5C. Flores Coal Bed Methane From Hazard to Resource

Ž .International Journal of Coal Geology 35 1998 3–26

Coalbed methane: From hazard to resource

Romeo M. Flores )

US Geological SurÕey, DenÕer, CO 80225, USA

Received 14 April 1997; accepted 1 May 1997

Abstract

Coalbed gas, which mainly consists of methane, has remained a major hazard affecting safetyand productivity in underground coal mines for more than 100 years. Coalbed gas emissions haveresulted in outbursts and explosions where ignited by open lights, smoking or improper use ofblack blasting powder, and machinery operations. Investigations of coal gas outbursts andexplosions during the past century were aimed at predicting and preventing this mine hazard.

ŽDuring this time, gas emissions were diluted with ventilation by airways e.g., tunnels, vertical.and horizontal drillholes, shafts and by drainage boreholes. The 1970’s ‘energy crisis’ led to

studies of the feasibility of producing the gas for commercial use. Subsequent research on theorigin, accumulation, distribution, availability, and recoverability has been pursued vigorouslyduring the past two decades. Since the 1970’s research investigations on the causes and effects ofcoal mine outbursts and gas emissions have led to major advances towards the recovery anddevelopment of coalbed methane for commercial use. Thus, coalbed methane as a mining hazardwas harnessed as a conventional gas resource. q 1998 Elsevier Science B.V.

Keywords: coal gas outburst; coalbed methane; hazard; resource assessment; recoverability

1. Introduction

Coalbed gas has been considered a major mine hazard since the early to mid 19thcentury when the first documented coal mine gas explosions occurred in the UnitedStates in 1810 and in France in 1845. Since the late 20th century coalbed methane hasreceived increased emphasis as a potential energy resource. Coal beds contain a mixture

) Tel.: q1-303-2367774; fax: q1-303-2367738; e-mail: [email protected].

0166-5162r98r$19.00 q 1998 Elsevier Science B.V. All rights reserved.Ž .PII S0166-5162 97 00043-8

( )R.M. Floresr International Journal of Coal Geology 35 1998 3–264

of gases in which methane makes up 80–99% and varies from 0.0003–18.66 m3rmetricŽ 3 . 3ton 0.01 to )600 ft rton with heat combustion ranging from 8455 to 9345 calrm

Ž 3. Ž .950–1050 Bturft Kemp and Petersen, 1988 . Minor amounts of carbon dioxide,nitrogen, hydrogen sulphide, and sulphur dioxide make up the other components of

Žcoalbed gas. A minimum amount of gas is contained as ‘free gas’ in fractures cleat.system , but it mainly occurs as sorbed gas on micropore surfaces in the matrix of coal

beds. In addition, some of the coalbed gas migrates from the coal into adjacentsandstones. Early research investigations of coalbed gas have concentrated on technol-

Ž .ogy to control and manage gas outbursts and explosions Lama, 1995 . MethaneŽresearch in the United States was separate from health and safety research Deul and

.Kim, 1986 . Since the 1970’s when coalbed methane was determined to be aneconomically viable energy source, investigations have focused on understanding itsorigin, occurrence, distribution, availability, producibility, and recoverability.

Investigations of coalbed gas in the United States underground bituminous coal mines9 3 Žin the mid 1970’s showed a production of 7=10 m rd )200 million cubic feet per

. Ž .day or mmcfgpd of methane per day Skow et al., 1980 . Degasification of undergroundcoal mines by draining methane either by horizontal boreholes at the base of mine shaftsor by outside mine entries and vertical boreholes in advance of mining have led toconcerns about the contribution of methane to the ‘greenhouse effect’ of the atmosphere.During the course of investigations concerning the gas emissions into the atmosphere, ithas become apparent that methane from underground coal mines is a viable energysource. In the United States this effort was enhanced by pioneering work of government

Žagencies e.g. US Bureau of Mines or USBM, US Department of Energy or DOE, and.Gas Research Institute or GRI developing the technology to recover coalbed methane.

However, it was not until the vertical wells unrelated to mining operations, were drilledin the central Appalachian, Black Warrior, and San Juan Basins in mid 1970’s thatcoalbed methane was pronounced a viable commercial energy commodity.

The most important factor that has influenced the producibility of coalbed methane inŽthe United States is enactment of the ‘Crude Oil Windfall Profit Tax of 1980’ Soot,

.1988 . This tax-credit incentive was proposed for production of unconventional fuelsŽ . Ž .from: 1 oil shale and tar sands, 2 gas from biomass, geopressured brines, or

Ž . Ž .Devonian shale, 3 liquid, gaseous or solid synthetic fuels from coal, 4 someŽ .processed wood fuels, and 5 steam from some agricultural by-products. This produc-

tion tax credit permitted coalbed methane producers to receive $0.75 per million Btu ofgas sold in 1986, which rose to $0.78 per million Btu in 1987. This tax credit wasprojected to increase $1.34 per million Btu in 2001. However, in order to qualify for thetax credit, wells must have been drilled by 1990; production from these wells is eligiblefor credit until 2001.

Thus, the current focus on coalbed methane is on providing safe mining operations,Ž .utilization of methane as a unconventional energy source and resulting tax writeoff ,

and its effect on the environment. In the past this progression of interests provided avehicle for research investigations that led to coalbed methane becoming a significantpart of the energy resource and a target for exploration and development worldwide.This paper summarizes the historical and geological perspectives of the state ofknowledge and research advances in coalbed methane as a conventional energy resource.

( )R.M. Floresr International Journal of Coal Geology 35 1998 3–26 5

2. Historical perspective in coal mining

Historically, coalbed methane was vented to conduct safe mining operations in orderto increase mine productivity. Coalbed methane was not a problem when coal wasmined from outcrops by stripping and shallow shafting in the United Kingdom and otherEuropean countries. As shallow coal resources were slowly exhausted at the end of the18th century and technology was improved to permit construction of large deep mines,coalbed methane in these mines was observed. In the early 19th century, coal mineexplosions were recorded in Britain, France, and United States. In the late 19th and early20th century minor to major disastrous explosions were reported in deep undergroundcoal mines in Australia, Canada, Belgium, Germany, Japan, Poland, Russia, and United

Ž .States. In all these cases, poor gas ventilation or no gas drainage Diamond, 1994allowed coalbed methane to accumulate in amounts which could be ignited either byopen lights, smoking or improper use of black blasting powder, and sparking frommining equipment. In addition, coal dust propagated explosions through large sections of

Ž .the mines. Outbursts were described by Hargraves 1983 as violent projections of coal,gas, and rocks from the floor and roof away from the freshly exposed coal face duringmining operations. These phenomena may result in explosion if an ignition source is

Ž .present; however, they do not always result in an explosion. Campoli et al. 1985indicate that outbursts are caused by high coalbed gas pressure and structural stresscreated by the load on the mine and are generally not common in the United States.Outbursts are not only restricted to underground coal mines but also occur in salt,

Ž .potash, and other mines Gimm and Pforr, 1964; Mahtab, 1982; Styles, 1995 . However,

Fig. 1. A diagram showing the relationship of annual fatalities from coal-mine explosions and the influence ofmine safety research. During the period of 1900–1940, the first application of rock dusting, permissible use ofelectrical equipment, and improved ventilation were enforced. During the period from 1940–1980 the coalmine health safety, rock dust-coal analyzer, methane degasification, and explosion-proof bulkheads were

Ž .enforced modified from Deul and Kim, 1986 .


these violent failures are more prevalent and pronounced in underground coal minesbecause of the development of high pressures and large quantities of methane, carbondioxide or both stored in the coal. For instance in 1981, the largest ever underground

3 Ž 3.coal-mine outburst in Japan expelled 4000 m 140,000 ft of coal and up to 600,0003 Ž . Ž . Ž .m 21 mmcf of gas Deguchi et al., 1995 . Lama and Bodziony this Special Issue

indicate that an equally large outburst previously occurred in 1969 in the Gagarin coalmine in the Donetsk Basin in Ukraine, which ejected 14,000 tons of coal and 600,000m3 of gas.

Although coal mining in the United States began in the early 18th century, mineexplosions in the Appalachian coal basin occurred intermittently in the early to middle19th century, becoming more frequent from the late 19th century to the middle of the

Ž .20th century as described by Deul and Kim 1986 . These workers indicate that theannual number of fatalities from explosions in underground coal mines in the United

ŽStates has diminished through the last 80 years because of research on mine safety see.Fig. 1 . In contrast, more than 15,000 coal-gas outbursts or explosions have occurred in

Ž .China during the same time Deguchi et al., 1995 with a resulting large number ofŽfatalities and injuries e.g., )10,000 to date in China, in Murray, 1996; Humphrey,

1960; Machisak et al., 1961; Moyer and Jones, 1968; Skow et al., 1980; Litwiniszyn,.1995 . Worldwide, most of these underground coal-mine gas outbursts or explosions

Ž .were caused by coalbed methane Anderson, 1995; Lama, 1995; Okten et al., 1995 .

Fig. 2. Relationship of gas pressure and content gradients to outbursting and non-bursting conditions in theŽ .Gemini coal seam, Leichhardt Colliery, Bowen Basin, Australia modified from Hanes, 1995 .


Outbursts involving the carbon dioxide component of the coalbed gas are more violentthan those related to methane because the sorptive capacity of coal for carbon dioxide is2–3 times greater than that for methane and the desorption rate of carbon dioxide is

Ž .much faster than methane, yielding a high pressure gradient Styles, 1995 . However,coalbed methane is a major factor in outbursting or explosions worldwide and a coalbedwith methane content greater than 9 m3rmt is considered coal and gas outburst proneŽ .Campoli et al., 1985 . In addition a high gas pressure gradient also contributes to

Ž .outbursting as shown in Fig. 2 Hanes, 1995 .Research on coalbed methane for the past several decades has been directed toward

its management, control, and prediction in order to reduce outbursts in underground coalŽmines Deul, 1964; Kozlowski, 1980; Janas, 1985; Tarnowski, 1988; Noack, 1995;

.Sergeev and Ivanov, 1995; Hatherly et al., 1995; Murray, 1996 . Because coalbed gasoutbursts occur in mines worldwide, a unified effort toward solving this problem started

Ž .before World War I Loiret and Laligant, 1923 . This effort has resulted in intensiveresearch investigations on the causes of underground coal-mine gas outbursts outside theUnited States where outbursts are more common. These investigations were designed tohelp predict, prevent, and manage coal-mine gas outbursts and include the origin andmechanism of coal-mine outbursts.

2.1. Origin and mechanism of coal-mine outbursts

Ž .It was suggested by Kotarba 1990 that rock aggregates in the earth’s crust by virtueof their physical and chemical characteristics consist of a network of structures thatinclude fractures, micro-cracks and pores, which were filled with gaseous and liquidsubstances. Coal is one such rock aggregate that accumulated gaseous substances suchas carbon dioxide, methane, andror nitrogen in these structures during coalification.Coal consists of organic and inorganic matters, which have undergone a series of

Ždevolatilization stages during coalification into higher grades or ranks e.g. lignite,. Žsubbituminous, bituminous, and anthracite . Low rank coals e.g. lignite and subbitumi-

.nous lose a minor amount of volatile matter during the process of coalification. HighŽ .rank coals bituminous and anthracite lose a large amount of volatile matter during this

process, producing methane, carbon dioxide, nitrogen, and large amounts of water.Ž .Coalbed methane generated at low temperature is of a biological biogenic origin and

Ž . Žthat generated at high temperature is of a thermal origin thermogenic Meissner, 1984;.Rightmire, 1984; Rice, 1993 .

There is a continuing debate on the mechanism responsible for outbursts in under-Ž .ground coal mines. Cheng and Ding 1971 suggested that the driving force of coal-mine

outbursts is the internal energy of the gas contained in the coal bed rather than thestressrstrain energy of the coal bed and surrounding rocks. Gas pressure and gas

Žquantity are significant factors in coal-mine outbursts Khodot, 1961; Christianovich,.1953; Christianovich and Salganik, 1983; Lama, 1995 . In addition, rock pressure and

strength are also important factors contributing to coal-mine outbursts as suggested byŽ .Christianovich and Salganik 1983 . These researchers argue that a continuous medium

Ž . Ž .e.g. coal bed is divided into several zones e.g. elastic, oriented cracks, plastic due to


existing strain. Mining activity is interpreted to displace these zones; gas is released andmigrates into the plastic zone, which serves as a sponge and a barrier. The thinner this

Ž .barrier, the greater the probability of a outburst. Mroz and Zacharski 1990 supportedŽ .this argument by indicating the existence of oriented cracks or ‘slices’ . ‘Thin slices’

provide conduits of gas flow between them. Rock ‘slicing’ is confirmed in laboratoryŽ . Ž .experiments by Bodziony et al. 1990 and Gawor et al. 1991 . This mechanism of

propagating coal-mine outbursts led to a concentrated effort to understand the topologyŽof continuous to multi-phase medium Ryncarz, 1989, 1990; Majewska, 1990; Litwin-

iszyn, 1987, 1995; Gotoh et al., 1995; Bodziony and Kraj, 1995; Chen et al., 1995;.Tarnowski, 1995; Topolnicki, 1995 . Other mechanisms of coal-mine outbursts are

directly related to microseismic activity propagated by reactivation of faults andŽ .explosives Davies et al., 1987; Styles, 1995 as well as indirectly associated with the

Ž .maceral composition of the coal Beamish and Crosdale, 1995 .

2.2. Prediction and preÕention of coal-mine outbursts

Knowledge gained through investigations of the origin of coalbed gas and mechanismof coal mine outbursts has enhanced the techniques of prediction and prevention of

Ž .outbursts and explosions. Prediction includes monitoring of gas emissions Lama, 1995 ,Žof acoustic signal spectrum characteristics in relation to structures in the rock mass e.g.

state of stress; Bobrov, 1995; Deguchi et al., 1995; Hatherly et al., 1995; Seto and. ŽKatsuyama, 1995; Birukov, 1995 , and of microseismic acoustic emissions Styles,

.1995; Talebi et al., 1995 .The techniques of prediction may be applied to control and prevent underground

coal-mine outbursts. For example measurements of gas content and pressure fromdrillholes on the surface and subsurface permits determination of threshold conditions

Ž .for outburst occurrence Zhang, 1995 . These measurements provide information on theirregular distribution of gas and change in gas trends allowing the emplacement ofmethods to control and prevent coal-mine outbursts. In addition, mining methods and

Žmachinery may be modified and designed e.g. influence on coal room and pillars,.longwall panel, etc. to account for rock-mass stresses, which could trigger coalbed gas

outbursts from an advancing mine face. Different methods of gas ventilation or drainagealso may be adopted such as removal of gas by vertical wells in advance of mining orvertical gob wells drilled into the cave area behind the longwall panel. Thus, informationon prediction, control, and prevention of gas emission and associated outbursts isimportant not only in planning the ventilation of mines but also in planning mine

Ž .workings, development, and production e.g., determining the length of the coal face ,Ž .which in turn, influence the total coal production Zabourdyaev, 1995 . This, in turn,

directly relates to mine safety, efficiency of mine operations, and mine economics.

3. Geological perspectives in coalbed methane development

Gas dilution by ventilation during active mining operations and post- and pre-miningmethane drainage activity mainly has been conducted in order to improve mine safety,


increase productivity, and improve mining economics. However, ventilation and drainageefforts related to underground mining has also led to production of coalbed methane by

Žconventionally drilled vertical wells Diamond et al., 1989; Diamond, 1994; Dunn,.1995 . Production was followed by successful recovery and sale of coalbed methane into

Ž .the conventional natural gas markets Dunn, 1984 . This economic utilization of coalbedmethane not only stimulated significant commercial interest but also focused interest andresearch on the geological factors that are directly related to their accumulation,

Ž .distribution, and recoverability Gamson and Beamish, 1992 .

3.1. Towards exploration of coalbed methane

Because coalbed methane exploration has gone beyond coal mining areas intoundeveloped coal-bearing basins, strategies of exploration require an understanding ofthe factors leading to concentrations or accumulations of methane. Coal rank may be themost traditional factor in locating concentrations of methane. Although an oversimplifi-

Ž .cation, it is believed that the type of coalbed gas methane vs. carbon dioxide generatedŽ .during the entire process of coalification varies with rank Fig. 3; Hunt, 1979 . In

Žgeneral, during early stages of coalification e.g., formation of lignite to subbituminous.rank coals a large amount of carbon dioxide is generated. During the later stages of

Ž .coalification e.g., formation of high volatile bituminous to anthracite rank coals a largeŽ 3 .amount of methane is generated about 100–300 cm rgm of coal . However, the

Žmethane yield is also influenced by the coal maceral content Fig. 4; Juntgen and.Karweil, 1966; Higgs, 1986; Levine, 1987 . Another factor to consider in the accumula-

ŽFig. 3. Diagram showing the amount of gas generated from coal during coalification. modified from Hunt,.1979 .


Fig. 4. Cumulative methane generation curves for a perhydrous German Tertiary coal and a subhydrousŽ .Carboniferous coal of the United States. Total gas generation shaded is about equal between the two coals

Ž .modified from Higgs, 1986 .

tion of methane is that coal may generate more methane than it can store; thus coalbedgas may be expelled and migrate to adjacent reservoirs, such as sandstone beds, during

Ž .coalification into higher ranks Rice, 1993 . In addition, methane storage capacity ofcoal increases with increasing pressure and decreases with increasing temperatureŽ . Ž .Meissner, 1984 . Levine 1991 argues that the storage capacity of coal is affected byits maceral composition, as well. The amount of inorganic matter also affects storagecapacity in a very significant way.

Successful exploration for methane accumulations also requires understanding ofŽ .areas where rock-mass permeability may have been altered Clark and Boyd, 1995 .

Increased permeability in rock masses occur in areas affected by shear or torsional loadsŽ .which may in turn be affected by local structural e.g. folding, faulting and regional

Ž .deformation e.g. compressional . Stress modeling utilizing these mechanisms stimulateschanges in rock volume, which are accompanied by modification in gas permeabilityand storage capacity. Permeability is also controlled by the fracture types and orienta-

Ž .tions of the coal bed. The fracture systems e.g. face and butt cleats in coal beds andŽ .their geometry e.g., orthogonal vs. perpendicular to bedding surfaces are best described

Ž .by Close 1993 . Although natural coal fracture systems result from coalification, stress


Ždue to tectonic or structural deformation and compaction by sediment loading Ammo-.sov and Eremin, 1960; Ting, 1977; Law et al., 1991 may also cause their development.

The density of the fracture systems, and therefore increased storage capacity for gas, hasŽbeen directly associated with coal composition, thickness, and rank Law et al., 1991;

.Levine, 1992; Law and Rice, 1993 . Thus, recognition of permeability of coal reservoirsis essential in understanding the accumulation of methane and its drainage; however, a

Ž . Žknowledge of associated exogenic fractures tectonic is equally important Decker et.al., 1992; Koenig et al., 1992 .

3.2. Distribution of coalbed methane and resource assessment

A simplified method of investigating the distribution of coalbed methane is associatedŽwith assessing coal resources in coal-bearing basins or coalfields Hobbs, 1978; Right-

.mire, 1984; Tyler et al., 1997 . Because coal resource assessment is directly related toŽ .finding potential minable beds in the shallow parts -915 m or -3000 ft of coal

basins or coalfields, investigation of high-potential areas for coalbed methane resourcesmay be extended into the deeper parts of these areas. In the conterminous United States,

Ž .ICF Resources 1990 analyzed in-place methane resources in major coal-bearing coalŽ .basinsrcoalfields in the United States Fig. 5 in which the coal beds range from

Pennsylvanian to Tertiary in age and from bituminous to subbituminous in rank. On thebasis of this study, in-place methane resources in these coal basins and coalfields were

3 Ž . 3 Ž .estimated to be between to be 11.3 Bm 400 Tcf of which 2.5 Bm 90 Tcf areŽ .potentially recoverable. However, the latest estimate by Tyler et al. 1997 of in-place

3 Ž .gas in the United States is about 19 Tm also see Bibler et al., this Special Issue . Thisin-place methane resource estimate is smaller than that of Alaska in which coal

Ž .resources 5.3 trillion metric tons or 5.8 trillion short tons exceed 40% of the totalŽ .resources in the conterminous United States Merritt and Hawley, 1986; Stricker, 1991 .

Ž . 3 Ž .Smith 1995 estimated that these coals contain more than 28 Tm 1000 Tcf ofŽmethane. In Alaska the coals are equally as high rank and as old Mississippian to

. Ž .Tertiary in age as those in the conterminous United States Stricker, 1991 . A majorityof these coals are contained in Cretaceous and Tertiary rocks. An estimate of the

ŽCretaceous and Tertiary coal resources subbituminous B to high-volatile bituminous in. Ž . Ž .rank by Stricker 1991, 1993 is 4.5 trillion metric tons 5 trillion tons . Based on this

Ž . Ž .estimate and additional information from Smith 1995 , Stricker 1993 and Flores et al.Ž .1997 , it is estimated that the in-place coalbed methane resource of 7 Cretaceous and

Ž . 3 Ž .Tertiary coal-bearing basinsrcoalfields in Alaska Fig. 6 is as much 22 Tm 786 Tcf .Thus, about 80% of the total methane resource of Alaska is contained in the Cretaceousand Tertiary coal basinsrcoalfields and majority of this resource lies beneath the

Ž .offshore and onshore North Slope and Cook Inlet Basins Fig. 6 .Site-specific evaluation of the distribution of coalbed methane in the coal basins in

Ž .the western conterminous United States is summarized by Tyler et al. 1992 . Thisinvestigation emphasizes the importance of regional deformation in predicting thedistribution of methane in association with fracture permeability. Thermal maturation

Ž .maps based on vitrinite–reflectance studies were made by Amuedo and Bryson 1977 ,

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Ž .Fig. 5. A map showing coal basinsrcoalfields in the United States and estimates of in-place coalbed methane resource. Modified from ICF Resources 1990 , Tyler etŽ . .al. 1997 and Bibler et al., 1998 this volume .


Fig. 6. A map of 7 Cretaceous and Tertiary coal basinsrcoalfields in Alaska and estimates of the in-placeŽ .coalbed methane resource Stricker, 1993; Smith, 1995; Flores et al., 1997 . Gray shades in the North Slope

and Cook Inlet Basins are offshore areas.

Ž . Ž . Ž . Ž .Freeman 1979 , Law 1992 , Waller 1992 , and Nuccio and Finn 1994 in order tomaximize efforts in exploring for high potential methane areas in the coal basins orcoalfields in the United States. In general, these studies indicate that the thermalmaturity of basins is due to burial history, circulation of hot fluids, and high heat flow

Ž . Ž .from a deep seated source Fig. 7 . Based on vitrinite reflectance R the deeper part ofoŽthe coal basins has achieved R )0.6% allowing thermogenic gas generation Rice,o

.1992; Law, 1992; Nuccio and Finn, 1994 . Where R values are -0.6% the coal-bearingo

basin is thermally immature for significant thermogenic gas generation but does notŽ .preclude biogenic gas generation Rice, 1992 . Based on these studies, most of the coal

basins in the United States have reached a sufficiently high thermal maturity to exceedŽthe threshold of significant methane generation Rightmire et al., 1984; Tyler et al.,

.1992; Waller, 1992 . However, a large amount of biogenic gas accumulations occur inŽ .six Tertiary coal-bearing basins in the northern Rocky Mountains region Fig. 8 . TheŽvitrinite reflectance trends in these basins show decreasing R values or greatero

.potential for biogenic gas accumulations toward the northeastern part of the RockyŽ .Mountains region Nuccio and Finn, 1994; Pontolillo and Stanton, 1994 . The decreas-

ing vitrinite reflectance values to the north and east shown in Fig. 8 are related to theŽmigration and younging of Paleocene Laramide deformation fronts Flores et al., 1994;

.Perry and Flores, 1997 . That is, coals formed in basins associated with early deforma-Ž .tion fronts see Fig. 8; Laramide uplifts 1 and 2 resulted in deep burial and rapid basin

subsidence; thus, high thermal conditions. Coals formed in basins related to laterŽ .deformations fronts see Fig. 8; Laramide uplift 3 are affected by shallow burial and

less rapid basin subsidence; hence, low thermal conditions. The Paleocene coals in these



Fig. 8. Map showing variations of vitrinite–reflectance values in six Tertiary coal basins in the northern RockyMountains region of the United States. Vitrinite–reflectance values in each basin decrease towards the north

Ž Ž .and east as influenced by younging of Laramide deformation fronts e.g., Laramide uplifts: 1 earlyŽ . Ž . . Ž .Paleocene, 2 middle Paleocene, and 3 late Paleocene . Modified from Pontolillo and Stanton 1994 ,

Ž . Ž .Nuccio and Finn 1994 , Flores et al., 1994, and Perry and Flores 1997 .

3 Ž .six basins probably contain greater than 0.9 Tm 32 Tcf of methane resources that areŽ .mainly biogenic in origin Rice, 1993 .

The approach in the United States to investigating the accumulation and distributionof coalbed methane in coal-bearing basins or coalfields containing abundant coal

Žresources is also used in Australia, New Zealand, China, and Europe Gray, 1991;Mallett and Russell, 1992; Vance and Cave, 1992; Murray, 1996; Gayer and Harris,

.1996 . In eastern Australia, interconnected Permian and Triassic coal basins have beenexplored for coalbed gas. There vitrinite reflectance, which ranges from 0.6% to 3.0%Ž .Fig. 9 , displays a level of thermal maturity in which thermogenic gas may have been

Ž .generated in the eastern parts of the basins Mallett and Russell, 1992 . The westernmargins of the basins exhibit -0.6% vitrinite reflectance, suggesting a possiblebiogenic methane source. The thermal maturity in the eastern part of the basins isprobably controlled by either high heat flow or deep burial. Other Permian andCarboniferous basins in eastern Australia display vitrinite reflectance values rangingfrom 0.35%–0.7%, which would allow generation of mainly biogenic methane with

Ž .subordinate thermogenic methane Durie et al., 1992 . A study of the isotopic composi-Ž .tion of bituminous coals in eastern Australia Smith and Pallaser, 1996 indicates that

Ž .Fig. 7. A map of a typical thermally mature coal basin Raton Basin in Colorado and New Mexico in theŽ .United States. The basin contains Cretaceous and Tertiary coals affected mainly by high heat flow HFU due

Ž . Ž .to igneous intrusions. Modified from Amuedo and Bryson 1977 and Dolly and Meissner 1977 .


Fig. 9. A map showing thermal maturity, as indicated by vitrinite–reflectance values of the Late Permian coalsŽ .in the Bowen–Gunnedah–Sydney Basins, Australia modified from Mallett and Russell, 1992 .

microbial reduction of carbon dioxide played a major role and thermal decomposition aminor role in methane generation.

In New Zealand the distribution of coalbed methane has also been associated withŽ .coal basins and coalfields containing abundant coal resources Vance and Cave, 1992 .

These workers indicate that New Zealand coalfields contain 15.7 Btu of in-place coalresources of which 65% are lignite and 35% are subbituminous and bituminous ranksŽ .very minor semi-anthracite and anthracite . Although lignite comprises a large part ofthe in-place coal resources, this low-rank coal resource is mainly found in a few

Ž .coalfields Fig. 10; Sherwood, 1986 . Most of the high-volatile bituminous coals arefound in coalfields in the northern part of South Island. Regional syntheses of thermalmaturity of these high rank coals in South Island based on vitrinite reflectance indicatesR values varying mainly from 0.45% to 1.2%, with extreme values from 0.3% to 1.7%oŽ .Suggate, 1959; Nathan et al., 1986 . Four major coalfields exhibit R )0.75%, whicho


Fig. 10. A diagram showing the range of coal ranks within New Zealand coalfields of Cretaceous and TertiaryŽ .age adopted from Sherwood, 1986 .

Ž .may indicate thermogenic gas generation Fig. 11 . The thermal maturity of these coalbasins and coalfields is controlled by heat flow from shallow to deep seated igneous

Ž .intrusions Nathan et al., 1986 .Investigations of the distribution of coalbed methane in China are concentrated in the

Ž .northern and eastern coal basins Dai et al., 1987; Rice, 1993; Murray, 1996 . Innorthern China, Permian and Carboniferous anthracite resources have been determined

Ž .to be a viable source of coalbed methane Murray, 1996 . Coals in this part of Chinarange from semi-anthracite to anthracite with R values ranging from 2.4% to 6.0%.o

These coals are well fractured by tectonic deformation, which makes them good gasreservoirs. The eastern China coals vary from Carboniferous to Tertiary in age and from

Ž .high volatile bituminous to anthracite with R values from 0.5 to 3.8% Rice, 1993 .oŽ .The study of Dai et al. 1987 indicates a direct correlation between rank and depth.

Coals with R values from 1.0% to 1.7%, or high volatile A to medium volatileo

bituminous, contain wet gas. However, coals at shallow depths with wide ranging RoŽ .values are methane-rich. Zhang and Chen 1985 identified the presence of biogenic

methane in some northeastern China coalfields.The Carboniferous coal-bearing rocks in England, Germany, and Poland have been

Ž .the objectives of coalbed methane exploration Gayer and Harris, 1996 . VariscanŽ .foredeep coal basins in England have been determined by Fails 1996 to have potential

coalbed methane accumulations. In western Germany, hardcoal resource, which is9 3 3 3 Ž .454=10 m of coal, may translate to 1=910 rm of in-place gas Juch, 1996 . The

Carboniferous coals of the Ruhr District may yield as much as 151=109 m3 of in-place


Fig. 11. Map showing variations of vitrinite-reflectance values of coals in Cretaceous and Tertiary coal-bearingŽ .basins and coalfields in northern South Island, New Zealand adopted from Nathan et al., 1986 .

Ž . Ž .gas Freudenberg et al., 1996 . Colombo et al. 1970 studied the carbon isotopiccomposition of coalbed gases in the coal district in western Germany, and found thatmethane becomes isotopically heavier at depth. These coals vary from high-volatile A

Ž .bituminous to anthracite R values of 0.8–4.9% . In Poland, Carboniferous coals,oŽwhich vary in rank from high-volatile A bituminous to anthracite R values betweeno

.1.1–2.6% , are considered potential sources of thermogenic methane gas accumulationsŽ .Kotarba, 1988 .


3.3. RecoÕerability of coalbed methane and production

Reservoir characterization of coal beds and its relation to recoverability and pro-ducibility of methane has been the focus of research since the late 1960’s. Ever since thefirst successful production from test wells in the Black Warrior Basin in the UnitedStates, research investigations into more efficient methods of recovering coalbed methane

Ž .have continued. Recoverability and volume in-place gas of methane accumulationsdepend on the rank, composition, quality, permeability, and porosity of the coalreservoirs; pressure–temperature conditions; and well completion and stimulation tech-

Žniques Ettinger et al., 1966; Faiz et al., 1992; Gamson and Beamish, 1992; Harpalani.and Chen, 1992; Paterson et al., 1992; Beamish and Crosdale, 1995 .

Ž .Faiz et al. 1992 indicated that the amount of gas retained in coal beds is controlledby rank, maceral and mineral composition, porosity, pressure, temperature, and related

Ž .structural–tectonic conditions. Ettinger et al. 1966 suggested that low- to medium-rankcoals and inertinite-rich coals have a higher capacity for methane sorption thanvitrinite-rich coals. However, in higher rank coals with both maceral types, methanesorption is similar in amounts. The methane sorption capacity of vitrinite is greater than

Ž .inertinite as shown by Beamish and Crosdale 1995 in their investigation of the coals inthe Bowen Basin in eastern Australia. Their study indicates that the inertinite-rich coalshave greater porosity than vitrinite-rich coals. For high- to low-volatile bituminouscoals, inertinite-rich coals are characterized by macropores and vitrinite-rich coals by

Ž .micropores. However, Beamish and Crosdale 1995 concluded that vitrinite-rich coalsappear to have a higher sorption capacity than inertinite-rich coals but vitrinite-rich coalshave a slower desorption rate than inertinite-rich coals.

Methane recoverability and production from coal beds and their relationships to coalŽ .type, microstructure, and gas flow were studied by Gamson and Beamish 1992 . TheseŽworkers show that a hierarchy of micro-sized fractures and microcavities 0.05–20 mm

.in width are related to coal lithotypes. That is, bright coals contain mainly microfrac-tures and dull coals contain mainly microcavities. These workers demonstrated that thesize, continuity, and connectivity of these microstructures play a significant role in thepermeability and flow of methane through the coal reservoir. Thus, methane flow in the

Ž .coal reservoir is governed by these microstructures microporosity and the accompany-Ž .ing macrostructures macroporosity that make up the cleat system. Harpalani and Chen

Ž .1992 investigated, in the laboratory, the relationship of these dual-porosity roles inŽ .coals. Their investigation focused on the behavior of the strain by volume on the coal

Ž .matrix with the microstructures and its effect on the intervening cleat system. TheyŽ .demonstrated that as the coal matrix volume decreases shrinkage with desorption as

Ž .methane pressure decreases, the cleat fracture porosity or aperture increases, which, inturn, leads to increasing permeability of the coal. Permeability in the coal reservoir maybe enhanced by acid leaching of secondary minerals as demonstrated in the laboratory

Ž . Ž .by Paterson et al. 1992 . Although permeability decreases at depth Fig. 11 , gasŽ .content increases but finally levels off at depth McKee et al., 1986 . Thus, the ‘rule of

Ž .thumb’ for methane exploration should be at least from 152 m 500 ft below the surfaceŽ . Ž .to 1830 m 6000 ft at depth Fig. 12 . The enhanced reservoir characteristics in

combination with other properties such as hydrology, coal thickness and continuity,


Ž .Fig. 12. Relationship of permeability and depth see shaded area for coal seams in some coal basins in theŽ .United States modified from McKee et al., 1986 .

basin-coalfield geology, and well completion and stimulation contribute to the pro-Žducibility of coalbed methane Durucan et al., 1992; Ellard et al., 1992; Tyler et al.,

.1992; Waller, 1992 .

4. Summary

Although the detrimental effects of coalbed gas on mining and development has beenknown for more than 100 years, harnessing the associated coalbed methane as an energyresource is still in its infancy. Release of coalbed gas during underground mining and itsmigration into the network of tunnels or mine workings have been the focus ofinvestigations because of safety and productivity. This research towards safe andproductive mining has led to understanding the origin, mechanism, prediction, andprevention of coalbed gas outbursts and explosions. These studies also have led to themethane drainage technology that is now applied to commercial recovery of coalbed gas.Control and management of this vented gas and the ‘energy crises’ of the mid 1970’sgave rise to commercial exploitation of coalbed methane 25 years ago. Since then, therehave been concentrated research efforts directed towards the origin, accumulation,distribution, availability, and recoverability of coalbed methane. Advances in multidisci-pline researches in coal mining and geology have truly moved coalbed methane from amining hazard to a new energy resource.

References

Ammosov, I.I., Eremin, I.V., 1960. Fracturing in coal, IZDAT Publishers, Office of Tech. Services,Washington, DC, 100 pp, translated from Russian, 1963.


Amuedo, C.L., Bryson, R.S., 1977. Trinidad-Raton Basins: model coal resource evaluation program. In:Ž .Murray, D.K. Ed. , Geology of Rocky Mtn. Coal., vol. 1, Colo. Geol. Survey Resource Ser., pp. 45–60.

Anderson, S.B., 1995. Outbursts of methane gas and associated mining problems experienced at TwistdraaiŽ .colliery. In: Lama, R.D. Ed. , Management and Control of High Gas Outbursts In Underground Coal

Mines. Westonprint, Kiama, NSW, Australia, pp. 423–434.Beamish, B.B., Crosdale, P.J., 1995. The influence of maceral content on the sorption of gases by coal and the

Ž .association with outbursting. In: Lama, R.D. Ed. , Management and Control of High Gas Outbursts InUnderground Coal Mines. Westonprint, Kiama, NSW, Australia, pp. 353–362.

Bibler, C.J., Marshall, J.S., Pilcher, R.C., 1998. Status of worldwide coal mine methane emissions and use. Int.J. Coal Geol. 35, 281–308, this volume.

Birukov, Y., 1995. Regional monitoring conception of rock mass properties and conditions. In: Lama, R.D.Ž .Ed. , Management and Control of High Gas Outbursts In Underground Coal Mines. Westonprint, Kiama,NSW, Australia, pp 169–170.

Bobrov, I.A., 1995. Investigations of the relationship between acoustic signal spectrum characteristics andŽ .state of mining rock mass. In: Lama, R.D. Ed. , Management and Control of High Gas Outbursts In

Underground Coal Mines. Westonprint, Kiama, NSW, Australia, pp. 133–138.Bodziony, J., Nelicki, A., Topolnicki, J., 1990. Investigations of experimental generation of coal and gas

Ž .outburst. In: Litwiniszyn, J. Ed. , Strata as Multiphase Medium. Rock and Gas Outbursts. Krakow:Wydawnictwo AGH, pp. 489–508.

Campoli, A.A., Trevits, M., Molinda, G.M., 1985. Coal and gas outbursts: prediction and prevention. CoalMin. 4p., reprinted.

Chen, X., Barron, K., Chan, D., 1995. A few factors influencing outbursts in underground coal mines. In:Ž .Lama, R.D. Ed. , Management and Control of High Gas Outbursts In Underground Coal Mines.

Westonprint, Kiama, NSW, Australia, pp. 39–48.Cheng, C., Ding, Y., 1971. A preliminary study of gas outbursts. Proceeding of the International Symposium

on Mining Technology and Science. China Inst. of Min. and Tech., pp. 35–42.Bodziony, J., Kraj, W., 1995. Investigations of instantaneous outbursts of coal and gas in laboratory condition.

Ž .In: Lama, R.D. Ed. , Management and Control of High Gas Outbursts In Underground Coal Mines.Westonprint, Kiama, NSW, Australia, pp. 31–38.

Christianovich, S.A., 1953. Outbursts of gas and coal. Izv. AH SSR Otd. Tech. Nauk. 12, 1689–1999.Christianovich, S.A., Salganik, B., 1983. Several basic aspects of the forming of sudden outbursts of coal

Ž .rock and gas. 5th Congress International Congress on Rock Mechanics, Melbourne, pp. E41–E50.Ž .Clark, I.H., Boyd, G.L., 1995. Geologic controls on coalbed methane accumulations. In: Lama, R.D. Ed. ,

Management and Control of High Gas Outbursts In Underground Coal Mines. Westonprint, Kiama, NSW,Australia, pp. 369–374.

Ž .Close, J.C., 1993. Natural fractures in coal. In: Law, B.E., Rice, D.D. Eds. , Hydrocarbon from Coal, Amer.Assoc. of Petrol. Geol. Studies in Geol., No. 38, pp. 119–132.

Colombo, U., Gazzarrini, F., Gonfiantini, R., Kneuper, G., Teichmuller, M., Teichmuller, R., 1970. CarbonŽ .isotope study on methane from German coal deposits. In: Hobson, G.D., Speers, G.C. Eds. , Advances in

Organic Geochemistry, 1966. Oxford, Pergamon Press, pp. 1–26.Dai, J., Qi, H., Song, Y., Guan, D., 1987. Composition, carbon isotope characteristics and the origin of

coalbed gases in China and their implication. Sci. Sin. B 30, 1324–1337.Davies, A.W., Styles, P., Jones, V.K., 1987. Developments in outburst prediction by microseismic monitoring

from the surface. Min. Eng. 147, 486–498.Decker, A.D., Davis, T.L., Klawitter, A.J., 1992. A case history of fracture detection methods used to locate

Ž .open fractures in coal. In: Beamish, B.B., Gamson, P.D. Eds. , vol. 2, Symposium on Coalbed MethaneResearch and Development in Australia. James Cook Univ. of No. Queensland, pp. 51–74.

Deguchi, G., Yu, B., Jiao, J., 1995. JapanrChina research co-operation on prevention of gas outbursts. In:Ž .Lama, R.D. Ed. , Management and Control of High Gas Outbursts In Underground Coal Mines.

Westonprint, Kiama, NSW, Australia, pp. 139–146.Deul, M., 1964. Methane drainage from coalbeds: program of applied research: Proceedings of 60th Meeting,

Rocky Mtn. Coal Min. Inst., pp. 54–60.Deul, M., Kim, A.G., 1986. Methane control research: Summary of results, 1964–80. US Bureau of Mines

Bull., vol. 687, 174p.


Diamond, W.P., Bodden, W.R., Zuber, M.D., Schraufnagel, R.A., 1989. Measuring the extent of coalbed gasdrainage after 10 years of production at the Oak Ridge pattern, Alabama. Proceedings of the 1989 CoalbedMethane Symp. Tuscaloosa, AL, pp. 185–193.

Diamond, W.P., 1994. Methane control for underground coal mines. US Bur. of Mines, Info. Circ. 9395, 44p.Dolly, E.D., Meissner, F.F., 1977. Geology and gas exploration potential, upper Cretaceous and lower Tertiary

Ž .strata, northern Raton Basin, Colorado. In: Veal, H.K. Ed. , Exploration Frontiers of the Central andSouthern Rockies. Rocky Mtn. Assoc. Geol. Symp., pp. 247–270.

Dunn, B.W., 1984. Coal as a conventional source of methane: a review analysis of a 312 well production areain the Mary Lee coal seam in Tuscaloosa County, Alabama: SPE 1983, SPErDOErGRI 12875.

Dunn, B.W., 1995. Vertical well degasification in advance of mining – a potential gas management methodŽ .for reducing gas emissions and outbursts. In: Lama, R.D. Ed. , Management and Control of High Gas

Outbursts In Underground Coal Mines. Westonprint, Kiama, NSW, Australia, pp. 267–275.Durie, R.A., Hawkins, P.J., Kukla, G.T., 1992. The Galilee basin coal measures: A potential methane

resource? – A case for a well planned, integrated exploration and R and D programme. In: Beamish, B.B.,Ž .Gamson, P.D. Ed. , Symposium on Coalbed Methane Research and Development in Australia. James

Cook Univ. of No. Queensland, vol. 1, pp. 81–97.Durucan, S., Creedy, D.P., Edwards, J.S., 1992. Geological and geotechnical factors controlling the occurrence

Ž .and flow of methane in coal seams. In: Beamish, B.B., Gamson, P.D. Eds. , Symposium on CoalbedMethane Research and Development in Australia. James Cook Univ. of No. Queensland, vol. 2, pp. 33–50.

Ellard, J., Roark, R., Ayers, W.B., Jr., 1992. Geologic controls on coalbed methane production: an exampleŽ .from the Pottsville Formation Pennsylvanian age , Black Warrior Basin, Alabama, USA. In: Beamish,

Ž .B.B., Gamson, P.D. Eds. , Symposium on Coalbed Methane Research and Development in Australia.James Cook Univ. of No. Queensland, vol. 1, pp. 45–62.

Ettinger, I., Eremin, I., Zimakov, B. and, Yanovskaya, M., 1966. Natural factors influencing coal sorptionproperties. I-petrography and sorption properties of coals. Fuel 45, 267–275.

Ž .Fails, T.G., 1996. Coalbed potential of some Variscan foredeep basins. In: Gayer, R., Harris, I. Eds. , Coalbedmethane and coal geology, Geol Soc., Spec. Pub. No., vol. 109. pp 13–26.

Faiz, M.M., Aziz, N.I., Hutton, A.C., Jones, B.G., 1992. Porosity and gas sorption capacity of some easternŽ .Australian coals in relation to coal rank and composition. In: Beamish, B.B., Gamson, P.D. Eds. ,

Symposium on Coalbed Methane Research and Development in Australia. James Cook Univ. of No.Queensland, vol. 4, pp. 9–20.

Flores, R.M., Stricker, G.D., Bader, L.R., 1997. Stratigraphic architecture of the Tertiary alluvial Beluga andŽ .Sterling Formations, Kenai Peninsula, Alaska. In: Karl, S., Vaughn, N., Ryherd, T. Eds. , Kenai Peninsula

Field Guidebook, Alaska. Geol. Soc., pp. 36–53.Flores, R.M., Roberts, S.B., Perry, W.J., Jr., 1994. Paleocene paleogeography of the Wind River, Bighorn, and

Ž .Powder River Basins, Wyoming. In: Flores, R.M., Mehring, K.T., Jones, R.W., Beck, T.L. Eds. ,Organics and the Rockies field guide, Wyo. State Geol. Surv., Pub. Info. Circ. No. 33, pp. 1–16.

Freeman, V.L., 1979. Preliminary report on rank of deep coals in part of the southern Piceance Creek Basin,US Geol. Survey Open-File Rept. 79-725, 10p.

Freudenberg, U., Schulter, L.S., Schutz, R., Thomas, K., 1996. Main factors controlling coalbed methaneŽ .distribution in Ruhr District, Germany. In: Gayer, R., Harris, I. Eds. , Coalbed methane and coal geology.

Geol Soc., Spec. Pub. No. 109, pp. 67–88.Gamson, P.D., Beamish, B.B., 1992. Coal type, microstructure and gas flow behaviour of Bowen Basin coals.

Ž .In: Beamish, B.B., Gamson, P.D. Eds. , Symposium on Coalbed Methane Research and Development inAustralia. James Cook Univ. of No. Queensland, vol. 4, pp. 43–66.

Gawor, M., Meier, E.A., Rysz, J., 1991. Experimental research on the rarefaction waves with the mixture ofcrushed coal and gas: Twenty Years Cooperation in Physics and Fluids, Gottingen-Krakow, pp. 81–103.

Gayer, R., Harris, I., 1996. Coalbed methane and coal geology. Geol Soc., Spec. Pub. No. 109, 344p.Gimm, W.A.R., Pforr, H., 1964. Breaking behavior of salt rock under rock bursts and gas outbursts, Proc. of

the 4th Inter. Conf. on Strata Control and Rock Mechanics, pp. 434–449.Gotoh, K., Matsui, K., Takemaru, Y., Li, Z.K., 1995. A theory of mechanics of coal and gas outburst. In:

Ž .Lama, R.D. Ed. , Management and Control of High Gas Outbursts In Underground Coal Mines.Westonprint, Kiama, NSW, Australia, pp. 25–30.


Ž .Gray, I., 1991. Gas from Australian coals: Where from where to. In: Bamnerry, W.J., Depers, A.M. Ed. ,Proc. of Symposium on Gas in Australian coals. Geol. Soc. of Australia. Symp. Ser. 2, pp. 31–40.

Ž .Hanes, J., 1995. Outbursts in Leichhardt colliery: lessons learnt. In: Lama, R.D. Ed. , Management andControl of High Gas Outbursts In Underground Coal Mines. Westonprint, Kiama, NSW, Australia, pp.445–449.

Hatherly, P., Murray, W., Stickley, G., Eisler, P., Tchen, T., 1995. Development of in-seam borehole loggingŽ .tools for detection of outburst prone structures. In: Lama, R.D. Ed. , Management and Control of High

Gas Outbursts In Underground Coal Mines. Westonprint, Kiama, NSW, Australia, pp. 93–100.Hargraves, A.J., 1983. Instantaneous outbursts of coal and gas – A review. Proc. Austr. Inst. Min. Metall. 285,

1–37.Harpalani, S., Chen, G., 1992. Effect of gas production on porosity and permeability of coal. In: Beamish,

Ž .B.B., Gamson, P.D. Eds. , Symposium on Coalbed Methane Research and Development in Australia.James Cook Univ. of No. Queensland, vol. 4, pp. 67–78.

Ž .Higgs, M.D., 1986. Laboratory studies into the generation of natural gas from coals. In: Brooks, J. Ed. ,Habitat of Paleozoic Gas in N.W. Europe, Geological Publication, vol. 23, pp. 113–120.

Hobbs, R.G., 1978. Methane occurrences, hazards, and potential resources: Recluse geologic analysis area,northern Campbell County, Wyoming: US Geological Survey Open-File Rept. 78-401, 20p.

Humphrey, H.B., 1960. Historical summary of coal-mine explosions in the United States, 1810–1958. U.S.Bur. Mines Bull., vol. 586, 280p.

ICF Resources, 1990. The United States coalbed methane resource. Quart. Review of Methane from CoalSeams Tech., 7, 10–28.

Hunt, J.M., 1979. Petroleum geochemistry and geology, Freeman, W.H. and Co., 617p.Janas, G., 1985. Neue Erkenntnisse auf dem Gebiete der Ausgasungvorausberechung: Glukauf, Forschung-

Ž .shefte 01 in German .Juch, D., 1996. Assessment of West German hardcoal resources and its relation to coalbed methane. In: Gayer,

Ž .R., Harris, I. Eds. , Coalbed methane and coal geology. Geol. Soc., Spec. Pub. No. 109, pp. 59–66.Juntgen, H., Karweil, J., 1966. Gasbilbung un gasspeicherung im steinkohlenflozen, Part I and II: Erdol

Ž .Kohle–Erdgas–Petrochemie, vol. 19, pp. 251–258, pp. 339–344 in German .Kemp, J.H., Petersen, 1988. Coalbed gas development in the San Juan Basin, New Mexico and Colorado: A

Ž .primer for the lawyer and landman. In: Fassett, J.E. Ed. , Geology and coalbed methane resources of thenorthern San Juan Basin, Colorado and New Mexico, Rcky. Mtn. Assoc. Geol., 257–280.

Khodot, W.W., 1961. Mechanism of coal and gas outbursts: Collection of Papers on the 20th Anniversary ofthe Institute of Mining, USSR Academy of Science: Wydawnictwa Gorniczy, Warsaw.

Koenig, R.A., Bocking, M.A., Forster, I., Enever, J.R., Casey, D.A., 1992. Experience with well testing andin-situ stress measurement in the Sydney Basin for evaluation of coalbed methane prospectivity. In:

Ž .Beamish, B.B., Gamson, P.D. Eds. , Symposium on Coalbed Methane Research and Development inAustralia, James Cook Univ. of No. Queensland, vol. 2, pp. 75–96.

Kotarba, M., 1990. Origin of gases accumulated in upper Carboniferous coal-bearing strata of Lower Silesiancoal basin and southern part of Rybnik coal district. Rock and Gas Outburst 1, 37–49.

Kotarba, M., 1988. Geochemical criteria for the origin of natural gases accumulated in the Upper Carbonifer-ous coal-seam-bearing formations in Walbrych Coal Basin: Stanislaw Staszio Academy of Min. andMetall. Scientific Bull. 1199, 11.

Kozlowski, B., 1980. Gas and coal outburst hazard in coal mining, PWN, Warsaw, Poland.Ž .Lama, R.D. Ed. , 1995. Management and control of high gas emissions and outbursts in underground coal

mines International Symp. Cum. Workshop: Westonprint in Kiama Wollongong, NSW, Australia, 618p.Law, B.E., 1992. Thermal maturity patterns of Cretaceous and Tertiary rocks, San Juan Basin, Colorado and

New Mexico. Geol. Soc. Amer. Bull. 104, 192–207.Ž .Law, B.E., Rice, D.D. Eds. , 1993. Hydrocarbons from coal, Amer. Assoc. Petrol. Geol. Studies in Geol., No.

38, 400p.Law, B.E., Rice, D.D., Flores, R.M., 1991, Coalbed gas accumulations in the Paleocene Fort Union

Ž .Formation, Powder River Basin, Wyoming. In: Schwochow, S.D., Murray, D.K., Fahy, M.F. Eds. ,Coalbed Methane of Western North America. Rocky Mtn. Assoc. of Geol., pp. 179–190.

Levine, J.R., 1992. Influences of coal composition on coal seam reservoir quality: A review: In: Beamish,


Ž .B.B., Gamson, P.D. Eds. , Symposium on Coalbed Methane Research and Development in Australia,James Cook Univ. of No. Queensland, vol. i, pp. i–xvii.

Levine, J.R., 1991. The impact of oil formed during coalification on generation and storage of natural gas incoal bed reservoir system, 3rd Coalbed Methane Symp. Proc., Tuscaloosa, AL, pp. 307–315.

Levine, J.R., 1987. Influence of coal composition on the generation and retention of coalbed natural gas, Proc.of the 1987 Coalbed Methane Symp., Tuscaloosa, AL, pp. 15–18.

Ž .Litwiniszyn, J., 1995. State of the art on the mechanism of outbursts in coal mines. In: Lama, R.D. Ed. ,Management and Control of High Gas Outbursts In Underground Coal Mines. Westonprint, Kiama, NSW,Australia, pp. 1–14.

Litwiniszyn, J., 1987. Gas emission from a crushed rock medium during its sudden outbursts. Archives of Min.Sciences: 32, 155–168.

Loiret, J., Laligant, G., 1923. Allgemeirner bericht zusammenfassung dertatsachen und beachtungen undŽ .richtlinien fur gruben mit gasausbruchen, Reichskohlenrat. Tagebuch No. 171, p. 7.30 in German .

Machisak, J.C., Wrenn, V.E., Jones, N.L., Reid, E.J., Rice, D.D., 1961. Injury experience in coal mining,1959. U.S. Bur. Mines IC 8067, 61p.

Mahtab, M.A., 1982. Geochemical aspects of gas outbursts in Louisiana salt mines. Assoc. Eng. Geol. Bull.19, 389–400.

Majewska, Z., 1990. Acoustic emission of coal during sorption of CO . Rock and Gas Outburst 1, 221–232.2

Mallett, C.W., Russell, N.J., 1992. The thermal history of Bowen – Gunnedah – Sydney Basins. In: Beamish,Ž .B.B., Gamson, P.D. Eds. , Symposium on Coalbed Methane Research and Development in Australia,

James Cook Univ. of No. Queensland, vol. 1, pp. 75–80.McKee, C.R., Bumb, A.C., Way, S.C., Koenig, R.A., Reverand, J.M., Brandenburg, C.F., 1986. Using

permeability vs depth correlations to assess the potential for producing gas from coal seams, MethaneFrom Coal-Seams Tech., pp. 415–26.

Meissner, F.F., 1984. Cretaceous and lower Tertiary coals as sources for gas accumulations in the RockyŽ .Mountain area. In: Woodward, J., Meissner, F.F., Clayton, J.L. Eds. , Hydrocarbon source rocks of the

greater Rocky Mountain region, Rocky Mtn. Assoc. Geol., pp. 401–431.Merritt, R.D., Hawley, C.C., 1986. Map of Alaska’s coal resources. Alaska Div. Geol. and Geophys. Surv.

Spec. Rept., vol. 37, 1 sheet, scale 1:2,500,00.Moyer, F.T., Jones, N.L., 1968. Injury experience in coal mining. U.S. Bur. Mines IC 8389, 88p.Mroz, Z., Zacharski, A., 1990. Coal layer deformation and rock-gas outburst initiation, Rock and Gas

Outburst., vol. II, pp. 537–570.Murray, D.K., 1996. Anthracite: A promising new target for coalbed methane exploration. Amer. Assoc.

Petrol. Geol. Bull. 80, 976.Nathan, S., Anderson, H.J., Cook, R.A., Herzer, R.H., Hoskins, R.H., Raine, J.I., Smale, D., 1986. Cretaceous

and Cenozoic sedimentary basins of the West Coast region, South Island, New Zealand. Sci. Infor. Publ.Centre, DSIR, Wellington, NZ, 90p.

Ž .Noack, K., 1995. Control of high gas emissions in underground coal mines. In: Lama, R.D. Ed. ,Management and Control of High Gas Outbursts In Underground Coal Mines, Westonprint, Kiama, NSW,Australia, pp. 15–24.

Nuccio, V.F., Finn, T.M., 1994. Structural and thermal history of Paleocene Fort Union Formation, central andeastern Wind River Basin, with emphasis on petroleum potential of the Waltman Shale Member. In: Flores,

Ž .R.M., Mehring, K.T., Jones, R.W., Beck, T.L. Eds. , Organics and the Rockies Field Guide. Wyo. StateGeol. Surv. Pub. Info. Circ., No. 33, pp. 53–68.

Okten, G., Biron, C., Saltoglu, S., Ozturk, M., 1995. Gas and coal outbursts of Zonguldak coalfield of TurkeyŽ .and preventive measures. In: Lama, R.D. Ed. , Management and Control of High Gas Outbursts In

Underground Coal Mines, Westonprint, Kiama, NSW, Australia, pp. 459–464.Paterson, L., Meaney, K., Smyth, M., 1992. Measurements of relative permeability, absolute permeability and

Ž .fracture geometry in coal. In: Beamish, B.B., Gamson, P.D. Eds. , Symposium on Coalbed MethaneResearch and Development in Australia. James Cook Univ. of No. Queensland, vol. 4, pp. 79–78.

Perry, W.J., Jr., Flores, R.M., 1997. Sequential Laramide deformation and Paleocene patterns in deepŽ .gas-prone basins in the Rocky Mountain region. In: Dyman, T., Wescott, W.A., Rice, D.D. Eds. ,

Geologic Controls of Deep Natural Gas Resources in the United States, US Geol. Surv. Bull., 2146-E, pp.49–59.


Pontolillo, J., Stanton, R.W., 1994. Vitrinite reflectance variations in Paleocene and Eocene coals of thePowder River, Williston, Hanna, Bighorn, and Bull Mountain basins, USA. The Soc. for Org. Petrol. Abst.with Progs., pp. 82–84.

Ž .Rightmire, C.T., 1984. Coalbed methane resource. In: Rightmire, C.T., Eddy, G.E., Kirr, J.N. Eds. , CoalbedMethane Resources of the United States, Am. Assoc. Petrol. Geol. Studies in Geology Ser., No. 17, pp.1–13.

Ž .Rightmire, C.T., Eddy, G.E., Kirr, J.N., Eds. , 1984. Coalbed Methane Resources of the United States. Am.Assoc. Petrol. Geol. Studies in Geology Ser., No. 17, 378p.

Ž .Rice, D.D., 1993. Composition and origins of coalbed gas. In: Law, B.E., Rice, D.D. Eds. , Hydrocarbonsfrom coal, Amer. Assoc. Petrol. Geol. Studies in Geol., No. 38, pp. 159–184.

Ž .Rice, D.D., 1992. Controls, habitat, resource potential of ancient bacterial gas. In: Vitaly, R. Ed. , Bacterialgas, Editions Technip., pp. 91–118.

Ryncarz, T., 1989. Stress and strain distribution around borehole drilled in a gas bearing coal seam prone tosudden outbursts. Archives of Min. Sci. 34, 29–45.

Ryncarz, T., 1990. Stresses in coal induced by gas content changes. Rock and Gas Outburst II, 469–486.Seto, M., Katsuyama, K., 1995. Estimation of hydrofractures in coal measures using acoustic emission. In:

Ž .Lama, R.D. Ed. , Management and Control of High Gas Outbursts In Underground Coal Mines.Westonprint, Kiama, NSW, Australia, pp. 161–168.

Sergeev, I.V., Ivanov, B.M., 1995. Complex methods to determine zones liable to sudden outbursts duringŽ .prospecting. In: Lama, R.D. Ed. , Management and Control of High Gas Outbursts In Underground Coal

Mines. Westonprint, Kiama, NSW, Australia, pp. 79–84.Sherwood, A.M., 1986. An outline of the geology of New Zealand coalfields, New Zeal. Geol. Surv. Record

15 ISSN 0112 465X, 27p.Skow, M.L., Kim, A.G., Deul, M., 1980. Creating a safer environment in US coal mines. U.S. Bur. of Mines,

Spec. Pub., 50p.Smith, T.N., 1995. Coalbed methane potential of Alaska and drilling results for the upper Cook Inlet Basin,

Intergas ’95, Proceedings of Symposium, May 15–19, 1995, The Univ. of Alabama, Tuscaloosa, AL, 21p.Smith, J.W., Pallaser, R.J., 1996. Microbial origin of Australian coalbed methane. Amer. Assoc. Petrol Geol.

Bull. 80, 891–897.Ž .Soot, P.M., 1988. Non-conventional fuel tax credit. In: Fassett, J.E. Ed. , Geology and coal-bed methane

resources of the northern San Juan Basin, Colorado and New Mexico. Rcky. Mtn. Assoc. Geol., pp.253–255.

Stricker, G.D., 1993. Coalbed methane in Alaska – is this a viable alternate resource for s state with abundantconventional energy supplies?. Focus on Alaska Coal ’93. Mineral. Industry Resear. Lab., Univ. of Alaska,p. 6.

Ž .Stricker, G.D., 1991. Economic Alaskan coal deposits. In: Gluskoter, H.J., Rice, D.D., Taylor, R.B., Eds. ,Economic Geology, US Geol Soc. Amer., The Geol. of North Amer. P-2, pp. 591–602.

Styles, P., 1995. Harmonic tremor seismic precursors and their implications for the mechanisms of coal-gasŽ .outbursts. In: Lama, R.D. Ed. , Management and Control of High Gas Outbursts In Underground Coal

Mines. Westonprint, Kiama, NSW, Australia, pp. 123–132.Suggate, R.P., 1959. New Zealand coals. New Zeal. Dept. Sci. Indus. Res. Bull. 134, 113.Talebi, S., Mottahed, P., Corbett, G.R., 1995. Outburst monitoring using microseismic techniques in the

Ž .Phalen colliery, Sydney, Nova Scotia, Canada. In: Lama, R.D. Ed. , Management and Control of HighGas Outbursts In Underground Coal Mines. Westonprint, Kiama, NSW, Australia, pp. 153–160.

Ž .Tarnowski, J., 1995. Calculations concerning coal and gas outbursts. In: Lama, R.D. Ed. , Management andControl of High Gas Outbursts In Underground Coal Mines. Westonprint, Kiama, NSW, Australia, pp.49–61.

Tarnowski, J., 1988. A comparative method for prognosticating coal and gas outburst hazard zones: How dothose forecasts agree with the actual state in variable geological conditions, 12th International Meeting onthe Ways on Coping with Rock and Gas outburst Hazard in Underground Mining, Radkow, pp. 19–23.

Ž .Topolnicki, J., 1995. Energy balance in an outburst. In: Lama, R.D. Ed. , Management and Control of HighGas Outbursts In Underground Coal Mines. Westonprint, Kiama, NSW, Australia, pp. 67–74.

Ting, F.T.C., 1977. Origin and spacing of cleats in coal beds. J. Pressure Vessel Tech. 99, 624–626.Tyler, R., Kaiser, W.R., Ambrose, W.A., Laubach, A.R., Ayers, W.B., 1992. Coalbed methane characteristics


in the foreland of the Cordilleran Thrust belt, western United States. In: Beamish, B.B., Gamson, P.D.Ž .Eds. , Symposium on Coalbed Methane Research and Development in Australia. James Cook Univ. of

Ž .No. Queensland, vol. 4 2 , pp. 11–32.Tyler, R., Kaiser, W.R., Scott, A.R., Hamilton, D.S., 1997. The potential for coalbed gas exploration and

production in the Greater Green River Basin, southwest Wyoming and northwest Colorado. The RockyMtn. Geol. 34, 7–24.

Ž .Vance, W.E., Cave, M., 1992. Coalbed gas in New Zealand. In: Beamish, B.B., Gamson, P.D. Eds. ,Symposium on Coalbed Methane Research and Development in Australia. James Cook Univ. of No.Queensland, vol. 4, pp. 31–44.

Waller, S.F., 1992. A successful operating company’s perspective of the key constraints upon profitableŽ .coalbed methane development. In: Beamish, B.B., Gamson, P.D. Eds. , Symposium on Coalbed Methane

Research and Development in Australia. James Cook Univ. of No. Queensland, vol. 4, pp. xxix–lv.Zabourdyaev, V.S., 1995. Gas content forecasting methods for mine developments, gas content reduction

Ž .means and prevention of sudden gas and coal outbursts. In: Lama, R.D. Ed. , Management and Control ofHigh Gas Outbursts In Underground Coal Mines. Westonprint, Kiama, NSW, Australia, pp. 229–236.

Zhang, G., 1995. Area prediction of danger of coal and gas outburst – example of application in JiaozuoŽ .mining area in China. In: Lama, R.D. Ed. , Management and Control of High Gas Outbursts In

Underground Coal Mines. Westonprint, Kiama, NSW, Australia, pp. 195–200.Zhang, Y.G., Chen, H.J., 1985. Concepts on the generation and accumulation of biogenic gas. J. Petrol. Geol.

8, 405–422.

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5C. Flores Coal Bed Methane From Hazard to Resource