related to explosions is most encouragingly 

downward. However, it must be recognized that methane is potentially an even 

more serious safety threat because of the need for higher productivity and the 

necessity to extract coal from deeper coalbeds. The trend could therefore 

reverse itself without improvement in control techniques and methodologies. 

Hence, increased productivity at deeper depths will not be possible without 

new, innovative, and acceptable control technologies. 

The disaster in 1969 provided the impetus for Congress to pass the Coal 

Mine Health and Safety Act of 1969 which provided the additional funds necessary to continue and expand the methane control research program pursued by 

the Bureau. The current research program has these objectives: Predicting 

methane concentrations in coalbeds; establishing the geological conditions 

that contribute to abnormal methane concentrations in coalbeds; assessing the 

physical properties of coal and adjacent strata that influence the retention 

and emission of methane; studying the effect of coal extraction on the emission of methane; and devising and testing methods for effectively draining or 

controlling methane emissions from coalbeds prior to and during mining. These 

objectives have provided the basis for the methane control research efforts at 

the Bureau of Mines for some time. Degasification techniques as a means of 

controlling methane emission was started about 1963 as a part of the methane 

control research program being pursued by the Bureau. 

An overall view of the methane control research program is shown graphically in figure 2. Selected applications of results from research efforts 

include a demonstration of water infusion techniques to reduce methane in face 

areas and the degasification of methane through vertical boreholes. Other 

applications of results are in process or are planned for the near future. 

Funding levels increased rapidly with passage of the Coal Mine Health and 

Safety Act and are presently at levels slightly lower than the high of 1971. 

While the safeguarding of life is the immediate concernof measures to minimize the effects of methane emission, other benefits are also reaped. By providing improved means of degasifying coalbeds and removing methane from coalbeds prior to mining an operator can maintain or improve methane control while 

at the same time provide increased productivity, decreased ventilation costs, 

and perhaps dispose of the methane commercially and help contribute to the 

solution of the energy problem. 

One of the major problems of moving newly developed technology from its 

laboratory and demonstration phases into active use by the industry is to show 

potential users the benefits that can be gained by incorporation of the new 

technology into their mining systems. To further this endeavor the Bureau has 
INFLUENCE OF SAFETY RESEARCH 

I-II-I-I 

' PERMISSIBLE 

I ETABLISHMENT OF 1 L. EXPLOSIVES 

I - BUREAU OF MINES COAL MINE 

I JULY 1,1910 HEALTH & 

I 

- SAFETY ACT 

500 - 

V) 

;ECK DUSTZ r 1 COAL DUST 

9 

V) 

I LANALYZER 

I I 2 400 - L 

5 I 

E 

2 

LL 

300 - 

- 

!I I 

a 

II 

a LL 

I ~XNITION 

11 SUPPRESSION 

5 200 - I pVlCES 

er 

a 

W I 

> I 

I [KPLOSIONI-( PROOF BULK100 - I pas 

I 

1900 1910 1920 1930 1940 1950 1960 1970 1980 

* 5 YEAR AVERAGES 

FIGURE 1. - Influence of safety research on deaths due to explosions. 
ODE

ME

ST

70 
created a Technology Transfer Group to which is given the responsibility to 

assist in promoting the utilization of new technology. This seminar is but 

one of the ways we attempt to inform you and the industry of newly emerging 

technologies. 

The techniques for improved methane control in underground mines that you 

will hear reported today are rigidly developed technologies and are ready for 

incorporation into the mines. You will have to make the judgment whether or 

not to incorporate these technologies into your mines. The technology is 

available to better and more effectively control methane emission. Our 

research personnel are prepared to offer to you the technical assistance relative to the adoption and/or adaption of these technologies into your particular mining system. 

Progress to date in this methane control research program has largely 

been the result of successful cooperative research efforts with the industry. 

In fact, without this cooperative attitude as exhibited between the Bureau and 

coal companies, advances would not be nearly so successful. We will continue 

in the future to seek cooperative cost-sharing research efforts in order to 

advance even further the state-of-the-art and develop the technologies necessary to control methane. 

Consequently, I invite you, in fact, I urge you to talk to our research 

people here today and tomorrow about your mining problems relative to methane 

control. 
METHANE CONTROL IN U.S. COAL MINES-AN OVERVIEW 

by 

M. G. Zabetak i s 

ABSTRACT 

Methane has been a problem in U.S. coal mines almost as long as underground mining has existed. This paper summarizes the procedures that have 

been used in the past to remove it and to dilute it to a safe level. In addition, the procedures currently being evaluated for use in assessing the magnitude of the methane problem as well as those now available for use in 

removing methane before and during mining are considered briefly. Examples 

are given of the results obtained in recent months in a number of U.S. mines. 

INTRODUCTION 

One of the primary goals of the Bureau of Mines is to decrease and, where 

possible, to eliminate the hazards associated with the mining of coal. In 

this connection, we have reexamined a potential problem area that has been 

associated with coal mining in this country for over 160 years--thepresenceof 

methane. Approximately one in eight deaths has been attributed to the ignition of methane and coal dust in the past 66 years in U.S. coal mines. Unfortunately, this ratio has increased in recent years, in spite of the fact that 

the frequency of occurrence of major mine explosions and the fatality rate 

associated with coal mining have both decreased (figs. 1-2) (2) . This may 

be due in part to the increased liberation rate of methane in today's mines. 

A recent study has shown that the methane emission rate (MER) depends on both 

the mine depth (.D) and on the coal production rate (CPR) (&). Figure 3 gives 

a composite of the methane emission rate data for mines in the Pittsburgh, 

Pocahontas Nos. 3 and 4, and the Illinois Nos. 5 and 6 coalbeds. Based on the 

results in this figure, we can anticipate a further increase in methane emission rates as mining rates and depths increase, unless steps are taken to 

remove this gas before it enters the ventilation air. As noted in the subsequent papers in this series, this can be done before mining starts in a 

l~esearch Supervisor, Methane Control and Ventilation, Pittsburgh Mining and 

Safety Research Center, Bureau of Mines, U.S. Department of the Interior, 

Pittsburgh, Pa. Currently, supervisory physical scientist, Mining Enforcement and Safety Administration, Washington, D.C. 

'underlined numbers in parentheses refer to items in the bibliography at the 

end of this chapter. 
KEY 

Coal product~on 

A Man shifts 

0 Major explosions 

YEAR 

particular area or while 

mining is in progress. A 

consideration of the basic 

principles involved in this 

work should be made; a brief 

summary of the results 

obtained to date in the 

eastern coal mines will follow the next section. 

BASIC PRINCIPLES 

According to Mott (x), 

6 

$4- 

LT 

> 

k 

A 

2 

2 

0 

fraction of this gas is 

retained in our eastern 

coals; the balance being 

lost to the atmosphere. In 

practice, the amount of 

methane that has been 

retained by a particular 

coal is determined in part 

by the coal itself, the 

moisture content and temperature of the coal, and the 

hydrostatic pressure at the 

location at which the coal 

is located. Thus, if we 

assume that the gas pressure 

at a particular location is 

exactly equal to the hydrostatic head pressure, then 

we can write: 

1880 1900 1920 1940 1960 1980 approximately 3,000 £I? of 

methane is produced in formFIGURE 1. - U.S. coal mine fatality rate; a, per thousand ing 1 ton of a medium rank 

300-day workers and 6, per mil lion man-hours bituminous coal, along with 

exposure. copious quantities of carbon 

dioxide and water. Only a 

1 

2O ' O o 

0 

'k_. 1 

2- b om 

KEY o D o -- 0 0- 0 a 5 - year average rate 0-o---- m rn Annual rate m 

FIGURE 2. - Underground coal production, man-shifts, where h is the height of 

and major coal mine explosions in U.S. water column above the coal. 

mines between 1850 and 1970 (5-year Knowing this pressure, we 

averages). can then measure the amount 

of gas that would be 

adsorbed by a ton of coal at 

a particular temperature. For example, Joubert (16) has found that the gas 

adsorbed by water-saturated coal in the Pittsburgh coalbed is given approximately by the equation: 
8 1 i I I I 1 1 1 1 Using equation 1, we can 

write this in terms of h. 

- Thus we have: 

6- 0'666h ft3/ton, (3) = 1+0.0017h 

D - + 

0 Pocahontas - where h again represents the 

U) height of the water column 

2 4- - above the coal. If we make 

& the turther assur~~p liun that 

W - - 2 h is essentially the height 

of the overburden, then we 

2- can determine the gas content of the coal at any loca- - - tion in the Pittsburgh coalbed. Unfortunately , severa 1 

0 2 4 6 8 10 difficulties are encountered 

when we attempt to use 

CPRxD. lo3 tpdx103ft equation 3. First, it is 

difficult to determine the FIGURE 3. - Methane emission rate versus coal produc- actual overburden height in 

t ion rate times depth for mines in the Pitts- mountainous areas. Second, 

burgh, Pocahontas Nos. 3 and 4, and illi- even when we know this 

nois Nos, 5 and 6 coalbeds. height, we may not necessarily know the actual hydrostatic head. For example, 

figure 4 gives the measured gas pressures as a function of well depth for a 

number of wells drilled into various coalbeds in the United States. This work 

is discussed in greater detail by Deul (6); for our present purposes, however, 

note that the gas pressure is actually below Phyd in most cases, so that equation 3 would tend to overestimate Vad. Nevertheless, this equation can serve 

as a first approximation if other data are not available. Finally, a comparison of the adsorbed gas volumes and the actual methane emission rates obtained 

from operating mines (fig. 3) shows that, as expected, emission rates are much 

higher. For example, using the data from mines in the Pittsburgh coalbed, the 

ratio of the methane liberation rate (MLR = MER/CPR) to Vad is approximately 4 

(fig. 5). Kissell E) has studied this in some detail and found even larger 

ratios in many cases. 

METHANE CONTROL IN THE UNITED STATES 

Although the Bureau of Mines has been interested in methane control for a 

number of years, very little was done in this area, other than in the field of 

ventilation, until fairly recently. Approximately 20 years ago, J. Venter and 

P. Stassen, Institut National de 1'Industrie Carbonniere, Belgium, prepared a 

paper on the drainage and utilization of firedamp in response to a request 

from the Bureau (37). During this period, Spindler, Poundstone, Merritts, and 

Ridenour @-28, 32-34) initiated a series of investigations on the use of 

horizontal and vertical holes to remove methane from virgin coal and on the 

use of water to block it at active face areas. Following this early work, 
Spindler and Poundstone (34) noted 

that: "Horizontal drilling in advance 

of underground mining appears to offer 

the most promising prospect, but effective and extensive application will be 

dependent upon the ability to drill 

long holes . . . " Also, 'Water infusion appears to offer some good prospects as an aid to degasification and 

in the control of gas liberation rates 

in producing sections and at working 

faces and should be investigated 

further. " 

0 

o A systematic study of methane 

1 I I 

0 500 1,000 1,500 2,000 control was initiated here about 10 

years ago. The initial results of 

DEPTH, ft this work were presented at a seminar 

FIGURE 4. - Shut-in pressure versus well held in Pittsburgh, Pa., in 1969 

depth (h). (2, 1, 12-13> 25, 2). In recent 

months, additional studies have been 

made by the Bureau and 

others on improved packers 

for use underground 

(L), the composition of 

coalbed gas (18-u) , the 

movement of methane in coal 

(1, g), the determination 

of the methane content of a 

coalbed from cores (22) , degasification through 

0 vertical boreholes (6) , 200 400 600 800 1000 degasif ication through horih, ft zontal holes (2-u), the use 

FIGURE 5. - Methane liberation rates and adsorbed gas of isolated panels U) Y 

volumes for mines in the Pittsburgh coalbed the effects geologic 

versus depth (h). factors (a g), the 

effects of oil and gas wells (z), methane control by 

water infusion (2-5) , gob degas if ication through vertical boreholes (8, 2) , the effects of bleeder systems (24), methane emission from operating mines 

(14, 23), and the ventilation of deep mines (17). This work has shown quite 

conclusively that many U.S. coalbeds can be successfully degasified before 

mining commences. We are now in the process of degasifying a producing mine 

in the Pittsburgh coalbed. Several phases of this work are discussed by 

Deul @), Fields e), Krickovic (z), and Cervik (3). 

Finally, while all underground mines must be ventilated, other methane 

control techniques can be considered under the provisions of Section 301(b) 
>\\\\ \\\\ \ii\- \ \ -.- ,\\\ \ - \\T - -?-\-\-7 

\ \\\\,\\\\ \\ . bslotteh vertical pipes . \ , \ \ \\\\\ \ \\ \\ 

'L'~\A\A ALLS\LLLL~ 

I I I I I 

0 20 40 60 80 100 

EFFICIENCY, pct 

FIGURE 6. - Efficiencies of various methane control techniques in eastern U.S. coal mines. 
coal mined, ventilation alone should be considered inadequate and that other 

methane control procedures should be utilized. This would include the use of 

vertical and horizontal holes to dewater and degasify an area before the onset 

of mining; the use of horizontal holes to infuse an active face area with 

water and thus divert the flow of methane; the use of long horizontal holes to 

dewater and degasify a section during mining; improvement of bleeder entries; 

the use of vertical holes and slotted pipes to drain a gob area; the outlining 

of isolated panels to degasify the panels prior to mining; hydrofracing a 

block of coal to increase its permeability; and rapid dilution of methane with 

air as it enters the mine. Detailed procedures can be found in a number of 

references included in the bibliography (39) . 

CONC LU ONS 

Methane control procedures must be utilized more extensively to prevent 

the anticipated increase in methane emission rates from underground mines as 

mining rates and depths increase. These should be incorporated in all phases 

of underground mining, beginning with the initial exploration and continuing 

until mining is completed. 
BIBLIOGRAPHY 

1. Bielicki, R. J., J. H. Perkins, and Fred N. Kissell. Methane Diffusion 

Parameters for Sized Coal Particles--A Measuring Apparatus and Some 

Preliminary Results. BuMines RI 7697, 1972, 12 pp. 

2. Cervik, Joseph. Behavior of Coal-Gas Reservoirs. BuMines TPR 10, 1969, 

10 PP* 

3. Cervik, Joseph, and Abdurrahman Cetinbas. Control of Methane by Water 

Infusion. Pres. at Tech. Transfer Seminar on Methane Control in Eastern U.S. Coal Mines, Morgantown, W. Va., May 30-31, 1973, 35 pp. 

4. Cetinbas, Abdurrahman, R. P. Vinson, Joseph Cervik, and M. G. Zabetakis. 

Methane and Dust Control by Water Infusion. Pittsburgh Coalbed 

(Fairview, W. Va.). BuMines RI 7640, 1972, 17 pp. 

5. Cobbs, J. H., and J. D. Hadden. New Packer Helps Control Methane in Coal 

Mines. Coal Age, v. 78, No. 1, January 1973, pp. 60-62. 

6. Deul, Maurice, and C. H. Elder. Degasification Through Vertical Boreholes. Pres. at Tech. Transfer Seminar on Methane Control in Eastern 

U.S. Coal Mines, Morgantown, W. Va., May 30-31, 1973, 15 pp. 

7. Elder, C. H. Use of Vertical Boreholes for Assisting Ventilation of 

Longwall Gob Areas. BuMines TPR 13, 1969, 6 pp. 

8. Ferguson, Pete. Methane Control by Boreholes. Coal Age, v. 77, No. 1, 

January 1972, pp. 76-77. 

9. Fields, Herbert H. Degasification Through Vertical Shafts. Pres. at 

Tech. Transfer Seminar on Methane Control in Eastern U.S. Coal Mines, 

Morgantown, W. Va., May 30-31, 1973, 25 pp. 

10. Fields, H. H., Stephen Krickovic, Albert Sainato, and M. G. Zabetakis. 

Degasification of Virgin Pittsburgh Coalbed Through a Large Borehole. 

BuMines RI 7800, 1973, 26 pp. 

11. Findlay, Charles. Private communication, 1973. Available upon request 

from Stephen Krockovic, Pittsburgh, Pa. 

12. Hadden, J. D., and Joseph Cervik. Design and Development of Drill Equipment. BuMines TPR 11, 1969, 11 pp. 

13. Hadden, J. D., and Albert Sainato. Gas Migration Characteristics of 

Coalbeds. BuMines TPR 12, 1969, 10 pp. 

14. Irani, M. C., E. D. Thimons, T. G. Bobick, Maurice Deul, and 

M. G. Zabetakis. Methane Emission From U.S. Coal Mines. A Survey. 

BuMines IC 8558, 1972, 58 pp. 
15. Jeran, P. W., and J. R. Mashey. A Computer Program for the Stereographic 

Analysis of Coal Fractures and Cleats. BuMines IC 8454, 1970, 34 pp. 

16. Joubert, James I. Private communication, 1972. Available upon request 

from James I. Joubert, Pittsburgh, Pa. 

17. Kalasky, J. D. Ventilation of Deep Coal Mines. Min. Cong. J., v. 58, 

No. 9, September 1972, pp. 43-48. 

18. Kim, Ann G. The Composition of Coalbed Gas. BuMinesRI 7762, 1973, 9 pp. 

19. Kim, A. G., and L. J. Douglas. Gases Desorbed From Five Coals of Low Gas 

Content. BuMines RI 7768, 1973, 9 pp. 

20. Kissell, Fred N. The Methane Migration and Storage Characteristics of 

the Pittsburgh, Pocahontas No. 3, and Oklahoma Hartshorne Coalbeds. 

BuMines RI 7667, 1972, 22 pp. 

21. Kissell, Fred N., and R. J. Bielicki. An In Situ Diffusion Parameter for 

the Pittsburgh and Pocahontas No. 3 Coalbeds. BuMines RI 7668, 1972, 

13 PP22. 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. 

23. Krickovic, Stephen, and Charles Findlay. Methane Emission Rate Studies 

in a Central Pennsylvania Mine. BuMines RI 7591, 1971, 9 pp. 

24. Krickovic, Stephen. Private communication, 1973. Available upon request 

from Stephen Krickovic, Pittsburgh, Pa. 

25. LaScola, J. C., and Joseph Cervik. Development of Recording Methanometers and Recording Anemometers for Use in Underground Coal Mines. 

BuMines TPR 15, 1969, 17 pp. 

26. McCulloch, C. M., and Maurice Deul. Some Geologic Factors That Cause 

Roof Instability, Methane Emission, and Water Control Problems in Mines 

in the Lower Kittanning Coalbed, Cambria County, Pa. BuMines RI 7769, 

1973, 25 pp. 

27. Merritts, W. M., W. N. Poundstone, and B. A. Light. Removing Methane 

(Degasification) From the Pittsburgh Coalbed in Northern West Virginia. 

BuMines RI 5977, 1962, 39 pp. 

28. Merritts, W. M., C. R. Waine, L. P. Mokwa, and M. J. Ackerman. Removing 

Methane (Degasification) From the Pocahontas No. 4 Coalbed in Southern 

West Virginia. BuMines RI 6326, 1963, 39 pp. 

29. Moore, T. D., Jr., and M. G. Zabetakis. Effect of a Surface Borehole on 

Longwall Gob Degasification (Pocahontas No. 3 Coalbed). BuMines 

RI 7657, 1972, 9 pp. 
30. Mott, R. A. The Origin and Composition of Coals. Fuel in Science and 

Practice, v. 22, No. 1, 1943, pp. 20-26. 

31. Perkins, J. H., and Joseph Cervik. Sorption Investigations of Methane on 

Coal: BuMines TPR 14, 1969, 6 pp. 

32. Ridenour, D. C. Core Drilling of Air Shafts and Manway Portals. Min. 

Cong. J., v. 43, October 1957, pp. 99-101. 

33. . Ventilation by Large-Diameter Boreholes. Mechanization, March 

1959, pp. 69-70. 

34. Spindler, G. R., and W. N. Poundstone. Experimental Work in the Degasification of the Pittsburgh Coal Seam by Horizontal and Vertical Drilling. Trans. AIME, v. 220, 1961, pp. 37-46. 

35. U.S. Code of Federal Regulations. Title 30--Mineral Resources; 

Chapter I--Bureau of Mines, Department of the Interior; Subchapter O-- 

Coal Mine Health and Safety; Part 75--Mandatory Safety Standards, 

Underground Coal Mines. Federal Register, v. 35, No. 226, Nov. 20, 

1970, pp. 17890-17929. 

36. U.S. Congress. Federal Coal Mine Health and Safety Act of 1969. Public 

Law 91-173, Dec. 30, 1969, 83 Stat. 742. 

37. Venter, J., and P. Stassen. Drainage and Utilization of Firedamp. 

BuMines IC 7670, 1953, 22 pp. 

38. Zabetakis, M. G., T. D. Moore, Jr., A. E. Nagel, and J. E. Carpetta. 

Methane Emission in Coal Mines--Effects of Oil and Gas Wells. BuMines 

RI 7658, 1972, 9 pp. 

39. Zabetakis, M. G., Maurice Deul, and M. L. Skow. Methane Control in 

United States Coal Mines--1972. BuMines IC 8600, 1973, 23 pp. 
METHANE IN COAL 

by 

F. N. Kissell 

ABSTRACT 

Recent Bureau of Mines research on methane movement through coalbeds has 

provided some insight into the major factors that govern the rate and manner 

by which methane is released into coal mines. Emissions from the solid working face and from broken coal are reviewed. The vital role of interstitial 

water is discussed. A method to predict approximately the gassiness of a 

prospective mine from exploration cores is presented. 

INTRODUCTION 

This morning, we will consider first some of the factors that govern the 

flow of methane underground. I do not think it is necessary to discuss how 

the methane got in the coal in the first place. Nor is it necessary to 

belabor the fact that a gassy coal mine can release some remarkable quantities 

of methane. Rather, I think it might be better for us to look at the problem 

in terms of a number of questions a practical mining man might ask the 

researcher to answer. Here are three: 

(1) Where does most of the methane come from during mining at the face? 

Does it come from deep within the coalbed? From coal at the face? From 

broken coal? From the roof and floor? 

(2) Why is so much gas given off from broken coal? 

(3) Why are some sections of a mine gassier than others? 

These are all practical questions about methane which I think our basic 

research program has substantially answered and which I hope to answer for you 

today. 

IPhysical research scientist, Pittsburgh Mining and Safety Research Center, 

Bureau of Mines, U.S. Department of the Interior, Pittsburgh, Pa. 
FUNDAMENTAL 

FAC TORS 

The Bureau 

Entry 

started its present methane 

research program 

by drilling holes 

and measuring gas 

pressures in the 

solid coal adjacent to the working face area. 

Figure 1 shows how 

two such holes 

might have been 

drilled. Typically they were 

3 in. in diameter, 

and perpendicular 

to the rib. After 

drilling, they 

were sealed with 

in£ latable packers 

and the gas pressure was measured. 

In general, higher 

pressures were 

found in hole 

No. 2 because the 

rib at this point 

had had less time 

to drain gas than 

that at hole No. 1; 

note that hole 

No. 2 is closer to 

the working face. 

Some typical FIGURE 1. - Plan view-coal mine entry with two boreholes. 

pressure curves 

for holes Nos. 1 

and 2 are given in figure 2. Most of the pressure curves we have obtained are 

similar to these; that is, zero pressure is found at or near the face or rib, 

followed by a pressure that increases with depth and gradually levels off deep 

within the coal. In a gassy mine in the Pittsburgh coalbed the highest measured pressures can be several hundred pounds per square inch. The actual 

value depends on the overburden height, and in many instances we have measured 

gas pressures that were about the same as the hydrostatic head for that depth. 

Unfortunately, these curves do not represent the real situation very well. 

For instance, figure 2 shows zero pressure at the working face and therefore 

we might expect zero amount of gas in the coal here. Of course, this is not 
I 1 I I I 1 I 1 1 

- - 

- 

- - 

- 

- d 

- 

- / 

/ 

- 

Hole I 

- / a A - 

- / 

/ - 

I / - I I I I 

10 20 30 40 50 60 70 80 90 

DEPTH OF HOLE, ft 

FIGURE 2. - Pressures measured within a coalbed. 

DISTANCE INTO COALBED FROM FACE OR RIB, ft 

FIGURE 3. - Gas amount and pressure curves. 
This is represented diagrammatically in figure 4 as a two-step process. Most 

of the gas in a typical working section emerges from these fractures, and it 

originates in that part of the coalbed where the pressure gradient is maximum. 

Obviously there will be exceptions, but this answers our first question about 

where most of the gas at the face comes from. In fact, it also answers the 

second question about gas in broken coal. Gas is retained in broken coal 

because coalbeds are solid lumps surrounded by fractures. 

This division of the gas flow into two steps also accounts for a number 

of coalbed features that are not easily explained otherwise. Two very different types of coal will be considered--those from the Pittsburgh and Pocahontas 

No. 3 coalbeds. 

- Coal 

Flow from Flow through 

Nature solid coal fractures 

Pittsburgh ............ Hard, blocky well-defined Slow. ... . . Fast. 

fractures . 

Pocahontas No. 3. ..... Soft, friable poorly defined Fast.. .... Slow. 

fractures . 

Underground, the permeability of the coalbed is controlled by the fractures. This means that the Pittsburgh coalbed is much more permeable, and for 

a given gas pressure, this coal will release gas more quickly than coal in the 
Pocahontas No. 3 coalbed. However, if we consider an individual lump of solid 

coal--say a lump on the conveyor belt or one taken back to the laboratory-- 

then the lump of Pocahontas No. 3 coal will give off gas more quickly, assuming that initial amounts are the same. 

Theoretical calculations for these pressure curves show that the curve 

for hole No. 1 is lower than it ought to be (fig. 2). The only way we can 

account for this is to assume that the rate of the second flow step (flow 

through fractures) increases with time. Apparently this occurs because tiny 

amounts of water originally trapped in the coalbed fractures block gas fl~w. 

Following mining, this water slowly drains into the mine unblocking these 

fractures and increasing their permeability. We can represent approximately 

the time variation of permeability with this table: 

Approximate permeability 

Pittsburgh coal (millidarcy) How obtained 

Virgin coalbed ................... 1 Vertical wells. 

Coal adjacent to working face .... 10 Horizontal holes. 

Coal adjacent to old ribs.. . . . . . . 200 Do. 

Much the same effect, but much less extreme, is observed in oil and gas 

wells. Figure 5 is a so-called relative permeability curve for coal. It 

gives the permeability of a 

lump of fractured coal 

versus the water saturation 

in the fractures. Note how 

a very small change in water 

saturation can greatly 

affect the gas permeability. 

What does this mean in 

practical terms? First of 

all, it shows why water 

infusion works. If draining 

water unblocks the fractures 

My own notion is that FIGURE 5. - Gas phase relative permeability of coal this relative permeability (Kg/Ka) versus water saturation, sw. effect also explains in part 

4- 

2 

why one section of a mine 

0 20 40 60 80 100 an increase in permeability. 

SW, pct 

imbibition) blocks them. 

then infusing water (called 

Secondly, it explains why 

our vertical shaft degasification is working so well. 

The methane drainage rate 

has remained high even 

though the pressure has 

fallen off--the reason being 

- \ lmbi bition 1: 

\ a - 

Pittsburgh coal 

- Ka =0.019 md 

I I I I I I 
may be gassier than another. If we keep in mind that: 1 

GAS FLOW a PRESSURE X PERMEABILITY 1 

and if we recall that small changes in water saturation can produce large 

changes in permeability, then we can at least rationalize large changes 

in gas flow from section to section. 

APPLICATIONS 

Now that we have answeredthe original three questions and dealt with the 

fundamentals, we can turn to something new. The emphasis today is on practical and workable things a mine operator can use, and one of the things I have 

been working on is a method to forecast approximately the methane emission 

from a prospective mine by measuring the methane content of an exploration 

coal core. Those of you who have been at an exploration site when a wet coal 

core was brought to the surface, may have noticed methane bubbles on the surface of the core. If instead of watching the bubbles, we enclose the core in 

a sealed container, we can measure the amount of methane in the core. In 

figure 6, emission from the core is used to displace water in an inverted 

graduated cylinder. This is not quite enough, however, for a way is needed to 

account for the methane lost from the core as it was being brought out of the 

vertical borehole. There is a way to do this (fig. 7). If the emission rate 

into the inverted graduated cylinder is plotted versus the square root of time, 

a backwards extrapolation to zero time can yield a figure for this lost gas. 

The next step is to correlate the gas in the core with the gas output of 

some existing mines. Figure 8 shows such a correlation for six mines. In 

FIGURE 6. - Apparatus used to measure gas emission from a coal sample. 
Beatrice a / 

/ 

/ Loveridge@ l Federal No.2 

1,600 / 

/ 

V 

2 4 6 8 10 12 I4 16 18 20 

DIRECT METHOD, cm3/g 

FIGURE 7. - Typical gas emission rate FIGURE 8. - Gas emission from coal samples 

curve from a coal sample. and from nearby operating mines. 

every case the vertical borehole from which the core was extracted was within 

a mile or so of the mine. Here, of course, the mines already existed, but 

there is no reason why this graph could not be used to predict the emission, 

at least approximately, for mines that have not yet been started. I have presented only the barest sketch of the method here. Additional details can be 

obtained from Bureau of Mines RI 7767.2 

2Kissel1, F. N., C. M. McCulloch, and C. H. Elder. The Direct Method of 

Determining Gas Content of Coalbeds for Ventilation Design. BuMines 

RI 7767, 1973, 17 pp. 
DEGASlFlCATlON THROUGH VERTICAL SHAFTS 

by 

H. H. Fields 1 

ABSTRACT 

Initial gas flows from seven holes drilled (average depth 618 feet) from 

the enlarged bottom of an 839-foot-deep borehole were 79,000 to 257,000 cfd. 

The maximum in situ gas pressure measured from a point 190 feet in the coalbed 

was 203 psig, and initial water flow averaged 6.8 gpmlhole. After 190 days of 

degasification the gas flow is averaging 508,000 cfd from all holes and a 

total of 97,000,000 ft3 of methane has been liberated. This is 83 percent of 

the gas calculated to be in the affected area of coal. In situ pressure is 

holding at 12.7 psig, and water flow averages 0.34 gpmlhole. 

INTRODUCTION AND STUDY AREA 

The Bureau of Mines has been interested in mine safety for more than 

60 years. In addition to other areas of safety, work is in progress in methane control, including removal of methane from virgin coalbeds and from 

actively pillared and old gob areas. The purpose of this study was to determine the effectiveness of long holes drilled into solid coal in very gassy 

virgin areas of the Pittsburgh coalbed. Methane exists under pressure in 

micropores, joints, and fractures of gassy coal bed^.^ In many areas, it is 

also present in adjacent strata at various distances above and below the 

coalbed. 

From the results obtained thus far, it is now evident that almost complete degasification can be effected wer a significant area if accomplished 

ahead of mining. This study is concerned with the drilling of long holes in 

the coalbed from the bottom of an enlarged borehole. The study area (fig. 1) 

is located in the 3 South mains, in a barrier pillar of Eastern Associated 

Coal Corp.'s Federal No. 2 mine. After drilling the holes into the coalbed, 

the gas is then bled off through a piping system to the surface where the 

total flow and system pressure is measured and then vented to the atmosphere; 

it may later be utilized by a gas company having gas lines nearby. As far as 

lMining engineer, Pittsburgh Mining and Safety Research Center, Bureau of 

Mines, U.S. Department of the Interior, Pittsburgh, Pa. 

'~ervik, Joseph. An Investigation of the Behavior and Control of Methane Gas. 

Min. Cong. J., v. 53, No. 7, July 1967, pp. 52-57. 
FIGURE 1. - Federal No. 2 mine location of multipurpose borehole. 
we know, this exact technique has not been undertaken elsewhere in this country. Some of the values of this type of degasification ahead of mining are: 

1. Reduce ignitions at the face,thus reduce the explosion hazards. 

2. Reduce ventilation costs. 

3. Increase coal production. 

4. Conserve natural gas. 

CONSTRUCTION OF THE MULTIPURPOSE BOREHOLE 

A 3-in diameter exploratory hole was drilled first to provide the geological information for drilling the 74-in diameter borehole through the coalbed. 

A large rotary drill rig was erected on a 20- by 20- by 3-ft-thick concrete 

pad (fig. 2). The drill has a "dry weight" capacity of 600,000 lb and weighs 

approximately 1,000,000 lb fully assembled. An 84-in diameter hole was then 

drilled 50 ft to sound rock and lined with a 74-in diameter steel casing, and 

cemented in place to prevent inflow of surface water (fig. 3). Subsequently, 

a 72-in-diameter hole was drilled 839 feet to the bottom of the Pittsburgh 

coalbed. The hole was lined with a variable thickness, 24-in-diameter steel 

casing (1-in at the bottom and 1/2-in at the top) and designed to withstand 

full hydrostatic head. Two 3-in and two 4-in pipes were installed by tack 

welding to the outside of the 24-in casing for electrical, dewatering, and 

degasification service to the borehole bottom. The casing was then cemented 

to the surface in four stages. 

SURFACE PLANT 

After removing the drill rig, the surface plant was constructed at the 

site (fig. 4). A mine hoist having a total capacity of 8,000 lb was installed 

and a tripod type head frame was erected over the borehole. A variable speed 

ventilation fan rated at 9,000 c£m at 12-in water gage was located 100 ft 

upstream from the borehole. (Because of methane gas all electrical equipment 

was permissible by U.S. Bureau of Mines standards.) 

A high-pressure degasification exhauster having a total capacity of 1,500 

cfm at 4 in of mercury was installed 200 ft from the ventilation fan and 

100 ft from the borehole. Total gas flow from the seven horizontal holes was 

measured by an 8-in turboflowmeter located at the surface. To keep the borehole dewatered during construction, a 50-gpm air-driven displacement type pump 

and a 50-gpm submersible pump were used. 
FIGURE 2. - Rotary drill rig. 
FIGURE 3. - Multipurpose borehole for degasification of virgin coal. 
multipurpose borehole. 

For the most part, the holes 

131 carbonaceous shale 

bolts (shale zone) 

Location of 2nd line rock 

bolts yein diamX 7ft long 

Zin No 9 gunite wire fabr~ca/ over K; lexible 

nt lube 

f?n horizonlol holes drilled 

lnto coolbed L4fl.I 6flFIGURE 5. - Lithology of borehole bottom. 

were inclined upward 114 

degree starting at a point 

approximately 34 in below 

the top of the coalbed and 

were drilled to a depth of 

55 ft. An NX drag bit 

fitted to a 10-ft packed 

hole stabilizer , 2-29/32 in. 

in diameter, followed by a 

10-ft drill rod and a 5-ft 

packed hole stabilizer was 

used from 55 to 100 ft in 

depth. 

The stabilizer assembly 

(fig. 7) then was changed to 

a single packed hole stabilizer, 5 ft in length, immediatelybehindthe same drag bit. 

The holes were advanced with 

this assembly to about 390 

ft, with surveys being made generally at 150, 300, and 400 ft. At a depth of 

approximately400 ft, the 5-ft stabilizerwas followedbyaweighted 2-112-in, 5-ft 

drillrod,andtheholeadvancedtoa depthof500 ft. All holes, except one, were 

advanced beyond 500 ft, assuming only minor characteristic deviations would be 

realized by using the two basic stabilizer assemblies described above. The 

holes were advanced in excess of 600 ft using the two-unit stabilizer assembly, 

then changed to the single stabilizer assembly; one hole was drilled to a 

maximum of 850 ft. 

A mechanical packer was inserted in the hole and the hole was shut in to 

prevent outflow of gas until all degasification holes were completed. The 

in situ pressure hole was "packed" with provision for measuring the gas pressure at four equally spaced locations. These later were replaced with one 

pressure point located 190 ft into the coalbed. 

Each hole was connected from the mechanical packer to a Bureau-designed 

water trap, orifice plate for measuring pressure in and flow from each hole 

and to a 24-in-diameter by 72-in-high receiver tank. The two 4-in steel pipes 

grouted behind the 48-in casing were connected to the tank 160 degrees apart 

(fig. 8). 
PLAN 

,4-in pipes to 

TYPICAL SECTION 

FIGURE 8. - Plan-typical section of collector system. 
+ In situ gas pressure 

(fig. 9) and volume measurements are made periodically 

(7 to 10 days) at the bottom 

of the borehole. In addition, total gas flow, pressure, and time also are read 

with the turbof lowmeter 

located on the surface. 

RESULTS AND DISCUSSIONS 

The initial gas flow 

rates are given in table 1. 

It is assumed that holes 7, 

8, and 1 are shielded from 

the wells by the other holes 

(particularly 2 and 6) , then 

the initial gas flow rate 

(GFR) in the absence of the 

wells would be given by the 

equation : 

GFR = (0.18 - 0.1 Cos 20) 

cfm/fP (1) 

where 8 is the angle (displacement) measured clockwise from the face cleat 

located between holes 2 and 

4. Note in particular the 

effects of the directional 

permeabi li ty on the flow 

(fig. 10) ; in the absence of 

wells, the maximum flow is 

from holes drilled along the 

butt cleats (B) and nearly 

perpendicular to the face 

cleats (F). However, as 

boreholes that pass near 

wells may have flow rates 

1 I I 1 I 

TIME, days above the predicted values, 

it is not surprising to find 

FIGURE 9. - In situ gas pressure. that the initial flow rates 

from holes 2 and 4 were 

approximately twice as high 

as those to be expected from equation 1. Further, comparing the flows from 

holes 4 and 7 (two diametrically opposed holes), we see that the flow from 

hole 4, which passes near a gas well, was about 2.5 times higher than that 

from hole 7, which does not pass near a well. This is in line with earlier 

1 

- 

180 

170 

160 

I5O 

140 

130- . - 

yl 

a 120 ti 

110- 

v, 

v, 100- 

QC 

a. 

3 90- 

I- - 

v, 

z 

- 70- 

60 

50 

40 

30 

- 

- 

- 

- 

- 

80-, 

- 

- 

- 

- 

- 

- 

- 

- 

holes connected 

- 

- 

- 

'3 holes connected - 

- 

- 

- 

- 

4 holes connected - 

- 

- 

"6 holes connected - 

- 

All 7 holes connected - 

I-- A A a - 

I I 1 I I I 

0 20 40 60 80 loo 

I 
1 I I I 1 

w I WI I I 1 - 

- WI 5 I 

X / 2 

I 

- 4 

- 

L X X 

- 

6 - X 

- x7. 

0.18-0.1 cos 28 

- - 

I I I 1 I I I D 

DISPLACEMENT, 8, deg 

FIGURE 10. - Methane flow and displacement (fig. 6). 

findings by zabetakis3 on the effects of oil and gas wells on emission of 

methane in coal mines. 

TABLE 1. - Initial data on the seven degasification holes 

No. ofhole (fig. 1) .............. 1 2 

Length ........................ ft.. 646 850 

Gas emission per 1,000 cfd. ....... Gas flow per sq ft of coal surface 

in holes .................... cfd.. 

Angle of hole with respect to face 

cleat1 ...................... deg .. Distance from gas well ........ ft.. 

Average water discharge ......gp m.. 

In situ gas pressure at 199-ft 

depth ........................ si.. 

lFace cleat is appreciably more pe meable t' .an the much shorter butt 

- 1 203 

cleat. 

3~abetakis, M. G., T. D. Moore, Jr., A. E. Nagel, and J. E. Carpetta. Methane 

Emission in Coal Mines--Effects of Oil and Gas Wells. BuMines RI 7658, 

1972, 9 pp. 
After the initial flow rates were measured, the seven bleeder holes were 

connected to a common collector. The total methane emission from these holes 

fell for approximately 50 days and then began to increase (table 2). Interestingly, the emission rate fell by a factor of 2 (fig. 11) , and the gas pressure in the coalbed fell by a factor 20 (fig. 9). However, during this period, 

a fair amount of water was removed from the coal (the average initial water 

flow rate was 6.2 gpm perho1e);in 50 days this figure fell to 0.5 gpm per 

hole and the gas permeability of the coal increased. As a first approximation, 

the initial methane emission rates (MER) are proportional to the increase of 

the square root of the elapsed time, t: 

MER = 970 ; 0 g t g 40 days J1 + t/lO 

This simple equation yields values within about 5 percent of the smoothed 

(curve) data given in figure 11. 

TABLE 2. - Total gas and water flows and in situ gas pressures 

24 hours after all holes connected to collector 

Initial .................................. Twenty-four hours after all holes 

connected to collector... ............... Days after above 24 hours: 

10 .................................... 20 .................................... 30.. .................................. 40 .................................... 50 .................................... 60.. .................................. 70. ................................... 80. ................................... 90 .................................... 100 .................................... 110 .................................... 120. ................................... 130 .................................... 140 .................................... 150 .................................... 160 .................................... 170 .................................... 180 .................................... 190 .................................... 200 .................................... 

Gas 

emission, 

1,000 cfd 

1,121 

971 

720 

511 

464 

444 

460 

490 

438 

529 

500 

543 

480 

498 

5 16 

495 

519 

509 

528 

538 

522 

495 

Average water 

discharge 

per hole, 

gpm 

6.2 

1.3 

1.2 

1.2 

.8 

9.5 

.5 

.5 

.5 

.5 

.5 

.5 

.5 

.45 

.45 

.45 

.45 

.45 

.34 

.34 

.35 

.35 

In situ 

gas 

pressure, 

psi 

203 

190 

18 

18 

17 

11 

10 

10 

13 

13 

13 

13 

12.7 

12.7 

12.7 

12.7 

12.7 

12.7 

12.7 

12.7 

12.7 

12.7 
20 40 60 80 

ELAPSED TIME, days 

FIGURE 11. - Methane emissions. 

A total of 102,000,000 ft3 of gas has been removed in 200 days from the 

virgin area involved. This is equivalent to 87 percent of the calculated gas 

in the area of coal involved. While the in situ gas pressure has dropped to 

12.7 psig and water flow to 0.35 gpmlhole, the gas flow has averaged 509,000 

cfd. 

TABLE 3. - Analyses of two samples from total gas emission 

Regarding the cost-effectiveness, it should be recognized that the 

expense of this study is very high ($848,000). A much more practical 

approach is for coal companies operating in very gassy coalbeds to consider 

planning more air shafts with smaller cross-sectional areas than is the 

increasing practice today. It would be adequate to sink the shafts 3 years 

ahead of need and degasify the virgin coal by long holes as accomplished in 

conjunction with the multipurpose borehole. 

Ethane (C,%) ....................pp m.. 

Carbon dioxide (C02) .............p ct.. 

Oxygen (0,) ...................... pct.. 

Nitrogen (N,) .................... pct.. 

Methane (CH4) ....................p ct.. 

Sample 1 

300 

9.5 

0.6 

2.0 

87.9 

Sample 2 

321 

9.0 

1.2 

2.4 

87.4 
CONCLUSIONS 

Based on the degasification results obtained in 200 days, it can be concluded that the multipurpose borehole is a useful technique. It is concluded 

that final degasification will exceed appreciably the estimated volume of gas 

calculated to be in the area involved. However, the cost of using the multipurpose borehole technique is quite expensive; therefore, it appears advisable 

to consider using the technique of drilling degasification holes in the coalbed from the bottom of planned air shafts (sunk by conventional mechanized 

methods) in virgin coal areas approximately 3 years ahead of closest mine 

workings. 
( THE USE OF ISOLATED COAL PANELS IN THE PITTSBURGH COALBED I 

I C. Findlay, S. Krick~vic,~ and J. E. Carpetta3 

I ABSTRACT 

The Bureau of Mines conducted methane emission rate studies duringdevelopmentof1,800 ft of a set of three headings within a major coal panel (2,700 by 

3,500 ft) which had been completely isolated by sets of headings for 12 months 

in a Pittsburgh coalbed mine in northern West Vir inia. Minimum, maximum, and P average emission rates were 2.1, 14.0, and 9.1 ft per ton of coal mined in 

the order named; and the maximum and minimum average production rates were 3.7 

and 3.0 tpm, respectively, with continuous penetration rates being judged to 

be in excess of 5 tpm. No methane problems were encountered, and the methane 

emission rate of the panel was estimated to be in excess of 70 percent lower 

than the rates measured in development within two virgin coal areas in the 

same mine. 

I INTRODUCTION 

Methane exists under pressure in the micropores, joints, and fractures of 

gassy coalbeds. In many mines it is also present in adjacent strata at various distances above and below the coalbed. An in situ gas pressure of 275 psi 

has been measured in the Pittsburgh coalbed, and permeability of the bed has 

been found to be high compared with that of other coal bed^.^ Because of this 

high pressure and permeability it is very advantageous safety-wise and 

production-wise to degasify the coalbed to the fullest extent practicable 

before mining. One procedure for draining methane from virgin coalbeds is to 

isolate major coal panels by developing sets of headings around them and to 

allow bleed-off for at least 1 year prior to mining within the panels. 

Some coal companies have achieved partial and almost complete isolation 

without actually planning it. Ventilation problems, difficult mining 

l~ining - engineer. " Supervisory mining engineer. 

3~ining engineering technician. 

All authors are with the Pittsburgh Mining and Safety Research Center, Bureau 

of Mines, U.S. Department of the Interior, Pittsburgh, Pa. 

*~ervik, Joseph. An Investigation of the Behavior and Control of Methane Gas. 

Min. Cong. J., v. 53, July 1967, pp. 52-57. 
conditions and the need for greater production are the usual reasons for the 

development in adjacent areas that resulted in the isolated conditions. Other 

companies, mining in very gassy coalbeds, develop butt headings for longwall 

panels ahead of need and degasify the isolated panels by drilling holes in the 

coalbed on approximately 100-ft centers and approximately 200 ft deep from 

both sides of the panels. In relatively few cases, where total isolation of a 

major coal panel is planned, mining within the panel is started promptly upon 

completion of the isolation. Although such a procedure improves safety and 

productivity to some degree, some time usually is needed to bleed off the 

methane for significantly greater advantage. 

LOCATION AND DESCRIPTION OF STUDY AREAS 

Figure 1 shows the locations of eight study areas in Federal No. 2 mine 

operated in northern West Virginia by Eastern Associated Coal Corp. 

Area 1 was located in the development of four headings of 2 South mains 

to complete the set of 10 headings of the major panel that had been isolated 

12 months before this mining was undertaken. Areas 3 through 6 and 8 were 

located in a set of three headings that were being developed in the isolated 

block (2,700 by 3,500 ft) to improve ventilation. The headings were developed 

1,800 ft at the end of studies. 

Area 2 was located in six of the 10 projected 2 North mains headings in 

virgin coal, and area 7 in seven of the 10 projected 2 South mains headings 

also in virgin coal. 

MINING METHOD AND EQUIPMENT 

The centers of headings and breakthroughs and widths of both in the isolated panel were 100, 80, and 13 ft, respectively. They were 90, 80, and 

13 ft in 2 North mains and 100, 90, and 14 ft in 2 South mains. 

Thickness of the coalbed was 9 ft, of which 7 ft were mined under 735- to 

845-ft-thick overburden. Mining was done with boring-type continuous miners 

in all study areas except No. 7, where a fullface ripper-type unit was used. 

Coal was discharged to the floor where conventional loaders transferred it to 

10-ton-capacity shuttle cars for transportation and unloading into the belt 

feeders for rapid handling and uniform discharge onto tail ends of belt conveyors in all study areas. Each miner was generally served with two shuttle 

cars. 

VENTILATION AND MONI~RING 

All study areas within the isolated coal panel were ventilated with one 

split of air, except area No. 1; the outside left and right headings were 

intake and return airways, respectively, and the middle (belt conveyor) heading a regulated intake (about 2,000 to 3,000 cfm) to prevent excessive velocity while maintaining the methane concentration below 1 percent. Areas 1, 2, 

and 7 were ventilated with two air splits, with a single return airway for 
FIGURE 1. - Location of study areas. 

each split, except area 7, which had two returns for one split and one for the 

other. The belt conveyor heading in each area was a regulated intake. 

All air velocities and methane concentrations were measured with handheld instruments. Airflow measurements were obtained by traversing at uniform 

speed with an anemometer across accurately measured cross-sectional areas 

every hour; methane concentrations were obtained at the average velocity 

points just inby the last masonry stoppings at 5- to 10-min intervals. When 

the miners were not operating and the belt conveyors were empty, intake 
I 

O a Intake alr volume 34.000 cfm No I ~ntake heading 

IIIl1lll111llllllllllll111111111111~~~1~~~~

Return atr volume 34.000 cfrn Na3 return headlng 

lllll~lllllllllllllIIIIl1IIIlIlIII11I~Il~~~~~~I

900arn 930 1000 1030 1100 I130 1200 1230 100 I30 200 230 300pm 

TIME 

FIGURE 3. - Data from study area 4-isolated panel. 

KEY 

M~nlng machne operating; total product~on 224 tons 

0 60 

Methane. cfm 

a I060 

Iw Methane, cfm 

I m 

No. 3 return a~r volume 32.000 cfm - 

.m I1 Ill IIIIIIIIIIII IIIlllllllllll, 

930om 1000 1030 1100 1130 1200 1230 1 00 1 30 200 2 30pm 

TIME 

FIGURE 4. - Data from study area 8-isolated panel. 
methane concentrations were measured at the last inby breakthrough to determine 

methane intake from other sections, main haulway, and the shaft bottom. Coal 

production was recorded in each study area. 

1 RESULTS 1 

Table 1 gives a summary of all pertinent data from methane emission studies in the isolated coal panel and in the two virgin areas. Particularly significant is the trend of methane emission as mining progressed in the isolated 

panel for a distance of 1,800 ft. Emission increased from 2.1 ft3 per ton of 

coal mined in study area 1 to 14 ft3 in study area 4 (800 ft from area 1), and 

decreased to 6 ft3 at the end of the next 1,000 ft in area 8. Undoubtedly, 

the emission rate would have decreased to nearly zero just before cutting 

through to the North airways (additional distance of 900 ft), because bleedoff to these headings had been in progress for 3-112 years when the studies 

were made. Cubic feet of methane per ton of coal mined was chosen as the unit 

of degasification because it is useful as an indicator of the low methane 

emission rate of the isolated panel relative to the virgin coal. 

Figures 2 through 4 show the methane emission rates during a single shift 

for three particular study areas and figure 5 shows the emission rates for the 

six studies within the isolated coal panel. 

Figure 6 shows that the continuous miner operating in virgin area 2 was 

stopped by the methane detector 19 times for a total of 36 min, due to the 

presence of 2 percent or greater methane concentration approximately 10 ft 

.ahead of the operator. The average emission in cubic feet per ton of coal 

mined was 33.8 (table 1) , or 3.7 times greater than that from the isolated 

panel. Similar stoppages of the continuous miner did not occur in study 

area 7 (2 South mains) because the coal production rate was only 88 tons during the study period. 

15 - - Study area No. 5 

Study area No. 4- 

10 - 

> - 

I I 1 1 I I 

O 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 

DISTANCE, 100 ft 

FIGURE 5. - Curve of methane emissions within an isolated panel. 
TABLE 1. - Summary of pertinent data from methane emission studies in the isolated 

panel of coal and in two virgin areas, in 1972 

NOTE.--Each area was studied during one operating shift. Air volumes in both active and idle splits were 

combined in study area 1 to more closely correspond to the three headings on the active air split 

in all other study areas. 

Date of 

study 

Feb. 23 

Apr. 13 

May16. 

June 14 

July20 

Sept. 1 

Mar. 22 

Aug. 7. 

'All study areas, except 2 and 7, are in the isolated panel; study areas 2 and 7 in virgin coal. 

2~11 study areas in isolated panel were ventilated with one split of air, except area 1 which had two air 

splits in four headings. 

30perating air split--two splits in section--total volume 79,000 cfm. 

4~oring-type continuous miner used. Cut cross-sectional area of 80 ft2. 

5 Operating air split--two splits in section--total volume 82,000 cfm. 

6~ipper-type continuous miner used. Cut cross-sectional area of 100 £9. 

Number 

of 

study 

area1 

1 

3 

4 

5 

6 

8 

2 

7 

Average methane 

emission volume, 

c fm 

Raw coal 

product ion, 

net tons 

330 

350 

350 

207 

203 

224 

240 

, 88 

Average 

total 

air 

volume ,2 

cfm 

38,000 

32,000 

34,000 

32,000 

35,000 

32,000 

332,000 

535,000 

Intake 

75 

81 

80 

88 

87 

96 

35 

578 

Continuous 

miner 

operating 

time, 

min 

113 

110 

94 

76 

104 

60 

90 

60 

Returns 

6 

40 

52 

30 

17 

22 

84 

53 

Total 

81 

121 

132 

118 

104 

118 

119 

94 

Total 

study 

period, 

min 

270 

360 

360 

360 

330 

300 

300 

210 

Average 

me thane 

emission, 

cubic 

feet per 

tonof 

coal 

mined 

2.1 

12.6 

14.0 

11.0 

8.7 

6.0 

33.8 

42.2 

Remarks 

Set of four headings. 

Set of three headings. 

Do. 

Do. 

Do. 

Do. 

set of six heading^.^ 

Set of seven heading^.^ 
Mining within a major coal panel in the Pittsburgh coalbed that had been 

completely isolated for 12 months showed a very significant reduction in methane emission rate per ton of coal mined. The average of 9.1 ft3 in all studies within the isolated panel is to be compared to 33.8 and 42.2 cft obtained 

when mining within the two virgin areas. This corresponds to a reduction in 

methane content of more than 70 percent. The average coal production rate in 

the isolated panel (3 tpm) could have been doubled without exceeding the 

allowable methane content in the return airway. 

Although the above data appear to be adequate to assure the advantages of 

isolating a major coal panel, and hopefully many or most of the coal companies 

operating in the very gassy Pittsburgh coalbed will determine their own costeffectiveness, the Bureau plans further studies. These will be conducted 

within partially isolated and unisolated panels, and in the development of 

sets of headings to isolate a major coal panel. Our objective is to determine 

the safety and cost-effectiveness with respect to methane, especially in the 

development of an isolated panel ahead of need and in mining four or five butt 

headings within the panel. Such data should be valuable for reaching a decision by any company operating in the very gassy Pittsburgh coalbed area. 
CONTROL OF METHANE BY WATER INFUSION 

by 

J. Cervik and A. Cetinbas* 

ABSTRACT 

Tests conducted in the Pittsburgh coalbed show that water infusion is an 

effective method of controlling methane at active faces of a section. Methane 

flows have been reduced ranging from 40 to 80 percent. The direction of the 

face cleat with respect to the direction of section advance is an important 

factor in determining the spacing of horizontal holes along the width of the 

section. No adverse effects on roof or floor have been noted. 

INTRODUCTION 

Water infusion or waterflooding of coalbeds in advance of mining is a 

method of controlling methane flows at active face areas during mining. 

Except for one piece of equipment, the technique can be applied with tools and 

equipment normally found in an operating section. In the Pittsburgh coalbed, 

a block of coal measuring about 150 by 500 ft in advance of the section can be 

infused over a weekend. 

Coalbeds are naturally fracturedand, therefore, one can characterize them 

as being made up of fractures and matrix (solid coal) . Generally, there are 

at least two sets of vertical fracture systems that intersect at right angles. 

These two fracture systems are referred to as the face and butt cleats and 

f orm an interconnected network throughout the coalbed. 

What part does the matrix (solid coal) play in the infusion process? The 

matrix contains a pore system that is interconnected. However, these pores 

are about the size of a methane molecule, which is too small to permit water 

to pass. Therefore, waterflooding of coalbeds is confined to the fracture 

system only. 

The fracture density of coalbeds, which is defined as the number of fractures per inch or per foot, varies. A blocky coal such as the Pittsburgh is 

Supervisory geophysicist . 2~ining engineer. 

Both authors are with the Pittsburgh Mining and Safety Research Center, 

Buxeau "1 Miaes, U. S. Department of the Interior, Pittsburgh, Pa. 
ane that causes ventilation problems during mining. The successful application of water infusion 

FIGURE 2. - Migration of water front through depends to a large extent upon the 

coa lbed. permeability of the fracture sysc 

tem of the coalbed. 

INFUSION OF COALBEDS 

Water infusion of coalbeds is 

affected byseveralfactors. Some 

can be controlled and others cannot. A discussion of these factors will help you to visualize 

and understand what happens when 

coalbeds are infused, precautions 

to be taken, and the effect on 

methane flows within the coalbed. 

Two waterflooding studies conducted under different conditions 

will be presented to illustrate 

the effects of some of these fac- FIGURE 3. - Waterflood front of two wells. tors on methane flows at face 

areas during mining. 
Figure 1 shows water being pumped down a wellbore and forced under pressure into a coalbed. The water flow rate will be governed by the water pressure in the wellbore and the fracture permeability of the coalbed. In order 

to simplify the discussion, we can assume that the permeability of the coalbed 

is constant and the same in all directions. Figure 2 shows a plan view of the 

migration of water through the coalbed under the assumed conditions. The 

water moves away from the wellbore uniformly in all directions. The circles 

in figure 2 show the sucessive positions of the waterfront with time. As 

water moves through the fracture system, it displaces the methane ahead of it. 

Figure 3 shows a coalbed being flooded by two wells separated by a distance, d. The flood fronts from each well will eventually merge and continue 

as one oval front. If three or more wells are used, the resulting flood front 

will become oval shaped. 

The preceding discussion is also applicable to horizontal holes drilled 

underground into coalbeds providing the infusion of the coalbed is from a 

small segment at the back part of the hole. This condition can be met by filling the horizontal hole with inflatable packers (fig. 4). If too few packers 

are used, the water tends to short circuit along the hole instead of penetrating into the coalbed. Good results are obtained when 5-ft packers are connected with joints of 5-ft pipes.3 

Packers 

Infusion segment 

FIGURE 4. - Packed hole for waterflooding. 

SCetinbas, Abdurrahman, R. P. Vinson, Joseph Cervik, and M. G. Zabetakis. 

Methane and Dust Control by Water Infusion. Pittsburgh Coalbed (Fairview, 

W. Va.). BuMines RI 7640, 1972, 17 pp. 
A typical section advancing into virgin coal may be about 500 ft wide. 

In order to reduce methane flows through the faces of the section, a continuous waterbank must be emplaced which spans the width of the section. The 

waterbank behaves like a barrier and prevents methane from flowing toward the 

faces of the section. Rather, it is directed around the water infus2d zone 

and enters the mine opening through the ribs outby the face areas of the 

section. 

The emplacement of a waterbank across the section requires two or more 

horizontal holes. The number depends upon the length of the holes. Generally, 

horizontal holes 100 to 150 ft in length can be drilled using the hand-held 

equipment used underground. In some cases, entries are advanced in about 

100-ft increments. Integrating a drilling and infusion phase using 100-ft 

holes into a mining cycle then presents no special problems. 

In figure 5 is shown a schematic of the infusion of a coalbed using a 

packed horizontal hole. Successive stages of migration of the flood front are 

shown and when the front first reaches the mine opening, water begins flowing 

from the face and ribs. At this time the diameter of the flooded region is 

about 200 ft. Further infusion of the coalbed will expand the water infused 

zone as well as increase the flow of water into the mine opening. If water 

deteriorates the floor, infusion should be terminated when the flood front first 

reaches the mine opening or pumping facilities shouldbeprovided to dispose of 

the water. 

The second hole should be drilled 140 to 170 ft from the hole shown in 

figure 5. The flood patterns of each hole will merge similar to those shown 

in the schematic in figure 3 when breakthrough occurs. This procedure is 

repeated with additional holes to produce a continuous waterbank across the 

section. 

There is no preferred 

sequence of infusing horizontal 

Successive f load holes. They may be infused 

fronts simultaneously or in sequence 

as they are drilled. The 

important aspect of the process 

is to leave no partially 

Pocked hole flooded or unflooded regions 

where methane can funnel 

through to the mine opening. 

In reality, coalbeds such 

I I as the Pittsburgh exhibit 

1 

strong directional permeabilir ties. For example, the face 

cleat permeability in the 

Pittsburgh coalbed is about 

FIGURE 5. - Water infusion of coalbed using a 10 times greater than the butt 

horizontal hole. cleat permeability. This difference in permeability affects 
direction 

direction 

FIGURE 6. - Elliptical flood fronts for face cleat 

perpend icu lor to sect ion advance 

direct ion. 

Elliptical flood 

fronts f Face cleat 

d i rection 

* Butt cleat 

Packed hole direction 

Section advance 1 direction 

FIGURE 7. - Ell iptical flood fronts for face cleat 

para I lel to section advance direction. 

Gas flow 

direction t Face 

-Butt cleat 

direction 

Section advance 1 direction 

the shape of the water 

infused zone. The mine 

opening, which is about 100 

ft from the infusion segment 

of the horizontal hole, has 

its effect on the shape of 

the infused zone as well as 

on the gas pressure in the 

coalbed, which increases 

with distance from the mine 

opening. The effect of 

these factors will be discussed briefly in the succeeding paragraphs. 

Directional Permeabilities 

When the permeability 

of the butt cleat is appreciably different from that 

of the face cleat, the successive stages of the waterflood front do not have the 

circular shape shown in figure 5, but will be distorted 

into an elliptical shape. 

In the case of the Pittsburgh coalbed, water will 

migrate faster along the 

face cleat than it does 

along the butt cleat. 

In figure 6 is shown a 

schematic for the case where 

the more permeable face 

cleat is perpendicular to 

the direction of advance of 

the section. This is an 

ideal situation because the 

water tends to run across 

the section. Four equally 

spaced holes across a 500-ft 

FIGURE 8. - Waterflooded section for face cleat section will emplace a waterbank free of unflooded or 

parallel to section advance partially flooded regions. d irect ion. 

If the face cleat is in 

the direction of advance of the section, the successive stages of the flood 

front are shown schematically in figure 7. Note that the distanceofmigration 

ofthe flood front at breakthrough is much less across than in the direction of 

advance of the section. Drilling and infusing four holes across a 500-ft 
Gas pressure increases with distance into the coalbed. Therefore during 

waterflooding operation, the flood front furthest from the mine opening experiences a greater resistance to flow than that closer to the mine opening. 

Because of the low gas pressure in the Pittsburgh coalbed at a depth of 100 ft 

(less than 30 psig), distortion of the flood front due to gas pressure is not 

expected to be as pronounced as the effects of the mine opening or directional 

permeabilities. However, in other coalbeds such as the Pocahontas No. 3' 

where a gas pressure of about 600 psig exists at a depth of 100 ft into coal, 

this effect could be as important as the mine opening or directional permeabilities effects. 

CASE STUDIES IN THE PITTSBURGH COALBED 

Two case studies were conducted in the Pittsburgh coalbed under similar 

conditions. The difference between the two tests was the direction of the 

more permeable face cleat with respect to the direction of section advance. 

Figure 10 shows a schematic of a test section. The section in both cases 

was about 500 ft wide and in the first case a six-entry system was being 

driven and nine in the second case. Both used a split system of ventilation. 

4Muskat, M. Flow of Homogeneous Fluids Through Porous Media. J. W. Edwards, 

Inc., Ann Arbor, Mich., 1st ed., 1946, pp. 468-472. 

 i is sell, F. N., and R. J. Bielicki. An In Situ Diffusion Parameter for the 

Pittsburgh and Pocahontas No. 3 Coalbeds. BuMines RI 7668, 1972, p. 3. 
as the outby instruments. 

- ----.c Intake air The sum of the two outby Return air =Mined before infusion 

Curtoin stopping ZMined after infusion instruments gave the total 

fi Permanent stopping methane flow rate from the 

100 OF faces of the section and the 

Scale, ft two outside ribs. The difFIGURE 10. - Location of horizontal holes, monitoring ference between outby and 

stations, and ventilation ~lan. inby methane flow rates 

is the flow rate of 

methane through the two outside ribs of the section. 

The first test was conducted in a section where the more permeable face 

cleat was at right angles to the direction of section advance. Referring to 

figure 7, this is an ideal condition because water tends to run across the 

section faster than toward the mine opening. A continuous waterbank is 

emplaced across the section and no zones exist where methane can funnel 

through. Figure 11 shows the effect of the waterbank on methane flows at the 

face areas during mining. 

The methane flow rate from the faces of the section (inby curve) averaged 

132 cfm before infusion and 28 cfm after infusion. The average flow rate was 

thus reduced approximately 79 percent. The average methane flow rate at the 

outby stations decreased from 243 before infusion to 166 ch after infusion, a 

decrease of about 32 percent. 
TIME, days 

FIGURE 11. - Total methane flow rates from study area where face cleat direction is perpendicular to section advance direction. 

The difference in methane flow rates between outby and inby stations 

represents the quantity of methane entering the mine opening through the two 

outside ribs. Before infusion, 111 c£m is entering through the ribs. After 

infusion, 138 cfm is entering through the ribs which represents a 24-percent 

increase. These data show that the emplaced water is diverting methane from 

the face areas of the section to the outside ribs. 

The second test was conducted in a section advancing parallel to the more 

permeable face cleat. Referring to figure 8, the infused water tends to run 

in the direction of section advance faster than across the section. Consequently, zones may exist between holes which have not been filled with water. 

These zones permit methane to funnel through to the faces of the section. 

Figure 12 shows the results of the infused water on methane flows for this 

case. 
represents a 38 percent reduction in methane flow rate. At the outby stations, 

the methane flow rate dropped from 306 cfm before infusion to 208 cfm after 

infusion and represents a 32-percent reduction. The difference in flow rate 

between outby and inby curves before infusion is 41 and 43 cfm, respectively, 

after infusion. These differences are not significant and indicate that methane is not being diverted from the face areas to the outside ribs. 

To improve the effectiveness of water infusion in the second case, two 

alternatives can be followed. First, hole depth can be increased to about 

200 ft. The infused water would tend to migrate further across the section 

before breakthrough occurs when compared with the case using shorter holes. 

Secondly, hole depth would remain the same, but the number of holes drilled 

across the section would be increased to six. Each of these alternatives 

tends to produce a continuous waterbank across the section. 

Mining Through an Infusion Hole 

After infusion has been terminated, the inflatable packers are removed 

and the hole is plugged at the collar to prevent infused water from draining 

out. Intercepting a water infusion hole during the mining of a crosscut does 

not create an unsafe condition because flow from the hole is water. Mining 

into a water infusion hole, although not expected to create unsafe conditions, 

is avoided by drilling all holes 5 to 10 degrees off the projected development 

of the entry. 
Effect of Water on Roof and Floor Strata 

A consistent argument heard throughout the coal industry is that infusing 

water into a coalbed causes roof and floor problems. However, there are arguments to show that this is not the case. 

Experience has shown that accumulations of water on a soft bottom does 

create haulage problems. Accumulation of water occurs during the drilling of 

horizontal holes, when the flood front breaks through at the face and ribs, 

and from the spray system of the miner. However, the effects of water on a 

soft bottom from these sources can be minimized by channeling the water, 

installing pumps,and disposing of the water before large accumulations occur. 

Most coalbeds contain inherent water that is stored in the fracture system. Horizontal holes drilled 400 to 500 ft in advance of mining produce 

water at persistent rates of 700 to 900 gpd in the Pittsburgh coalbed. These 

flows are observed even in sections that are considered "dry." Vertical boreholes drilled into virgin coal in coalbeds throughout the United States must 

have water pumps installed to clear the wellbores of water in order to maintain gas production. Therefore, just as methane is normally associated with 

coal, one can add water to the sys tem. 

Because water does not wet coal and gravity, water is assumed to be in 

the bottom part of the coalbed. Observations show that the bottom 1 ft of 

coal along an outside entry is wet and the remainder of the coal is generally 

dry. If the bottom is in contact with inherent water, infusion of water into 

a coalbed does not create conditions that have not existed for ages. Therefore, there is doubt that water infusion will affect even a soft bottom. 

The exposure of roof rock to water during infusion is not expected to 

produce any effect that would weaken and cause roof failures. The roof is in 

contact with the infused water only where fractures in the coalbed terminate 

at the roof. Fracture widths in coalbeds range from perhaps 1116-in to hairline cracks. For a blocky type coal such as the Pittsburgh, the area of water 

contact with the roof is small in comparison to the areal extent of the 

infused zone. 

In some instances, parting occurs along the coalbed-roof interface. In 

this case water wets the roof completely. However, this parting exists around 

the mine opening and probably does not extend beyond 10 to 15 ft into the 

coalbed. 

No roof or floor problems have been observed due to water infusion. In 

one case haulage was affected in an area where drill water and breakthrough 

water accumulated and was absorbed in the bottom. However, there are means of 

avoiding this situation. 

INFUSION IN DEEP COALBEDS (1,500 TO 2,000 FT) 

Infusion pressures in the Pittsburgh coalbed range from about 275 to 410 

psig and infusion rates range from 8 to 20 gpm. In other coalbeds suchas the 
Hydrofracing is a process whereby the pressure in the wellbore is raised 

very rapidly until the formation fractures. When this occurs there is an 

abrupt drop in wellbore water pressure. 

1,400 

1,200 

1,000 

. - 

V) 

a 

W 

rr 800- 3 

V) 

A hydrofrac experiment was attempted to determine if a zone of reduced 

permeability surrounds horizontal holes drilled into the coalbed. A 1-in pipe 

was gr~uted to a depth of 195 ft in a 200-ft hole. The gas flow rate from the 

5 ft of open hole was 300 cfd. 

- Pocahontas No. 3, gas pressure at a depth of 100 ft is 

about 600 psi. Consequently, 

infusion pressures in excess 

of 600 psi are required. - - There are, however, other 

problemsassociatedwith 

deep, friable type coalbeds 

that need to be solved 

- - before water infusion can be 

successfully applied. 

Bureau tests conducted in 

the Pocahontas No. 3 coalbed 

showed that water infusion 

- rates at 1,200 psi infusion 

pressures are less than 0.6 

V) 

W 

CE 

[L 

rr 600- - w Secondary 

I- fracturing a 

3 

400 - - 

a-filling up thewaterline - 200 - 

and borehole 

b-Occurrence of hydraulic 

fracturing *-a- b 

3 I I I A 

gpm, which is too low to 

integrate the infusion phase 

into the mining cycle. 

There are possibly two 

reasons for the low infusion 

rates in the Pocahontas 

No. 3 coalbed. First, the 

permeability of the coalbed 

is extremely low in which 

case there is not much one 

can do to improve the infusibility of the coalbed. 

Secondly, because of the 

friable nature of the coal 

and overburden pressures, 

the coal surrounding a horizontal hole becomes imperme0 10 20 30 40 able or suffers a partial 

TIME, min loss of permeability. Under 

these conditions, gas flow 

FIGURE 13. - H~drofrac of horizontal hole. out of the hole and infusion 

of water into the coalbed 

are inhibited. In the oil 

industry, this effect is called borehole damage and in some cases a hydrofracing process is used to increase the permeability of the damaged zone. 
Figure 13 shows the pressure history in the hole during the test. The 

waterlines and hole were initially filled with water. Then the water pressure 

in the hole was raised very rapidly. Fracturing occurred at about 1,200 psi 

followed by an abrupt drop in water pressure. A secondary fracture occurred 

shortly afterwards. Water flow rate into the coalbed after the frac treatment 

was 15 gpm which was the maximum capacity of the pump. Gas flow monitored 

from this hole about 1 month later was 13,000 cfd. Both water infusion and 

gas flow rates were improved. 

CONC LU S ION 

Waterflooding is an effective method of controlling methane at active 

face areas and thereby improving the safety conditions in an operating section. 

We have attempted to present the mechanics of water infusion in a simplified 

fashion so that those associated with production of coal and not necessarily 

familiar with fluid dynamics might have a better understanding of the process. 

I hope that this presentation will be helpful in diagnosing and solving problems associated with the application of this technique by mine personnel. 
DEGASlFlCATlON OF A COAL SEAM-LONGWALL GOB AREA 

by 

P. A. Ferguson l 

ABSTRACT 

Thirty-five boreholes have been drilled into longwall panels and conventional pillar sections of the Bethlehem Mines Corp.'s mines Nos. 32 and 33 

operating in the Lower Kittanning seam near Ebensburg, Pa. These have been 

found useful in reducing the methane in the returns and now handle up to 

80 percent of the methane from pillared areas. As expected, mining rates have 

increased in these mines. 

INTRODUCTION 

Bethlehem Mines Corp., Cambria Division, is located in Cambria County, 

Pa., near Ebensburg. Mines Nos. 32 and 33 are operating in the Lower Kittanning or "B" seam and are mining down the west flank of the Wilmore syncline. 

The lower coal measures in this area are all gassy and the cover over the B 

seam varies from 500 to 1,000 ft. 

The immediate overlying strata is of the Pennsylvanian age and consists 

of carbonaceous shales, argillaceous carbonaceous sandstones, coals, and some 

argillaceous limestones. Studies have shown that methane can be drawn from 

the upper coal seams: The Upper Freeport (E), Lower Freeport (D), Upper 

Kit tanning (C ' ) , and Middle Ki ttanning (C) . 

Mine No. 33 was opened in September 1964 by driving a slope on a 30- 

percent grade 2,700 ft to the B seam. Ventilation was established with a 

return shaft and then entries were driven to the Cambria Portal shaft for 

additional intake air. Small quantities of methane were encountered during 

entry development and averaged approximately 500,000 cfd. Three exhaust fans 

presently handle the ventilation requirements of the mine, discharging a total 

of approximately 900,000 cfm. 

The first pillar extraction began in December 1966 and methane liberation 

increased to approximately 2 million cfd 2 months after pillaring had started. 

After 4 months of pillaring in two headings, methane liberation reached a high 

lGeneral Superintendent, Cambria Division, Bethlehem Mines Corp., Ebensburg, 

Pa. 
of 3,380,000 cfd. This substantiated that the fracturing and caving of the 

upper strata was liberating large volumes of methane into the mine. 

First mining in this seam was known to be very costly because of extensive roof pressures and high caving, and the possibility of limited pillar 

production because of large quantities of liberated methane in the mine made 

necessary a detailed study of the mining projections and tonnage requirements. 

This study initially centered around ventilation, power requirements, and air 

shaft locations since larger quantities of air would be needed as mining 

progressed. 

METHANE CONTROL 

The study of the methane problem at mine No. 33 was started in January 

1968. We found that there was an apparent correlation between the methane 

liberation rate from pillared areas and the coal production rate and gob area 

exposed during mining. This study also showed that exhausting this methane 

through the mine ventilation system would be very costly because of the need 

for additional shaft installations, airway maintenance, and increased quantities of air. 

On March 28, 1968, the U.S. Bureau of Mines, Pittsburgh Mining Research 

Center, contacted us and proposed a study at mine No. 33 as follows: 

1. An analysis of cuttings from a churn drill hole would be made with a 

log of the strata. Samples would be taken on 5-ft intervals, starting at the 

Lower Freeport D coal and including all coal formations below this to the 

B coal. 

2. These data would be used to determine an approach to be used in this 

mine. 

Three holes were subsequently drilled in February 1971--one 95 ft horizontally into the seam, one 38 ft at 39 degrees up from the horizontal, and 

one 33 ft vertical. Pressure measurements made at various locations in the 

holes showed low gas pressures with minimal flows. These studies by the 

Bureau substantiated our findings that the methane is contained in overlying 

strata which has a high porosity but low permeability. The methane is stored 

in the rock and the resultant exposure of surface area from caving provides a 

means for the methane to be liberated into the mine. 

At this time, we were also concerned about the concentrated pillar tonnages being planned for our first longwall face and decided to drill a drainage borehole from the surface into the solid coal near the center of the 

longwall face. A rotary air drill was used to start this hole on March 19, 

1968. This borehole (No. 1) was drilled 594 ft into the B seam and reamed to 

a 12-in diameter. An 8-in casing with the two bottom joints slotted was set 

in the hole, and the bottom of the pipe stopped at the C seam approximately 

29 ft above the B coal. The hole was packed off above the upper slots and 

then grouted. 
The hole was approximately 675 ft ahead of the longwall face when completed, and a 170-cfm vacuum pump was installed on the surface. Trial runs of 

this pump in the solid produced approximately 250 cfd at 80 to 90 percent 

methane before flow would stop at a vacuum of 20 in of mercury. 

The longwall face cut into the borehole on June 18 and the pump operated 

at full flow with a vacuum of 1 in of mercury; methane was not present in the 

pump exhaust. On the following day, June 19, the face had advanced 16 ft 

beyond the hole and the exhaust gas was found to contain methane. Continuous 

pumping for 1 month averaged 150 cfm or approximately 210,000 cfd at 89.5 percent methane; this procedure was used to remove 4.8 million ft3 of methane 

from the mine (average: 172,000 cfd). At this point, we decided to try a 

larger pump of the same design capable of delivering 700 cfm and pumping was 

stopped to make the changeover. Interestingly, we discovered the hole developed a natural flow of 215,000 cfd of methane, indicating the smaller pump had 

actually restricted flow from the hole. The larger pump was put into operation and evacuated an average of 335,000 cfd of methane for 4 months or 35.8 

million ft3 of methane. 

In an attempt to evaluate the effect of this drainage on the mine ventilation system, the pump was shut down for a 24-hour period and the increased 

methane volume in the returns was found to be approximately equal to the 

methane previously exhausted by the pump. We, therefore, concluded that the 

borehole was removing methane that would otherwise be carried in the returns. 

Since our first borehole was put into operation in June 1968, we have put 

eight drainage boreholes into service in mine No. 32, and 27 in mine No. 33. 

Of these 35 boreholes for the two mines, 27 were in longwall panels and eight 

in conventional pillar sections . Variations were tried in methods and equip - 

ment in several of these holes. However, rather than describe each installation, a summary of the experiments and our conclusions is given in the following paragraphs. 

At an early stage, we recognized that freezing problems would be encountered with the water in the original vacuum pump; also, the high horsepower 

requirements and low efficiency made it undesirable for this application. We 

have since incorporated a 7-112-hp, 1,500-cfm blower of aluminum construction 

as a pumping medium. While this blower is rated for 1,500 cfm at 10 oz pressure, by changing the impeller and front cover it will deliver 1,660 ch at 

20 oz pressure. These latter impellers are installed on holes in active longwall panels. Then, as the panel is mined out, these are replaced with the 

original impellers as the methane concentration in the exhaust falls off. 

The borehole depth has been varied to evaluate the effects of depth on 

methane liberation. We have stopped the hole above the B seam on several 

occasions and found these holes were also successful. Presently, holes are 

still being drilled into the B coal, and the bottom of the casings are stopped 

approximately 125 to 130 ft above the seam. 

Packer locations have been varied in an attempt to stay below the waterbearing strata and to try to bleed off the methane from the highest possible 
point in the cavity created by caving in the mine. We now locate a packer on 

the end of the 8-in casing which is set from 20 to 40 ft above the C' seam 

(120 to 140 ft above the B seam). The hole is then grouted for about 75 ft 

above the packer. This method eliminates the problem of the borehole casing 

extending into the C' coal and concern for the casing in future mining in this 

seam. 

Our standard borehole is 12 in. in diameter; this hole is cased with an 

8-in steel pipe. However, we are giving some thought to experimenting with 

both larger and smaller boreholes. A study will be made to determine the 

advantages and disadvantages of these compared to the boreholes now in use. 

We have also vented the space between the 12-in hole and the 8-in casing 

to the atmosphere in order to bleed off any methane induced by cracks in the 

strata above the level at which the hole is grouted. To date, this has produced up to 230,000 cfd by free flow for one vent pipe in addition to the methane extracted by the pumps. 

General safety precautions taken during the drilling and casing operations, and the operation of the drainage pumps are: 

1. Blowers are never operated when the methane percentage drops below 

25 percent. 

2. Discharge pipes at the boreholes are kept a minimum of 15 ft above 

the ground. 

3. Drainage holes in accessible areas are fenced and warning signs are 

placed around all sites. 

4. All active boreholes are visited at least once daily and checks are 

made of the equipment and flow coming from the hole. 

Our studies have shown that methane liberation as related to pillar tonnage varies from 0.29 to 1.42 c£m of methane per ton of coal mined in pillars. 

The use of drainage boreholes has reduced the amount of methane handled in the 

re turns of the mine to the range 0.15 to 0.89 cfm per ton of coal mined. This 

shows we are now handling up to 80 percent of the methane liberation from pillar areas through the drainage boreholes. 

CONC LUS IONS 

The methane drainage boreholes have proved to be a safe and effective 

method of removing large quantities of methane from the mine atmosphere. This 

reduction has allowed mining to progress at maximum rates with a substantial 

reduction of methane content in the bleeder returns of the mines. This 

increases materially the coal production by utilizing high-cost, rapid-mining 

equipment more efficiently. 

The methane drainage boreholes have proved so beneficial that additional 

holes are normally planned as part of our mine projections for methane drainage from pillar production areas of both longwall and conventional systems. 
GOB DEGASlFlCATlON RESEARCH-A CASE HISTORY 

by 

J. G. Davis and S. Krickovi c 

ABSTRACT 

A degasification hole was drilled in advance of mining over the longwall 

panel at the Blacksville No. 1 mine early in 1972. This well was especially 

designed to provide research data on gob gas control as part of a Bureau of 

Mines contract3 with Consolidation Coal Co. 

Drilling and completion procedures are described, and research procedures 

and techniques are discussed. The latter include the use of wire line well 

logs to define overburden lithology, radioactive bullets in the side of the 

hole to trace subsidence, and use of a unique flow detector to locate points 

of gas entry into the well bore. 

Performance of the hole and its effects on the panel bleeders is traced 

from the start until the mine was sealed following a fire in the summer of 

1972. 

ACKNOWLEDGMENTS 

Valuable suggestions and technical assistance concerning test procedures 

were received from the Continental Oil Co.'s research department in Ponca City, 

Okla. Messrs. R. H. Minor and Herman Liddle of Consol's Blacksville No. 1 

mine were very helpful in arranging for the underground part of the study. A 

portion of the data presented here was obtained by Mr. Raymond Mazza of Conoco, 

who is now conducting the field research under this contract. 

INTRODUCTION 

Early in 1972, Consolidation Coal Co. (Consol) initiated a research program in cooperation with the Bureau of Mines to study methane control in gob 

areas. Of particular interest were the development of efficient techniques 

for the removal of gas from newly pillared areas and from older gob. 

l~ield Research Superintendent, Continental Oil Co., Morgantown, W. Va. 2 Supervisory mining engineer, Pittsburgh Mining and Safety Research Center, 

Bureau of Mines, U.S. Department of the Interior, Pittsburgh, Pa. 

3 Contract No. H0322851. 
Attention centered on the use of vertical holes drilled from the surface since 

this approach has the potential of removing gas from the mine in the most 

direct manner. A series of field experiments was designed to reveal sources 

of gas in the overburden, the gas flow network that forms as gob is formed, 

and changes that occur in both source and flow path with time. 

The total program was divided into two phases. In the first, a study was 

to be made of gas control in new gob where holes could be drilled safely over 

solid coal slightly in advance of mining. In the second, studies would be 

made in older gob where explosive gas mixtures might exist and safe drilling 

techniques require development. In the first study, an analysis was made of 

the data obtained from 15 holes drilled earlier for gob gas control in 

Consol 's Christopher Division. Additional tests were conducted on several of 

these holes, and four new holes were drilled in advance of mining for special 

study. These new holes, which probably contain the material of broadest general interest, are the subject of this presentation. The first of these will 

be discussed in detail. The second has been completed but not yet pillared 

under. 

EXPERIMENTAL 

The first new test hole 

(No. 1-M) was drilled in 

advance of the longwall at 

Blacksville No. 1 mine 

(fig. 1 . This area was 

selected because the mine 

was new and only development 

work had taken place. Consequently, the overburden 

was still undisturbed, and 

the test would not be 

af fected by previous subsidence. Also, the data would 

be available for comparison 

later with that from more 

common room and pillar 

mining. 

The general plan for 

these test holes was as 

follows: 

1. Drill to the vicinity of the Waynesburg coal 

/ seam. Set and cement casing I to exclude the upper water I 

zones. 

FIGURE 1. - Outline of Blacksville No. 1 mine in area of 

methane research we l Is. 2. Core, drill, and 

est various intervals in 
the overburden from the bottom of the casing to a point about 30 ft above the 

Pittsburgh coal. 

3. Run a suite of wire line logs. 

4. Implant radioactive bullets in the wall of the open hole and log 

these to establish index points for future subsidence studies. 

5. Run a slotted liner to prevent caving of the open hole section. 

6. Conduct subsidence and gas flow tests for 1 year or more after the 

hole is mined under. 

The hole was located about 480 ft from the start of the 2,700-ft long and 

430-ft wide panel. Mining had not yet started on the longwall proper when the 

hole was drilled. 

Past experience gave no reason to expect any gas flows above the 

Waynesburg coal that could affect the mine. Consequently, a 9-518-in casing 

was set just above the Waynesburg and cemented to the surface. All drilling, 

both above and below the Waynesburg, was done with air. 

The original plan had been to cut a 4-318-in-diameter core through most 

of the interval between the Waynesburg and the Pittsburgh. This would be used 

to aid interpretation of the wire line well logs. Coring was very slow, however, and the decision was made to drill ahead to a point just above the 

Sewickley coal before coring was resumed. It was still desirable to get the 

lower core, since this is the immediate overburden to the mine and a probable 

source of mine gas. Four drill stem tests were run so that the entire hole 

section below the casing was tested at one time or another. There was no significant show of gas at any point, although there were some very weak blows. 

There was no pressure buildup on any of the tests. Some water was observed, 

and the rate of water inflow when the well was at total depth was 0.05 gpm 

from the Waynesburg coal and 0.10 gpm from the Sewickley coal. 

Two wire line logs were run at total depth. One was a combination gamma 

ray and side wall neutron. This log's fundamental use is for estimating formation porosity, but it is also very useful in determining formation lithology. 

For instance, shale will show a very high porosity and so will coal. They can, 

therefore, be picked from the less porous limestone and sandstone. Shale contains radioactive materials, however, and gives a high gamma ray count. 

Because coal is not radioactive, coal and shale can be separated from each 

other. 

The other log was a combination gamma ray and formation density. This 

records rock density which is useful in determining lithology and in serving 

as an aid in the interpretation of the neutron log. 
FIGURE 2. - Gamma ray log of cobalt tracer bullets immediately 

after test hole cornplet ion. 
Benwood limestone 

Benwood limestone 

KEY 

SS-Sandstone LS-Limestones SH-Shale Sa-Sandy 

Sha-Shaley 

FIGURE 3. - North-south cross section of overburden 

through Blacksville wells 1-M and 2-M. 

high, sharp gamma ray peaks. 

A section of this log is 

shown in figure 2. 

Finally, a 7-in liner 

was run in the well and hung 

from the casing head. The 

lower 353 ft of the liner 

contained a profusion of 

114-in-wide by 4-in- long 

slots to permit gas to enter 

the pipe. The upper 218 ft 

was left blank and will 

serve as a guide for test 

equipment run in and out of 

the hole. 

A second hole (No. 2-M) 

was drilled by Consol 

4Reference to specific 

brands is made for identification only and does 

not imply endorsement by 

the Bureau of Mines. 
1,330 ft down the panel from No. 1-M. It was completed in much the same manner but without cores, drill stem tests, or tracer bullets. It is to serve as 

a regular degasification hole, but would, in the process, provide important 

data for the research work. 

RESULTS 

Data from logs of No. 1-M and No. 2-M and from two nearby diamond core 

holes drilled earlier by Consol were used to construct the cross section 

shown in figure 3. This includes the zones from the Waynesburg sandstone to 

the Pittsburgh coal. All of this section from the base of the Waynesburg 

sandstone down is open to the well bore in the test holes. 

The drill stem tests run during drilling showed very little evidence of 

gas in the overburden. A methane detector installed on the rig's air exhaust 

line did pick up small indications near the top of the Benwood limestone and 

again in the Sewickley sandstone and coal seam (fig. 4). 

Eight monitoring stations were set up underground to measure methane off 

the longwall gob. These are shown in figure 5. Nearly all the methane off 

the gob exits through the main bleeder at Station 7. The data for the underground bleeders are compared 

METHANE IN EXHAUST AIR, ppm 

0 200 400 600 800 1,000 

Y- C

[ Upper Sewickl / 

'- T. D.= 571 ft GLM 

600 t Probable Pi ttsburqh 

Top= 595 ft GLM 

AIR VOLUME, cfm 

0 

m 

4,000 

Ground level = 

FIGURE 4. - Methane detector data, well No. 1-Me 

with those from the surface 

hole in figure 6. 

The longwall passed 

under the hole on May 1, 

1972, and gas production 

started almost immediately. 

It peaked at 300 scfm, 

declined very rapidly, and 

the hole started intaking 

air. Pressure returned at 

the wellhead after a brief 

shut-in, and gas production 

resumed as shown in 

figure 6. 

There are numerous 

similarities between degas 

hole performance and the gas 

in the underground bleeders. 

Both appeared responsive to 

the rate of mining. For 

instance, the rate of mining 

increased significantly on 

June 7, and this is 

reflected by an immediate 

increase in gas both at the 

surface and in the bleeders. 
June 23, and gas dropped & 250 

a immediately in the bleeders. 

a The effect of shutting in 

s 

q 200 the well was an irmnediate 

LL bleeder gas increase of at 

W 

z least 30 percent. This 2 150 dropped back when the well 

Iw was reopened. 5 

100 The quantity of me thane 

in both the bleeders and the 

50 well increased as work 

resumed following the vaca0 tion. Everything was shut 

5 10 15 20 25 5 10 15 20 25 5 10 15 20 25 in when the mine was sealed 

25 -MOyJuneAJuly July 24 following a mine 

fire. The area drained by FIGURE 6. - Plot of all methane off the longwall l an el the hole is still sealed, 

underground of the gas production from but No. 1-M is 

test hole No. 1 -M. again. ~t currently averages about 60 sch. It 

is still producing by 

free-flow, as it has throughout its life. 
FIGURE 7. - Underground subsidence studies using 

The second log was run 

a short time later when the 

Underground subsidence 

was followed by monitoring 

the positions of the radioactive bullets with a gamma 

sonde. Results of the first 

two such surveys are shown 

in figure 7. Movement of 

the bullets are plotted in 

terms of their apparent dis - 

placement from the original 

position. The latter is 

denoted by the solid vertical line. The first survey 

was runwhen the longwall 

was about 40 ft past the 

hole. There appears to be 

no significant break until a 

depth of about 480 ft, which 

is about 30 ft above the 

Sewickley coal. At that 

time, two bullets were missing, and there was considerable displacement of the 

rest. The initial break 

appeared to have reached 

about 110 ft above the coal 

200- I 1 I I I I I 

1 - 

- W 

> 

W 

J - 

Z 

3 

- 

Face 170 ft past hole - 

w 

fY 

coba It tracer bu 1 lets, longwall was about 170 ft 

past the hole. The logging 

unit used at that time was less accurate; this could account for some of the 

variations seen in figure 7. There definitely seems to be a trend, however, 

suggesting additional movement up to a depth of about 400 ft. This is about 

200 ft above the coal. Other logs have been run since. We do not see any 

further break upward, but there is evidence that the portion from the 

-2.0 I. 0 1 1.0 2.0 3.0 4.0 5.0 6.0 sea,. 

COBALT TRACER BULLET DISPLACEMENT, f t 

3 

2 y 500- 

s 

I- 

[L 

W 

o 

600. 

Sewickley down is recompacting. 

i 

------- 

-- --* 

/ 

,' - i >--- --- -----eN : 

1 rA6 ft, Pittsburgh coal I I I I I I 

Movement of the ground surface along the centerline of the panel was very 

pronounced as is shown in figure 8. This survey was made when the longwall 

was about 200 ft past No. 1-M. The wellhead had sunk nearly 6 in at that 

time, and the maximum surface subsidence appears to have approached 2 ft. 

The locations where gas entered the borehole were detected by means of a 

flow logging device designed and built especially for these tests. Other more 

"conventional" methods had been considered and one was tried, but none was 

applicable. These included temperature surveys, mechanical spinners,and a 

type of hot wire anemometer. The latter was the one actually tested. 
-- .-- - 

Direction of mining Start of 

200 100 0 100 200 300 400 500 600 

HORIZONTAL DISTANCE, f t 

FIGURE 8. - Ground surface subsidence along the centerline of the longwall l an el as of 

May 18, 1972. 

The flow logging device used here is shown schematically in figure 9. It 

is run into the hole in two sections on an electric conductor cable. The 

lower section consists of a storage reservoir of radioactive krypton gas in 

nitrogen and a means of releasing small pulses of this gas on command from the 

surface. The second section is a gamma sonde located about 20 ft above the 

krypton emission unit. Release of the gas pulse is noted by a surface 

recorder that has a high-speed paper feed. The gas is carried up the hole 

past the gamma sonde by the upward flow of methane in the pipe. Passage 

across the sonde is also noted on the chart. The resulting transit time 

interval can be converted to a flow rate if it is assumed that the majority of 

the flow is confined to the inside of the slotted liner. 

Runs can be made at different levels in the hole and the results used to 

plot the percent of total flow at the various levels. Two such runs are shown 

in figure 10. Only about 20 percent of the gas appears to enter the hole 

below the Sewickley coal. About 90 percent appears to enter in the first 

200 ft above the coal. This corresponds to the zone of subsidence detected by 

the movement of the radioactive bullets. 

Several modifications have been made in the logging equipment since this 

first work was done. These include the installation of a collar locator in 

the gamma tool to improve downhole accuracy on the bullet surveys; purchase of 

a slip ring for the hoist so that continuous gamma logs can be run; and the 

use of a powered hoist so that deeper holes can be surveyed. 
4-Conductor armored 

A Gamma sonde 

Gamma crystal 

/2- Conductor armored 

C 

port 

device 

ca ble 

cable 

, Discharge port 

Solenoid valve 

Discharge chamber 

(-13cm3at STP) 

Filling orifice 

Pressure regulator 

(10-50 psig) 

Valve 

N2/K-85 supply 

I (Initial = 800 psig) 1 PMetal case 

\ 1 

-/ 

FIGURE 9. - Pulse type flow logger developed for methane, 
4 Sewickley coaly 

TOTAL FLOW, pct 

Waynesburg coal 

200 I 1 1 1 I 

FIGURE 10. - Pulse hole data from test hole No. 1-M. 

t + 

2 2 300- 

Additional work is planned for the original test hole and for its companion (No. 2-M) if mining is eventually resumed on this panel at Blacksville. 

Meanwhile, the second test hole has been completed at Consol's Humphrey No. 7 

mine, and test work will begin shortly. 

I KEY I I i 

- 

, Face* 5 10 ft past well 

Face- 330 ft past well X 

xc 

' *I-' 
DEGASlFlCATlON THROUGH VERTICAL BOREHOLES 

by 

M. Deul and C. H. Elder 

ABSTRACT 

Experimental work is being conducted on degasification of coalbeds in 

advance of mining in major coal-producing areas in the United States in cooperation with coal mining companies. Work is being done in eight different 

coalbeds in eight States on properties mined by 10 different companies. Only 

one site yielded too low a gas flow to warrant further work. All other test 

patterns are being monitored for gas and water production. We know that water 

in coalbeds, universally present in our test sites, reduces the permeability 

of the coalbeds to gas flow and substantially impedes gas flow. The key to 

degasification is dewatering, so well stimulation methods are being tested to 

increase water flow rates so that gas flow can be increased. Such stimulation 

also will increase the drainage radius of the wells. 

Progress to date is summarized and production trends analyzed. 

INTRODUCTION 

The degasification of coalbeds from the surface in advance of mining has 

long been the goal of researchers in mine safety. Various efforts have been 

made to successfully accomplish this and the best recorded early efforts are 

3 those of Spindler (3), Spindler and Poundstone (A), and Merritts, Poundstone, 

and Light (2). To date no technique for degasification of coalbeds from the 

surface far in advance of mining has been found economically acceptable. 

Attempts were made by the Bureau of Mines to utilize exploration core 

drilled holes placed by coal mining companies for formation testing in the 

Pittsburgh coalbed but these were unsuccessful because of the small diameter 

casing (only 2 in) and the limited size of stimulation equipment that could be 

used. This work started about 1965, was enlarged in scope somewhat to permit 

Supervisory geologist. 

~eolo~is t . Both authors are with the Pittsburgh Mining and Safety Research Center, 

Bureau of Mines, U.S. Department of the Interior, Pittsburgh, Pa. 

3~nderlined numbers in parentheses refer to items in the list of references at 

the end of this chapter. 
4-in casing to be placed in an exploratory hole in the Pocahontas No. 3 coalbed in Buchanan County. The experience gained from these holes, essentially 

negative information, has been summarized in a report by Cervik and Elder U). 

Much of the recorded experience with these attempts at degasification 

through vertical boreholes was apparently contradictory. Very high gas pressures measured in borehole shut-in tests yielded low gas flow rates, on the 

order of 1,000 cfd for the Pocahontas No. 3 coalbed whereas shut-in pressures 

of only 28 psi were measured in the Pittsburgh coalbed in a well that yielded 

a flow of 24,000 cfd (4). 

There was much hearsay on profuse flows of gas from vertical holes 

drilled into coal-bearing strata during exploration. Tales of drill strings 

of tools forced out of drill holes and of violent outflows of gas are common. 

Our direct experience with 53 holes, in that none of these holes exhibited 

such behavior, is that this would be a very rare occurrence. 

Large gas flows have been encountered in drilling holes in fractured rock 

over subsided strata where longwall mining is conducted. Very high rates of 

methane emission, on the order of several million cubic feet per day, have 

been measured in such boreholes that could not be completed to the gob areas. 

But in this instance we know that the gas was emitted from sandstone horizons 

that had yielded flows of gas on the order of 40,000 cfd in the unfractured 

state; after subsidence these strata were fractured and the initial flow rates 

were increased manyfold. All of these experiences and the observations made 

in the conduct of our other research on methane control reviewed by Zabetakis, 

Deul, and Skow (6) logically led us to conclude that certain physical factors 

must be considered in conducting further experiments on degasification through 

vertical boreholes. 

PHYSICAL FACTORS 

The physical factors we consider important have, at first thought, been 

relatively obscure. They are: 

(1) Coal, unlike most other gas-producing formations, has a low porosity, 

especially in contrast with sandstone which has a large interstitial porosity. 

(2) The permeability of coalbeds may be directional--some coalbeds 

exhibit much greater along the face cleat than along the butt cleat. 

(3) Most coalbeds are water saturated and, as a consequence, exhibit a 

low gas permeability. 

(4) Coal, because it has a low mechanical strength, readily suffers formation damage; this in turn may substantially reduce the permeability at the 

periphery of the holes drilled into coalbeds. 

(5) Coalbeds do not exhibit uniform physical and chemical properties. 

These factors must be understood before any large-scale efforts at degasification of coalbeds can be successfully undertaken. Currently, the Bureau 

is completing a comprehensive program to test candidate coalbeds and to produce gas from these coalbeds along projected development areas of existing and 

newly developing mines in these coalbeds. 
DEGASIFICATION TEST SITES 

Several important criteria were applied in selecting sites for experimental vertical degasification holes. These were: 

(1) Known or suspected high methane content in coalbeds. 

(2) Large block of unmined coal for drilling. 

(3) Planned mining of block within 3 to 5 years of drilling. 

(4) Favorable geological conditions. 

(5) Cooperative agreement and ready acquisition of right-of-ways for 

drilling. 

Usually all these criteria were met before drilling was started. In one 

instance mining conditions were such that the mining company has gone out of 

business so mining projections will not be met on schedule; in another, what 

had been expected to be a serious situation insofar as gas in horizons irnmediately above and below the coalbed mined has not yet materialized from the well 

tests but may yet yield useful data when mining causes relaxation of strata. 

Data useful to mine planning are expected from all the patterns. 

Medium- and high-volatile 

bituminous coal 

3- Drill hole sites SCALE, miles 

FIGURE 1. - Vertical degasification sites in the bituminous coalfields of the conterminous 

United States. 
A* 

FIGURE 2. - Northern Appalachian degasif ication sites. 
a, I a,* 

cd - 'g: 8 om g v5 -TI Cow Om ;k .a L, cd kk Plu I OC!J -C I m F 

F: rl C U. a, a,. a, cd rl 

mo 3 QO *o a s 4 rl P 

gs am6c k az 3 a, 3 cd k &OXH 5 U 

C I4 

a) 

allow a-I4 mu 
RESULTS TO DATE 

Water and gas are being produced from most of the patterns drilled. One 

hole in each pattern is generally not put in production but is used as a 

monitoring hole to measure gas pressures and to determine the extent of interference from production of the other holes in the pattern. 

All of the holes on production yield water and gas. Water in the fractures and macropores of a coalbed reduces the flow rate of gas from the coalbed. Consequently, all the drill holes are outfitted with pumps to remove the 

water intermittently. Generally, as the water is pumped from the formation 

the flow rate of methane increases. 

Gas pressures are determined either by standard drill stem tests or by 

measurement of the height of the water level as gas flow is arrested by the 

equalized pressure of the water column in the casing. Where permeability is 

very low and the gas flow rate is so low that the normal time allotted to the 

drill stem test for bottom hole pressure is inadequate, no successful measurement is possible using standard drill stem test procedures. All the producing 

patterns are now being fitted with a bottom hole device to measure pressures 

at will; these data will soon be acquired. 

Dewatering is of utmost importance. As water flow rates decline, all 

other factors being equal, the gas flow rates increase from a vertical borehole in a coalbed. Figure 3 is a plot of the water flow and gas flow rates 

versus time for a single hole in the Alabama pattern. 

COMPOSITION OF COALBED GASES 

Gas samples taken from vertical boreholes have variable compositions 

depending upon location. Table 2 lists typical analysis from the Pittsburgh, 

Pocahontas, and Mary Lee coalbeds. 

TABLE 2. - Composition of gas from vertical degasification holes 

. These analyses will be compared with those from samples collected at 

varying intervals to determine the nature of the compositional changes with 

time as desorption proceeds. 

Coalbed 

Pittsburgh: 

Washington County, Pa.. .......... Marion County, W. Va.. ........... Monongalia County, W. Va. ........ Pocahontas No. 3: 

Buchanan County, Va. ............. Wyoming County, W. Va... ......... Mary Lee: Jefferson County, Ala. .. 

98.0 

92.1, 92.4 

90.7, 90.8 

97.9, 97.6 

97.6, 99.1 

96.0 

O2 

0.0 

0.3, 0.2 

0.3, 0.3 

0.2, 0.1 

0.6, 0.2 

0.1 

N2 

1.0 

1.0, 0.7 

1.1, 1.1 

1.0, 0.8 

1.8, 0.7 

3.5 

C02 

0.7 

6.5, 6.6 

7.3, 7.2 

0.78, 0.4 

0, 0 

0.1 
TIME, month 

FIGURE 3. - Gas and water production, No. 3 SW hole, Oak Grove mine, Alabama. 

DISCUSSION 

The relatively low gas flow rates from the vertical degasification boreholes as compared with those from early degasification experiments can be 

readily explained by the fact that the blocks of coal in which these tests are 

being conducted are remote from active mining areas and have not yet been 

dewatered. Research being conducted at the University of Pittsburgh under a 

grant agreement shows that "the effective permeability to gas increases most 

rapidly with decreasing water saturation over the higher water saturation 

range" (5). This means that low gas flow rates are to be expected until the 

coalbed is dewatered around the vertical borehole. 

Knowing that coalbeds are water-saturated, we can now proceed to hydrofracture selected sites to increase the permeability of the coalbeds and the 

flow rate of methane gas, and to substantially extend the drainage radius of 
each borehole. Water removal is the key to degasification. Simple free 

drainage will not succeed because the water column forced into boreholes by 

gas pressure will eventually equalize the reservoir pressure and shut the 

wells in. 

The scientific program of analysis of coalbeds as gas producing reservoirs that will result from this study will ultimately provide realistic 

criteria for evaluation of degasification of coalbeds. These studies, coupled 

with the results of studies such as those reported by Fields in this seminar, 

and novel method& of drilling long holes in coalbeds parallel to the bedding 

will yield means of demonstrating the feasibility of degasifying coalbeds 

which exhibit moderate and high gas permeability. Coalbeds which exhibit low 

permeability will require further research. 
REFERENCES 

1. Cervik, Joseph, and C. H. Elder. Removing Methane From Coalbeds in 

Advance of Mining by Surface Vertical Boreholes. Proc. Conf. on the 

Underground Environment, Univ. Mo.--Rolls, Oct. 27-29, 1971, 

pp. 209-228. 

2. Merritts, W. M., W. N. Poundstone, and B. A. Light. Removing Methane 

(Degasification) From the Pittsburgh Coalbed in Northern West Virginia. 

BuMines RI 5977, 1962, 39 pp. 

3. Spindler, G. R. Degasification of Coal Seams. Coal Mine Modernization, 

1953, Am. Min. Cong., pp. 206-220. 

4. Spindler, G. R., and W. N. Poundstone. I3xper-imental Worth in the Degasification of the Pittsburgh Coal Seam by Horizontal and Vertical Drilling. 

Trans.ACME,v. 220, 1961, pp. 37-46. 

5. Taber, J. J., P. F. Fulton, and A. A. Reznik. Development of Techniques 

and the Measurement of Relative Permeability and Capillary Pressure 

Relationships in Coal Grant Agreeement No. G-0122006. Quart. Tech. 

Rept., Sept. 1-Oct. 31, 1972, 12 pp. 

6. Zabetakis, M. G., Maurice Deul, and M. L. Skow. Methane Control in 

United States Coal Mines--1972. BuMines IC 8600, 1973, 23 pp. 
PANEL DISCUSSION 

Panelists: 

John Ashcraft, West Virginia Department of Mines, Charleston, W. Va. 

Robert Dalzell, U.S. Bureau of Mines, Pittsburgh, Pa. 

James Davis, Continental Oil Co., Morgantown, W. Va. 

Peter Ferguson, Bethlehem Mines Corp., Johnstown, Pa. 

William Laird, Eastern Associated Coal Corp., Pittsburgh, Pa. 

James Micheal, U.S. Bureau of Mines, Morgantown, W. Va. 

J. J. Yancik, U.S. Bureau of Mines, Washington, D.C. 

M. G. Zabetakis, U.S. Bureau of Mines, Pittsburgh, Pa.; moderator. 

Dr. Zabetakis. Before continuing with the panel discussion, I have been 

asked to give the highlights of the material presented here today. Basically, 

what we have attempted to show is that there is a lot of gas in our coal, and 

that as mining rates and depths increase, the gas emission rates will also 

increase unless we exercise some control over the gas; we are going to have to 

think seriously about degasification. We have seen instances here today where 

some mine operators and Bureau of Mines investigators have been successful in 

liberating up to 80 percent of the gas in a particular area, using fairly conventional techniques. Where gas is still a problem, we now have procedures 

that are usable in blocking the flow of the gas to the face. 

Horizontal and vertical boreholes are quite useful in degasifying virgin 

coal and gob areas, respectively. In the first case, we have found methane 

emission rates to be about 0.1 cfm/ft2 of surface area from 3-in boreholes. 

This is about an order magnitude more than the emission rates from exposed 

ribs. This means, therefore, that if you want to complete a degasification 

job in a short period of time, you either have to drill long holes or larger 

diameter holes, or, perhaps, hydrofrac these in order to increase the surface 

area, provided that the hydrofracing operation will not damage the roof significantly. To reduce gas emission rates to a manageable level, we must plan 

ahead. Many of the European mines are recovering 50 percent of their gas-- 

even in their very deep mines. We feel this can also be done here. 

With this thought, then, let me very briefly introduce our panelists. We 

have to my right, Mr. John Ashcraft, director of the West Virginia Department 

of Mines, whom I am sure you all know; to his right is Mr. Robert Dalzell, 

chief of the ~ureau's Ventilation group, Technical Support Center in Pittsburgh; to his right is Dr. Joe Yancik, who spoke to us earlier and, I am sure, 

needs no further introduction. To my left we have Mr. James Micheal, district 

manager, District No. 3, Health and Safety--all those of you in this area know 

Jim quite well. To his left is Mr. James Davis who talked to us earlier; to 

his left is Mr. Pete Ferguson, who also spoke to us earlier; and to his left 

is Mr. Bill Laird, vice president--engineering, Eastern Associated Coal Corp., 

who has been extremely helpful to us in the conduct of our work in the Federal 

No. 2 mine. 

Before we proceed with questions from the floor, let us hear from our 

panelists. First, Bob Dalzell. 
Mr. Dalzell. Good afternoon, gentlemen. It has been a pleasure to sit 

in on the meetings with you today. I am sure that it has been an education to 

me. It has been a revelation to learn of some of the techniques that have 

become available for use in control of methane in underground mines. Gentlemen, methane and methane control has been a problem in underground coal mines 

since the inception of mining in the United States. The classic method of 

control of methane in underground mines has been by the controlled movement of 

air to the underground passageways and the use of adequate quantities to 

dilute, render harmless, and carry away the methane that was introduced into 

the mine environment. 

Unfortunately, every ventilation system, regardless of whether it is the 

one that includes the entire mine or the face ventilation system that is 

employed from the last open crosscut to the working face, has a capacity. If 

we exceed the methane dilution capacity of the system, then we have a problem. 

Hazards increase and the probability of ignition becomes more predominant. It 

is not at all uncommon to have in some of the gassy coal mines, methane concentrationsof0.2 to 0.3 percent on the intake airstream; in some cases, even 

higher percentages of methane are found. Now if we are talking in terms of a 

quantity of air being used to ventilate a working place, say, 10,000 cfm, then 

this means that the total vo-lume of air that has been delivered to that point 

has a capacity for dilution of 100 ft3 of methane. If our intake air is contaminated by 0.2 or 0.3 percent methane, then we have reduced the capacity of 

our system for dilution of methane in the immediate face area by 30 percent 

before we start mining coal. 

Today we have heard a number of techniques described which give clear 

indications that tools may be available whereby we can control the influx of 

methane from rib liberation and, possibly, from liberation at the immediate 

face area. Gentlemen, if we could reduce, in my hypothetical example, the 

concentration of methane in our intake airstream, it would increase the capacity of our system at the face by 10 percent with a simple reduction of 0.1 

percent in the intake air courses. I believe that the ventilation system must 

be made the primary technique for control of methane underground. However, 

papers that have been presented today and t h e s t a t e - o f - t h e - a r t i n d i c a t e s that 

additional very strong tools are available whereby we can, perhaps, reduce the 

amount of methane introduced into our coal mines, and thereby decrease the 

hazards to the miners who are working in our mines and, also, reduce the cost 

of ventilation as we go into deeper coal seams with anticipated higher methane 

concentrations . 

Dr. Zabetakis. Next, we will hear from Mr. John Ashcraft. 

Mr. Ashcraft. Gentlemen, as the director of the Department of Mines of 

the Nation's leading coal producing State, I am very happy to have the opportunity to attend your seminar. I must admit, however, that appearing as a 

panelist is not one of my favorite pastimes. 

Since safety in our coal mines is a prime objective of our department, we 

are vitally interested in any innovation or technology that might be geared 

toward that goal. Since methane does constitute a constant hazard to the 
mining industry, we are extremely interested in the degasification programs 

carried on in our various mines. I was invited and attended the initial meeting at the Federal No. 2 mine and given an opportunity to express my ideas, 

both pro and con, on the subject. 

Our department has participated in an active manner since that program 

started and I am kept abreast of the program as it progresses. I feel certain, 

as we get further into degasification of mines, that more and greater problems 

will arise and I am sure that each one present here today will, by necessity, 

become deeper involved. The persons that presented the papers should be 

highly commended for the job that they have done. Their papers were well prepared, very well presented, and to me, very educational. Thank you. 

Dr. Zabetakis. Our next panelist needs no further introduction; however, 

let me say that I have had a number of inquiries over the past 2 years regarding our use of special equipment underground. The man who inspects this equipment and keeps us on the straight and narrow in this area is Jim Micheal and 

the other members of District 3. 

Mr. Micheal. Thank you. I think the persons that are responsible for 

this program today, particularly those who participated on the prograqare to 

be commended for a splendid job. In Health and Safety, of course, our primary 

responsibility is enforcement and administering the ~ederal Coal Mine Health 

and Safety Act of 1969. This also includes, as Dr. Zabetakis stated, serving 

as a kind of watchdog over the research programs that are conducted underground and on the surface at our coal mines. This responsibility includes, in 

cooperation with the research, technical support, the approval of the kinds of 

equipment, the inspection of the equipment, the approval and subsequent inspection of such installations, and approval of work procedures that are used 

underground. In the past we have cooperated fully with the operating people 

in the mine, with the miners themselves, and with the State department of 

mines; in all cases, our goals in these programs are the same, only our ideas 

as to how to attain these goals sometimes differ. But so far we have been 

successful, and, knowing the history of the mines, particularly in the northern part of West Virginia, we can appreciate the need for a degasification 

program. We will continue to support the program and do everything in our 

power and within our authority to see that this program is carried on. Thank 

you. 

Dr. Zabetakis. Jim Davis, again, needs no introduction, so I will merely 

pass the microphone on to him. 

Mr. Davis. I have been given a choice on what to talk about. However, I 

want to stay on the technical side and make a couple of comments on one subject that has come up several times--that is, hydraulic fracture. 

I do not know how well acquainted everyone is in the room with this technique. It was developed about 20 years ago in the oil industry, and it followed years of using acids and nitro shooting to try to stimulate production 

from oil wells and it thoroughly turned the oil industry inside out. It is 

one of the finest things that has ever been developed for stimulating flow 
from oil and gas wells. But it does have some limitations. I would like to 

comment on a couple of them before some people get into trouble. 

One is, that you have got to have good well completions if you are to 

contain the breakdown pressures. By this I mean that the technique that works 

extremely well on some of the degas holes that are cemented on the outside of 

the pipe is likely not to work in other cases. You must control the fractures. 

You do not want to break up on the outside of the pipe and get into roof zones 

or some other area of the mine. 

The other point is that hydraulic fractures want to follow the easiest 

path. One of the things that both helps us and plagues us in the Pittsburgh 

seam is the highly directional nature of the permeability. Joe Cervik quoted 

a 10 to 1 figure this morning as the ratio of the permeability along the face 

and butt cleavage planes. However we start the fracture, it probably will 

follow the face cleavage because this is an easy path. What we will do is to 

increase the permeability in the very direction along which we have already 

got a high permeability. I am not sure of Maury Deul's fracturing plans, but 

I am sure he will have taken these factors into account, and we will see some 

attempts at frac jobs in which he will try to cut across the face cleavage 

somehow to open up the coal. Thank you. 

Dr. Zabetakis. Mr. Pete Ferguson, our next panelist, indicated that he 

did not have too much to add to his talk. However, is there anything else 

that you would like to say at this time? 

Mr. Ferguson. Well, perhaps I can expand on the talk. Our problem is 

unique in that we can mine within the seam and not really be hampered too much 

by methane liberation from the coal. We are fortunate in this respect and 

also that our large concentrations of methane are in our roof strata up at 

least 30 ft; this gas is retained there by an impervious clay bed under the C 

prime seam. So in our thinking we have confined our thoughts to this area in 

the upper strata. We are now satisfied that vertical boreholes are doing a 

good job for us and we will continue to try to take more of the methane out of 

our boreholes. For the future, we may try to confine this methane in our longwall blocks by actually constructing stoppings in the crosscuts after we have 

completed our mining. This we are doing in conjunction with the Bureau and 

some of their research teams. We feel that the more we can take out through 

our boreholes, the more efficient and more safely we can mine underground. 

The only thing is that if there are questions, I would entertain them. 

Dr. Zabetakis. We are going to come back to the questions shortly. With 

that in mind, if there are any questions, let us hold them for just a few more 

minutes. Now we will hear from Mr. Bill Laird. 

Mr. Laird. I thank you for the opportunity to be here today. It gave me 

an opportunity to find out what others are doing in the area of degasification. 

As you know, Federal 2 is located in Monongalia County near Bula, W. Va., on 

Miracle Run. This mine produces between 8 and 11 million ft3 of gas in 24 

hours. We have worked closely with the Bureau of Mines in attacking the problem of degasification. We hope to provide a safe and healthy environment for 

our coal miners, to increase productivity, and conserve our natural resources. 
Under a cooperative agreement with the U.S. Bureau of Mines, we have 

drilled a 1,030-ft, 24-in-diameter hole in the 2 North mains. This is the 

area that Steve Krickovic noted released 33.7 ft3 of gas per ton of coal mined; 

the entry development in this area was halted because of high gas liberation. 

I might add that the 24-in-diameter hole can also serve as an escapeway in the 

event of an emergency. Our plan is to lay 8-in pipe from the borehole into 

the gassy area. This is phase I of a larger program. The work will be done 

in stages to determine if what we are doing is successful; if it is, this will 

encourage us to go on to set up a degasification system for the entire coal 

mine. We are now in the process of setting up the ventilation system, and 

putting power back into the section so that we can cut through to the borehole 

pipe which will be fitted with anescapehatch similar to that in a submarine, 

so that it can be opened quickly by turning a big wheel and dropping the lid. 

A pipeline will be laid along two entries to permit us to drill holes 

1,000 to 2,000 ft long about 5 degrees off the centerline; this will open up a 

large area and will permit the gas to flow to these holes. The multipurpose 

borehole will serve as a guide in this work. As you heard earlier, Herb 

Fields noted that he is draining about 150 ft3 of gas per day per foot of 

borehole. So if we go to a depth of 1,000 ft, we should have something like 

150,000 ft3 of gas per day to contend with. In reviewing this problem with 

Mr. Micheal, we were reminded that we must keep the gas out of the present 

returns. So we must set up a negative pressure system to drain the gas while 

we drill. This will involve drilling through a stuffing box which is connected to a compressor on the surface. If the gas is of sufficient quality, 

we will try to get it to a gas distribution system. However, the main purpose 

of this study is the degasification of the mine ahead of mining. 

To start this program, we first had a meeting at the mine office and 

invited the safety committee, the president of the local district UMW, 

Mr. Micheal, and others from the Research and Technical Support groups of the 

U.S. Bureau of Mines. We have discussed all aspects of this work; the safety 

committee is well informed, and it is our intention to keep them abreast and 

to make them a part of this program. If we are successful in the first phase, 

then we will proceed to the second phase, which is to extend the pipeline to 

other parts of the mine. In particular, one area is sealed at the present 

time; it contains gas. We hope to tap this gas and send it into our pipeline. 

It might be advisable to put down other borehole shafts instead of laying 

more pipeline. But at the present time, we are planning on laying pipe as we 

drill additional holes. We do not know exactly how long we will be able to 

produce gas, so we are only considering the first phase at present. If there 

are any questions, I would be more than glad to answer them at this time. 

Thank you very much. 

Mr. Krickovic. Bill, how far have the West mains been driven? 

Mr. Laird. The progress of West mains is slow because they are in virgin 

area, and are advancing with five or six entries. They have advanced about 

700 ft and have about 5,700 ft to go. 
Question. do you plan to do with this gas? 

Mr. Laird. I was in Germany about 2 years ago and found that their gas 

was piped back to the shaft and brought to the surface where it was used in 

their boilers and bathhouse. Perhaps we can do the same thing initially. 

Question. What does Bethlehem do with their gas? I 

Mr. Ferguson. We are still involved in trying to determine who owns it. 1 

Question. Are you venting it right now? I 

I Mr. Ferguson. Yes, we are presently venting it to the atmosphere. I 

Dr. Zabetakis. Are there any other questions? These may be directed to 

any of the panelists or to the speakers. 

Question. Mr. Davis, will you enlighten us a l i t t l e b i t on what you 

people have done in research as far as quality control is concerned. 

) Mr. Davis. What do you mean? 

Question. Well, I know that you have been doing some research on what 

has to be done to the quality of methane involved in degasification. I am 

quite sure that a lot of people here do not realize that it (methane) is not 

considered a marketable product as it comes out of the mine. And there are 

some problems of getting the methane to a marketable state before it goes into 

a pipeline system. 

Mr. Davis. I am going to disappoint you because we have not really 

looked at this problem very much. We have found that the gas from our gob 

drainage wells is not typically an oilfield type gas. It is very very lean; 

it is comprised, as far as hydrocarbons are concerned, usually only of methane, 

with a slight trace of ethane; seldom do we see propanes, butanes, and pentanes. So we end up with a product that at the very best, if it were pure 

hydrocarbon gas, would be about 1,000-Btu gas where typically oilfield gases 

will run somewhere from maybe 1,050 to 1,150 Btu's (per cubic foot). Also, 

the gas may contain 1 or 2 percent carbon dioxide. We feel that if we eliminate the air we can get a salable product. 

While I have done very little work on the composition of these gases, I 

do think I have seen a trend; as we get farther to the west toward Blacksville, 

and Federal No. 2, there is a higher carbon dioxide content--perhaps 8 to 10 

percent rather than 1 or 2 percent. So I think that we must either enrich the 

gas with propane or go the other way and scrub out the CO, since propane is 

scarce. 

In the last hole that we have completed, we have also found a small 

amount of $S. This may be easier to get rid of than the C4. I know %S can 

( be scrubbed-out too, but whether it is economical at present, I do not know. 
Question. Have you ever considered using this gas for your own purposes 

at the mine? 

Mr. Davis. We have used it; but when we first started toying with the 

idea of trying to put it into somebody's pipeline we thought that we could 

make a trade with the company selling us gas in the area. Actually, one of 

our degasification holes produces in a week or two, more gas than we use in a 

year. So this use is only a drop in the bucket compared with the amount of 

gas that can be produced. 

Dr, Zabetakis. In connection with this question, we have issued a 

request for a proposal to study the economic feasibility of recovering and 

utilizing this gas. Hopefully in about a year, we should have some answers to 

such questions in terms of gas production rates and mine location. 

Question. Has anybody determined the legality of who owns this gas yet? 

Dr. Zabetakis. This is one of the items that is to be studied. 

Question. All of our discussion has been on single seam mining, what 

will you do in a. multiple seam mine where anticipated gas is in more than one 

seam and you plan to mine the upper seam first? What could you do toward 

degasifying that seam and the lower seam prior to any mining and use? Would 

the hole itself possibly cause problems with gas in the lower seam while 

degasifying in the upper level? 

Dr, Zabetakis. The question has to do with multiple seam mining which is 

encountered in European mines to a greater extent than it is here, although as 

time goes on, of course, it will be encountered here too. Does anyone care to 

comment on this? 

Mr. Deul. We just had a little bit of experience with this and the picture is not very clear. For example, Pete Ferguson was telling you about the 

mining in the Lower Kittanning coalbed where there is not much gas, although 

there is gas in the Upper Kittanning with relatively low pressure. We have a 

similar situation in the Illinois No. 6 as related to the Illinois No. 5 coalbed where our preliminary measurements show that the Illinois No, 6 coalbed is 

relatively higher in gas content than the Illinois No. 5 which is not very far 

below it. The picture as I see it right now is that we cannot answer this 

question very simply because of the problem of migration of gas during the 

early stages of coalification, because gas is produced not only from the coal 

but also from the carbonaceous matter in the adjacent strata. And as these 

are compacted, the whole sequence of coalbeds and intermediate strata may have 

to be considered as a unit; therefore, we are going to have to do more work to 

determine what this interrelationship is. Now, certainly, where there are 

coalbeds widely separated by a thick sequence of rocks then each coalbed or, 

perhaps, each sequence of coalbeds becomes a separate problem. But this is 

much too early to answer these questions right now. 

Question. Has there been any work done on this water infusion from the 

surface or has it all been inside horizontal holes? 
Mr. Cervik. We have never attempted any water infusion of coalbeds using 

vertical boreholes. It has all been underground water infusion. 

Question. Sir, could you give us some information on the equipment 

required, drilling equipment for water infusion and type of drill power, and 

so forth? 

Mr. Cervik. Generally when we do a water infusion job we prefer to use 

an air drill because it is lightweight and can be moved and set up very 

quickly; we use a hand-held air drill that consumes about 200 cfm of air at 

100 psi. We use a drag bit and EX casing; there is nothing critical about the 

casing. There is no reason why, perhaps, you could not use an auger as long 

as you are drilling the hole with water. 

Question. What size average diameter hole do you drill for water 

infusion? 

Mr. Cervik. For water infusion we standardize on a 3-in-diameter hole 

mainly because our packers are 3 in. in diameter. Of course, there is no 

reason why the hole cannot be grouted in. 

Question. What maximum depth do you use? 

Mr. Cervik. When we use hand-held equipment, we limit our depth to about 

125 ft. There is nothing sacred about this distance other than that in some ' 

cases, entries are advanced in 100-ft increments. Generally you can advance, 

say, one break in a week. But if you want to use a 200-ft hole, then you can 

mine for a much longer period before reinfusing. 

Question. Mr. Cervik, what would be the feasibility of infusing a panel 

of coal once it is isolated to degasify a coal mine? 

Mr. Cervik. There is no problem with infusing a panel. However, we 

infuse panels for dust control, not methane control. 

Dr. Kissell. Why would you want to infuse a panel? Most of the gas is 

trapped in the solid coal and is not in the fractures. When you push water 

through you push it through the fractures; this forces out only the gas in the 

fractures which constitutes only 5 to 10 percent of the total. At the same 

time the infused water would reduce the permeability and block the flow of 

gas. 

Question. That is not my question. Is it feasible to infuse a panel? 

Dr. Kissell. Oh yes. Water can be pumped into it. 

Dr. Zabetakis. In the experiments described by Mr. Cervik, holes were 

drilled when a panel was outlined for degasification purposes; water was never 

put back in the degasification holes except to decrease the dust content. 

Bob Vinson can give us a little more information on this subject. 
Mr. Vinson. No, there was very little noticeable effect of water infusion on methane. But we did find a 40 to 79 percent decrease in dust levels. 

Infusion was particularly successful in the Pocahontas No. 3 coalbed because 

it seems the dust is inherent in the coal--it is a very friable coal. 

Mr. Krickovic. I would like to emphasize a methane control technique 

that has not been discussed today, which I think is very significant. And it 

supplements what Bob Dalzell said in connection with a good ventilation system. 

I refer to safely accessible bleeders. I think a ventilation system is not 

adequate and complete without a safely accessible bleeder system. That is, 

one that would permit an adequate pressure differential to develop across the 

gob so as to keep the gas movement away from the working face. This, in my 

opinion, is required regardless of any supplementary degasification methods, 

such as the vertical borehole. Actually, boreholes may be 300 to 500 ft from 

the beginning of a pillar line and gas must be bled from the gob even before 

borehole interception. 

Incidentally, based on my many years of experience in ventilation, there 

are too many open splits. I found as many as three in some cases; this should 

not be allowed. Every active split in a mine should be regulated to some 

degree to provide the flexibility that is required to control the volume of 

air in the different splits as the demand requires. 

Dr. Van Dolah. I would like to thank Pete Ferguson and Jim Davis for 

taking the time to be with us and present their papers. I would also like to 

thank the other panel members and each of you for coming. We think we have a 

story to tell; we are happy to have an audience. Again you are welcome to 

visit us at Bruceton any time. Please come. Thank you. 
QUESTIONS SUBMITTED AFTER THE SEMINAR 

Question. How was the multipurpose borehole enlarged? 

Answer. The borehole was enlarged manually with chipping hammers and 

pavement breakers after ventilation had been established in the borehole. 

Question. What are your thoughts regarding the placement of a 24-indiameter borehole at the back end of a bleeder panel and utilizing a permissible high pressure fan on the surface to move 12,000 to 15,000 cfm of air/gas 

mixture and thus maintain a greater pressure differential across pillar 

workings? 

Answer. We feel this is desirable in all cases where a dead end is 

created. 

Question. Why turn mining over to the drillers? Could the (Federal 

No. 2) project be done with a combination of vertical boreholes and a minimum 

number of mine entries? 

Answer. We would hope that the drilling operations associated with methane control can ultimately be incorporated into the mining cycle; the underground operations would then be handled by the miners. 

Question. What about gas rights where a coal company does not own them? 

Answer. A. D. Little, Inc., has recently been awarded a contract to 

determine the economic feasibility of recovering and utilizing methane emitted 

by coal. As part of this study, the contractor is to consider the legal problems associated with the collection and use of such gas. 

Question. Will there be problems associated with the compression of mine 

gas before pumping it into a transmission line? 

Answer. The most critical procedure associated with such an operation is 

the detection of air in the mixture to be compressed. However, this is not 

unique to our operations; monitors are available to assure that only suitable 

gas is compressed. 

Question. Is water injection feasible from the surface? 

Answer. Yes; however, it would be a rather expensive procedure in deep 

mines . 

Question. Is any work being done to separate mine gas (from air) at the 

mine fan? 

Answer. No. However, we have asked A. D. Little, Inc., to consider the 

methane in the exhaust air in their study of the economic feasibility of 

recovering and utilizing methane emitted by coal. 
Question. What type of pumps are used in dewatering coal? 

Answer. None. The water is forced out by the gas liberated by the coal. 

Question. Is water infusion similar to the water drive procedure used in 

the oil and gas business? 

Answer. No. Basically, we are advocating the use of water to block 

methane rather than drive it from an active face. 
REGISTRATIOX LIST 

Seminar on Methane Control in Eastern U.S. Coal Mines 

U.S. Bureau of Mines Technology Transfer 

May 30-31, 1973 

James Adkins 

Island Creek Coal Co. 

Holden, W. Va. 

Erman Altizer 

Youngstown Sheet & Tube Co. 

Dehue, W. Va. 

Donald D. Born 

Mountaineer Coal Co. 

Fairmont, W. Va. 

James E. Bresinger 

U.S. Bureau of Mines 

Johnstown, Pa. 

John Ashcraft Walter E. Bullers 

West Virginia Department of Mines R & P Coal Co. 

Charleston, W. Va. Indiana, Pa. 

Ken Austin 

Calvert Western Explosives- Co. 

New Concord, Ohio 

L. B. Burke 

Carbon Fuel Co. 

Charleston, W. Va. 

James A. Barlow Joseph Cervik 

West Virginia Geological Survey U.S. Bureau of Mines 

Morgantown, W. Va. Pittsburgh, Pa. 

C. 0. Bartron 

Westmoreland Coal Co. 

Quinwood, W. Va. 

D. A. Bayer 

Bethlehem Mines Corp. 

Madison, W. Va. 

W. B. Berry 

Consolidated Gas Supply Corp. 

Clarksburg, W. Va. 

L. M. Bianchi 

West Virginia University 

Morgantown, W. Va. 

C loyd B lankenship 

U.S. Bureau of Mines 

Mt. Hope, W. Va. 

W. T. Boyd 

U.S. Bureau of Mines 

William D. Conner 

Columbia Gas Transmission Corp. 

St. Albans, W. Va. 

Henry Cook 

Carbon Fuel Co. 

Winifrede, W. Va. 

Thomas J. Crocker 

U.S. Bureau of Mines 

Spokane, Wash. 

Robert Dalzell 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

J. G. Davis 

Continental Oil Co. 

Morgantown, W. Va. 

Russell L. Dawe 

Department of Mines and Minera 1 s 

Frankfort , Ky . Springfield, Ill. 
Maurice Deul 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

Robert L. Dodd 

West Virginia Department of Mines 

Charleston, W. Va. 

John C. Draper 

Duquesne Light Co. 

Pittsburgh, Pa. 

William E. Eckard 

U.S. Bureau of Mines 

Morgantown, W. Va. 

Pete Ferguson 

Bethlehem Mines Corp. 

Johnstown, Pa. 

H. H. Fields 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

Dennis Frailey 

Old Ben Coal Corp. 

Chicago, Ill. 

D. Geary 

Fenix Scissons 

Tulsa, Okla. 

Thomas Glover 

U.S. Bureau of Mines 

Springfield, Ill. 

James R. Gray 

Bethlehem Mines Corp. 

Barrackville, W. Va. 

Charles A. Gregory 

Westmoreland Coal Co. 

Tams, W. Va. 

R. H. Hamrick 

Westmoreland Coal Co. 

Big Stone Gap, Va. 

Dick Harris 

Loffland Bros. Co. 

Tulsa, Okla. 

Stephen P. Harrison 

Consolidation Coal Co. 

Glendale, W. Va. 

R. E. Havener 

Mine Safety Appliances Co. 

Pittsburgh, Pa. 

Ray M. Henderson 

Consolidation Coal Co. 

Morgantown, W. Va. 

R. Hidalgo 

West Virginia Geological Survey 

Morgantown, W. Va. 

John Hymes 

U.S. Bureau of Mines 

Beckley, W. Va. 

James I. Joubert 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

George L. Judy 

George L. Judy Assoc. 

McLean, Va. 

A. L. Julian 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

J. D. Kalasky 

Island Creek Coal Co. 

C leveland, Ohio 

James Kish 

U.S. Steel Corp. 

Gary, W. Va. 

F. N. Kissell 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

J. H. Kelley 

West Virginia University School of 

Mines 

Morgantown, W. Va. 

Tony B. Kitzmiller 

Consolidation Coal Co. 

Wana, W. Va. 
W. J. Kmetz 

Y & 0 Coal Co. 

Martins Ferry, Ohio 

C. A. Komar 

U.S. Bureau of Mines 

Morgantown, W. Va. 

John Kost 

Bituminous Coal Research 

Monroeville, Pa. 

Alex Kott 

Youngstown Sheet & Tube Co. 

Nemacolin, Pa. 

Bill Knepp 

Capata Coal Corp. 

Sharples, W. Va. 

Stephen Krickovic 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

William Laird 

Eastern Associated Coal Corp. 

Pittsburgh, Pa. 

Emmett T. Lang 

Tunnelton Mining Co. 

Johns town, Pa. 

James E. Lough 

U.S. Bureau of Mines 

Monroeville, Pa. 

Charles M. McCulloch 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

Roger McHugh 

Duquesne Light Co. 

Greensboro, Pa. 

A. C. McInnes 

Mine Safety Appliances Co. 

Pittsburgh, Pa. 

Ray Mazza 

Continental Oil Co. 

Morgantown, W. Va. 

Paul Meek, Jr. 

Westmoreland Coal Co. 

Madison, W. Va. 

H. Lester Merrifield 

Bethlehem Mines Corp. 

Barrackville, W. Va. 

Donald F. Metheny 

Bethlehem Mines Corp. 

Bethlehem, Pa. 

J. D. Micheal 

U.S. Bureau of Mines 

Morgantown, W. Va. 

T. D. Moore 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

Keith Morgan 

George L. Judy Assoc . McLean, Va. 

Charles H. Myers 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

Frank H. Neely 

U.S. Steel Corp. 

Uniontown, Pa. 

Jerry Omer 

Pittsburgh & Midway Coal Co. 

Madisonville, Ky. 

W. R. Park 

U.S. Bureau of Mines 

Mt. Hope, W. Va. 

James Parrott 

Youngstown Sheet & Tube Co. 

Coalwood, W. Va. 

Martin E. Patterson 

Bethlehem Mines Corp. 

Bethlehem, Pa. 

George Radomsky 

Florence Mining Co. 

Seward, Pa. 
Donald E. Ralston 

U.S. Bureau of Mines 

Washington, D.C. 

Vincent H. Ream 

Christopher Coal Co. 

Osage, W. Va. 

Albert Saina ta 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

William B. Schmidt 

U.S. Bureau of Mines 

Washington, D.C. 

D 'Arcy A. Shock 

Continental Oil Co. 

Ponca City, Okla. 

Samuel E. Shrader 

Pocahontas Fuel Co. 

Pocahontas, Va. 

Jinnny L. Shumate 

U.S. Bureau of Mines 

Mt. Hope, W. Va. 

Wilbur T. Simon 

Consolidation Coal Co. 

Morgantown, W. Va. 

D. R. Skidmore 

Eastern Associated Coal Corp. 

Pittsburgh, Pa. 

Milford Skow 

U.S. Bureau of Mines 

Washington, D.C. 

Paul W. Smith 

Beckley Coal Mining Co. 

Whitesville, W. Va. 

E. N. Strang 

Westmoreland Coal Co. 

Big Stone Gap, Va. 

William A. Thistlethwaite 

U.S. Bureau of Mines 

Monroeville, Pa. 

Michael Trainor 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

Chester N. Truax, Jr. 

American Mining Congress 

Washington, D.C. 

Clyde V. Turner 

U.S. Bureau of Mines 

Johnstown, Pa. 

R. W. Van Dolah 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

W. J. Vicinelly 

Pennsylvania Bureau Deep Mine Safety 

Harrisburg, Pa. 

Robert Vinson 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

John E. Weekly 

U.S. Bureau of Mines 

Mt. Hope, W. Va. 

J. S. Whittaker 

Consolidation Coal Co. 

Library, Pa. 

Joseph J. Yancik 

U.S. Bureau of Mines 

Washington, D.C. 

John Yonkoske 

Greenwich Colliers Co. 

Ebensburg , Pa. 

M. G. Zabetakis 

U.S. Bureau of Mines 

Pittsburgh, Pa. 

Raymond D. Zinn 

Interim Compliance Panel 

Washington, D.C.