Bureau of Mimes Report of Invastigatioas/l975 

Measuring the Methane Content 

of Bituminous Coalbeds 
Report of Investigations 8043 

Measuring the Methane Content 

of Bituminous Coalbeds 

By C. M. McCulloch, J. R. Levine, F. N. Kissell, and Maurice Deul 

Pittsburgh Mining and Safety Research Center, Pittsburgh, Pa. 

UNITED STATES DEPARTMENT OF THE INTERIOR 

Rogers C. B. Morton, Secretary 

Jack W. Carlson, Assistant Secretary-Energy and Minerals 

BUREAU OF MINES 

Thomas V. Falkie, Director 
CONTENTS 

Page 

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

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

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

Previous work ............................................................ 2 

Collection and desorption of coal samples ................................ 3 

Drilling and coring ................................................. 3 

Measuring desorbed gas ............................................... 3 

Calculating "lost" gas .............................................. 5 

Estimating "residual" gas ........................................... 6 

Application of direct method ............................................. 9 

Conclusions .............................................................. 10 

References ............................................................... 12 

Appendix A.--Description of equipment .................................... 13 

Appendix B . -- Example of calculations for a coal core sample from the 

Pittsburgh coalbed. Greene County. Pa .................................. 14 

Appendix C.--"Lost1' gas charts for coal core samples ..................... 17 

Appendix D.--Data on degasification samples .............................. 22 

ILLUSTRATIONS 

Diagram of desorption equipment .................................... 4 

Decline curves for Pittsburgh and Beckley coals .................... 4 

Desorption curves for Pittsburgh and Pocahontas No . 3 coals ........ 6 

"Lost" gas graph for Pocahontas No . 3 coalbed ...................... 6 

"Lost" gas plus desorbed gas versus "residual" gas ................. 7 

Percent "residual" gas versus fixed carbon percent ................. 8 

Percent "residual" gas versus Hardgrove index ...................... 8 

Percent "residual" gas versus depth of coal ......................... 9 

Gas content of coal versus actual mine emission .................... 10 

"Lost" gas curve for Pittsburgh coalbed sample ..................... 16 I I Lost" gas emission curves: Samples from the Mary Lee. Beckley. 

Blue Creek. and Pittsburgh coalbeds .............................. 17 I I Lost" gas emission curves: Samples from the New Castle. Blue 

Creek. Pittsburgh. and Beckley coalbeds .......................... 18 It Lost" gas emission curves: Samples from the Pittsburgh and 

Hartshorne coalbeds .............................................. 19 

"Lost" gas emission curves: Samples from the Illinois No . 6. 

Pocahontas No . 3. Illinois No . 5. and Castlegate coalbeds ........ 20 11 Lost" gas emission curves: Samples from the Pond Creek. Beckley. 

and Sewell coalbeds .............................................. 21 

TABLES 

B.1 . Pittsburgh coalbed. Greene County. Pa .............................. 15 

B.2 . Data for "lost" gas graph .......................................... 16 
MEASURING THE METHANE CONTENT OF BITUMINOUS COALBEDS 

by 

C. M. McCulloch, J. R. ~evine,' F. N, Kissell, 2 and Maurice Deul3 

ABSTRACT 

The methane content of virgin bituminous coalbed can now be measured 

accurately in the field with exploration core samples from vertical boreholes. 

The gas content of the coal per unit weight can be used either to design a 

mine ventilation system or to determine if degasification of the coalbed will 

be necessary before mining, and to determine the gas resources in the coalbed. 

The equipment necessary to conduct the test costs less than $50. The gas content of the coal in place in the ground is determined by summing the gas lost 

from coring, gas measured during desorption, and the residual gas in the coal. 

Upon removal from the borehole, the core sample is placed in an airtight 

container and desorbed for several weeks until the desorption rate is below 

0.05 ~n?/~ for 5 consecutive days. The gas lost from the core while it was 

being cored and the residual gas are estimated by a new graphical method. 

The amount of gas remaining depends upon whether the coal is friable or 

blocky. Friability appears to relate to the depth of the sample below the 

surface, fixed carbon percentage, Hardgrove grindability index, and proximity 

to tectonic disturbance. Friable coals emit nearly 96 pct of the total gas 

during desorption whereas a blocky coal emits only 60 pct of its total gas. 

Coalbeds that are ill defined as to their blocky or friable nature must be 

tested in the laboratory for unambiguous analysis. 

INTRODUCTION 

The large volumes of methane gas emitted in underground coal mines from 

the coal and surrounding rock constitute a serious fire and explosion hazard that 

can necessitate costly shutdown of machinery and requires constant ventilation 

of the working area. A major objective of the Bureau of Mines Health and 

Safety program has been to develop cost effective means for preventing and 

predicting hazardous accumulations of methane in underground mine workings. 

lGeologist. 

Physical research scientist. 

3~esearch supervisor. 
This approach attempts to predict in advance the amount of gas that a 

specific coalbed would emit during mining. If this amount is known, plans 

may be made for the proper ventilation needed to handle the gas or for the 

design of an adequate degasification plan. Kissell, McCulloch, and 

Elder (5)4 have investigated two methods for making such predications : 

(1) An "indirect" method that measures the gas pressure at the bottom of a 

drill hole in the coalbed, and (2) a "direct" method that measures the gas 

released by a coal core extracted from the coalbed and degasified in an 

airtight container. 

The direct method has been found to be accurate, simple, and inexpensive. 

It can easily be incorporated into the standard exploration procedures used 

to evaluate coal property. The necessary equipment costs less than $50. The 

revised direct method also provides a simplified procedure for estimating the 

quantities of residual gas. 

ACKNWLEDGME NTS 

The authors thank the officials of the mining companies who supplied the 

coal cores that were necessary for this study. The staffs of the following 

companies were helpful in the collection of data: Carbon Fuel Co., Consolidation Coal Co., Inland Steel Co., Island Creek Coal Co., Jones & Laughlin 

Steel Corp. , New River Coal Co., Pickands-Mather Co. , United States Pipe and 

Foundry, United States Steel Corp. , and Youngstown Sheet and Tube Corp. 

The authors also thank Bruce Bevins of the Chesapeake and Ohio Railway 

Co., Huntington, W. Va. ,Richard Laprairie of Consolidation Coal Co. , Bluefield, 

W. Va., and Ralph Gray of the U.S. Steel Research Laboratory, Monroeville , Pa. , for thoroughly reviewing the manuscript and offering many helpful suggestions 

for its improvement. 

The authors especially thank Sylvester Sudduth of the Federal Bureau of 

Mines, Pittsburgh Mining and Safety Research Center, Pittsburgh, Pa., for his 

assistance in degasifying the coal cores in the laboratory. 

PREVIOUS WORK 

The direct method was first used in France by Bertard , Bruyet , and 

Gunther (4) in 1970. Horizontal holes were drilled into the virgin coalbed 

from the working face, and the cuttings were collected and sealed in a container. The gas emitted in the container was measured wer a period of weeks 

until desorption stopped. The main difficulty with the direct method was 

that it offered no simple way to calculate this residual gas in the coal 

sample after it had ceased to desorb gas. Bertard used a laboratory procedure 

in which the coal was crushed to a fine powder and the residual emission 

measured. 

In 1973, Kissell, McCulloch, and Elder @) developed a variant of the 

direct method in which cores were obtained from vertical boreholes and the 

'underlined numbers in parentheses refer to the items in the list of 

references preceding the appendixes. 
methane in the coal was estimated. Now Kissell's method has been modified to 

eliminate laboratory determination of the "residual" gas and to provide a 

graphical solution for determining it. 

COLLECTION AND DESORPTIaJ OF CQAL SAMPLES 

Drilling and Coring 

All core samples used in this project were taken from holes drilled 

vertically from the surface to intersect the coalbed. The procedure presented 

here are similar to those in BuMines Report of Investigations 7767 (6) with 

some modifications. 

The diameter of the hole and the time required to drill to the top of 

the coalbed are not important. The hole can be cored from the surface or 

drilled to the top of the coalbed and then cored. The core diameters ranged 

from 1-1/8 to 4-1/2 inches. The cooling medium used in coring can be air, 

mist, water, or mud. The only difference this makes is in the calculations 

of the "lost" gas. The hole can be either cased or uncased. Once the coal 

is cored, the core barrel should be removed without delay and the core placed 

in the container immediately upon removal from the core barrel to minimize 

the lost gas. The O-ring seal on the container must be inspected before the 

container is sealed to make sure it is free from coal particles that would 

prevent an airtight seal. 

This determination can be conducted successfully with only 100 grams of 

coal, but errors of measurement will be less for larger (1,000 grams or more) 

samples. More than one sample may be taken from a single core, and several 

desorption tests can be run simultaneously. 

Measuring Desorbed Gas 

Once the sample has been sealed in the container, the gas pressure 

builds up and should be released periodically. To prevent leakage, the pressure in the container should not exceed the strength of the seal. The 

strength of the seal varies with the type of container used, but the pressure 

should not exceed 9 lb/i* . The initial emissions of gas from the coal are 

the largest; the emission rate decreases slowly as desorption time increases. 

The first few readings should be taken at short intervals, as often as every 

10 min for a very gassy coal (see appendix B). Within a few days, the 

emission rate becomes low enough to require only one reading per day. Because 

the gages used are often not very sensitive or accurate at low pressures, gas 

should he released at least once a day, even if the gage does not register any 

pressure at all. Because the temperature at which the sample is kept can 

affect the emission rate, the coal should be kept at a fairly constant temperature (approximately 70" F) throughout desorption. 

To measure emission, the desorbed gas is conducted through a tube 

attached securely to the valve head into an inverted graduated cylinder 

filled with water (fig. 1). When the valve is opened, gas flows into the 

cylinder until atmospheric pressure is attained in the container. The water 
level is read before and after the gas is released. The volume of water displaced is equal to the volume of gas emitted. The valve is then closed 

securely until the next reading. To insure an airtight seal on the valve, the 

tube is removed and a cap is placed over the valve stem. This is done because 

a needle valve can become worn with repeated use and allow gas to escape. 

After each reading, the date, time, volume of gas released (cm3), and the emission rate (cm31g/day) are 

recorded. It also is useful 

to keep a running total of 

30 lb/in2 g the gas emissions. 

To calculate the gas 

emissions, the weight of the 

sample must be known to the 

nearest gram. The cylinder 

with valve and fittings is 

weighed before the coal 

sample is added and again 

before the sample is removed. 

The difference between the 

two weighings gives the 

weight of the coal sample. 

The daily emission rate 

(cm3 /g) should be calculated 

by dividing the daily emisFIGURE 1. - Diagram of desorption equipment. sion by the sample eight.^ 

51f the emission is unmeasured for several days, it 

mustbe averaged over that 

number of days. For - example, if a sample is 

left over the weekend, - measured on Monday, and 

150 cm3 of gas are - released, the average 

daily emission for Satur- 

- day, Sunday, and Monday 

will be 50 cm3. This is 

- important because the emission rate decreasesas the 

pressure builds up, and - 

consequently the average 

over several days may be 

deceptively low. For 

example, if the container 

is left for 5 days and the 

emission rate averages 

5 9 13 17 21 25 29 33 37 41 0.04 cm3 /g, measurements 

TIME, days should not be discontinued because the next FIGURE 2. - Decline curves for Pittsburgh and Beckley single day's emission 

coals. might exceed 0.05 cm3 Ig. 
When the daily emission is less than 0.05 cm3/g for 5 consecutive days, 

measurements should be discontinued, and the "residual" gas should be estimated by the procedure described later. 

Figure 2 shows the decline curves for samples from the Pittsburgh and 

Beckley coalbeds. Irregularities in the curve are due mainly to changes in 

the temperature and the irregular intervals at which measurements were made. 

Level areas on the curve correspond to a reading taken after several days and 

averaged wer that number of days. 

Calculating "Lost" Gas 

The core sample actually begins giving off gas before it is placed in the 

container. This amount of "lost" gas depends on the drilling medium and the 

time required to get the core into the container. If air or mist is used as 

the cooling medium, it is assumed that the coal begins giving off gas inunediately upon penetration by the core barrel. With water or mud, desorption is 

assumed to begin only when the core is halfway out of the hole; that is, when 

the gas pressure is assumed to exceed that of the hydrostatic head. 

The "lost" gas can be calculated quite accurately because for the first 

few hours of emission, the amount given off is proportional to the square root 

of the desorption time. A plot of the total emission after each reading 

against the square root of the tim that the sample has been desorbing produces a straight line. After approximately 10 hours, the emissions are too 

irregular to predict . 

In figure 3, two very different coals (Pittsburgh and Pocahontas No. 3) 

showed similar behavior although their desorption rates were different. These 

samples were gasified under pressure in the laboratory (6) and then degasified. 

Hence, there was no "lost" gas time for these samples. Both samples weighed 

approximate ly 1,000 grams. 

The Pocahontas No. 3 coal, which is friable, gave off gas much more 

quickly than the blocky Pittsburgh coal, and the curve for the Pocahontas coal 

is much steeper. 

If degasification were prolonged, the points would begin to deviate to 

the right of the line defined in the first few hours (figs. C-1 through C-5 

given in appendix C). Therefore, the sample should be placed in the container 

as quickly as possible so as to minimize "lost" gas time. 

If it is assumed that all coal samples behave like those in figure 3, 

such a graph can be plotted from the desorption data, starting when the sample 

is sealed into the container. When a sample is placed in the container, it 

has already been desorbing gas for several minutes. To calculate the correct 

slope for the sample, one must start at the point on the X axis equal to the 

square root of the "lost" gas time, fi. 

Figure 4 shows what the "lost" gas for the Pocahontas No. 3 sample of 

figure 3 might have been if it had been placed in the container 25 min after 
JTIME IN CANISTER, (mi&) TIME IN CANISTER +25, (mini) 

FIGURE 3. - Desorption curves for Pittsburgh FIGURE 4. - "Lost" gas graph for Pocaand Pocahontas No. 3 coals. hontas No. 3 coal bed. 

it began giving off gas. Since $e = = 5, the first point is plotted at 

5 (min1Ia ) on the X axis. For the next reading taken 5 min later, after 

300 cI$ of gas had been released, Jf = = 5.5 (min1 /a ) and so on, for 

at least 400 min (the square root of which is 20 min).= The line is then 

drawn back until it intersects the Y axis. This point is the amount of "lost" 

gas ; in this case, it was 1,500 cld . 

Estimating "Residua 1" Gas 

Even after the daily desorption rate is less than 0.05 cI$/g, the coal 

contains residual gas. How much depends on the fracture network that defines 

coal friability. To estimate the "residual" gas in the Bureau of Mines experiments (6), the procedure used in the past was to crush a sample of the coal 

eFor a more complete discussion see BuMines RI 7767. 
Y 

24 in a mechanical grinder to I I I I I 1 I - 

about 200 mesh inside a 

A - large sealed box filled with 

nitrogen. The residual 

20 - - methane, which desorbed rn quickly from the fine 

- - particles into this chamber, 

8 A A A was determined by gas 

- chromatography. 

KEY This method is 

A Friable coal 

o Blocky coal obviously not suited for 

- field use, and a much simpler 

graphical procedure was 

developed. Unfortunately , - no quantitative relationship, 

such as the one used for the - "lost" gas, is known. The 

bes,t relationship was found 

- by graphing the proportion 

of "residual" gas to - desorbed gas plus "lost" gas 

for the 20 samples analyzed - by gas chromatography 

(fig. 5). The two lines 

5X (one for blocky coals and 

RESIDUAL GAS, 1.000 cm3 one for friable coals) were 

determined by a least 

FIGURE 5. - "Lost" gas plus desorbed gas versus 6 6 

squares statistical 

residual" gas. evaluation .7 

The blocky coals tend to release their gas more slowly and thus have much 

more "residual" gas than the friable coals at the end of measurement. The 

blocky coals (fig. 5) retained approximately 40 pct of their total gas, whereas 

the friable coals retain only about 6 pct. 

To evaluate the "residual" gas, using the graph in figure 5, one must 

first determine whether the sample is friable or blocky. Friable coals are 

?An alternative solution to calculating the "residual" gas, other than 

graphically, is the placement of several largk ball bearings in the 

canister while it is being filled with the coal sample. By rotating the 

cylinder on any suitable tumbler after desorption of the sample, the coal 

would be crushed and the remaining gas given off . This method was 

determined by Mr. Bruce Bevins of the Chesapeake and Ohio Railway Co. 

It would require slight modification of the equipment (the cylinder would 

have to be made of steel not aluminum as was the cylinder in this study). 

The only drawback is that the sample would be crushed to a powder (approximately 100 mesh), but if the crushing of the sample is not detrimental 

then this method would be an excellent alternative. 
FIGURE 6. - Percent "residual" gas versus fixed 

70 

d 

m 

2604 " 

n 

W 

x 

LL 50- 

carbon percent. 

KEY - 

Frioble cools A Friable coal 

A 0 ~~ocky coal 

- -.--- ' -.---.-.-.-- 0 0 

0 0 0 0 

~locky coals o - 0 

I I I I I I 

KEY 

A Friable cool 

0 Blocky coal 

d 10 20 30 - 40 50 60 70 

RESIDUAL GAS, pct 

FIGURE 7. - Percent "residual" gas versus 

Hardgrove index. 

40 

easily degraded into small 

pieces, whereas blocky coals 

will generally break into 

larger pieces. Typically, 

Pittsburgh coal, which is 

blocky, has a cleat spacing 

of 1 inch; whereas Beckley 

coa 1, which is friable , has 

a cleat spacing of 1/16 inch. 

Why coals are friable is not 

completely understood. Friability appeared to be 

related to the fixed carbon 

(fig. 6), Hardgrave grindability index (fig. 7), the 

depth of the coalbed beneath 

the surface (fig. 8), and 

degree of tectonic activity. 

The fixed carbon percentage 

appears to be the best indicator of friability. All 

blocky coals tested had less 

than 57 pct fixed carbon; 

all friable coals had more 

than 57 pct. 

I 1 I I 1 I 

The Hardgrove grindability index measures the degree 

to which a 16- by 30-mesh 

sample of coal can be pulverized to a fine powder under 

specific tests conditions 

(7). It is a reasonably 

good indicator of friability 

(fig. 7). Except for 

Alabama coals, all the 

Hardgrove grindability 

indexes were less than 70 

for all blocky coals tested 

and more than 70 for all 

friable coals tested. 

0 10 20 30 40 50 60 

RESIDUAL GAS, pct 

Although -depth alone 

is not a good indicator, it - 

supports the correlation of friability with Hardgrove index and fixed carbon 

percentage. Most of the blocky coals were from shallow depths, less than 

800 feet below the surface, and all of the friable coals were from depths 

below 600 feet. Some coals, like the Mary Lee coals, behave like friable 

coals in spite of low Hardgrwe indexes and low fixed carbon percent because 

of the degree of deformation. The Mary Lee coals, obtained from the heavily 

faulted Warrior Basin, were so badly broken that it was often difficult to 

recover core samples. 
APPLICATION OF DIRECT METHOD 

The sum of "lost" gas, desorbed gas, and "residual" gas yields the total 

gas content of a coal sample. The gas content in cubic centimeters per gram 

Coalbeds, like the 

Pittsburgh, known to be 

blocky may well have different characteristics at 

greater depth, and one must 

be prepared to deal with 

transitional zones in coalbeds occurring in widely 

different terrains. A friable Pocahontas coal may be 

friable even under very 

little cwer. The relationships discussed here are 

best applied where the friable or blocky nature of 

the coal is well defined; 

where there is no clear 

definition, the "residual" 

gas will be best determined 

in the laboratory. 

Having determined 

whether the coal is blocky 

(lower line, fig. 5) or friable (upper line, fig. 5), 

add the quantities of "lost" 

and desorbed gas and find 

the point on the Y axis that 

corresponds to this sum. 

Follow this line over until 

it intersects the corresponding friable or blocky line 

on the graph. The quantity 

of "residual" gas can then 

be read directly on the X 

axis. For example, if a 

2.4 

2.0 

+ 1.6 YO 

0 

4 - 

-i 

a 8 1.2 

& 

I 

kA w 

0 

.8 

.4 

0 

RESIDUAL GAS, pct sample of a friable coal 

desorbed 8,000 cu? gas, and 

FIGURE 8. - Percent "residual" gas versus depth d coal. 500 em3 was lost the total 

of 8,500 cd is found on the 

Y axis. This is projected horizontally to the friable line and from there 

vertically to the X axis to read 500 c$ "residual" gas. All the samples previously measured by the direct method (5) were checked against the graphically 

determined values. With the graph, the total gas was estimated with an 

accuracy of about f 11 pct for the blocky and about t4 pct for the friable 

coa 1s. 

I 1 I I , I I 

A 

A 

KEY 

- A Friable coal - 

o Blocky coal 

- - 

h - 

- - 

A~ 

A 

Friable coals @ A - -- ;ZST---~~. --- 

&A Blocky coals 

A 0 

0 

o - - 

- o 

I I I I a I I 

20 40 60 80 
CONCLUSIONS 

3.2- 

2.8 

2.4 

mz u2.6 

- 

1.6 f 

E 

5 

z 

LA ""1 

Z 

V, ° 

'P 

5 

W 

It has been shown that the methane content of a virgin coalbed can be 

estimated in the field using simple, low-cos t equipment. The "residual" gas 

can be evaluated graphically instead of by the complicated laboratory procedure used previously. The graphic method gives an acceptable level of 

accuracy provided that a distinction is made between friable and blocky coals. 

Friable coals tend to have a higher gas content and to emit gas more quickly 

than blocky coals. Whether coal is blocky or friable correlates with depth 

of burial, rank, cleat spacing, and proximity of tectonic disturbances. 

*Taken from BuMines RI 7767, for more complete discussion see RI 7767. 

, , I I I may be converted to cubic feet per ton 

using the conversion factor of 32. For - - 

- Beatrice mine - 

- 7 - 

/ - - 

- - / 6Howe mine 

- - 

Loveridge - - mine3 4 Federal No.2 mine 

- - 

- - / - / - 

- 

- -8"esta mine - 

- Mary Lee No.1 mlne 

- Inland mine 

I I I I. 

0 4 8 12 

example, 5 cd/g is equal to 160 ft3/ton. 

The total methane content of any 

coalbed area can be calculated by multiplying the total tonnage estimated for 

that area by the methane content per 

unit weight determined by the direct 

method. This is useful for resource 

evaluation where the methane may be 

recovered or for estimating ventilation 

requirements for mines (fig. 9) .* These 

data indicate that the methane emitted 

from a mine can be estimated using the 

results of the direct method. The 

me thane emission from a mine in cubic 

feet per ton of coal mined is greater 

than the calculated cubic feet of 

methane per ton of coal in place. This 

is because the rib and face coal, roof, 

floor, pillars, gob areas, and old workings all give off gas in addition to 

small amounts of gas emitted from the 

l6 extracted coal (I). 

DIRECT METHOD, ~rn3/~ 

In figure 9, cubic feet of methane 

FIGURE 9. - Gas content of coal versus ac- emitted per ton of coal mined is plotted 

tual mine emission, adapted versus the methane content of the sample. 

from reference 6. The correlation is good for mines that 

are large and deep, have a sustained 

coal production of at least several thousand tons a day, and have been in 

operation for a number of years. New mines emit less methane per ton of coal 

mined than older mines with extensive old workings and gob areas that still 

bleed gas. Hence an es t imate using figure 9 may be too high for a new mine, 

but after the mine has been worked for some time, the emission will approach 

the relationship in figure 9. 
Based on the calculated methane contentlunit weight, the total gas 

content of the coalbed for a mine property can be estimated. Additionally, 

an estimate may be made as to the amount of gas that a mature mine may be 

expected to emit. These figures may be used to design a suitable ventilation 

system for a given mine or to establish the need for degasification in advance 

of mining. 
REFERENCES 

1. Aresco, S. J. , C. P. Haller, and R. F. Abernethy. Analysis of Tipple 

and Delivered Samples of Coal (Collected During the Fiscal Year 1956). 

BuMines RI 5332, 1957, 67 pp. 

2. - .Analysis of Tipple and Delivered Samples of Coal (Collected 

During Fiscal Year 1957). BuMines RI 5401, 1958, 59 pp. 

3. - .Analysis of Tipple and Delivered Samples of Coal (Collected 

During Fiscal Year 1958). BuMines RI 5489, 1959, 54 pp. 

4. Bertard , D. , B. Bruyet , and J. Gunther . Determination of Desorbable Gas 

Concentration of Coal (Direct Method). Internat. J. Rock Mech. and 

Min. Sci., v. 7, 1970, pp. 43-65. 

5. Kissell, F. N. The Methane Migration and Storage Characteristics of 

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

BuMines RI 7667, 1972, 22 pp. 

6. Kissell, F. N., C. M. McCulloch, and C. H. Elder. The Direct Method of 

Determining Methane Content of Coalbeds for Ventilation Design. 

BuMines RI 7767, 1973 , 17 pp. 

7. Kissell, F. N., and M. Deul. Effect of Coal Breakage on Methane Emission. 

SME Trans. , v. 256, June 1974, pp. 182-184. 

8. McCulloch, C. M. , M. Deul, and P. W. Jeran. Cleat in Bituminous Coalbeds. 

BuMines RI 7910, 1974, 25 pp. 

9. Mitchell, D. R. (ed. by). Coal Preparation. AIME, New York, 1950, 

p. 43. 

10. U.S. Bureau of Mines. Analysis of Tipple and Delivered Samples of Coal 

(Collected During Fiscal Year 1969). BuMines RI 7346, 1970, 29 pp. 

11. . Analysis of Tipple and Delivered Samples of Coal (Collected 

During Fiscal Year 1971). BuMines RI 7588, 1972, 20 pp. 

12 Van Krevelen, D. W. , and J. Schuey . Coal Science (Aspect of Coal 

Constitution). Elsevier Pub. Co. , Amsterdam, 1957, pp. 273-275. 
APPENDIX A. --DESCRIPTION OF EQUIPMENT 

One of the main advantages of the modified "direct" method is the 

simplicity of the equipment. All that is needed is an airtight container that 

can withstand up to 30 lb/ir?g, a valve fitting for the container, flexible 

tube, graduated cylinder, ring stand, clamp, and pan. This can all be built 

or bought for about $50 and can be used repeatedly. 

In the Bureau experiments, containers were fabricated from 4-inch 

aluminum pipe. The bottom of the pipe was sealed shut. A flange was welded 

to the top, and a lid was sealed on with an O-ring in the flange. The lid was 

also equipped with a gage and a valve. The container was checked at a pressure of 30 lb/ir?g for several days to make sure there were no leaks. A 

standard needlepoint valve was used with a sealing cap abwe the valve on 

the stem. 

Any flexible tubing can be used to run from the valve stem to the 

graduated cylinder that is filled with water and inverted in a pan approximately 2 inches deep. The cylinder (250, 500, or 1,000 ml) is held 314 to 

1 inch above the base of the pan by a ring stand and clamp (fig. 1). The 

tube is run into the pan and up into the cylinder. The valve should be 

opened slowly so that the flow of gas from the container to the cylinder is 

gradual. The use of plastic cylinders is reconmended in the field. 
APPENDIX B. --EXAMPLE OF CALCULATIONS FOR A CML CORE SAMPLl3 

FROM THE PITTSBURGH COALBED, GREENE COUNTY, PA. 

1. Cori- and Collection of Samples 

Coring began at 11:15 a.m.; an NX core barrel (2-1/8-inch ID) was used with 

water as a drilling medium. At 12:12 p.m., the coal was intersected at a depth of 

675 feet. Coring was continued through the coal and finally stopped at 12:28 p.m. 

At 12 :35 p.m. , the core started out and at 12 :40 p.m. , it was on the surface. Two 

6-inch pieces were cut from the top and bottom of the core and placed in separate 

cylinders, which were sealed at 12:52 p.m. From this time onward the emission was 

monitored . Since the hole was drilled with water, it is assumed that the coal began giving off gas halfway out of the hole (approximately, 12:37 p.m.). Therefore, the 

"lost" gas time was (12:52-12:37) 15 min. 

(Note: If the core had been drilled with air or mist the "lost" gas time 

would have been (12:52-12:12) 40 min.) 

Sampleweight =(cannister+sample)weight- canisterweight=1,382grams ofcoal. 

2. Desorption of the Coal in the Container 

Gas was released fran the container about every 15 min for the first few hours, 

and then once a day for 34 days until the emission rate per day had fallen below 

0.05 cn? /g for 5 consecutive days. At this time, 3,603 cU? of gas had been desorbed 

(table B-1). 

3. Calculation of "Lost" Gas (fig. B-1) 

Since the "lost1' gas time was 15 min, the first measurement of zero is at 

= 3.87 (min1/ 2 ) . Fifteen minutes later the valve was opened and 92 cn? of gas 

released. Therefore, the second point is at Jm = 5.48 (min1/ a ) and 92 cu? . Fifteen minutes later, 84 cn? of gas were released. The third point is, therefore, 

at -3+lb = 6.71 (min1l2) and at 92-i-84 = 176 cm3. A table of all points used in 

the "lost" gas graph (fig. B-1) appear in table B-2. The graph shows a quantity of 

240 cn? "lost" gas. 

4. Calculation of "Residual" Gas 

Desorbed gas + "lost" gas = 3,603+240 = 3,843 cn? . This point is found on the 

Y axis of figure 5, taken over to the blocky coal line and read down to the X axis 

as 2,450 cn? of "residual" gas. The sample was actually crushed and released 1,617 

cU? "residual" gas. This difference of 833 cd' , 15 pct of the total, is relatively 

large but acceptable. 

5. Final Results 

Total gas = "lost" gas + desorbed gas, + "residual" gas = 240 + 3,603 + 1,617 

= 5,460 cn?, and total gas/sample weight = 59460 = 3.95 cm3 lg. Using the conversion 

factor of 32, this represents 126 ft3/ton for a virgin coalbed. Based on figure 9, 

this would correspond to 800 ft3 of gas per ton of coal mined, and a mine producing 

2,000 tons of coal per day would require ventilation for 1.8 MMft3 of gas. 
TABLE B-1. - Pittsburgh coalbed, Greene County, Pa. 

Started coring coal. ............................................... 12:12 p.m. 

Started out of hole ................................................ 12:35 p.m. 

Began giving off gas........................ ....................... 12:37 p.m. 

Core at surface.......................... ....................... 12:40 p.m. 

Core in canisters................. ................................. 12:50 p.m. 

Weight of sample ............................................g rams.. 1,382 

Total gas, cd 

9 2 

Date 

04-17 

04-18 

04-19 

04-20 

04-21 

04-22 

04-23 

04-24 

04-25 

04-26 

04-27 

04-28 

04-29 

04-30 

05-01 

05-02 

05-03 

05-04 

05-05 

05-06 

05-07 

05-08 

05-09 

05-10 

05-11 

05-12 

05-13 

05-14 

Desorbed 

"Lostt' gas ............................................... cd.. 

"Residual" gas.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . cn? . . 3 Total.......................................... cm .. Gas content of coal .................................... c$/g., 

lAverage reading. See footnote 5 in.text. 

Time 

1:05 p.m. 

1:20 p.m. 

1:35 p.m. 

1:50 p.m. 

2:05 p.m. 

2:20 p.m. 

4:00 p.m. 

10:15 a.m. 

8:10 a.m. 

3:45 p.m. 

No reading 

No reading 

8:30 a.m. 

8:00 a.m. 

11:lO a.m. 

8:00 a.m. 

8:40 a.m. 

No reading 

No reading 

8:15 a.m. 

8:40 a.m. 

3 :25 p.m. 

9:45 p.m. 

3:20 p.m. 

No re ad ing 

No reading 

3:09 p.m. 

No reading 

2:45 p.m. 

No reading 

2:10 p.m. 

No reading 

No reading 

10:30 a.m. 

8:30 a.m. 

gas 

Gas released, cd 

92 

84 

34 

3 6 

40 

33 

232 

670 

300} 375 

7 5 

- 

- 

508 

158 

83 

64 

124 

- 

- 

330 

123 

90 

0 

5 5 

- 

- 

5 6 

- 

140 

- 

90 

- 

- 

133 

50 

............................................. 

Emission rate, cd /g/day 

- 

- 

- 

- 

- 

- 

1,202 

485 

27 1 

- 

- 

123 

I114 

6 0 

46 

90 

- 

- 

I80 

89 

6 5 

0 

40 

- 

- 

14 

- 

I51 

- 

I33 

- 

- 

I32 

36 

cd.. 
TABLE B-2. - Data for "lost" pas praph 

"Los t I' gas time : 

Placed in canister... ................................................ 12:52 

Began emission. ...................................................... 12:37 

Minutes.................. ............................................ 15 

Reading 

1 

2 

3 

4 

5 

6 

7 

8 

5 

4 

3- 

r+) 

E 

U 

0 2- 

0 - 

cn" 

(3 

0 

W 

rn 

a 

o vI w a -I3~ 

Gas re leased, cn? 

0 

9 2 

84 

34 

36 

40 

33 

23 2 

* I 1 I I I 

- - 

0 - 

0 

Pittsburgh coalbed 0 

I0---- ------- 

1 / I / m(rnin2) - I ! - 

/ 

/ 

>Lost gas. 240 cm3 

/ 

- 

I I I I I 

2 4 

Time 

12 :50 

1:05 

1:20 

1:35 

1:50 

2 :05 

2:20 

4 :OO 

Total gas , cg 

0 

92 

176 

2 10 

246 

2 86 

3 19 

55 1 

- I* 10 12 

-, (rnin2) 

FIGURE B-1. - "Lost" gas curve for Pittsburgh 

coalbed sample. 

Time since 

placed in 

can, min 

0 

15 

30 

45 

60 

75 

90 

190 

/Time in can+lb 

(min1 1" ) 

3.87 

5.48 

6.71 

7.75 

8.66 

9.49 

10.25 

14.32 
APPENDIX C.--"LOST" GAS CHARTS FOR COAL CORE SAMPLES 

Figure C-1 presents the "lost" gas emission curves for samples from the 

Mary Lee, Beckley, Blue Creek, and Pittsburgh coalbeds. Figure C-2 presents 

the "lost" gas emission curves for samples from the New Castle , Blue Creek, 

Pittsburgh, and Beckley coalbeds. Figure C-3 presents the "lost" gas emission 

curves for samples from the Pittsburgh and Hartshorne coalbeds. Figure C-4 

presents the "lost" gas emission curves for the samples from the Illinois 

No. 6, Pocahontas No. 3, Illinois No. 5, and Castlegate coalbeds. Figure C-5 

presents the "lost" gas emission curves for samples from the Pond Creek, 

Beckley , and Sewe 11 coa lbeds . 

I 

-I 

Lost gas, 850 cm3 

Blue Creek coalbed 

0 

-I (rninz) 

Lost gas, 870 cm3 

.8 

Beckley coalbed 

.4 

.2 

0 / I 

-. 2 / W4(minz) 

/ 

.4 / / 

/ Lost gas, 850 cm3 -=- / 

/ 

.8 

. 2b&~ost gas. 240 crn3 4 

FIGURE C-1. - "Lost" gas emission curves: Samples from the Mary 

Lee, Beckley, Blue Creek, and Pittsburgh coalbeds. 
FIGURE C-2. - "Lost" gas emission curves: Samples from the New Castle, Blue Creek, 

Pittsburgh, and Beckley coalbeds. 

- I I I I I 

- 

- 

Beckley coalbed 

0-- / // Y.: 

/ - 

/ I 

- / / VX5irni4)- 

/ 

/' ' Lost gas, 1,880 cm3 - 

I.=-/ / - 

I I I I 1 1 

0 

0 2 4 6 8 1012140 2 4 6 8 101214 

2.0 

1.6- 

1.2- 

.8- 

.4- 

-.4- 

.a 

1.2- 

. 2.0, 

0.0.5 - 

Ui' .4- a 

13 

a .3 

W 

m 

E .2- 

0 

v, 

W .I 

a 

0 

-.I 

-'- 

.3 

.4- 

.5 

I I I I I 1 

- 

0 

- Pittsburgh coalbed 0 - 

-Y 0 

- 

- - 

-- 

/ 

/ I 

- 1 VFE(rnin3) - / 

/ 

- ' Lost gas, 240 crn3 

1. 

- - 

- 

+ I I I I I I 
0 

- 

- 

- 

/ - I 

/ 

-.4- / 

/ VGZZ (min*) - 

/ 

.84~ Lost gas, 810 cm3 - 

- 

- 

- 

- I ' 6Z6(rnin21 -.5 - 1 

/ 

/ 

Lost gas, 

1.0fk,175 cm3 

- 

Pittsburgh 

coal bed 

--. 

-.I - i - 

1 

- 

-* 2:r"r: 1 I - - 

.9 7 I GE (rninz) - 

bLost gas, 960 cm3 

1 .o I I I I 4 

FIGURE C-3. - "Lost" gas emission curves: Samples from the Pittsburgh and 

Hartshorne coalbeds. 
FIGURE C-4. - "Lost" gas emission curves: Samples from the Illinois No. 6, Pocahontas 

No. 3, Illinois No. 5, and Castlegate coalbeds. 
.04 - / - 

/ 

ost gas, 85 cm3 - 

- 

- 

- .IOi I I I I I I 

2.4 111111 

- - 

2.0 - 

- Beckley coalbed 

- 

- 

- 

/ 

Lost gas, 640 cm3' 

- 

.8. I I I 

2.411r111, 

1.6 - 

/ GZZ(minP) 

-.8 - / - 

/ - 

Lost gas. 220 cm3 

- 

2.0'I'I1l * 02 4 6 8 1012 14 

FIGURE C-5. - "Lost" gas emission curves: Samples from the Pond Creek, 

Beckley, and Sewell coalbeds. 
APPEN'DIX D.--DATA ON DEGASIFICATION SAMPLES 

C oa lbed 

Blocky coals: 

Pittsburgh .......... Do ................ Do ..................... Do ................ Do ..................... Castlegate No . 3 .... Illinois No . 5 ...... Illinois No . 6 ........... Pond Creek .......... Do ..................... Friable coals: 

Sewell .............. Beckley .................. Do ..................... Do ..................... Do ..................... Mary Lee ............ Blue Creek ............... Do ..................... New Castle ............... Pocahontas No . 3 .... Do ................ 

Loca ti an 

Washington County. Pa ..... Marion County. W . Va ...... do ................... Greene County. Pa ......... do ................... Carbon Fuel Co .. Utah ..... Jefferson County. I11 ..... do ................... Pike County. Ky ........... do ................... 

Raleigh County. W . Va ..... do ................... do ................... do ................... do ................... Tuscaloosa County. Ala .... do ................... do ................... do ................... Wyoming County. W . Va ..... Buchanan County. W . Va .... 

Depth of 

sample. feet 

427 

850 

850 

675 

675 

1. 016 

7 93 

733 

500 

150 

680 

990 

875 

830 

740 

1. 076 

2. 185 

1. 099 

2. 137 

762 

1. 430 

Gas content. 

C* 1% 

2.93 

6.50 

6.57 

3.95 

6.50 

4.69 

.98 

1.92 

1.28 

.70 

9.34 

12.55 

14.13 

15.36 

13.71 

6.55 

16.24 

13.56 

16.42 

8.90 

13.62