UNITED STATES DEPARTMENT OF THE INTERIOR 
Report of Investigations 8241 

Water Infusion of Coalbeds 

for Methane and Dust Control 

By Joseph Cervik, Albert Sainato, and Maurice Deul 

li N I'I'EI) SI'A'I'ES DEPARTMENT OF THE INTERIOR 

(;t~ciI L). Andrus, Secretary 

HliKE:AU OF MINES 
This publication has been cataloged as follows: 

C'ervi k, Joseph 

Water infusion of coalbeds for methane and dust control / 

by Joseph Cervik, Albert Sainato, and Maurice Deul. [Washington] : U.S. Dept. of the Interior, Bureau of Mines, 1977. 

27 p. : ill., diagrams ; 26 cm. (Report of inve\tigation\ - Bureau 

of hlines ; 8241) 

13ibliography: p. 26-27. 

1, ( oal mines and mining - Ilust control. 2. Alethane. 3. ( oal 

mines and mining - Kater supply. I. Sainato, AIbert, joint author, 

11. Ileul, ilaurice, ]oint author. 111. United States. 13ureau of 

Ll~nes. I\'. Title. V. Series: [Jnited States, I3ureau of hlines. 

Keport of in\e\tigation\ - 13ureau of hlines ; 82 ',I. 

TN23.U7 no. 8241 622.06173 

1J.S. Ilept, of the Int. I>lbrar) 

- 
CONTENTS 

Page 

Abstract ............................................................... Introduction ........................................................... European drilling and infusion procedures .............................. Coalbed characteristics ................................................ Infusion procedures .................................................... Infusion of a development section ................................. Methane flows during infusion., .............................. Location and length of horizontal holes ...................... Directional permeabilities ................................... Effect of mine opening ....................................... Effect of gas pressure in coalbed ............................ Infusion of a retreating longwall ................................. Case studies ........................................................... Methane ........................................................... Dust .............................................................. Mining through an infused zone ......................................... Effect of water on roof and floor strata ............................... Drilling procedures and equipment ...................................... Water infusion pressures and equipment ................................. Sumary ................................................................ References ............................................................. 

European infusion methods ......................................... Flow into coalbed through vertical borehole ....................... Migration of waterfront through coalbed ........................... Waterfront of two wells ........................................... Packed hole for water infusion .................................... Water infusion of coalbed through a horizontal hole ............... Completed infusion of one hole .................................... Water-infused section ............................................. Elliptical waterfronts for face cleat perpendicular to section 

advance direction ............................................... Elliptical waterfronts for face cleat parallel to section 

advance direction ............................................... Water-infused section for face cleat parallel to section 

advance direction ............................................... Cusping of waterkront ............................................. Infusion of longwall with one or two holes ........................ Test section showing location of horizontal holes, methane 

monitoring stations, and ventilation plan ....................... Total methane flow rates from study area where face cleat is 

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

parallel to section advance direction ........................... Methane flow rates from faces of section in Upper 

Kittanning coalbed . ............................................. 
ILLUSTRATIONS.. Continued 

Test section in Upper Freeport coalbed ............................ Mining through infused zone ....................................... Three-blade drag bit .............................................. Three-cone roller bit ............................................. Ten-foot stabilizer ............................................... End view of 10-ft stabilizer ...................................... Short centralizer (2-15/16-inch-diameter) ......................... Handheld air drill ................................................ Drill and power units ............................................. 

TABLES 

1 Infusion of . development section ................................... 2 Infusion of . longwall .............................................. 3 . Infusion pressure and flow rates ................................... 4 . Infusion pump characteristics (three-piston) ...................... 
until the infused zone is mined through. Depending on the permeability of the 

coalbed, infusion pressures ranged from 300 to 2,200 lb/in2. 

Face emissions in the Upper Kittanning coalbed were reduced by 89 pct; 

reductions of 38 to 79 pct were measured in the Pittsburgh coalbed depending 

on the relationship between the face cleat direction and mining direction. 

Respirable dust levels were reduced by about 75 pct on a longwall section in _ - -- the Pocahontas No. 3 coalbed and by about 50 pct on a development section ir 

the Upper Kittanning coalbed, but no statistically reliable reduction was 

found in the respirable dust levels in the Pittsburgh coalbed. 

INTRODUCTION 

Water infusion of coalbeds is a method of controlling methane flows at 

active face areas and, in some cases, of suppressing dust during mining. 

Water infusion is practiced widely in Europe and is reported to be the best 

means of combating dust (l5) .* 

Supervisory geophysicist. inin in^ engineering technician. 

3~esearch supervisor, Methane Control and Ventilation. 

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

of Mines, Pittsburgh, Pa. 

*underlined numbers in parentheses refer to items in the list of references at 

the end of this report. 
In Germany, experience has shown that infusion must provide a minimum of 

1.6 gal of water per ton of coal to suppress dust (2). German regulations 

require infusion of coalbeds where possible and over 50 pct of their longwalls 

are infused (I&). In France, water infusion is the basic dust prevention 

technique (8). Water infusion is widely practiced and covers 89 pct of the 

coal produced in the northern coalfields. In Belgium (g), a quantity of 

infused water equivalent to about 2.4 gal/ton of coal suppresses 95 pct of the 

particles between 0.5 and 5 microns produced at the face. 

Water infusion is not practiced as widely in the United Kingdom as on the 

Continent (9). In the Welsh coalfield, "short hole1' infusion is carried out 

at the face but with doubtful effectiveness, and in the Stadfordshire coalfield, no significant improvements in dust conditions were noted during an 

infusion test. In the Durham and Lancashire coalfields, infusion is practiced 

effectively on retreat mining; dust reduction of 50 pct is reported on three 

Durham faces and somewhat lower on the Lancashire coal faces. 

In the United States, a study on a retreating longwall in the Pocahontas 

No. 3 coalbed showed that both total and respirable dust levels were reduced 

40 to 79 pct by infusion (6). Morton (12) found water infusion of longwall 

faces in the Eagle coalbed at Carbon Fuel Co. No. 20 Mine to be an effective 

and economical means of controlling airborne dust created by the mining 

operation. 

This report attempts to present the mechanics of water infusion in a 

simple manner so that coal producers unfamiliar with fluid dynamics will understand the process. It is intended as a guide for diagnosing and solving 

problems associated with the application of water infusion by mine personnel 

and describes equipment and procedures for accomplishing drilling and infusion 

through short horizontal holes. 

EUROPEAN DRILLING AND INFUSION PROCEDURES 

The predominant mining system in the United Kingdom and Europe is the 

advancing longwall. In the United Kingdom (9), for example, only 7 pct of the 

840 major longwall faces are worked on retreat. The integration of a drilling 

and infusion phase is more difficult on an advancing longwall than on a 

retreating one. Figure 1 shows three European procedures for infusing advancing longwalls (2): 

1. Horizontal holes are drilled into the face to a depth of approximately the daily advance of the panel (shallow infusion). The distance 

between holes is about twice the length of the holes. Thus, if the daily 

advance rate is 10 ft, hole length is 10 ft and the distance between holes is 

20 ft. If the panel is 400 ft wide, about 20 holes are necessary to infuse 

the panel. In some instances, holes are drilled to depths of about 40 ft 

(deep infusion). The spacing between holes is 80 ft and on a 400-ft face, 

about five holes are required. 

2. The second procedure is known as remote infusion, or infusion from 

outside of the mined coalbed. If there is a roadway above the panel being 
C INFUSION FROM ADVANCE ROADS 

FIGURE 1. - European infusion methods, 

the infusion hoses are damaged when the top coal 1 

infusion phases in one shift. 

Although deep infusion 

requires fewer holes, more 

time is needed to infuse a 

larger volume of coal. In 

France, continuous face 

infusion is practiced in 

certain special situations 

on plow faces (2). Infusion 

holes are drilled in the 

upper part of the coalbed 

and infusion is performed 

during mining. A plow mines 

the lower portion of the 

coalbed and the top coal 

with the holes falls. Continuous infusion can be 

carried out only on plow 

faces that advance 

slowly. In some cases, 

falls. 

With remote infusion or infusion from outside the coalbed, harder or more 

abrasive rocks make drilling more expensive and require special drills. This 

method is not used widely. 
Drilling of holes in the advance gate roads does show promise, providing 

certain operational problems can be solved. At present, advance headings on 

high output faces in Germany (2) are ahead of the face only about 75 to 89 ft, 

even though these headings are manned 24 hours. Therefore, holes are drilled 

on weekends only. If problems develop during the drilling or sealing of the 

hole, infusion must be postponed until the following weekend. In France (9, 

longwalls are infused from the advance gate roads and complemented by infusion 

into the face of the longwall. 

In spite of the operational difficulties of incorporating drilling and 

infusion cycles on an advancing longwall and not withstanding production 

delays, water infusion for dust suppression is a widespread practice in 

Europe. 

COALBED CHARACTERISTICS 

Coalbeds are naturally fractured and can be characterized as being made 

of fractures and matrix (solid coal) (3). Generally, there are at least two 

sets of vertical fractures that intersect at right angles to form an interconnected network throughout the coalbed (11). These two fracture systems are 

known as face and butt cleats. 

The matrix (solid coal) plays no part in the infusion process. Although 

it contains an interconnected pore system, these openings, which are about 

5 AO (2 by inches) in diameter (I.), are too small to permit water to pass. 

Therefore, infusion of water into coalbeds is confined to the fracture systems 

only. 

Fracture density of coalbeds, that is the number of fractures per inch, 

varies. Blocky coals, such as the Pittsburgh and Beckley, are characterized 

by a fracture spacing of 1 to 6 inches. Friable coals, such as parts of the 

Freeport, Kittanning, and Pocahontas No. 3 coalbeds, are characterized by a 

fracture spacing of about one-fourth of an inch. The ability of a coalbed to 

transmit fluids, such as water and methane, is determined by its fracture 

systems and is called the fracture permeability. Generally, blocky coalbeds 

are more permeable than friable coalbeds. 

INFUSION PROCEDURES 

Although the migration of water through a coalbed during infusion cannot 

be observed, associated problems can be diagnosed and solved if the mechanics 

of infusion are understood. Definite relationships exist among parameters 

such as hole length, spacing between holes, quantity of infused water, and 

panel or section width. 

Infusion of a Development Section 

Figure 2 shows water being pumped down a well bore and forced under pressure into a coalbed. The water flow rate will be governed by the water pressure in the well bore and the fracture premeability of the coalbed. Figure 3 

is a plan view of the migration of water through the coalbed. The fracture 
tal holes drilled underground into coalbeds, water FIGURE 3. - Migration of waterfront through coalbed. should enter the coalbed from 

a small segment (10 to15ft) at the rear of the hole. This condition can be 

met by filling the horizontal hole with inflatable packers (fig. 5). Good 

results are obtained when 5-ft packers are connected with 5-ft lengths of 

pipe (2). If too few packers are used, the water at the rear of the hole 

tends to short circuit along the hole instead of penetrating the coalbed. As 

an alternate procedure, 314- or 1-inch plastic pipe can be grouted into the 

horizontal hole (6). 

Methane Flows During Infusion 

Figure 6 shows the start of infusion in a 4-ft thick coalbed. Water 

flows into the coalbed from the rear of a 125-ft horizontal hole. As the 

waterfront, which has the shape of a right circular cylinder, moves outward, 

water which is being pumped into the coalbed at a rate of 15 gal/min, for 

example, moves outward through the sidesofthis imaginary cylinder at the same 

rate, because water is incompressible. When the cylinder is 50 ft in radius, 

the lateral surface area of the cylinder is about 1,256 ft2. Therefore, water 

is flowing through each square foot of lateral surface area of the cylinder at 

a rate of 0.012 gal/min/ft2. Methane is being displaced by the water at the 

same rate or 0.0016 ft3/min/ft2. 
moves toward the face, methane is pushed ahead of it, which would tend to 

increase gas flow through the face. However, observations during water infusion operations show no increase in methane flow at the face, Instead, a 

gradual decrease is observed from the start of infusion until the waterfront 

breaks through at the face. Thus, blocking action of infused water dominates 

its action. 

As water reaches the face of the entry near the hole, it spreads until 

the face is covered. The calculations based on the example above show that 

the water flow rate from the face is about 0.005 gal/min/ft". Water appears 

on the face as droplets of water. When the face area (80 ft2) is completely 

covered with droplets, the flow rate into the entry is 0.4 gal/min. Infusion 

is continued until droplets of water are observed for a short distance along 

the rib. If the floor is deteriorated by water, infusion should be terminated 

when water droplets cover the face. 

Location and Length of Horizontal Holes 

A typical section advancing into virgin coal may be about 500 ft wide. 

To reduce methane flows through the section faces, a continuous waterbank must 

be emplaced to form a barrier across the width of the section. This prevents 

methane from flowing toward the faces and routes it around the water infused 

zone, allowing it to enter the mine opening through the ribs outby the face 

areas of the section. 
FIGURE 6. - Water infusion of coalbed through a horizontal hole. 

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

horizontal holes, depending on the length of the holes. Generally, horizontal 

holes 125 to 150 it in length can be drilled with handheld drill equipment 

used underground. In some mines, entries are advanced in about 100-ft increments. Integrating a drilling and infusion phase into a mining cycle presents 

no special problems when 125- to 150-ft long holes are drilled. 

Figure 7 is a schematic of the infusion of a coalbed through a packed 

horizontal hole (125 ft). When the waterfront first reaches the mine opening, 

the diameter of the infused zone is about 250 ft. The second hole should be 

drilled 140 to 170 ft from the hole shown in figure 7. When breakthrough 

occurs, the infused zones of each hole will merge like those in figure 4. 

This procedure is repeated with two additional holes to produce a continuous 

waterbank across the section (fig. 8). 

There is no preferred sequence of infusing horizontal holes. They may be 

infused simultaneously or in sequence as they are drilled. The important 

thing is to leave no partially infused zones where methane can funnel through 

to the mine opening. 
advance of the section. At 

breakthrough, the distance 

of migration of the waterfront across the section is 

much less than in the direction of advance of the 

section. Drilling and infusing four holes across a 

500-ft section can result in 

an infused zone where coal 

between holes may not have 

been swept by water (fig. 11). 

Such zones permit methane to 

FIGURE 8. - Water-infused section. bleed through to the faces 

of the section, thereby making the blocking action of water less effective. Six horizontal holes may be 

necessary to emplace a water bank across the section. 
Butt cleat 

direction 

FIGURE 9. - El liptical waterfronts for face cleat perpendicular to section advance direct ion. 

t Effect of Mine Opening 

Face cleat 

d i recti0n The proximity of the 

- infusion segment of the hori- Butt cleat 

direction zontal hole .to the mine opening affect's the shape of the 

Section advance waterfront, although the 

direction effect is not as critical in 

.I7 t figures 8 and 9 as it is in - - 

figure 11. As the waterFIGURE 10. - Elliptical waterfronts for face cleat front migrates toward the 

to section advance direction. opening, the elliptical 

shape is distorted. This 

distortion is called cusping 

(12). Figure 12 shows the cusping of successive stages of the waterfront as 

it travels toward the mine opening. Cusping causes premature breakthrough of 

the waterfront with a corresponding decrease in lateral migration. 

Effect of Gas Pressure in Coalbed 

Gas pressure increases with distance into the coalbed from the mine opening. Therefore, during water infusion, the waterfront farthest from the mine 

opening encounters a greater resistance than one closer to the mine opening. 

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

(less than 30 Lb/in2g), distortion of the waterfront due to gas pressure 

should not be as pronounced as the effects of the mine opening or directional 
Gas flow 

nnnritir 

FIGURE 11. - Water-infused section for face cleat para[- 

let to section advance direct ion. 

permeabilities. However, in 

coalbeds such as the Pocahontas No. 3 (lo), - where the 

gas pressure is about 600 

1b/inzg at a depth of 100 ft 

into coal, its effect could 

be as important as that of 

the mine opening or the 

directional permeabilities. 

Infusion of a Retreating 

Longwall 

Unlike a room-andpillar section, a retreating 

longwall can be infused with 

f one or at most two holes drilled from 

Face cleat the rib sides of the panel (fig. 13). direct ion Thereafter, the water spreads through - Butt cleat the panel in much the same way as in 

direction room-and-pillar infusion. To infuse a Formation of 500-ft panel with one hole drilled from 

the rib side, the hole is drilled to a 

depth of about 275 ft which is about 

25 ft beyond the centerline of the panel. 

Plastic pipe is grouted into the hole to 

approximately 255 ft, leaving about 50 

ft of open hole for infusion of the 

panel. When completely infused, water FIGURE 12. - Cusping of waterfront. will have traveled about 225 ft to the 

left and right of the hole and to both 

ribs of the panel. The total quantity of infused water will be about 15,000 

gal/ft of coalbed height. Fracture porosity of the coalbed is assumed to be 

1 pct. For the two adjacent infused zones to merge, the adjacent hole should 

be spaced approximately 400 ft or less from the infused hole. 

Analternateprocedure is to drill and infuse from both sides of the panel. 

Two holes are drilled to a depth of 150 ft and plastic pipe is grouted to a 

depth of 135 ft. When both holes are infused, the infused zones from each 

hole will merge and water will have spread about 135 ft to the left and right 

of the holes. The adjacent pair of holes should be located about 200 ft outby 

the infused holes. 

The use of short holes drilled and infused from both sides of the panel 

is recommended. Long holes are difficult to drill because they may terminate 

prematurely in the roof or floor rock. They are also more difficult to grout 

since the grout may set prematurely because of the greater length. Possible 

disadvantages of drilling from both sides of the panel are that power may not 

be available on both sides of the panel and that drilling space is limited 

because of the conveyor belt. However, both these disadvantages can be 

avoided by drilling the holes during the development of the panel. 
- 

Scale, ft 

FIGURE 13. - Infusion of longwall with one or two holes. 

inby methane flow rates is the flow rate of meth 

ribs of the section. 

the immediate returns. The 

sum of the readings of the 

inby instruments gives the 

total methane flow rate from 

the faces of the section. 

Two other sets of instruments 

were set up in the returns 

about 600 ft outby the faces 

of the section. The sum of 

the two outby instrument 

readings gives the total 

methane flow rate from the 

faces of the section and the 

two outside ribs. The difference between outby and 

le through the two outside 

A first study was conducted in the Pittsburgh coalbed in a section where 

the more permeable face cleat was at right angles to the direction of section 

advance (5). Referring to figure 9, 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, leaving no zones where methane 

can funnel through. Figure 15 shows the effect of the waterbank on methane 

flows in the face areas during mining. 
M LEGEND 

- - Intake air *stopping with door Return air =Mined before infusion 

Curtain stopping ZMined after infusion 

Permanent stopping 100 

OScole, ft 

ribs. 

A second study was 

conducted in a section 

(Pittsburgh coalbed) advancing parallel to the more permeable face cleat. Referring FIGURE 14. - Test section showing location of horizontal to figure 11, the infused 

holes, methane monitoring stations, and water tends to run in the 

ventilation plan. direction of section advance 

faster than across the 

section. Consequently, zones which have not been filled with water may exist 

between holes and may permit methane to funnel through to the faces of the 

sect ion. 

In figure 16, the average methane flow rate from the immediate face areas 

of the section (inby curve) is 265 ft3/min before infusion and 165 ft3/min 

after infusion, that is, a 38-pct reduction in methane flow rate. At the 

outby stations, the methane flow rate has dropped from 306 ft3/min before infusion to 208 ft3/min after infusion and represents a 32-pct reduction. The 

difference in flow rate between outby and inby curves is 41 ft3/min before 

infusion and 43 ft3/min after infusion. 

These differences, which are not significant, indicate that no large 

volumes of methane are being diverted from the face areas to the. outside ribs. 
TIME, days 

FIGURE 15. - Total methane flow rates from study area where face cleat is perpendicular to 

sect ion advance direct ion. 

To improve the effectiveness of water infusion, two alternatives are available. 

The first is to increase the hole depth to about 200 ft. The infused water 

will then tend to migrate further across the section before breakthrough 

occurs. The second alternative is to leave hole depth the same, but to 

increase to six the number of holes drilled across the section. Each of these 

procedures tends to produce a continuous waterbank across the section. 

The third study was conducted in a friable coalbed (Upper Kittanning) 

where fracture permeability tends to be constant and the same in all directions, allowing infused water to spread uniformly outward from the hole 

(fig. 8). In this case, methane flow rate from the faces of the section 

averaged 90 ft3/min before infusion and 10 ft3/min after infusion (fig. 17). 

This represents an 89-pct reduction in methane at the faces during mining. 
TIME, days 

FIGURE 17, - Methane flow rates from faces of section in Upper Kittanning coalbed, 
same length. 

- Dust 

Several water infusion studies for dust control have been conducted but 

not all have been successful. In two cases, water was channeled through large 

fractures and short circuited to the mine opening. In other cases in the 

Pittsburgh and Upper Freeport coalbeds, valid conclusions could not be drawn 

because of large variations in dust measurements. However, several tests have 

been conducted successfully and their results are summarized below. 

Table 1 shows the results of an infusion test in a development section in 

the Upper Kittanning coalbed. Dust levels were reduced by 25 pct in spite of 

a 63-pct increase in production. If the data are corrected for the increase 

in production and air velocity during postinfusion sampling, the dust reduction due to water infusion is about 50 pct. 

TABLE 1. - Infusion of development section 

Preinfusion.. . . . Postinfusion .... NAP--Not applicable. 

Average dust 

concentration 

(MRE mg/m3) 

2.4 

1 .8 

Average 

production 

(tons/ shif t) 

67 

109 

Average air 

velocity 

(ft /min) 

33 2 

397 

Percent 

reduct ion 

(normalized) 

NAP 

50 
In two trials on a longwall in the Pocahontas No. 3 coalbed, an 81-pct 

dust reduction was achieved in the infused zone (table 2). If the data are 

corrected for lower tonnage during postinfusion sampling, the dust reduction 

is 79 and 69 pct for tests 1 and 2, respectively (6). 

TABLE 2. - Infusion of longwall 

NAP--not applicable. 

Preinfusion .......,...... 

Postinfusion (test 1). . . . Postinfusion (test 2). . . . 

Dust measurements are aade with MSA Monitare Model G personal dust samplers. Reproducible results are obtained when cyclones are separated from 

the dust pumps. In a development section, four cyclones are hung in the 

immediate return from the section to measure the effects of water infusion on 

dust generation during mining and reproducibility. On a longwall, cyclones 

are mounted near the tailgate (100 ft upstream) of the panel. 

MINING THROUGH AN INFUSED ZONE 

Dust 

concentration 

(MRE mg/m3) 

9.6 

1.8 

1.8 

When a section is water infused through holes drilled to 125 ft, the 

infused zone is about 250 ft deep and spans the width of the section. Starting on the left side of the section, two entries are advanced in increments 

alternately to 100 ft and the crosscut between these entries is also driven in 

increments (fig. 19). The continuous miner continues this cycling across the 

section until the section has been advanced one break, or about 100 ft. The 

miner then moves to the left side of the section and begins to advance the section on the second 100-ft increment, still within the infused zone. As the 

miner completes driving entries and crosscuts on the left side of the section, 

the hole drilling and infusion phases should be repeated. When the miner 

completes the advance on the right side of the section and moves back to the 

left side, the left side has been reinfused and the hole drilling and infusion 

phases are completed on the right side. Initially, the section should be 

infused over a weekend to avoid possible methane problems. Thereafter, drilling and infusion phases are incorporated into the mining cycle. Integrating 

the drilling and infusion phases into the mining cycle creates no serious 

problems and does not delay production. 

The quantity of water infused on a development section (500 ft) ranges 

from 15,000 to 25,000 gallons for coalbeds from 4 to 6 ft in thickness. This 

amounts to 1 or 2 gal per ton of mined coal, as compared with an average water 

consumption of 6 gallton on a shearer and an average of 7.5 gallton on a cont inuous miner. 

Production 

(tonslshift) 

2,104 

1,900 

1.260 

If the section is not infused after the second 100-ft increment has been 

mined, the flow of methane into each entry will begin to increase slowly. At 

this time, the infused zone is thin. Methane tends to drive the.water in the 

Average 

air velocity 

(f t /min) 

450 

450 

450 

Percent 

reduction 

(normalized) 

NAp 

79 

69 
FIGURE 19. - Mining through infused zone. 

coalbed aside and gradually methane flow through the faces increases. No 

abrupt surges of methane have been observed. Therefore, mining through an 

ir~fused zone presents no special safety hazards. As always, sufficient air 

must be available to dilute methane to permissible levels. 

Intercepting a water infusion hole during crosscut operations does not 

create an unsafe condition because flow from the hole is water. Mining parallel and into a water infusion hole, although not expected to create unsafe conditions, can be avoided by drilling all holes a few degrees off the direction 

of projected development of the entry. 
EFFECT OF WATER ON ROOF AND FLOOR STRATA 

Like methane, water is normally associated with coal. Most coalbeds contain inherent water which is stored in the fracture system. In the Pittsburgh 

coalbed, horizontal holes drilled 400 to 500 ft in advance of mining produce 

water at persistent rates of 700 to 900 gal/day, even in sections that are considered "dry." In coalbeds throughout the United States, vertical boreholes 

drilled into virgin coal must have water pumps installed to clear the well 

bores of water in order to maintain gas production (1). 

Because water does not readily wet coal and because of gravity, water is 

assumed to be in the bottom part of the coalbed. Observations show that the 

bottom I foot 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, infusing water into a coalbed will not create conditions that have not already 

existed for ages. Thus, it appears doubtful that water infusion would affect 

even a soft bottom adversely. 

The exposure of roof rock to water during infusion is not expected to contribute to roof failures. The roof is in contact with the infused water only 

where fractures in the coalbed terminate at the roof. Since fracture widths 

in coalbeds range from perhaps one-sixteenth of an inch tohairline cracks, the 

area of water contact with the roof is small in comparison to the area of the 

infused zone. 

In actual practice, no roof or floor problems have been observed due to 

water infusion. One infused area was thoroughly investigated several months 

after the section advanced through the area. There were no indications in the 

roof or floor that the area had been infused. In one area, haulage was 

affected by accumulated drill water and breakthrough water which had been 

absorbed in the bottom. Such situations can be avoided by channeling water or 

installing pumps. 

DRILLING PROCEDURES AND EQUIPMENT 

Coal is a soft brittle material and presents no special drilling problems. 

Water infusion holes are drilled with two types of 3-inch bits, One is a 

three-blade drag bit (fig. 20) and the other is a three-cone roller bit 

(fig. 21). The drag bit costs less and only the blades are replaced when worn. 

Under comparable conditions, the drag bit penetrates coal three to four times 

faster than the three-cone roller bit (A), which is used only when rock is 

encountered. The penetration rate of the drag bit in rock is nil. Flush 

joint drill casing is used in horizontal drilling work conducted by the Bureau 

of Mines. For holes drilled to 500 ft, EW flush joint casing is used which is 

1-13/16-inch ID and weighs 28 lb per 10 ft. The drill casing is in 10-ft 

lengths for ease in handling underground. Shorter lengths of casing require 

more frequent interruptions in drilling. 
The 10-ft stabilizer cannot be turned or redirected because of the close fit between the wall 

of the hole and the outside diameter of the 

stabilizer. 

After the hole has been collared, it is 

drilled as rapidly as possible. Generally, 125- 

to 150-ft holes can be drilled in 1.5 to 2 hours. 

However, if the hole must be redirected, more 

time will be required to complete the hole. 

If the hole must be redirected, the 10-ft 

stabilizer is removed from the drill string. 

Procedures for redirecting a hole depend on the 

trajectory of the hole. If the trajectory is 

toward the top, the drill string consists of a 

drag bit and EW casing. This drill string is 

rotated at high speed and low thrust. This tends 

to wear the bottom side of the hole, causing it 

to drop. In some cases, after every 10 ft of 

advance, several slow reaming passes are made to 

increase the wear on the bottom side of the hole, 

causing it to drop faster. 

FIGURE 20, - Three-blade 

drag bit. 
develops enough power to 

drill horizontal holes 500 

ft (15). It can be placed 

on a frame and pushed manually. An alternate method 

is to pull the drill with a 

1-ton "come-along." This 

drill unit can be moved from 

one site to another and set 

up rapidly in comparison to 

an electrohydraulic drill 

unit . -- Power for the electrohydraulic drill (fig. 26) is 

FIGURE 21. - Three-cone roller bit. supplied by a 15- to 20-hp 

electric motor which drives 

two hydraulic pumps in 

tandem. One pump drives an hydraulic motor which rotates the drill string; 

the other pump powers dual cylinders which provide the thrust on the drill 

string. A fire-resistant fluid is used in the hydraulic system. 
FIGURE 23. - End view of 10-foot stabilizer. 
SCALE

FIGURE 24. - Short centr
FIGURE 25. - Handheld air drill. 
WATER INFUSION PRESSURES AND EQUIPMENT 

The pressure required to infuse a coalbed depends on such factors as gas 

pressure, fracture permeability, and length of open hole through which the 

coalbed is infused. In many coalbeds, gas pressure is less than 75 1b/inzg at 

depths of 100 ft. Thus, gas pressure is not an important factor, except in 

the Pocahontas No. 3 coalbed, where a pressure of about 600 1b/inzg increases 

the infusion pressure significantly. 

The length of open hole through which the coalbed is infused affects 

infusion rate and pressure. Infusion piston pumps are constant volume pumps. 

Consequently, as the length of open hole increases, infusion flow rate remains 

constant but the infusion pressure decreases. However, there is a limit to 

the acceptable open-hole length. In an extreme example, if the length of open 

hole in a 100-ft hole is 80 ft, the infusion pressure will be extremely low 

but within minutes the infused water will be short-circuiting through the face 

of the entry. Open-hole length should not exceed 10 to 15 ft. 

Fracture permeability of the coalbed is the dominant factor affecting 

infusion pressure. Table 3 gives ranges of pressure and flow rates for several coalbeds. Length of open hole through which the coalbed is infused is 10 

to 15 ft. In the Pittsburgh coalbed, the mine's water supply pressure is 

adequate to infuse the coalbed. Except for this coalbed, infusion pumps will 

generally be required. 
TABLE 3. - Infusion pressure and flow rates 

In Bureau infusion work, piston pumps are used. Their pressure range can 

be altered by changing the piston diameter. Table 4 shows pressure ranges of 

a piston pump and corresponding flow rates. 

TABLE 4. - Infusion pump characteristics (three-piston) 

Flow rate 

(gal/min) 

8 to 20 

8 to 12 

7 to 16 

15 

Coalbed 

Pittsburgh ........... Upper Kittanning ..... Upper Freeport ....... Pocahontas No. 3... .. 

Infusion pressure 

(lb/in2) 

300 to 400 

700 to 1,150 

1,000 to 1,800 

1,500 to 2,200 

SUMMARY 

Piston size (inches) 

2.................... 

1-314 ................ 1-1/2.. .............. 1-114 ................ l.................... 

Water infusion is an effective method of controlling methane during mining. In the Pittsburgh coalbed, a 79-pct reduction in methane flowisobserved 

when the face cleat is perpendicular to the section advance direction. When 

the section advances parallel to the face cleat, only a 38-pct reduction in 

methane flow is observed. In the Upper Kittanning coalbed, emission rates 

were reduced 89 pct. 

Generally, the spacing of holes across the section should be less than 

twice the length of the grouted portion of the hole. All holes should be the 

same length approximately. The coalbed may be infused progressively as each 

hole is drilled, or all holes may be infused simultaneously. 

Maximum pressure 

(lb/in2) 

870 

1,140 

1,550 

2,200 

3,500 

Infusion pressures range from 300 to 2,200 1b/inzg. In the Pittsburgh 

coalbed, the mine water supply pressure is sufficient to infuse the coalbed. 

However, in other coalbeds, infusion pumps are necessary. 

Flow rate 

(gal/min) 

36 

27 

20 

14 

10 

Water infusion is effective in reducing respirable dust in the Pocahontas 

No. 3 and Upper Kittanning coalbeds. Tests in the Upper Freeport and Pittsburgh coalbeds were not conclusive because of large variations in dust 

measurements . 
REFERENCES 

1. Anderson, R. B., J. Bayer, and L. J. E. Hofer. Equilibrium Sorption 

Studies of Methane on Pittsburgh and Pocohontas No. 3 Seam Coal. 

Coal Sci., Advances in Chemistry, ser. 55, pp. 386-399. 

2, Becker, H. Seam Infusion in High-Speed Workings. Proc. Conf. Tech. 

Measures of Dust Prevention and Suppression in Mines, Luxemburg, 

I Oct. 11-13, 1972, pp. 273-281. 

3. Cervik, J. An Investigation of the Behavior and Control of Methane Gas. 

Min. Cong. J., v. 53, No. 7, July 1967, pp. 52-57. 

4. Cervik, J., H. H. Fields, and G. N. Aul. Rotary Drilling Holes in 

Coalbeds for Degasification. BuMines RI 8097, 1975, 21 pp. 

5. Certinbas, A., R. P. Vinson, J. Cervik, and M. G. Zabetakis. Methane and 

Dust Control by Water Infusion. Pittsburgh Coalbed (Fairview, W. Va.). 

BuMines RI 7 640, 197 2, 17 pp. 

6* - .Methane and Dust Controls for Longwalls: Pocahontas No. 3 Coalbed, Grundy, Va. BuMines RI 7849, 1974, 16 pp. 

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

Paper in Proceedings of the Symposium of the Bureau of ~ines/Industry 

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

BuMines IC 8621, 1973, pp. 73-81. 

8. Ducrocq, D. Low-Pressure Water Infusion. Proc.Conf.onTech.Measures of 

Dust Prevention and Suppression in Mines. Luxemburg, Oct. 11-13, 1972, 

pp. 283-295. 

9. Hamilton, R. J., and A. G. French. Dust Control for Face ~achines. 

Proc. Conf. onTech. Measures ofDust Preventionand Suppression in Mines, 

Luxemburg, Oct. 11-13, 1972, pp. 409-423. 

10. Kissell, R. N., and R. J. Bielicki. An In-Situ Diffusion Parameter for 

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

11. McCulloch, C. M., M. Deul, and P. W. Jeran. Cleat in Bituminous coalbeds. 

BuMines RI 7910, 1974, 25 pp. 

12. Morton, H. C. Try Water Infusion. Coal Min. and Processing, v. 4, No. 8, 

August 1967, pp. 48-50, 64-65. 

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

Edwards, Inc., Ann Arbor, Mich., 1st ed., 1946, pp. 468-472. 
14. Neels, P. V., and G. Dequildre. General Remarks on Advance Remote Infusion of Water in a Campine Colliery. Proc. Conf. on Tech. Measures of 

Dust Prevention and Suppression in Mines, Luxemburg, Oct. 11-13, 1972, 

pp. 318-328. 

15. Pot, F. Third Tech. Sess.--Dust Suppression During Mining. Proc. 

Conf. on Tech. Measures of Dust Prevention and Suppression in Mines, 

Oct. 11-13, 1972, Luxemberg, p. 264. 

16. Schlick, D. P. Respirable Dust Control in Mines in West Germany. 

BuMines IC 8490, 1970, 16 pp. 

17. Williamson, T. N. Evaluation of Horizontal Drilling Techniques in Coalbeds. BuMines Open File Rept. 34-72, 1970, 131 pp. Available for 

reference at BuMines Libraries in Twin Cities, Minn., Denver, Colo., 

Spokane, Wash., Pittsburgh., Pa., and Central Library, U.S. Department 

oL the Interior, Washington, D.C. 

U.S. GOVERNMENT PRINTING OFFICE: 1977-703-001 90