Bureau of Mines Report of Investigations/ 1972 

Methane Emission Rate Study in a Deep 

Pocahontas No. 3 Coalbed Mine 

in Con junction With Drilling 

Degasification Holes in the Codbed 

UNITED STATES DTSgARTMJ3NT OF THE INTERIOR 
Report of Investigations 7703 

Methane Emission Rate Study in a Deep 

Pocahontas No. 3 Coalbed Mine 

in Con junction With Drilling 

Degasification Holes in the Coalbed 

By Stephen Krickovic and J. D. Kalasky 

Pittsburgh Mining and Safety Research Center, Pittsburgh, Pa. 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Rogers C. B. Morton, Secretary 

BUREAU OF MINES 

Elburt F. Osborn, Director 
CONTENTS 

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

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

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

Description of study area ................................................ 2 

Mining method and equipment .............................................. 3 

Ventilation .............................................................. 3 

Monitoring ............................................................... 3 

Drilling horizontal methane control holes into coalbed ................... 6 

Results .................................................................. 8 

Conclusions .............................................................. 11 

ILLUSTRATIONS 

1 . Location of study area .......................................... 2 

2 . Arrangement of ventilation, haulage, and locations of recording 

instruments ........................................................ 4 

3 . Sequence of mining by shifts and dates during study period ........... 5 

4 . Locations of in-situ pressure and degasification boreholes drilled 

in coalbed ......................................................... 7 

5 . Sum~ary of pertinent res'ults obtained from degasification holes 

in coalbed ......................................................... 10 

TABLES 

1 . Smrmary of drilling data ............................................. 6 

2 . In-situ gas pressure measured in hole 1 .............................. 8 

3 . Sumrnary of all monitoring data ....................................... 9 
METHANE EMISSION RATE STUDY IN A DEEP POCAHONTAS NO. 3 

COALBED MINE IN CONJUNCTION WITH DRILLING 

DEGASlFlCATlON HOLES IN THE COALBED 

Stephen Krickovic 1 and J. D. ~alask~ 

ABSTRACT 

A degasification experiment was conducted in a Pocahontas No. 3 coalbed 

mine in Virginia. It involved (1) drilling holes in the coalbed in the outside headings of a set of five being developed in virgin area, and (2) conducting a methane emission rate study as mining progressed and additional 

holes were drilled. 

Degasification from all drill holes except the longest in each of the 

outside headings and the first three drilled (excluding the in-situ pressure 

hole),was erratic and inconsequential in methane emission rates. The two 

longest holes liberated 66 and 79 cfm of methane, which is significant for the 

coalbed, but such quantity lasted a relatively short time; the first three 

were uniform but low in methane emission. 

INTRODUCTION 

Methane is contained under pressure within the micropores, joints, and 

fracture systems in gassy coalbeds. Breaking coal from solid faces produaer 

considerable coal surface areas that when added to the newly exposed solid 

coal surfaces3 increases methane emission rates appreciably. 

The 1969 Federal Coal Mine Health and Safety Act requires that a minimum 

of 9,000 cfm of air be conducted to the last open breakthrough in any pair or 

set of developing headings. An additional requirement is that the miniram 

quantity of air in any coal mine reaching each working face shall be 3,000 cfm 

unless a greater quantity is needed to dilute the methane concentration, as 

require$ by the 1969 act. The dimensions and configurations of most 

continuous-mining equipment presently used at the face make it difficult to 

comply with the act generally and, in very gassy mines, practically impossible. 

1 Supervisory mining engineer. 

=Mining engineer (now employed by the Island Creek Coal Co.). 

"Cervik, Joseph. An Investigation of the Behavior and Control of Methane Gar. 

Min. Cong. J., v. 53, No. 7, July 1967, pp. 52-57. 
The objective of this study was to determine the effect on methane emission rates from the innnediate face areas of holes drilled in the coalbed as 

mining progressed, 

The cooperation of the mine management of the Island Creek Coal Co. of 

Cleveland, Ohio, and Keen Mountain,Va., and of J. D. Hadden, mining engineer, 

Pittsburgh Mining Research Center, and his drilling crews is greatly 

appreciated . 

DESCRIPTION OF STUDY AREA 

The study area consisted of a set of five headings and breakthroughs 

being developed in virgin coal. Figure 1 shows the area and its relationship 

to the nearest mine workings and to projected mine plans on either side. 

FIGURE 1. - Location of Study Area. 
MINING METHOD AND EQUIPMENT 

A two-step, ripper-type continuous miner was used in development of the 

set of five headings on 80- and 95-ft centers, with breakthroughs on 94-ft 

centers. Width of places averaged 17 ft, and thickness of coalbed mined, 

53 in. The miner was equipped with a methane detector located 10 ft ahead of 

the operator. When the detector indicated a methane concentration of 2 pct, 

the power was automatically disconnected. 

Owing to the very gassy condition of the coalbed, the miner was advanced 

usually only 4 ft in each lift (one-half the width of the working face) after 

which it had to be maneuvered to the other half of the place. This procedure 

would involve 10 maneuvers for the full 20-ft-deep cut, at the end of which 

the operator was under the last line of roof support. The miner then was 

trauuned to the next face in the cycle where the aforementioned mining procedure was repeated, and bolting of roof was undertaken in the preceding place. 

Coal was discharged by the miner directly into 5-ton-capacity cable reel 

shuttle cars that traveled to the feeder at the tailpiece of the 36-in belt 

coweyor for unloading. Two shuttle cars serviced the miner. 

VENTILATION 

Figure 2 shows the arrangements of ventilation, haulage, and locations of 

recording instruments with respect to working faces at the start of study. 

Headings 2-4 served as intakes. Next to the last complete line of breakthroughs, the air was divided by plastic stoppings and line brattice into two 

splits, one ventilating only heading 5, and the other ventilating the remaining headings. When headings 3 and 4 were mined, the areas ventilated were 

more evenly divided. In all cases, air was conducted to the working face by 

line brattice erected to facilitate movement of intake air wer the men and 

equipment and to prevent obstruction of travel to mine equipment. 

MON IMRING 

Recording anemometers and methanometers were installed at stations A and 

B in headings 1 and 5, respectively, and recording methanometers, only at 

stations C and D in headings 1 and 5, respectively (fig. 2). 

Locations for instrumentation were selected to obtain reasonably uniform 

air velocities in the cross-sectional areas. At stations A and B, a grid 

system of horizontal and vertical strings that formed 1-ft squares was set up 

in the cross-sectional areas. Air velocities were measured in each square 

with the sensing head of a recording anemometer, and the square in which the 

air velocity most closely approached the average for the cross-sectional area 

was selected. The sensing heads of the continuously recording methanometers 

and anemometers4 were installed in the velocity square with value closest to 

4La Scola, J. C., and Joseph Cervik. Development of Recording Methanometers 

and Recording Anemometers for Use in Underground Coal Mines. BuMines Tech. 

Prog. Rept. 15, May 1969, pp. 9-14. 
LEGEND I00 200 

1-5 Entry number - Intake air OPlastic stoppings w Return air Scale, feet 

--- Plastic line brattice 4 Belt loading station 

Permanent stopping -H+ Track 

R Regulator 

FIGURE 2. - Arrangement of Ventilation, Haulage, and Locations of Recording Instruments. 

the average. Area at station A in heading 1 was 73.9 sq ft, and average 

velocity was 347 fpm. The area with 350-fpm velocity was used. The corresponding values at station B in heading 5 were 72.0 sq ft, 285 fpm, and 290 fpm 

(fig. 2). At stations C andD, the sensors of the methanometers were located 

at the point of average methane concentrations in the cross-sectional areas as 

determined by three hand-held methanometer readings at each location. 

The air volumes measured at stations A and B were used also for stations C and D, since air leakage through stoppings between the two sets of 

stations was negligible. 

A monitoring team consisted of the following: A mining engineer, who 

time-studied the miner, observed unusual conditions at the face affecting 

methane emissions, measured the methane content in the intake air 5 ft inby 

the belt conveyor tailpiece, and secured other pertinent data; and two technician~ who maintained the instruments in satisfactory operating condition by 

adjusting them, by replacing weak or dead batteries and malfunctioning instruments with spare units, and by making check readings periodically with handheld instruments. 

Although the mine worked two shifts per day, monitoring was conducted 

mostly on the first shift (8 a.m. to 4 p.m.). Owing to transportation problems, 

the monitoring crew could not start the instruments until 10 or 11 a.m., and 

all instruments could not be started simultaneously. The monitoring time, 
Recording -eter. 

instalkd 6-26-70 

(fording methanometer, 

installed, 6-26-70 

LEGEND inby faces at start of study. 

Date 1-5 Entry numb 

T25 study were made on day shift # Permanent stopping - Intake air 0 

Machine break u Return air 

Limit of workhgs at stwt of study 6-21-70 7 Faces at start of study 

4 Belt loading station 

FIGURE 3. - Sequence of Mining by Shifts and Dates During Study Period. 
therefore, was based on the recording methanometer having the shortest operating 

period, and the data recorded on the other three units for the corresponding periods 

were used. 

The areas mined and the sequence of mining are shown in figure 3. 

DRILLING HORIZONTAL METHANE CONTROL HOLES INTO COALBED 

A 56-lb ~hor' hand-held air drill equipped with EW, 1-13116-in-dim smoothwalled drill casing 2-31132-in-OD centralizers, and a 3-in Blue Demon threepronged insert bit were used. A 1-ton hand-operated hoist provided the thrust for 

the drill, and water was used as the flushing agent. 

' Eight holes were drilled in the coalbed (fig. 4 and table 1) ; hole 1 (in-situ 

gas pressure) was packed with nine packers spaced with 5-ft lengths of 314-in pipe. 

Fifteen ft of the hole was left open at the front end, and 10 ft, at the back end. 

TABLE 1. - Sumnary of drilling data 

SReference to specific brands is made for identification only and does not imply 

endorsement by the Bureau of Mines. 

Angle of hole in 

coalbed 

Parallel to headings. 

4' angle with respect 

to rib in heading 1. 

5' angle with respect 

to rib in heading 5. 

10' angle with 

respect to rib in 

heading 5. 

10' angle with 

respect to rib in 

heading 1. 

Unrecorded angle with 

respect to outside 

rib in heading 5. 

Unrecorded angle with 

respect to outside 

rib in heading 5. 

10' angle with 

respect to rib in 

heading 5. 

Hole 

1 

2 

3 

4 

5 

6 

7 

8 

Hole terminated in 

Coal. 

Do. 

Do. 

Roof rock. 

Coal. 

Roof rock. 

Bottom rock 

Coal. 

Depth of 

hole, ft 

108 

255 

259 

95 

503 

140 

90 

300 

Hole 

drilled 

1970 

06-27 

06-28 

06-29 

07-01 

07-19 

07-23 

07-25 

07-26 

Hole started 

Inby rib of breakthrough 

between headings 2 and 3. 

12 in below binder left rib 

of heading 1. 

24 in below binder left rib 

of heading 5. 

12 in right of hole 3 in 

heading 5. 

12 ft back from face of 

heading 1. 

Near hole 3 in heading 5. 

Near hole 3 in heading 5. 

190 ft from hole 3 and 

30 ft outby face inheadinn 5. 
Faces at end of 2d 2-week Faces 

study period. 7-7-70 to 

/ 

study p

7-18-70- Minefsl on vacation 7-31-7

during 1st week. 

\ recordi

Faces at end of 1st 2- Faces 

during 2d week. 

Recording anemometersand methanomet 

Installed. 6-21-70 

Removed, 7-31-70 

LEGEND eters and ane

ration during 

1-5 Entry number -Intake air 

Plastic stoppings -Return air 

R Regulator --- Horizontal drill hole 0 100 

# Permanent stopping 4 Belt loading station _C 

? Faces at start of study *-- Track Scale, feet 

FIGURE 4. - Locations of In-Situ Pressure and Degasification Boreholes Drilled in 
A 1-112-in-dim plastic pipe was grouted a distance of 8 to 10 ft in 

holes 2-5. The pipe was extended just outby the recording methanometers at 

stations C and D in headings 1 and 5, respectively, except that pipe from 

hole 4 was tapped into pipe from hole 3. A 50-ft-long EW rod was inserted in 

hole 5 prior to the grouting of the plastic pipe. Drill casing was placed in 

hole 8, and the plastic pipe was attached to it and extended outby the recording methanometers as were the others. Holes 6 and 7 were left open, because 

neither liberated any measurable quantity of methane. 

RESULTS 

The lowest pressure in table 2 is not representative for the total study 

period, because the usefulness of the hole was negated July 14 (fig. 3-4), 

after which holes 5-8 were drilled. 

TABLE 2. - In-situ gas pressure 

measured in hole 1 

Date, July Gas pressure, psi 

1 64 9 

2 650 

8 645 

9 642 

10 640 

13 636 

Approximate overburden at hole 1 was 1,450 ft. 

Table 3 is a summary of all monitoring data obtained during the study 

period, and figure 5 shows the effect of the holes drilled in the coalbed on 

methane emissions from the face areas. 

As holes 2-4 were completed, there was some uniformity in methane emissions from them, reaching a maximum of 42 cfm (60,500 cfd) upon completion of 

hole 4. It is doubtful that hole 1 (in-situ pressure) contributed a measurable quantity of methane. 

From July 1 until hole 5 was completed on July 19, and during which 

period mining in the study area continued for 6 consecutive days, the emission 

rates from the holes were erratic and, with three exceptions, practically nil. 

Unknown conditions in the holes, possible errors in instrumentation, relatively short monitoring periods for 8 days, and personal errors could be the 

explanation for the erratic values. 
betveen vare prorated. 

'Methane enfssions frm holes in coalbed obtained by subtracting fra the total rate obtained at stations A and B, the sution of clisaioes obtained at stati

k.tb.ae 

WSlioll 

in face 

aru of 

atatim 

C .ad D. 

liars 

rtbe in 

intake 

air 

- 

- 

- 

- 

- 

162 

120 

111 

102 

92 

106 

65 

76 

84 

79 

76 

80 

76 

69 

60 

70 

113 

126 

117 

155 

134 

160 

134 -- 127 

116 

93 

135 

117 

137 

UO 

171 

151 

224 

205 

173 

248 

openring 

bud-held 

Pace 

adv-a. 

ft 

- 

42 

31 

38 

37 

67 

43 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

18 

37 

33 

43 

39 

26 

33 

- 

65 

61 

43 

22 

48 

- 

39 

67 

42 

29 

35 

42 

73 

of entries; 

TABU 3. - Sum of %mitorim data 

ktlun

UilWi

frm 

rib

betwe

statio

C and 

statid 

A .ad 

c

66 

66 

65 

63 

62 

62 

61 

61 

61 

61 

61 

58 

58 

58 

58 

58 

57 

57 

57 

56 

56 

56 

56 

53 

53 

53 

52 

52 

52 

52 

51 

51 

51 

51 

51 

44 

day

instr

Con1 

pro- 

&ction, 

tons 

- 

131 

97 

119 

116 

209 

134 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

56 

115 

102 

133 

121 

81 

101 

- 

189 

177 

125 

64 

139 

- 

113 

1% 

122 

83 

100 

122 

228 

inst-ts 

stations 

Worm face' 

Idle.. . . . . . . . . . . . 

(4-5) .5,(4-5). . . . 5,4 ............ .. 2.0-2) ,2.. . . . . . . 1.(2-1),1 ........ 1, (2-1) ,2,1.. . . . . 

Idle.. . . . . . . . . . . . ..do.. . . . . . . . . . . . ..do ............ ..do ............. 

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

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

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

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

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

3.2.3.2 .......... 3.2.3.2.. . . . . . . . . (3-2).1.(2-1) .I.. 

1.(2-1).1,(2-1),2 

(3-4) .4.(3-4). . . . 4,(3-4).4,(3-4).. 

3.4.. . . . . . . . . . . . . (3-4) (4-3). . . ... 5.(4-5). . . . . . . . . . 4,5.(4-5). . . . . . . . 

Idle.. . . . . . . . . . . . 2.O-2).2 ........ 1.2.3,(3-2) ...... 

1,(2-1) .......... 1,2,3 ..... . ... . . . 

2.3.0-2). . . . .. . . 

3.2.3.2 .......... 

by theuelves 

in intake air 

frm 0-1 ribs 

nte 

06-22-70 

06-22-70 

06-23-70 

06-24-70 

06-25-70 

06-26-70 

Average 

06-26-70 

06-27-70 

Average 

06-28-70 

06-29-70 

06-30-70 

07-01-70 

Avengs 

07-07-70 

07-08-70 

07-09-70 

07-10-70 

Average 

07-13-70 

07-14-70 

07-15-70 

07-16-70 

07-17-70 

07-18-70 

Average 

07-19-70 

07-22-70 

07-23-70 

07-24-70 

07-25-70 

Average 

07-26-70 

07-27-70 

07-28-70 

07-29-70 

07-30-70 

07-31-70 

Aver-. 

08-20-70 

'Numbers 

'Methane 

'mthane 

monitoring 

mr 

rocking 

- 

136 

91 

105 

79 

122 

107 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

69 

154 

106 

179 

143 

113 

127 

- 

% 

83 

78 

35 

73 

- 

51 

101 

65 

41 

47 

61 

197 

represent 

obtained 

mtbne 

in 

intake 

at bit aitt 

3 

1 

1 

1 

1 

1 

2 

3 

1 

2 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

1 

appuring 

volu 

bled-off 

Miner 

on 

split, 

min 

- 

64 

28 

46 

14 

47 

40 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

4 

72 

13 ' 

75 

78 

75 

53 

- 

54 

48 

42 

15 

40 

- 

27 

45 

A3 

30 

30 

33 

79 

hyphervted 

Jut 

the, rin 

Idle Total 

480 480 

269 405 

204 295 

160 265 

201 280 

258 380 

218 325 

480 480 

480 480 

480480 

480480 

480 480 480 480 

480 480 

480 480 

115115 

389 389 

140 140 

480 480 480 480 480 480 395 395 

81 150 

28 182 

59 165 

40 219 

108 251 

62 175 

63 190 

-- 

384 480 

397 480 262 340 

175 210 

305 378 480 480 

269 320 

379 480 

140 205 

73 1l4 

153 200 

203 264 

158 3-55 

faces 

by hand-held 

tailht pi=+ 

0.23 

.24 

.25 

.25 

.27 

.27 

.25 

.25 

.24 

.23 

.22 

.21 

.22 

.19 

.19 

.19 

.19 

.19 

.21 

.22 

.22 

.23 

.23 

.21 

.22 

.22 

.22 

.22 

.22 

.22 

.20 

.21 

.22 

.22 

.24 

.25 

.23 

.21 

entries. 

aa 

Left anlit 

A 

ch 

25,200 

25,000 

24.700 

20,800 

21.900 

21,000 

22.700 

24.800 

26.100 

26.200 

26,900 

25.800 

30,000 

28.200 

27.700 

26,100 

26.500 

26.300 

26,500 

26,300 

25.200 

/25,700 

26,400 

23.000 

24,000 

27.400 

25.300 - 24,800 

24.500 

27,400 

27,500 

26.000 

25.900 

24.100 

25.000 

26.100 

23.500 

21.900 

24.100 

26.600 

umbers 

inby belt betwem monitoring 

C& 

105 

105 

105 

105 

105 

105 

105 

105 

105 

.24105 

105 

105 

105 

105 

.22105 

104 

104 

100 

104 

104 

104 

104 

104 

104 

104 

104 

104 

103 

103 

103 

103 

103 

103 

102 

102 

102 

102 

102 

102 

102 

several 

A, 8 and C, D 

pet SUtion 

C 

- 

- 

- 

- 

- 

- 

- 

0.41 

.37 26,800.35.54 

27,000.33.52 

.36 

.31 

.35 

.33 

.34 

.33 

.30 

.33 

.30 

31 

.31 

.36 

.49 

.34 

.40 

.64 

.55 

.47 

-- 

.47 

.42 

.42 

.52 

.46 

.59 

.43 

.59 

.42 

.71 

.75 

.57 

.61 

and by us obtained by recording methanowters on mhift 2, June 26. 

on 

split, 

dn 

- 

72 

63 

59 

65 

75 

67 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

- 

65 

82 

93 

104 

65 

38 

75 

- 

42 

35 

36 

20 

33 

- 

24 

56 

32 

11 

17 

28 

118 

in 

duriq 

Station 

A 

0.55 

.63 

.67 

.72 

.62 

.77 

.6E 

.63 

.58 

.56 

.50 

.52 

.48 

.56 

.52 

.51 

.SO 

.51 

.50 

.51 

.53 

.6E 

.54 

.56 

.75 

.71 

.63 

.70 

.73 

.73 

.83 

.75 

.74 

.81 

.75 

.72 

.92 

.88 

.81 

.74 

appearing 

tailpiece 

Air, 

eb. 

19,600 

18,700 

17,900 

20,400 

17.400 

18,600 

18,600 

17.300 

17,200 

17,100 

17.300 

17,900 

21.800 

21,200 

18,900 

20,000 

28.100 

28,100 

27,900 

28,300 

28.100 

24,100 

22.300 

21,500 

21,800 

21,500 

21,500 

22.100 - 

21,400 

21.300 

18.500 

18,300 

19.900 

25.000 

24.300 

22,300 

20,100 

19.400 

19,000 

21,000 

22,000 

parentheses 

idle 

pet xution 

0 

- 

- 

- 

- 

- 

- 

- 

0.71 

.69 

.67 

.50 

.42 

.42 

.47 

.45 

.39 

.33 

.33 

.30 

.34 

.53 

.47 

.60 

.76 

.39 

.52 

.55 

.53 

.55 

.44 

.53 

.51 

.35 

.53 

.57 

.71 

.81 

.74 

.66 

.86 

shift 

Air. 

cfm 

44,800 

43.700 

42,600 

41.200 

39.300 

39.600 

.7941,300 

42.100 

43,300 

-7443,500 

44,800 

47,600 

51,200 

47,100 

.6347,700 

54,200 

54.600 

54,200 

54,800 

54,500 

.6149,300 

48,000 

47,900 

44,800 

45,500 

48,900 

47,400 

46,200 

45,800 

45,900 

45.800 

45,900 

50,900 

48,400 

47,300 

46,200 

42,900 

40,900 

45,100 

48,600 

to 

July 26 

Sution 

8 

0.45 

.48 

.63 

.87 

1.03 

.92 

.78 

.77 

.66 

.M 

.59 

.68 

.40 

.39 

.39 

.40 

.40 

.69 

.75 

.91 

.54 

.62 

.6E 

.63 

.69 

.59 

.69 

.65 

.49 

.68 

.75 

.85 

.82 

.86 

.80 

.89 

refer 

on 

mthm 

Stations 

C 

Pet 

- 

- 

- 

- 

- 

0.67 

.53 

.50 17.600.64.7044.400.47207.61270.24105 

.38 

.38 

.37 

.39 

.34 

.33 

.32 

.30 

.32 

.44 

.48 

.46 

.58 

.52 

.54 

.50 -------- .50 

.48 

.43 

.52 

.48 

.47 

.48 

.58 

.55 

.76 

.75 

.61 

.72 

breakthroughs 

and 

Statfona 

A 

6 

0.50 

.56 

.65 

.80 

.80 

.84 

.73 

.69 

.65 

.56 

.55 

.53 

.61 

.45 

.44 

.45 

.45 

.45 

.57 

.6E 

.63 

.73 

.65 

.67 

.65 

.66 

.71 

.67 

.78 

.71 

.62 

.75 

.75 

.77 

.88 

.89 

.80 

.S1 

periods 

and D 

Ch 

- 

- 

- 

- 

- 

267 

225 

216 

.63.6944.100.45197.59259.24105 

.48211 

170 

181 

189 

184 

.38181 

184 

180 

173 

164 

174 

217 

230 

221 

259 

238 

264 

238 

230 

219 

196 

238 

220 

240 

232 

273 

253 

326 

307 

275 

350 

idle 

. 

8 

227 

246 

278 

328 

314 

333 

300 

291 

281 

.63273 

251 

262 

271 

287 

.56267 

244 

240 

243 

247 

244 

281 

326 

303 

328 

296 

328 

310 

305 

325 

307 

356 

326 

316 

363 

354 

356 

378 

364 

361 

394 

between 
Z 

9 

g 200 

8 

E 

d o I00 Miners' Vocation 

3 

s 

0 

400 IIIIIIIIIIIIIIII~IIIII~IIII~~III~I~

KEY 

Methane emission frome--4 Face areas 300 - - - From holes 0 

i Gops in curves indicate 

9 9 no monitoring. 

V) 

Hole 5 completed - 

50-Yt EW rod inserted 

W 

1 

Z 

a 

I ti loo- - 

Z 1:15pm -0 

0 ' 

5 

TIME, months 

FIGURE 5. - Summary of Pertinent Results Obtained From Degasification Holes in Coalbed. 

It is reasoned that on July 18, when face production was 81 tons and 

methane emission from the face areas was 160 cfm, emission from holes 2-4 was 

nil. After completion of the 503-ft-deep hole 5 on July 19, methane emission 

from the coal-producing faces dropped from 160'cfm on July 18 to 93 cfm on 

July 24, but methane emission from hole 5 increased from 22 to 58 cfm. 

Hole 6 (140 ft deep) was drilled during this period and showed no measurable 

methane emission. Although a significant reduction in face emission during 

July 19 to July 22 can be attributed to the 3 idle days, contribution from 

hole 5 also was significant due to 3 coal-producing days during the period 

(189, 177, and 125 tons during monitoring shift). It is not determinable why 

hole 5 required 2 full days to become more productive. However, there is the 

desirable correlation between production, lower methane emission from the face 

areas, and higher methane emission from hole 5. This was expected from the 

study . 
Although the 24-cfm emission rate from hole 8 (300 ft deep) is low, drilling of the hole was completed on July 26 after monitoring was stopped. Thus, 

most of the 24 cfm can be assumed as being liberated from hole 5. 

During the period from July 26 to July 29, holes 5 and 8, particularly 

the latter, generally had a positive effect on reducing the methane emission 

from the face areas during mining. Face emission dropped from 137 cfm on idle 

July 26 to 130 cfm on July 27 when production was 113 tons. Increase in the 

face emission rate to 171 on July 28 was 32 pct; the production increase was 

72 pct. This could explain the apparent discrepancy. At the same time, tubing from hole 5 was disconnected prior to completing monitoring on the same 

date, which permitted both methanometers in the same heading to record the 

emissions from hole 5. 

Thus, it appears that emission rates from holes 5 and 8, 59 cfm (85,000 

cfd) and 79 cfm (113,800 cfd), respectively, were somewhat significant, considering the relatively low permeability of the coalbed. 

Other results not related to methane emissions from the holes in the coalbed may be noted in table 3. They are as follows: 

1. Methane concentrations in the left air split reached a high of 0.92 

pct during the study. In the right air split the high was 1.03 pct; the next 

highest was 0.92 pct. However, the methane detector on the continuous miner 

disconnected the power at 2.0 pct concentration too frequently. This occurred 

despite the fact that the air volume measured at monitoring station A ranged 

from 20,800 to 30,000 cfm, and at station B, from 17,100 to 28,300 cfm. 

2. The methane volume in the intake air measured inby the comteyor belt 

tailpiece was 105 cfm (151,200 cfd) at the start of the study and 102 cfm at 

the end of the study. This is a significant volume that accumulated from the 

bottoms of intake shafts, from the intake airways to the study area, and 

mostly from the 3,400 ft of three intake airways of the particular section. 

Coal in cars and on belt conveyors wherever located outby the study section 

also contributed to the volume of methane. All of these factors could account 

for the insignificant change in the intake air methane volume. 

3. Methane emission from the ribs and parts of breakthroughs (to the 

stoppings) between monitoring stations A and C in heading 1 and monitoring 

stations B and D was 66 cfm (95,000 cfd) at the start of study and 44 cfm 

(63,000 cfd) at the end of study (58 days). The bleed-off is significant in 

a total distance equivalent to a single heading 2,000 ft long. 

CONCLUSIONS 

The behavior of methane emissions from the holes drilled in the coalbed, 

as described under "Results," strongly indicates the need for further research 

in the dmelopment of (1) the most effective spacing and length of holes; 

(2) proper angle of holes with respect to the outside ribs; (3) the possible 

use of strong slotted plastic pipe in the holes to prevent closure; and 

(4) other possible techniques to obtain greater and more lasting methane 
emission rates. It is theorized that the somewhat sudden reduction in methane 

emissions from holes 5 and 8 was caused by closure. 

Although not included in the objective of the study, development of techniques for more effective face ventilation and for degasification of gassy 

coalbeds or major panels before mining within them is needed. With respect to 

face ventilation, there is an urgent need in very gassy mines to develop airduct systems for mounting on predominantly used continuous miners. Also 

needed is telescoping tubing to be used back of the miners in conjunction with 

reinforced tubing and auxiliary fan. The arrangement would provide greater 

volume of air as close as practicable to the cutting head while the miner is 

breaking coal. 

U.S. GOVERNMENT PRINTING OFFICE: 1972-709-1U:S43