UNITED STATES DEPARTMENT OF THE INTERIOR 

BUREAU OF MINES 

1963 
UNITED STATES DEPARTMENT OF THE INTERIOR 

Stewart L. Udall, Secretary 

BUREAU OF MINES 

Marling J. Ankeny, Director 

The work upon which this report is based was done under a cooperative agreement between the Bureau of Mines, 

U.S. Department of the Interior, and the Olga Coal Co., Coatwood, W. Va 
This publication has been cataloged as follows : 

1 

Merritts, William M 

Removing methane (degasification) from the Pocahontas No. 

4 coalbed in':shfber;l W&<:yjrgijia, by W. M. Merritts [and 

others. ~oshlh&oil' b:'S..' det: :of the Interior, Bureau of .....a .................... :-: MI~R$E$Y~I *:: : 1 : :-. .: : : -..I :.: ; ........... .................. ............................... ii, 3.9. e.. illus.,.r?b!e.s. 27-.cm,. (.U, $,.Qure?u of Mines. Report 

of inF*s.tl&ti{ag 63261.: : : *. : : -: :: : . . : ..... . .I. ..a . - ' . Based on work' done in cooperation witK the Olga Coal Co., Coalwood, W. Va 

1. Methane. 2. Mine ventilation. I. Title. (Series) 

TN23.U7 no. 6326 622.06173 

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

Abstract ............................................................... Introduction ........................................................... Acknowledgments ........................................................ Degasification test site ............................................... Location .......................................................... Coalbed ........................................................... Mine development .................................................. Previous degasification ................................................ Degasification experiments ............................................. Free-flow drainage by horizontal bleeder hole^..................^. 

Equipment .................................................... Drill ................................................... Continuous methane recorders ............................ Recording anemometers ................................... Miscellaneous ........................................... Procedure .................................................... Results ...................................................... Water infusion of horizontal bleeder holes ........................ Equipment .................................................... Procedure .................................................... Infusions of bleeder holes in 5 Left Main entries ............ Discussion of infusion results. 5 Left Main entries .......... Infusions of bleeder holes in Left Side entries .............. Discussion of infusion results. Left Side entries ............ Infusions of bleeder hole 18 ................................. Discussion of infusion results. hole 18 ...................... Infusions of bleeder hole 19 ................................. Discussion of infusion results. hole 19 ...................... Migration testso- anhydrous ammonia ..................................... Conclusions ............................................................ 

Fig . 

1 . 

2 . 

ILLUSTRATIONS 

Section of Pocahontas No . 4 coalbed at Olga No . 2 mine ............ Section of Pocahontas No . 4 coalbed in a want area at Olga No . 2 

mine ............................................................ Plan of 5 Left section where degasification tests were conducted .. Sequence of cuts to advance a set of five entries before 

degasification .................................................. Bureau of Mines continuous methane tnonitoring device .............. Flow of air samples through continuous methane monitoring device .. Methane analyzing and recording uni.ts ............................. Bureau of Mines continuous recording anemometer ................... Plan of pipeline installation at high-pressure pump ............... 

Page 

1 

1 

3 

3 

3 

4 

5 
1. Drilling time and methane released into immediate returns while 

drilling holes 1 and 2........................................... 14 

2. Drilling time and methane released into main returns while drilling 

holes 13 through 17.............................................. 15 

3. Summary of free-flow drainage data from horizontal bleeder holes.. . 16 

4. Pertinent water infusion data collected and methane released during 

infusions of some holes 1 to ................................... 23 

5. Methane released at 12 locations in the working area before, 

during, and after infusions of holes 11 and 12................,.. 29 

6. Methane released from holes 1 through 10 before, during, and after 

infusions of holes 11 and 12 ..................................... 3 0 

7. Pertinent infusion data collected and methane released during 

infusions of some holes 15 to lg................................. 33 
REMOVING METHANE (DEGASIFICATION) FROM THE POCAHONTAS 

NO. 4 COALBED IN SOUTHERN WEST VIRGINIA 

by 

W. Ma Merritts, 1 C. Rw Waine,2 L. P. Mokwa, 3 and Ma J. Ackerman 

Tests were conducted in the Pocahontas No. 4 coalbed in southern West 

Virginia to determine if successful degasification techniques, developed 

during an earlier study in the Pittsburgh coalbed, would be effective in 

removing methane from those usually more gaseous coals. 

Specially designed long-hole dri 1 li.ng equipment and Bureau of Mines 

continuous recording devices were used t:o measure the quantity and methane 

content of the ventilating air during the investigation. Infusions were made 

with water at normal waterline pressures ranging from 200 to 220 psi or at 

pump pressures ranging from 400 to 650 psi, 

Results of the tests showed that methane emissions from free-flow bleeder 

holes were as much as 131 cfm. Infusions of some of the holes increased the 

methane emission from other holes and from the exposed coal surfaces near the 

working areas as much as 1,540 cfm. The methane content in the main returnair currents after infusion was reduced more than 86 percent of the amount 

recorded before tests were made. 

INTRODUCTION 

Under a cooperative agreement betwesen the Bureau of Mines and the Olga 

Coal Co., a field study was undertaken a,t the Olga No. 2 mine, operated in the 

Pocahontas No. 4 coalbed in southern West Virginia, to remove methane from 

virgin coal areas in advance of mining. This study concerns one phase of a 

broad Bureau program devoted to coal mining research. General opinion is that 

methane gas is entrapped in voids in the coalbed, in the pores of the coal, 

'nining methods research engineer, Pittsburgh Mining Research Center, 

Pittsburgh, Pa. 

2~ssistant chief mining engineer, Olga Coal Co., Coalwood, W. Va. 

3~ining engineer, Pittsburgh Mining Research Center, Pittsburgh, Pa. 

Work on manuscript completed January 1963. 
and in the adjacent strata. In many instances where the strata have been disturbed by geologic movements the gas has escaped from the coalbeds and is 

confined in pockets and void spaces in the overlying strata, usually under 

high pressure. Gas emissions during mining are neither regular nor continuous 

but usually vary with the rate of coal extraction. When methane is contained 

in crevices under considerable pressure, it may be released during mining in 

large gas outbursts , 

High methane emissions in coal mines create production problems, causing 

operational downtime of highly productive mining machines, which in turn 

causes severe decreases in production rates and resulting increases in production costs. 

Before continuous mining equipment was used in American mines, underground gas emissions that could not be diluted to a harmless mixture by 

increasing the volume of ventilating air occurred in only a few ultragassy 

mines. In areas where emissions were excessive, mining was discontinued 

until the methane could be diluted to a harmless mixture. Downtime caused by 

gas accumulations resulted in loss of production in such areas, but often 

other producing areas of the mine increased production to offset this loss. 

The introduction of the multiple purpose continuous mining machines 

created two additional problems: (1) The rate of extraction was more rapid, 

usually increasing gas emissions and requiring greater quantities of ventilating air to dilute the gas and (2) the bulk of the continuous mining 

machines virtually precludes continuous flow of air across the face, where 

gas may accumulate. 

Accumulations of methane in mine workings and subsequent ignition have 

caused many coal-mine explosions, resulting in loss of life and destruction 

of property. Unless the gas is removed from the face by some means, the 

emitted gas must be diluted and rendered harmless by the working face ventilating air current. Therefore, large volumes of air must be circulated in 

these areas so that the gas can be removed from the mine in a harmless mixture. 

The problem of maintaining a safe condition at the working faces requires constant monitoring of the methane content of the ventilating air. 

If degasification techniques can be applied successfully to remove gas 

from virgin coal before and during mining, they would decrease operational 

downtime and minimize the hazards inherent to excessive gas emissions. 

A survey of foreign publications showed that practical and economical 

degasification techniques have been developed in the United Kingdom, Europe, 

and other major coal-producing countries. A recent report stated that 135 

collieries removed more than 17 billion cubic feet of methane in 1958.~ 

4~oyd, W. T., and Harry Perry. Degasification of Coalbeds in Advance of 

Mining. Pres. 47th Nat. Safety Cong. and Exposition, Chicago, Oct. 20, 

1959, Trans. Nat. Safety Cong., v. 7, 1959, pp. 21-34. 
Review of the literature indicates that European degasif ication techniques probably would not be adaptable to existing natural conditions or 

mining methods used by the U.S. coal industry. Longwall mining is practiced 

extensively in Europe, while room-and-pillar mining predominates in the United 

States. In longwall mining the roof subssides as mining progresses, resulting 

in redistribution of roof pressures, and breaking and cracking of the overlying 

strata. When the pressure on the longwall face is relieved by the breaking of 

the overlying strata, much of the gas in the coalbed is released, some coming 

out of the working face and percolating through cracks in the overlying strata. 

In room-and-pillar mining, the roof pressure remains fairly stable until the 

pillars are removed during retreat mining and the gas enters the mine workings, 

or remains in the coal pillars and immediate adjacent strata. Other differences in mining conditions and practices such as the number of beds worked 

simultaneously , interval between workable coalbeds, attitude of the beds, and 

the character of the adjacent strata have a marked effect on the success of 

all degasification techniques. 

An initial study of degasification methods at the Humphrey No. 7 mine, 

operated in the Pittsburgh coalbed in northern West Virginia was completed and 

the results published.5 Because of the encouraging results of these tests, it 

was decided to make a similar study in the Pocahontas No. 4 coalbed in southern 

West Virginia. 

The cooperation and assistance of the following mine officials of the Olga 

No. 2 mine are gratefully acknowledged: D. C. Ridenour, general manager; 

Homer Hickam, general superintendent; Adam Robinet t , chief mining and industrial engineer; Clarence Hickam, general mine foreman; R. W. Wotring, safety 

director; and C. A. Beasley, mining engineer. 

DEGASIFICATION TEST SITE 

Location 

The 5 Left section of the Olga No. 2 mine, a peninsular area of virgin 

coal, Olga Coal Co., Caretta, McDowell County, West Va., was selected as a 

study site. At this mine irregular peninsula-shaped areqs of coal are nearly 

cut off from the main coalbed by want areas of shale and sandstone, and 

usually these areas are very gassy. 

This area was partly mined before the degasification study was begun, 

but considerable operating-time delays were experienced because of high-gas 

emissions. Consequently the section was idled for about 6 months to allow 

gas to drain from the face areas. When mining was resumed, large gas emissions 

again caused operating delays, and soon thereafter the degasif ication work was 

begun. 

'~erritts, W. M., W. N. Poundstone, and B. A. Light. Removing Methane (Degasification) From the Pittsburgh Coalbed in Northern West Virginia. BuMines 

Rept. of Inv. 5977, 1962, 39 pp. 
shows a columnar section of the 

immediate roof, the coalbed, and 

the bottom in a want area. The 

main roof usually is sandy shale FIGURE 1. - Section of Pocahontas No. 4 Coal bed but may be laminated and contain 

at Olga No. 2 Mine. coal partings near the want areas. 

The floor is not affected by water but will break during development and 

will heave excessively during pillar extraction in some areas. 

A typical analysis of coal at this mine is as follows: 

Moisture......... ..............p ercent 1.5 

Volatile matter..................do... 16.0 

Fixed carbon.....................do... 77.5 

A~h.,............................do... 5.0 

Sulfur.................,........,do,.. 0.5 

Calorific value..........Btu per pound 14,600 
Sandy shale 

Coal 

Dark sandy fireclay 

FIGURE 2. - Section of Pocahontas No. 4 

Coalbed in a Want Area at 

Olga No. 2 Mine. 

Mine Development 

The coalbed was entered through five 

shafts, each approximately 680 feet deep, 

and a multiple-entry block system was 

used to develop the coalbed. Main 

entries were developed in sets of 8 to 12 

except in areas between wants where fewer 

were driven. Entries were driven about 

16 feet wide, on 90-foot centers; crosscuts were driven on 80-foot centers, and 

pillars were extracted on retreat. 

The 5 Left section was developed by 

either five or seven entries (fig. 3). 

After the main entries were advanced to 

the want area, a set of five entries, 

designated as Right Side entries, were 

driven to the right from entry 1 of the 

5 Left Main entries. When the Right 

Side entries were extended to the want 

area, a set of five entries, designated 

as Left Side entries, were driven to the 

left from entry 5 of the 5 Left Main 

entries. After the Left Side entries 

were developed to the want area, five 

roans were driven to the left from entry 

1 of the Left Side entries. After the 

rooms were driven 160 feet, pillar 

extract ion was begun. 

One ripper- type continuous mining machine mined the coal, loaded it 

directly into cable-reel shuttle cars that transported the coal to a ramp,and 

then discharged it into 10-ton steel mine cars. Trolley locomotives moved 

the mine cars to the shaft bottom, where self-dumping skips hoisted the coal 

to the surface. 

During development, the roof was supported by 4-foot-long roof bolts on 

4-foot centers across the face and in the direction of advance with rib bolts 

2 feet from each rib. Percussion drill:; were used t o d r i l l the roof-bolt 

holes. After the continuous miner advanced 20 feet, it was moved to another 

working place while roof bolts were installed. 

During pillar mining, posts with cr:ossbars were set on 5-foot centers to 

support the roof instead of using roof bolts. After a pillar cut was mined, 

the roof was supported temporarily by two rows of posts on 4-foot centers 

across the face, with two or more steel safety jacks between the last row of 

posts and the face. 

The mine was classed gassy by the West Virginia Department of Mines and, 

at the time of the study, was liberating about 6 million cubic feet of methane 

per day. About 872,000 cfm of air was circulated through the mine by two 

exhaust fans and two forced-air fans. 

A split system of ventilation was used to deliver 9,300 to 50,000 cfm of 

air to the last crosscut in each section and from 28,000 to 75,000 ch of air 

to the intake end of the pillar lines. 

In the 5 Left section, 120,000 ch of air was available for ventilation. 

Intake air was coursed through the center entries, split near the active faces, 

and returned through the outside entries to a 78-inch-diameter upcast shaft 

(borehole) shown in figure 3. This shaft was 700 feet deep and equipped on 

top with an exhaust fan. 

Air currents were directed to the working faces by means of brattice 

cloth faced with thin sheets of plastic on the high-pressure side of the 

cloth to minimize leakage. By installing line brattices on the return side 

instead of the intake side of the working places, the input of ventilating 

air at the faces was disturbed less frequently, as mining equipment generally 

could travel to and from the working places without passing under a line 

brattice, or check curtain. 

Figure 4 shows the ventilating system, general arrangement of mining 

equipment, and sequence of 36 cuts for advancing entries before degasification 

tests. At the time degasification tests were begun, alternate entries 1, 3, 

and 5 were being driven 80 feet and entries 2 and 4 were advanced in sequence 

with crosscuts to connect all entries. The more desirable practice of advancing entries consecutively had been discontinued, because too many operational 

delays had occurred due to excessive gas liberations at the faces. 

While greater production normally was realized when entries were driven 

consecutively than when alternate entries were driven, production by the 

latter plan increased, because downtime to dilute gas was reduced appreciably. 

From the method used, the following advantages were obtained: A limited number of places were worked at one time; the amount of ventilating air at the 

working faces could be controlled more effectively because line brattices and 

check curtains were disturbed less frequently; and gas emissions at the faces 

could be diluted more readily. 

PREVIOUS DEGASIFICATION 

Previous degasification at this mine was limited to (1) the normal drainage of methane from large blocks of coal outlined by bleeder entries, and (2) 

in very gassy sections, drainage from vertical boreholes, ranging from 6 to 78 

inches in diameter, drilled from the surface to the entries and used later for 

ventilating upcast shafts .' 

6 Ridenour, Do C. Core Drilling of Air Shafts and Manway Portals. Min. Cong. 

J., October 1957, pp, 99-101. 

Ventilation by Large-Diameter Bloreholes. Paper pres. at joint 

meetings of West Virginia Coal Min. Inst. and Central Appalachian Section, 

AIME, Nov. 1, 1958. Mechanization, v. 23, No. 3, March 1959, pp. 69-70. 
FIGURE 4. - Sequence of Cuts to Advance a Set of Five Entries Before Degasification. 
Equipment 

Drill 

A hand-held pneumati

drill capable of drilling 

holes rapidly was used to 

the holes. The drill stem 

sisted of a 10-foot flute

having a 2- inch-diameter 

prong bit followed by hol

foot pipe extensions thro

which water flowed to flu

tings from the hole. 

FIGURE 5. - Bureau of Mines Co

Methane Monitorin
tinuous methane analyzing and recording devices. These continuous recording 

units were designed and built by Bureau engineers. Figure 5 shows an overall 

view of one of the methanometers. 

The recording unit is battery powered. Air samples are pulled through 

flexible rubber tubing to the methanometer by the vacuum resulting from the 

controlled expansion of dichlorodifluoromethane from a cylinder. Analysis 

and recording of the methane concentration was continuous. 

The detecting principle of the instrument depends on the change in 

resistance resulting from the combustion of the methane by an electrically 

heated catalytic filament imbalancing a bridge circuit. Two filaments 

(pellements) are combined in a wheatstone-bridge circuit in the methane 

detector (fig. 6). One pellement is active and one inactive. The inactive 

pellement is identical with the active one except that it is not impregnated 

with a catalyst. Upon application of current to the bridge circuit both 

pellements heat to the same temperature. In the presence of methane the temperature of the active pellement increases and produces a change in resistance 
FIGURE 7. - Methane Analyzing and Recording Units. 

which imbalances the bridge circuit. The meter of the recording unit resp

directly to this change.7 Methane percentage is recorded on a carbon-back

chart at approximately 3-second intervals. Figure 7 shows a closeup of th

instrument. 

The source of power for the bridge circuit is a 2-112-volt rechargea

nickel-cadmium battery. A voltmeter and a variable resistor control the v

age in the bridge circuit. The energy for powering the chart drive of th

recording section of the methane monitoring device is provided by a 7-1/2- 

volt dry-cell battery. 

7~ellers, D. H. Developments in Methane Monitoring. Paper pres. 49th Na

Safety Cong., Chicago, Oct. 16 to 18, 1961, 9 pp. 
FIGURE 8. - Bureau of Mines Continuous Recording Anemometer. 

Recording Anemometers 

Bureau of Mines recording anemometers were used to record continuously 

the velocities of the air currents in the main returns of the 5 Left section. 

One of these velocity recording devices is shown in figure 8. The anemometer 

is mounted on the end of a 6-foot length of :rigid copper tubing. Its vanes, 

when rotating in an air current, intersect a beam of light emitting from a 

light bulb set in the housing of the anemometer. The number of intersections, 

depending on the velocity of the air current around the anemometer are transmitted as electric impulses to a tachometer. Velocity of the air current in 

feet per minute can be read on the velocity meter and/or recorded on a chart 

for a permanent record. Two 6-volt dry cells and a 1-112-volt battery are 

used as the source of power for the tachometer and the bulb, respectively. 
Miscellaneous 

In addition to the units described, additional equipment such as portable 

M. S .A. W-8 and ~iken' methane detectors, oxygen and carbon dioxide analyzers, 

permissible flame safety lamps, barometers, thermometers, psychrometers, pitot 

tubes, and volumeters were used. 

Procedure 

In previous Bureau degasif ication studies , more methane was liberated 

from the ribs and faces of outside entries than from other entries when mining 

in virgin coal. Therefore, initial tests consisted of drilling long bleeder 

holes into the solid rib of the face of each outside entry of the 5 Left Main 

entries under development and measuring the gas emissions from the holes. The 

initial test area was about 2,400 feet irlby the upcast ventilation shaft. 

All drilling was done on the intake air end of the line brattice so that 

any gas released would flow directly into the returns. Two-inch-diameter 

holes were drilled to depths ranging from 30 to 230 feet at various angles to 

the direction of the headings. The holes were positioned so that the gas would 

be emitted directly into the returns when the crosscuts connecting the entries 

were driven. In addition to rib holes, several holes were drilled in advance 

of the center entry. 

Pressures, velocities, and methane c~oncentration of the gas were measured 

to record the gas emissions from the holes. At selected places in the immediate return-air courses, air velocities and entry dimensions were taken to 

compute the volume of ventilating air. Methane percentages were read simultaneously on a Riken or on M.S.A. W-8 methane detector, and the quantity of 

methane in the air was computed. 

The quantity and quality of the air coursing through the main return airways were determined from data recorded by continuous methane recorders and 

recording anemometers. The location of t:hese instruments in the main return 

airways is indicated by figure 3. The anemometers were positioned in the 

vertical cross-sectional plane of the airways at the point of average velocity 

determined by anemometer traverses. 

Results 

At the end of the last operating shift and 2 days before the beginning of 

the degasification study, the amount of methane in the immediate return-air 

currents was 800 cfm and in the main return-air currents it was 2,000 cfm. 

While conducting the degasification tests, 19 horizontal bleeder holes 

were drilled during the development of 9,000 feet of entries. All holes 

except two emitted gas during drilling operations and continued to do so for 

-- -- - -- - 

8 Reference to specific models of equipment mentioned in this publication is 

made to facilitate understanding and does not imply endorsement by the 

Bureau of Mines. 
 

Finish drilling. 

- 

Table 2 summarizes the actual drilling time and the amount of methane 

released into the main return-air courses during the drilling of holes 13 

through 17. 

I \ 230 I 85 I 326 1 - 

Table 3 is a summary of pertinent data for all the horizontal bleeder 

holes. On completion of holes 2 and 7, the velocity of gas was 6,000 fpm, and 

each of the two holes emitted 131 cfm of gas (188,600 cubic feet per day). 

Despite considerable leakage through cracks in the coal at the collar of the 

hole, hole 2 had a shut-in pressure of 63 psi. The shut-in pressure of hole 7 

was only 5.8 psi. The data show that the greatest amount of methane was 

released from rib holes in the outside entries. 

- 

 ethane released includes emission from drill holes plus normal emission. 

'~ush of methane from hole 2 when drill stems and auger were removed. 
TABLE 2. - Drilling time and methane released into main returns 

while drilling holes 13 through 17 

Hole 

Depth 

of hole, 

feet 

Drilling 

time , min 

Methane released. c£ml 

Left I Right 

return return 

Remarks 

Start drilling. 

Finish drilling. 

Start drilling. 

Finish drilling. 

Start drilling. 

Finish drilling. 

Start drilling. 

Finish drilling. 

Start drilling. 

Finish drilling. ' ethane released includes emission from drill holes plus normal emission. 

2~ethane emitted from hole 13 after drilling was only 0.4 c£m. 

3~o perceptible emission of gas from hole 15. 

When a bleeder hole was sealed near its collar, and provided no mining was 

done in the immediate area, the time required for the gas to reach maximum shut-in 

pressure ranged from several minutes to several hours. After maximum pressure was 

reached, it was possible to open the seal, bleed off the gas, reseal the hole, and 

again reach the previous shut-in pressure. ,A pressure gage connected to the seal in 

the hole fluctuated continuously until the maximum pressure was reached; these 

fluctuations were more pronounced where there was less leakage around the seal. 

Generally, gas emissions from bleeder holes immediately after drilling 

increased the amount of methane in the return air above the amount before drilling, 

and the increase was as much as 200 ch. However, in a few exceptional instances, 

methane was emitted in sporadic gushes up to 400 c£m immediately after drilling. 

Methane concentrations in the immediate return-air currents were measured with 

portable Riken and M.S.A. W-8 methane detectors. The readings indicated that 

occasionally, after bleeder holes were drilled at the faces of the outside entries 

at a projected crosscut, a slight reduction in the amount of methane released was 

realized at the working faces during mining operations. This reduction in methane 

liberation at the face area, however, was only temporary and the methane content in 

the face ventilating air gradually increased as entries advanced inby the crosscut. 

After entries were driven about 40 feet beyond the crosscut or one-half the distance 

to the next crosscut, the amount of methane in the air again approached the amount 

recorded before the holes were drilled. Consequently, a sustained reduction of 

methane releases at the working faces was not realized. The methane concentration 

readings in the immediate return air reflected the changes in methane emissions at 

the working faces; the methane concentration readings in the main return air 

included not only the face gas emissions, but also gas emissions along the solid 

ribs between the sampling points in the immediate and main returns. 
TABLE 3. - Summary of 

Drilling 

time, 

min 

42 

40 

2 0 

90 

75 

75 

70 

Bole 

1 

2 

3 4 

5 6 

7 

8 

Depth 

of 

hole, 

feet 

155 

230 

50 

230 

185 

190 

2 10 

115 

Entry 

l5,5~ 

1,5L 

'2-3,5~ 

1,5L 

5,5L 

5,5L 

1,5L 1,5L 

Angle 

of 

hole 

with 

entry, 

degrees 

30 31 

0 

30 

3 2 

33 3 4 

3 3 

Lo

o

j 

1 

1 

1 

1 

1 
'Entry 5, 5 Left. 

21n crosscut between projected entries 2 and 3, 5 Left. 

3~ntry 1, Left Side. 

4~ntry 1 between projected rooms 2 and 3, Left Side. 
The long horizontal bleeder holes were drilled at various times while 

developing the 5 Left Main entries and the Left Side entries. Some of these 

bleeder holes were used also for water-infusion purposes before all holes 

were drilled. 

Water Infusion of Horizontal Bleeder Holes 

Water infusions were made in several of the bleeder holes. The injected 

water probably infiltrated the natural crevices or cleat planes within the 

coalbed and displaced the gas. Initial water infusion studies by the Bureau 

were made to control air-borne dust by increasing the surface moisture of the 

coal in advance of mining. These studies showed that in addition to allaying 

dust, water infusion also partially degasified the coal in place at the working faces. 9 

A later study on the removal of gas from the Pittsburgh coalbed before 

mining showed that infusions of gas bleeder holes proved effective in increasing the release of gas from the solid coal above that released by free flow. 

Because of these results, tests were made to determine the effect of water 

infusion on the release of gas from solid coal in the Pocahontas No. 4 coalbed. 

Water used to infuse the coalbed for degasification tests was obtained 

from an underground stream encountered about 100 feet below the surface while 

drilling the ventilating shaft in the 5 Left section. The water was collected 

by a water ring in the shaft and piped to the working places through 2-inch 

and 3 14-inch pipelines. 

At prearranged connection points along the 314-inch pipeline, 50- foot 

lengths of 314-inch high-pressure hose were connected to obtain water for 

water- infusion experiments. The static waterline pressure at the working 

area, because of the difference in elevation between the source of water and 

the face region, was about 220 psi. Normal waterline pressures ranged from 

200 to 220 psi. Waterflow during infusions was measured with a flowmeter. 

Equipment 

A high-pressure pump was used to produce pressures above the normal waterline pressures. The pump was a triplex-plunger type capable of delivering up 

to 35 gpm of water at a pressure of 400 psi. Pressure adjustment could be 

made to obtain pressures up to 650 psi. Figure 9 shows the general arrangement 

of the water pipelines at the pump site. This arrangement permitted the water 

to flow through the pump to the location where it was to be used at normal 

waterline pressures when the pump was not in operation. 

Figure 10 shows details of a water-infusion seal. When the seal was 

inserted in a hole and the inby nut tightened, the 1-inch pipe was moved 

toward the collar of the hole. This compressed the rubber washers, causing 

'~ackson, E. O., and W. M. Merritts. Water Infusion of Coal Pillars Before 

Mining, Independent Coal & Coke Co., Kenilworth, Utah. BuMines Rept. of 

Inv. 4836, 1951, 25 pp. 
Heading High-pressure 

Pump 

FIGURE 9. - Plan of Pipeline Installation at High-Pressure Pump. 

them to expand and grip the wall of the hole firmly, making a watertight seal. 

The outby nuts acted as jam nuts to keep the 112-inch pipe from turning when 

the inby nut was turned to release the rubber washers for removal of the seal. 

In some water-infusion tests a wetting agent was added to increase the 

penetration effect of the water solution. Wetting agents reduce the interfacial tension between the solid and the liquid. The liquid wetting agent 

was injected into the infusion water by means of a constant-volume gear pump 

at the rate of 144 cc per minute. 
Rubber washers 

FIGURE 11. - Arra
Procedure 

Some of the bleeder holes were infused with water under pressure t

mine the effect of emission of gas from the face and ribs compared with 

flow. Figure 11 shows a typical arrangement of the equipment used to i

a bleeder hole. 

The water infusion seal usually was set about 3 feet in the hole. 

coal at the collar of the hole was badly cracked permitting the water t

past the seal, the seal was set deeper in the hole. 

The path and distribution of the water injected into the hole were 

by noting small gas-water bubbles appearing on coal surfaces at the fac

gradually spreading to adjacent faces and ribs, fig. 12. Occasionally, 

rescent dye with alkali added to make the dye more soluble in water was 

injected into the infusion water. The progress of the infused water wa

by means of an ultraviolet light approved for use in gassy mines. 
Because the foregoing infusion tests were performed while the mine was 

idle, larger amounts of methane were removed than would have been advisable 

when the mine was operating. During operating shifts water infusion pressures 

were reduced to lower the amount of methane released by regulating the rate of 

water injection between 2 to 4 gpm to maintain a water-infusion seal pressure 

of only 50 psi. 

At the close of the first operating shift following vacation, mine officials stated that no gas was detected at the active working faces in the 

infused area. In their opinion, airborne dust was decreased, visibility was 

increased, and the coal mined easier. Shuttle-car roadways were damp and 

compacted. 

Hole 3 was infused three times at throttled pressures under operating 

shifts for 3 successive days. Infusions were stopped when shifts were not 

operating; water was sealed in the hole, and sealed-in pressures of about 20 

psi were recorded. Data collected during these throttled infusions are given 

in table 4. 
Infused 

hole 

, Order 

of 

I water 

1 infusion 

2d to 10th 

inclusive. 

11th to 

13th 

inclusive. 

TABLE 4. - Pertinent water infusion data collected and methane rele

during infusions of some holes 1 to 12 

Quantity 

of water 

used, 

gal 

Flow rate 

of water 

infusion, 

gPm 

Maximum 

pressure 

at waterinfusion 

seal, 

Infusion 

time, 

min 

Sealed- in 

pressure 

after 

water 

infusion 

of hole, 

psi 

90 

90 

- 

- 

- 

- 

20 

40 

60 

- 

- 

40 

8 

I Total 

methane 

I increase 

for both 

I immediate 

I 

returns, 

chl 

720 

138 

} 492 

789 

91-512 

290 

- 

- 

- 

I 

I - 

- 

I 

Total 

methane 

incr eas e 

for both 

main 

returns, 

chl 

1,542 

206 

985 

1,394 

517-1,313 

904 

267 

26 7 

2 13 

2 13 

200 
TIME, hours 

FIGURE 14. - Water-Infusion Seal Pressures During, and Sealed-in Pressures 

After Infusion at Hole 1 Versus Time. 
FIGURE 15. - Plan of 5 Left Entries at the Time Holes 11 and 12 Were Drilled. 

Shows locations of holes 1 through 12, and 12 places air measurements were taken. 

As the 5 Left Main entries were advanced, bleeder holes 4 through 12 were 

drilled at three successive crosscuts inby holes 1, 2, and 3 as shown in 

figure 15. Holes 11 and 12 were infused alternately during idle shifts until 

hole 11 had been infused three times, and hole 12 infused twice. 

Before hole 11 was infused, 32,500 ch of air containing 1.8 percent 

methane (585 ch) was measured in the left main return and 44,500 ch containing 0.7 percent methane (312 ch) was measured in the right main return. 

Following 30 minutes of infusion at hole 11, the methane content in the left 

main return increased to 2.35 percent (764 ch). Also, after 60 minutes of 

infusion at hole 11, the methane content in the right main return increased 

to 0.90 percent (400 ch). Portions of the recording charts showing these 

methane increases are reproduced in figure 16. 

After about 3 hours of infusion of hole 12, the auxiliary exhaust fan at 

the top of the upcast shaft was stopped for 150 minutes and again for 30 minutes for routine idle-day maintenance when all personnel were out of the 

mine. Although the volume of methane in the main returns remained the same 

during fan stoppages, the percentage of methane increased materially because 
LEFT MAlN RETURN 

RIGHT MAlN RETURN 

TIME, minutes 

FIGURE 16. - Portions of Recording Charts Showing Percentages of Methane in the Return 
FIGURE 17. - Portions of Recording Charts Showing Percentages of Methane in the Return Air Durin

When Fan Was Stopped. 
recording charts, showing the variations in the percentage of methane in the 

main return-air currents when the first fan was stopped, are reproduced in 

figure 17. 

Before the second infusion of holes 11 and 12, hole 12 was sealed and a 

pressure of 0.5 psi was measured. After 150 minutes of infusion, the pressure 

increased to 7 psi. The seal then was opened and gas containing 70 percent 

methane issued from the 112-inch opening at a velocity of 6,000 fpm. Hole 12 

was sealed again and infusion of hole 11 continued for 150 additional minutes, 

and the sealed-in pressure in hole 12 rose to 9 psi. In the first hour of 

infusion, water seepage, as noted on the exposed coal surfaces surrounding the 

collar of hole 11, traveled 21 feet longitudinally and 0.25 feet vertically. 

Near the end of infusion of hole 11, the outside ribs of entries 1 and 5 were 

wet 160 feet outby the faces; all the faces on the section were wet, and water 

was dripping from holes 6 through 10. 

Immediately after the second infusion of hole 11 was stopped, hole 12 was 

infused a second time. Twenty-four hours after this infusion, hole 11 was 

infused a third time. A summary of the infusion data is given in table 4. 
After this test was completed, methane liberations at the face were 

reduced sufficiently to permit entry development by driving crosscuts from 4 

to 5 rather than from 5 to 4, fig. 18. Operating time and production increased 

because less time was spent in tramming equipment. 

Before, during, and after infusion of holes 11 and 12, the volume and 

methane concentrations of the ventilating air were measured at 12 sampling 

points to determine the distribution of methane emissions across the section. 

These sampling points are shown in figure 12 and the data collected is summarized in table 5. 

TABLE 5. - Methane released at 12 locations in the working area before, 

during, and after infusions of holes 11 and 12 

see figure 15. 

Gas emissions from holes 1 through 10, except hole 3 which entry development had rendered useless as a bleeder hole, were measured before, during, and 

after infusion of holes 11 and 12 to determine the effects of infusion on the 

quantity and quality of the methane removed. This data is given in table 6. 

Before infusion, 100 percent methane was issuing from all holes except 9 and 

11, but during infusion, the percentage of methane decreased to as low as 50 

percent at one hole. The amount of methane emitted from the holes during 

infusion, however, was considerably greater than the amount emitted before 

infusion. 

~ocation' 

1 ........ 

2.. . . . . . . 3.. . . . . . . 4.. . . . . . . 5 ........ 

6.. . . . . . . 7.. .. . . . . 8.. . . . . . . 9 ........ 10.. . . . . . . ll........ 

12.. . . . . . . 

Discussion of Infusion Results, 5 Left Main Entries 

After infusion tests at holes 1, 2, 3, 11, and 12 were completed, the 

methane liberations in the 5 Left section were the lowest ever measured in the 

section. Methane content of the ventilating air in the immediate and main 

returns was 120 cfm and 500 cfm, respectively, which represented a decrease 

of 680 cfm and 1,500 cfm, respectively, from amounts recorded before the 

degasification study was begun; this was equal to a methane reduction of 85 

percent in the immediate return-air courses and 75 percent in the main returnair courses. 

Before infusion During infusion After infusion 

Air, 

cfm 

25,920 

21,660 

16,326 

25,250 

54,450 

14,640 

5,950 

14,760 

36,464 

18,160 

28,800 

38,130 

Air, 

cfm 

28,800 

22,080 

16,380 

26,260 

54,450 

15,200 

6,035 

15,030 

37,100 

18,400 

29,280 

39,525 

Air, 

cfm 

32,160 

22,800 

16,650 

27,775 

65,300 

16,400 

6,200 

15,300 

39,750 

18,560 

29,520 

41,850 

Methane 

concentration 

Methane 

concentration 

Percent 

0.50 

0.41 

0.33 

0.16 

0.01 

0.02 

0.10 

0.19 

0.20 

0.31 

0.43 

0.50 

Methane 

concentration 

Percent 

1.30 

1.08 

0.80 

0.45 

0.01 

0.10 

0.50 

0.53 

0.40 

0.60 

0.75 

1.00 

Cfm 

130 

89 

54 

40 

5 

3 

6 

28 

73 

56 

124 

191 

Percent 

0.25 

0.18 

0.04 

0.02 

0.01 

0.01 

0.02 

0.02 

0.04 

0.06 

0.11 

0.16 

Cfm 

374 

238 

131 

118 

5 

15 

30 

80 

148 

110 

220 

395 

Cfm 

80 

41 

7 

6 

7 

2 

1 

3 

16 

11 

32 

67 
Continuous methane readings were not taken in the next 40 days because 

the continuous methane recording units were removed from the mine for adjustment and recalibration, but analyses of the mine air for methane were made 

regularly by mine officials. 

In this 40-day period, the 5 Left entries and the Right Side entries off 

5 Left had been developed to the want area and mining in these areas was completed (fig. 3). Methane liberations sufficient to require operational downtime were not encountered during this period. 

Infusions of Bleeder Holes in Left Side Entries 

Methane monitoring units were again placed in the 5 Left Main returns 

when the Left Side entries were begun. The methane volume in the left and 

right main returns was 256 cfm and 123 c£m, respectively, and these amounts 

were used as a comparative basis for assessing the degasification results. 

As the Left Side entries approached the want area, methane volumes in the 

left and right main returns increased to 326 cfm and 167 ch, respectively. 

In view of these increased emissions, further degasification in this area 

was deemed advisable. 
HBH '1 16 

\ 

HBH 

LEGEND I 

1-5 Entry numbers - intake air 

M Return air 

# Permanent stopping 

t--$- Curtain 

HBH Horizontal k 

bleeder hole 3 

* 

I - 1 

HBH I{/ 

- 3' outby corner of X-cut and 

HBH 13 

HBH 14 

FIGURE 19. - Plan of Left Side Entry Faces at the Time 

Holes 13 Through 17 Were Drilled. 

Five bleeder holes, 13 

through 17, were drilled in 

the outside entries as shown 

in figure 19. Holes 13 and 

14 were drilled in entry 1 

and the other three were 

drilled in entry 5. Hole 16 

was above and parallel with 

hole 15. 

When infusion in the 

Left Side entries began, 

entry 1 had been driven 

about 40 feet inby hole 14, 

and entry 5 had been driven 

about 80 feet inby holes 15 

and 16. The roof of entry 1 

was irregular and contained 

coal streaks; the upper part 

of the coalbed contained 

sandstone boulders, fig. 20. 

Hole 15 was infused 

using the high-pressure pump 

and normal waterline pressures a week after drilling. 

Pertinent data collected is 

summarized in table 7. 

Water, sealed in the hole in 

the 14 minutes between the 

first and second infusion 

reached a pressure of 

100 psi. 

Holes 16 and 17 were 

not sealed before commencing 

infusion of hole 15, and 

water flowed from hole 16 

after 11 minutes and from 

hole 17 after 26 minutes. 

Both holes then were sealed 

and the pressure, 5 psi 

recorded at hole 17 after 

161 minutes of infusion, 

increased to 10 psi while 

the pressure at hole 16 

reached 5 psi near the end 

of the infusion period. 

Although no pressures were 

indicated at holes 13 and 14, 

gas containing 90 percent 

methane issued from hole 14 

at a velocity of 125 fpm. 

TABLE 7. - Pertinent infusion data collected and methane released during infusions of 

Infused 

hole 

Order of 

water 

infusion 

Flow rate 

of water 

infusion, 

g Pm 

1s t 

2d 

3d 

4 th 

1st. 

2d 

3d to 12th 

inclusive. 

3d to 12th 

inclusive. 

1s t 

2d 

Quantity 

Infusion of 

1 time, solution 

, 

min used, 

gal I psi 

messure 

- 

I Pump 

pressure, 

psi 

I pressure 

after 

infusion 

of hole, 

psi 

To

met

incre

in b

imme

retu

+ 

- - - - - - 

Infused with water. 

'infused with water mixed with a wetting agent and fluorescein dye. 
Bleeder hole 18 was drilled in the left rib of Left Side entry 1 between 

projected rooms 2 and 3, fig. 22. A total of 12 infusions of hole 18 were 

made using normal waterline pressures and the high-pressure pump alternately. 

To aid in tracing the paths of water migration, fluorescein dye and a liquid 

wetting agent was added to the water used for holes 18 and 19. A summary of 

infusion data is given in table 7. 

After 30 minutes of infusion at normal waterline pressures, the solution 

was noted to have traveled 22-112 feet longitudinally and 3 inches vertically 

along the surface of the left rib. After 10 minutes of infusion using the 

high-pressure pump, the solution was noted on the coal surface and had traveled 10 feet longitudinally and 1-112 inches vertically. After the second 

infusion, the solution was traced about 400 feet from the infused hole along 

the rib of entry 5 of 5 Left Main entries. When rooms were developed off Left 

Side entry 1 the solution had penetrated the solid coal the full 160-foot 

depth of these workings. 
FIGURE 21. - Face Area, Entry 5, Left Side, at the Time Hole 15 Was Initially Infused. 
I I- -Projected HBH 19- - 

LEGEND - Intake air R1-R5 Projected rooms 

-c-c Return air --- Projected development 

# Permanent stopping HBH Horizontal bleeder hole 

--------------------------- -I 

I 

----I 11 ----- -I i----- 1 I------- I iII I' I I I I 

II I I I I I I 

I1 I I I I I I 

I I 

lR2 I IR~ 1 iR41 

I I 

I 

1R51 

,,-,-, 1 L -- 1 L -- I ------I L 

-- --C 

1 ------ I- - - - - - -I ,- - - - - I 

1'1 

I1 I 

II 

II 

I I 

HBH'~~, I I 

I I 

I I I I I 

I I 

I I 

I I 

I I I I 

- I I - I I I1 No. 1 entry, Left Side I 

FIGURE 22. - Projected Plan of Development of Five Rooms off Entry 1, Left Side, at the 

Time Hole 18 Was Drilled. Also shows location of projected hole 19. 

t 7. -. -. -. 

J 

Discussion of Infusion Results, Hole 18 

m 

Although previous infusions had af f ect ed this area, the methane content 

of the ventilating air decreased from 378 c£m before, to 306 cfm after infusions of hole 18. The amounts of methane released varied, but were greater 

when using the high-pressure pump. 

I I I 

Water infusions appeared to be effective in reducing airborne dust in the 

working sections. From visual observations by Bureau personnel, infusions 

made with water containing wetting agents at pump pressures were more effective in allaying dust than those with water alone at normal waterline pressures. These observations were substantiated by a study made by management 

before, during, and after infusions of hole 18. A dust counter was used in 
this study to sample the airborne dust at the working faces and other strategic locations in the working section. 

Infusions of Bleeder Hole 19 

After rooms 1 through 5 were advanced to the last crosscut, hole 19 was 

drilled into the solid coal off Main entry 5, 5 Left, about 30 feet outby and 

paralled with the last projected crosscut connecting room 1 and Main entry 5. 

The projected location of hole 19 is shown in figure 22. Two infusions of 

hole 19 were made while developing the last crosscut connecting the rooms, and 

water with a wetting agent and fluorescein dye added was injected into the 

hole. A summary of infusion data is given in table 7. 

Discussion of Infusion Results, Hole 19 

At the end of the infusions in hole 19, the methane concentration of the 

ventilating air in the left and right immediate returns was 8 ch and 39 ch, 

respectively, and in the left and right main returns was 120 and 153 ch, 

respectively. 

At the time of the last infusion test at hole 19, extraction of pillars 

was begun, and the degasification study in virgin coal in this section was 

concluded. 

MIGRATION TESTS--ANHYDROUS AMMONIA 

Tests to determine whether gas migration is preferentially along or 

across bedding planes were conducted using anhydrous ammonia as a tracer. 

Five holes were drilled in a freshly exposed working face as shown in figure 23. 

Roof 

L" to bony shale 

Hole 4 

0 

16"-8" hard band of coal A\ 

- 6' 

Hole 3 t- Hole 2 Airflow 

i Floor - 

1- Ammonia gas released into Hole 2 

I - 16' *w _I - I 

FACE ELEVATION 

FIGURE 23. - Spacing of Holes in Coal Face for Migration Tests. 
A 4-foot length of 1/8-inch-diameter rubber tubing was inserted 6 inches and 

sealed in each hole except hole 2. 

A piece of red litmus paper and a piece of cloth saturated with a weak 

solution of hydrochloric acid were attached to the free end of the tubes. 

These tubes were held by an observer. While an observer sniffed the hand-held 

tubes, the ammonia was released under pressure of 80 psi from a cylinder 

through an infusion seal placed in hole 2. As the gaseous ammonia passed 

through the coalbed to the open tubes sealed in the coal, it was detected by 

its pungent odor, fuming of the acid-soaked cloth, and the change in color of 

the litmus paper. 

It required 20 seconds for ammonia gas to pass from hole 2 to hole 1; 

25 seconds from hole 2 to hole 3; 40 seconds from hole 2 to hole 4; and 55 

seconds from hole 2 to hole 5, showing that the gas traveled faster along the 

bedding planes than across the planes. 

CONCLUSIONS 

From observations made and data collected, these methane drainage experiments proved that methane can be removed from the Pocahontas No. 4 coalbed 

before and during mining by drilling along horizontal bleeder holes in the 

coalbed, and infusing them with water. 

During the degasification study, the amount of methane in the main 

return-air currents was reduced from 2,000 cfm to 270 cfm, a reduction of 

more than 86 percent. 

Gas liberations by free flow from horizontal bleeder holes drilled 30 to 

230 feet deep in the coalbed in advance of mining reached a maximum of 131 cfm 

immediately after drilling. The flow from the holes decreased steadily over 

periods ranging from several hours to several days, although some of the holes 

continued to emit gas at decreasing rates for several months. Shut-in pressures of the horizontal bleeder holes were as high as 63 psi. 

Infusing some of the bleeder holes with water, or a solution of water 

mixed with a wetting agent, increased gas emissions from virgin coal areas. 

During one infusion when the mine was idle, gas liberations from the coalbed 

were increased 1,540 cfm. 

Infusions of bleeder holes proved effective in releasing large amounts of 

gas from the coalbed before mining, and as a result, gas emissions while mining, were reduced materially. Operational downtime to dilute gas liberations 

to safe concentrations in the ventilating air that occurred frequently before 

degasification was eliminated. 

Gas releases that were excessive while infusing at normal waterline pressures were reduced by decreasing the water-infusion seal pressures. This was 

done by 'regulating the rate of water injection. 
In confirmation of results obtained in previous tests, maintaining a 

sealed-in pressure in infusion holes resulted in greater methane emissions 

than would have occurred if the hole had been drained immediately after infusion. Usually, the amount of gas released varied with the sealed-in pressures. 

Sealing water in the holes after infusion retards the escape of water from 

crevices in the coalbed and presumably prevents return of the gas into the 

infused area. 

Because gas is emitted from long horizontal bleeder holes for relatively 

long periods of time and the release of gas from the coalbed is increased during infusion of holes, investigators believe that most of the gas was held in 

the coalbed rather than in the adjacent strata. 

Infusion water did not penetrate the sandstone roof, nor the shale floor, 

and no damage from water was observed on either the roof or floor of the mine. 

Observation and results of tests indicated that water infusions at normal 

waterline pressures reduced the amount of airborne dust at the face during 

mining, but were more effective in allaying dust when a wetting agent was 

added to the solution and infusions were made at pump pressures. 

Experiments with tracers introduced into the infusion water and released 

under pressure into a horizontal bleeder hole proved that water and anhydrous 

ammonia travel through the coalbed. Infusion water mixed with a wetting agent 

and fluorescein dye traveled 400 feet through coal. 

Various rates of travel of water or solutions used in infusions as 

detected on exposed coal surfaces were as follows: 

1. Water at normal waterline pressure traveled 21 feet laterally and 

3 inches vertically per hour. 

2, Water and wetting agent with fluorescein dye at normal waterline 

pressure traveling 45 feet laterally and 6 inches vertically per hour. 

3. Water and wetting agent with dye at pump pressure of 400 psi 

traveled 60 feet laterally and 9 inches vertically per hour. 

Anhydrous ammonia under pressure released into a horizontal borehole 

traveled 12 fpm horizontally, 5 fpm vertically, and 6 fpm diagonally, through 

the coalbed.