ACKNOWLEDGEMENTS

First and foremost, we would like to thank God Almighty for his guidance and help in

giving me the strength to complete this report. In particularly, we would like to express our

sincere and deep appreciation to our lecturer, Prof. Madya. Issham Ismail for his knowledge,

wisdoms and encouragement. We will always value his guidance, advices and motivation

throughout this work. Lastly, our sincere appreciation also extends to our entire course mates

and the others who have contributed their views and useful tips. Deepest thanks to all of them

who gave a helping hand in the process of doing this report. May God protect and guide all of

you.

1

ABSTRACT

Coal is a unique rock type in the geological column; it has a wide range of chemical and

physical properties and has been studied over a long period. The essential property that

distinguishes coal from other rock types is that it is a combustible material. In chapter 1, we

discussed the introduction of coal bed methane (CBM), coal as an alternative source, usage of

coal and coal transportation. The environment of deposition CBM and its reserve worldwide

was highlighted in Chapter 2. The process to develop or extract the hydrocarbon from CBM

which is enhanced CBM recovery using Nitrogenase enzyme and microorganism will be

discussed in Chapter 3 and CBM product water management and carbon dioxide (CO2)

Sequestration with Enhanced CBM Recovery will be discussed in Chapter 4.

2

TABLE OF CONTENTS

CHAPTER TITLE PAGE

ACKNOWLEDGEMENTS 1

ABSTRACT 2

TABLE OF CONTENTS 3

LIST OF FIGURES 6

1 INTRODUCTION OF COAL BED METHANE

1.1 Preface 7

1.1.1 Fossil fuels’ past, present, future 7

1.1.2 Coal as an Alternative Energy Source 8

1.1.3 Gas in Coal 9

1.2 Coal Use 101.2.1 Electricity generation 10

1.2.2 Iron and Steel Production 11

1.2.3 Industrial Use 11

1.2.4 Domestic Use 11

1.3 Coal Transportation 12

3

2 THE ENVIRONMENT OF DEPOSITION OF COAL BED METHANE

AND ITS RESERVE WORLDWIDE

2.1 Introduction 12

2.2 Gas generation in coal 13

2.3 Coal bed stratigraphy 14

2.4 Adsorption and gas capacity 16

2.5 Porosity and permeability 17

2.6 Reservoir pressure 18

2.7 Reservoir temperature 18

2.8 Worldwide Coal bed Methane Reserve and Resources 19

2.8.1 Australia

19

2.8.2 China 20

2.8.3 Eurpoe 21

2.8.4.Canada 21

2.8.5 Indonesia 21

3 PROCESS TO DEVELOP OR EXTRACT THE HYDROCARBON FROM

COAL BED METHANE (CBM)

3.1 Introduction 22

3.2 Enhanced Coal Bed Methane Recovery 23

3.2.1 Enhanced Coal Bed Methane recovery using

Nitrogenase enzyme 26

3.2.2 Enhanced Coal Bed Methane using Microorganism 26

4 THE CHALLENGES OF OIL AND GAS INDUSTRY IS FACING IN

SOURCING THE HYDROCARBON

4.1 Introduction 32

4

4.2 CBM product water management 32

4.2.1 CBM development reduce flow to streams, springs

and wells 32

4.2.2 The quantity of the CBM product water 33

4.2.3 The quality of CBM product water and its effects on soil 33

4.2.4 The quality of CBM product water and its effect on plants

34

4.2.5 Managing CBM product water 35

4.3 Carbon Dioxide (CO2) Sequestration with Enhanced CBM

Recovery 35

5 CONCLUSION

4.1 Conclusion 38

REFERENCES 39

5

LIST OF FIGURES

FIGURE NO. TITLE PAGE

1.1 The world energy mix, past, present and future 8

1.2 The stages from coal delivery to electricity generation in a modern

power station 10

2.1 Coal Bed Methane Reserves 2P in Australia by Basins 19

2.2 Top 9 Coal Bed Methane Basins in China 20

2.3 Coal bed methane Basins in Europe 21

3.1 Schematic system in cleat system of coal 23

3.2 Desorption of methane 24

3.3 General trend of methane production for various ECBM techniques 24

3.4 Basic Setup on the ECBM using Nitrogenase Enzyme 27

3.5 Molecular Structure of Nitrogenase enzyme

28 3.6 Explanation of ammonia in coal seam

28 3.7 The Langmuir isotherm and break through curve for

ammonia 29 4.1 Example of soils of eastern Montana

23

4.2 CO2 sequestration with enhanced coal bed methane recovery at 34

BP’s Tiffany Field.

6

CHAPTER 1

INTRODUCTION TO COAL BED METHANE

1.1 Preface

Sedimentary sequences containing coal or peat beds are found throughout the world and

range in age from Upper Paleozoic to Recent. Coals are the result of the accumulation of

vegetable debris in a specialized environment of deposition. Such accumulations have been

affected by synsedimentary and pos-sedimentary influences to produce coals of differing degrees

of structural complexity, the two being closely interlinked.

1.1.1 Fossil fuels’ past, present, future

Coal was the fuel of choice in the nineteenth and early twentieth century, but was

gradually superseded by oil right after World War II. In the past three decades natural gas has

slowly but progressively increased its share of the energy mix. These three fossil fuels account

for more 85% of the world’s primary energy. And this has not changed over time as shown in

Figure 1.1. Other energy sources (nuclear, hydro and renewables) play a far smaller role by

comparison. Thirty years ago, when worldwide energy demand was 60% of current levels, fossil

fuels were the source of nearly 90% of the world’s energy supply.

Today, the Energy Information Administration of the U.S. Department of Energy (Energy

InformationAdministration, 2008) forecasts that this is not likely to change in the future, with

7

86.5% of the total energy mix coming from fossil fuels in 2030 despite-or perhaps because of -

an expected increase in total energy demand of 62% by then. However, many question whether

such growth and energy mix is sustainable both in environmental terms and with the remaining

fossil fuel reserves much beyond 2030 (Wood et al. 2007). In spite of programs going back more

than 30 years that have subsidized alternative forms of energy at substantial costs to consumers

(Koplow, 2006), fossil fuels will still represent more than 85% of the world’s primary energy

mix.

Fig. 1.1: The world energy mix, past, present and future [1]

1.1.2 Coal as an Alternative Energy Source

The essential property that distinguishes coal from other rock types is that it is a

combustible material. In the normal course events, coal is burnt to provide warmth as a domestic

fuel, to generate electricity as a power station feed stock or as a part of the industrial process to

create products such as steel and cement. Coal, however, is more versatile than this and has been,

and still is, able to provide alternative forms of energy. This may be from its by-products such as

8

gas, through chemical treatment to become liquid fuel and by in situ combustion to convert coal

to liquid and gaseous products.

The development of these energy alternatives is important, particularly in those areas

where coals are too deep for exploitation or where underground mining has ceased for economic

reasons. Those coalfield areas once thought to be exhausted can still provide large amounts of

energy through the use modern technology. In addition, the understanding of the origins of oil

and natural gas shows coal to be a contributory source rock. Although the bulk of coal utilization

is and will continue to be, by direct handling and combustion, the alternatives uses of energy

from coal are increasing in significance, and are being developed in all major coal producing

countries.

1.1.3 Gas in Coal

Bituminous coals contain a number of gases including methane, nitrogen, carbon dioxide

and ethane. The amount of gas retained and held by coal depends on various factors such as

pressure, temperature, pyrite content and the structure of the coal. Fresh coal contains more gas

than coal which has been subject to oxidation. Large volumes of gas can be accommodated on

the internal surfaces of the coal as a result of adsorption. It is released by the removal of

pressure, usually by mining or drilling. The gas may migrate into associated strata such as porous

sandstones which release the gas into openings such as boreholes and mine excavations.

The associations of gases with coal have been constant problem in mine workings since

underground coal mining first began. In underground workings, methane is released from coal

exposed at the coal face, plus the broken cola being transported through the mine. Methane is a

flammable gas and is explosive between a lower limit of 5% and upper limit of 15% when mixed

with fresh air. The highly combustible gas is known as “firedamp”. The faster the coal is mined,

the larger the amount of methane released into the workings, so that it is essential that an

adequate ventilation system is in operation. A danger is that of methane collecting in roof

pockets and in the upper parts of “manholes” or cuts in the roadway sidewalls where the rock

9

sequence may still be exposed. The methane content of the coal is usually referred to as coal-bed

methane (CBM).

1.2 Coal Use [4]

Coal is a versatile fuel and has long been used for heating, industrial processes and power

generation. Coal provides around 23% of global primary energy needs and generates about 38%

of the world’s electricity, generating some 4800Twh. (WCI 2001). In addition, 17% (600Mt) of

the world’s total black coal production is currently utilized by the steel industry, 70% of which is

dependant on coal.

1.2.1 Electricity generation

Electricity generation is singled out as one or the largest causes of pollution of the

atmosphere. The rapid growth of the demand electricity has led to large increases in production

and large increases in emissions, which in turn has brought attendant environmental problems.

Figure 1.2 shows the stages from coal delivery to electricity generation in a modern power

station

10

Coal mine

Coal Preparation Plant

Transport

Handling & Storage

Miling

Combustion

Steam TurbineFGD

Coal mineAdditional Unit Generation capacity

Particulates Removal

Electricity to Grid

Figure 1.2: The stages from coal delivery to electricity generation in a modern power station

1.2.2 Iron and Steel Production

Coal is heated in an oxygen-free environment until the bulk of volatile constituents have

been driven off. The solid residue is known as coke and its principal use is to provide heat

energy and to act as a reducing agent iron for iron ore in the blast furnace. Coke has to be a

strong material, able to withstand handling and be capable of supporting the overlying weight of

coke as it moves the blast furnace. Coke can be produced from a single coal or a blend of

selected coals. Only coals with specific range of rank and type are capable of forming coke, and

particular the coke produced

1.2.3 Industrial Use

Although the electricity generation and iron and steel production make up the bulk of the

use of coal by the industrial sector, coal is used in number of industries for heating. The principal

effect of coal on the environment is the venting of waste gases to the atmosphere. The share of

coal’s contribution to this has been reduced due to the fact modern industry has made substantial

reductions in the use of coal for conventional heating, having replaced it with gas or oil.

However, industries such as manufacture of cement still utilize significant quantities of coal.

Cleaning of the flue gas and reducing the particulate emissions are both contributing to the

improvement of air quality

1.2.4 Domestic Use

Coal as a household fuel has almost disappeared in most well developed countries. Strict

regulations on air quality in urban areas have led to the replacement of coal by gas an oil heating.

The thick smogs of large cities are now a thing of the past, although photochemical smog

produced by the internal combustion engine is still reality. In less developed countries, domestic

11

heating using using coal is still prevalent. In the China and Europe coal is plentiful, oil and gas

are expensive or not available, so atmospheric pollution can still reach high levels.

Improvements in industrial use and the gradual replacement of coal for heating will reduce the

problem, but this is likely to be a long term prospect.

1.3 Coal Transportation [4]

Table 1.1 shows the transportation of coal by road, rail and conveyor on land, and by

barge and oceangoing vessels on water.

Type of transportation Descriptions

Road transport

Coal is moved from mine to the customer by lorry fleets. This

means using public roads can cause problems such as wear and

tear, traffic congestion and dust from coal loads,

Rail transport

The overland transport of large shipment of coal by rail is

established means throughout the world. Rail transport has

little effect environmentally other than dust and noise at the

loading/ unloading areas. Where coal is loaded/ unloaded

automatically, such effects are minimized.

Conveyor

Overland conveyors are used to transport coal from mine to the

stockyard. Conveyors are usually covered and have no adverse

effect on the environment

Water transport

Coal transported by barge or ocean-going vessel has only a

dust problem on loading/unloading, and some coals has

propensity for spontaneous combustion

Table 1.1: Types of Coal Transportation

12

CHAPTER 2

THE ENVIRONMENT OF DEPOSITION OF COAL BED METHANE AND ITS

RESERVE WORLDWIDE

2.1 Introduction

In recent decades, coal bed methane reservoirs are rapidly being commercialized around

the globe and have become one of the important sources of energy in United States, Canada, and

other countries. Coal is defined as a rock composed of more than 50% organic matter by weight

and is thus by definition the rock type that is richest and organic matter. For this reason, coal is

considered an important petroleum source rock and important reservoir for natural gas. Other

than natural gas, coal also contains other significant gases such as carbon dioxide, hydrogen

sulfide and nitrogen. These common byproducts of oil and gas production are among the most

pollutants to the atmosphere and lead to green house effects.

A spectrum of geology factors including stratigraphy, sedimentology, structural geology,

hydrogeology, geochemistry and coal petrology will determines the properties of coal as a source

and reservoir rocks. Generally, coal contains diverse form of organic matter spanning abroad

range of chemical composition, and this compositional variability combined with geologic

history determine what types of hydrocarbons can be generated. Research of investigating the

mechanisms of hydrocarbon generation and geochemical relationship among organic matter, oil

and natural gas has been extremely active and is driven by mankinds due to the increasing need

13

for energy resources coupled with the necessity of developing these resources in an

environmentally responsible manner.

2.2 Gas generation in coal

Kerogen and coal undergo significant mechanical and chemical changes during burial,

and these changes are driven by compaction, biological activity and thermal kinetics. These three

factors are complexly interrelated and can be effective throughout the full depositional and

tectonic history of sedimentary basin. Metabolism of organic compounds by anaerobic bacteria

can generate large quantities of methane and humid acid. However, it will highly dependent on

temperature, nutrient flux and the flow of underground water. In general, most oil generation

occurs at temperature between 50 to 150oC and large volume of carbon dioxide can be generated

in this temperature range. Major thermogenic generation of gaseous hydrocarbon is thought to

begin at temperature 100 to 225oC and significant volume of nitrogen can be generated between

temperatures 100 to 150oC. Thermal cracking is important in this range, and as thermal maturity

increases and an increasing proportion of hydrogen is given off from coal structure, long chain

hydrocarbon can be transformed into short chain structure such as methane. In addition, bacterial

methanogenesis is thought to be an important mechanism of gas generation in coal.

2.3 Coal bed stratigraphy

Coal-bearing strata can be characterized using the petroleum systems concept, which

states that sedimentary basins contain integrated systems of source rocks, migration pathways,

reservoirs and seals. The possibility of coal as an oil- and gas-prone source rock controls on the

retention and expulsion of hydrocarbons generated from coal and the relationship of coal to a

spectrum of petroleum reservoir and seals. However the effectiveness of coal as an oil-prone

source rock is unclear, while the effectiveness of coal as a gas-prone source rock is practically

doubtless. The primary line of evidence is sheer predominance of gas-prone vitrinite to type III

kerogen. In addition, the large volume of natural gas that provides a mining hazard as well as an

economic resource in coal has led to the widespread interpretation that coal is principally a self-

resource natural gas reservoir.

14

Pyrolysis experiment had been conducted on both opened- and closed-system at high

temperature and low pressure to investigate the volume of natural gas that can be generated from

coal. The results showed that in closed-system pyrolysis indicate that about 3 to 20 times more

gas can be generated than can be retained. Therefore, it follows that an extremely large volume

of thermally generated natural gas has been expelled from coal and that coal can be considered as

a major source rock for natural gas in a range of reservoir types.

Once generated, hydrocarbon can migrate within coalbed into other formations or escape

to the surface. The major mechanisms of flow in coal include Darcian flow through

interconnected pores, including fractures and diffusion through coal matrix. Darcian flow is

influenced primarily by pressure gradients, density gradients and compaction, whereas diffusion

occurs in response to concentration gradients. These mechanisms can happen in other type of

rock such as carbonate, limestone or siliceous rocks depending on their permeability. However,

diffusion appears to be an extremely important mechanism for the expulsion and migration of

natural gas. Diffusion for oil appears to be of limited significance because of the diffusion

coefficient tends to be one to three orders of magnitude lower for oil than for gas.

Hydrocarbon and other gases can also be transported by dissolution in formation water.

The solubility of hydrocarbons in water decreases as the carbon number of the hydrocarbon

increases. For most hydrocarbons, solubility increases with increasing reservoir temperature but

decreases with increasing salinity. Other gases generated during coalification, including carbon

dioxide and nitrogen are soluble in formation water and may play role in the expulsion and

transport of hydrocarbons. Carbon dioxide is miscible in a broad range of hydrocarbon and

increases the mobility of oil by reducing its viscosity.

Other than above, sealing bed play a critical role in the migration and trapping of

hydrocarbons in porous rock. Faults zones can be migration pathways or reservoir seals, and

fault properties depend on a number of factors such as lithologic, juxtaposition, cataclasis, clay

smearing and cementation. Trapping mechanism for natural gas in coal and shale reservoirs

shows a big contrast with those in conventional hydrocarbon reservoirs. It is because a major

15

fraction of the retained hydrocarbon is adsorbed on internal rock surface. Adsorbed hydrocarbon

cling to the surface by van der Waals forces and storage capacity increase substantially with

confining pressure. In hydrocarbon reservoirs dominated by adsorption, no seal is required for

retention of large quantities of natural gas. However, some gas can be stored as a free phase in

coal macro pores, including cleats, and can form a significant gas resource.

Minor amounts of oil have been produced from coal. However, this production is

typically no more than a few barrels per well and is regarded by producers as more of a nuisance

than an economic resource. The dominance of adsorption as a gas storage mechanism in coal

gives rise to extremely complex reservoir dynamics.

2.4 Adsorption and gas capacity

Adsorption is a process in which gas or liquid molecules stick on to a surface, thereby

forming a monolayer or multilayer film. For gases in coal, an adsorbate film can approach liquid

density at a much lower pressure than it is predicted in ideal gas law. A monolayer is a film with

the thickness of one molecule, whereas a multilayer is a film with a thickness of two or more

molecules. Adsorption is thought to be a respond to a natural bonding deficiency that exists

along surfaces and development of a monolayer or multilayer effectively satisfies this deficiency.

It takes place by the process of physisorption and chemisorptions.

Physisorption is adsorption by van der Waals force, which is a weak intermolecular

attraction that takes place below the critical temperature of the adsorbate and can result in the

development of a monolayer or multilayer. Chemisorptions by contrast involve strong covalent

bond between the surface and the adsorbate can take place at supercritical temperature and

always in a monolayer. In general physisorption is considered to be dominant mode of

adsorption for gases on coal, although some maybe considered a monolayer adsorption due to

limited space in coal nanopores.

Gas capacity is expressed in terms of the adsorption isotherm, which determines how gas

capacity varies with pressure at a constant temperature. Adsorption curves in isotherm plots have

16

distinctive shape in which the slope of the curve is steepest near the origin and decreases as

pressure and gas capacity increase. Coal has nanoporous aromatic fabric with an extremely large

internal surface area where gases can be absorbed. The adsorption capacity of coal varies greatly

depending on the composition of the gas being adsorbed and the composition of the coal. Several

factors explain why the adsorption performance of different gases can vary so greatly. Large

molecules by definition form a thicker monolayer than small gas molecules and this account for

most of the differences among gases. Other factor such as the polarity and fugacity of the sorbate

molecule, as well as the ability of the molecule to satisfy sorbate surface bonding deficiency

through van der Waals force or covalent bonding, influence the volume of gas that can adsorb

onto a solid.

The gas content in coal must be estimated to determine the quantity of gas in place and

the level of gas saturation in coalbed methane reservoir. Direct volumetric and gravimetric

methods are commonly used to estimate the gas content. Volumetric methods involve the

determination of gas content by measuring changes or pressure caused by desorption in a

canister. In coalbed industry, gas content is typically determined from cores and results of

desorption studies indicate that gas content can be extremely variable but typically increases with

the depth. Ultimately, the same factors that influence sorption capacity are those that influence

gas content, and differences in the burial, thermal, and hydrologic history of a sedimentary basin

can result in highly variable levels of gas saturation.

2.5 Porosity and permeability

Coal contains a complex network of nanopores (<2 nm), mesopores (2–50 nm), and

macropores (>50 nm) in which fluids can be stored and can flow. The principal source of

nanoporosity in coal is apparently associated with the aromatic molecular structure of the

biopolymers that are preserved in coal, and, this is where the vast majority of adsorbed

compounds, including gases are stored.

Cleat systems are closely spaced (cm- to mm-scale), orthogonal fracture systems in coal

that are analogous to joint systems in other rock types. Face cleats are systematic fractures; that

17

is, they tend to be planar, exhibit a high degree of parallelism, and strike parallel to the maximum

horizontal stress direction during formation. Butt cleats, by contrast, are cross-fractures; they can

curve or have irregular surfaces, tend to strike perpendicular to face cleats, and tend to terminate

at intersections with face cleats.

Cleat height within a coal bed can be highly variable. Primary cleats are strata-bound

fractures that extend through a complete bench or bed of coal (height ¼ bed or bench thickness).

Many coal beds contain closely spaced primary cleats, which can give coal a columnar, or

“matchstick,” appearance. Secondary cleats are developed within a bed or bench (height < than

bed or bench thickness). Tertiary cleats are those that are restricted to a single coal band,

particularly vitrinite.

Most coal bed methane reservoirs have permeability on the order of 10 to 100 mD, and in

some areas coal as shallow as 700 m can have permeability lower than 1 mD. Permeability and

production performance can be influenced by the abundance and openness of natural fractures,

and characterizing the regional structural framework can be important for identifying

productivity sweet spots.

2.6 Reservoir pressure

Reservoir pressure which consist of lithostatic pressure and hydrostatic pressure play an

important role to control the gas capacity and reservoir behavior. Lithostatic pressure controls on

permeability, while hydrostatic pressure determined how much gas can be adhere in coal. A wide

range of hydrostatic pressure regimes have been identified in coalbed methane reservoirs.

Abnormal reservoir pressure is also common in coalbed methane reservoirs and consists of

underpressure where hydrostatic gradients are below the normal pressure. Extreme

underpressures where hydrostatic pressure gradients have been lowered below 5kPa/m are

known in areas of coalbed methane production that have been affected by dewatering associated

with longwall coal mining.

2.7 Reservoir temperature

18

Gas molecules become increasingly excited and less prone to remain in an absorbed state

as temperature increase. This will influenced the adsorption capacity and gas content of coal.

Reservoir temperature in coal bed methane reservoirs typically range from 21to 65oC, and over

this range, the adsorption capacity of given coal sample can vary almost 30%. Some substances,

like CH4 and N2, are gases that exhibit under all conceivable pressure-temperature conditions in

coal. Other gases, such as CO2, SO2 and H2S can exhibit distinct phase changes or non-ideal

pressure-volume-temperature behavior within the range of common reservoir conditions.

2.8 Worldwide Coal bed Methane Reserve and Resources

2.8.1 Australia

Australia is the world's fourth largest coal producer and the world's largest coal exporter.

The Australian Gas Association (Gas Statistics Australia, 2002) estimates that total Australian

resource coal bed methane is about 220 tcf. The majority of Australia’s Coal bed methane

resources occur in the eastern coast of Australia, primarily in the Australian states of Queensland

and New South Wales. Based on HIS data, proven reserves in Australia have been estimated at

nearly 9 tcf. Most of CBM reserves (about 7 tcf) have been discovered in Bowen-Surat Basins

followed by Galilee-Eromanga, Sydney, Otway onshore and Gunnedah basin (500 bcf each) Fig

2.1 shows Coal bed methane reserves (proven + probable) in Australia.(3)

19

Fig 2.1: Coal bed methane Reserves 2P in Australia by Basins

2.8.2 China

Coal bed methane resource in China is very abundant and the geological coal bed

methane resource volume is the third in the world next to Russia and Canada. From the newest

statistics of resource assessment, the methane-bearing area is of 41.54 x104 km2 under the buried

depth less than 2000min 45 coal-accumulating basins and the geological reserves is 36.8 x 1012

m3(36.8 tcm). There were 9 major coal bed methane basins (Odors, Qinshui, Junggar,

Diandongqianxi, Erlian, Tuha, Tarim, Tianshan and Hailaer) in China, each having geological

reserves of more than 1 x 1012 m3(1 tcm), as showed Fig 2.2. Their total reserve is 30.9 x1012

m3(30.9 tcm), which is 84% of the total resources of China. The geological reserves under the

buried depth less than 1000 m are 14.3 x 1012 m3(14.3 tcm) and the recoverable resources are

6.3 x1012m3(6.3 tcm). The geological reserves buried from the depth of 1,000 m to 1,500 m are

10.6 x 1012 m3(10.6 tcm) and the recoverable resources are 4.6 x1012 m3(4.6 tcm). The

geological reserves buried from the depth of 1500 to 2000 m are 11.9 x1012 m3 (11.9 tcm). Each

of the part domains one third of the coal bed methane reservoir reserves and the coal bed

methane reservoir under the buried depth less than 1000 m is of the largest commercial value.(1)

20

Figure 2.2: Top 9 Coal Bed M Basins in China

2.8.3 Europe

In the UK some of these exploration efforts resulted in the discovery of 15 fields with

total reserve size of 120 bcf, based on IHS data. Two of them are producing in the Midland

Valley Graben. In southern Poland, the coal bed methane resources is located at Upper Silesian

Coal Basin. The upside potential is estimated at some 1.0 tcf of gas (3). Figure 2.3 shows coal

bed methane Basins in Europe.

Figure 2.3: Coal bed methane Basins in Europe

2.8.4 Canada

It is estimated that Canada’s coal bed methane resources is about 540 TCF. The majority

of the CBM resources in Canada are found in Western Canadian Sedimentary Basin (WCSB).(2)

2.8.5 Indonesia

21

The untapped resources of coal bed methane in Indonesia are estimated to be at 453 tcf.

The majority of coal bed methane resources in Indonesia are found in the coal bearing basins of

South Sumatra and Kalimantan. (3)

CHAPTER 3

PROCESS TO DEVELOP OR EXTRACT THE HYDROCARBON FROM COAL BED

METHANE (CBM)

3.1 Introduction to Conventional Technique

Coal Bed Methane (CBM) is a natural gas containing 100% methane produced from coal

seam reservoirs. There are two methods to produce methane from coal bed. The first method is

through conventional technique by pumping large volumes of water in order to release the water

pressure that traps gas with the coal (M.V.Jadhav). The methane is adsorbed into solid coal

matrix and methane is released when coal seam depressurized. Wells are drilled into coal seam,

the seam is dewatered then methane is extracted, compressed and piped to market. Water is

pumping into the well for allowing methane to desorb from coal and flow as gas up to the well.

While dewatering is occurring, the operator should make sure that the pump jack is not

running too long. If the water level is pumped too low, this will allow the gas to travel up the

tubing into the water line, causing the well to become "gassy". The main objective is not to put

the gas in the water line, but to allow it to flow up the backside of the well (casing) and into the

pipeline, where it can be transported to the compressor station and delivered to the customer for

sales. Once the gas goes up the tubing, it is usually recovered in a water-gas separator at the

surface. However, pumping water and gas is inefficient and can cause pump wear and

breakdown.

22

The mass transport in the coal model consist two step processes. The first is on gas

diffusion from matrix to matrix in to the fractures, then a laminar fluid flow through the

fractures. Methane is physically bound to individual coal particles. The coal seam structure

consists of a coal matrix broken up by a system of natural fractures called cleats. Gas production

from CBM reservoirs is governed by a complex interaction of single phase gas diffusion through

primary porosity while two phase gas and water flows through cleat system.

The cleat system acts as a pathway in methane production; as shown in Figure 1. The

cleats are normally complete water saturated. Gas production starts as water is drained from the

cleats. When the reservoir pressure is reduced, gas molecules desorb from coal and diffuse

through the matrix to a cleat.

Figure 3.1: Schematic system in cleat system of coal

3.2 Enhanced Coal Bed Methane Recovery

The other method is through new technologies of extraction and recovery of CBM.

Usually, the methane recovery can be done by injection of various gases. One used enhanced

coal bed methane recovery using nitrogenase enzyme. Another enhanced CBM recovery is via

microorganisms. The primary recovery using water pumping, methane can be recovered up to

50– 60 % (M.V.Jadhav and J.N.Vishnukumar) but with new technologies, it can be recovered up

to 80% of methane produced.

23

Enhanced CBM recovery is done by injecting another gas in order to maintain the

reservoir, not for depressurized but reducing the partial pressure. The adsorption- desorption

behavior gases on coal plays important role in ECBM, as portrayed in Figure 3.2

(J.N.Vishnukumar).

Figure 3.2: Desorption of methane

Trend of Coal Bed Methane recovery is represented in Figure 3.3. Usually the secondary

recovery is done using the following techniques:

a) Selective adsorption of Carbon Dioxide, which in turn displaces methane.

b) Increasing cleat pressure and use of partial pressure mechanism by injecting Nitrogen gas

to displace methane.

24

Figure 3.3: General trend of methane production for various ECBM techniques

The conventional secondary recovery using the gas injection is around 6 – 8% and total

recovery using primary and secondary will be approximately 60%, which significantly less than

natural gas recovery (75 – 80%). Using gas injection, there are some disadvantages occurs in

this method:

1. It is difficult to purify the CO2 from a mixture of flue gases.

2. Coal swelling may occur.

3. Using N2 to reduce the partial pressure may have early breakthrough in CBM production.

25

2. Immobilization of the enzyme in suitable media.

3. Application of semipermeable membrane to prevent loss of nitrogen and enzyme.

4. Injection of enzyme with appropriate substrate.

7. Ammonia passes through the membrane into coal seam.

8. Selective adsorption of Ammonia is favoured on coal surface due to high adsorptivity.

9. Higher amount of methane is desorbed which leads to better recovery.

5. Injection of nitrogen.

3.2.1 Enhanced Coal Bed Methane recovery using Nitrogenase enzyme

Since Nitrogen gas is most easily available, a biogenic enzyme is used to fix the Nitrogen

as Ammonia (CH3). Ammonia has a higher adsorptivity on coal surface compared to Nitrogen,

thus Ammonia is more efficient in desorbing the methane. Therefore, better production of

methane can be expected. The basic equation of conversion from Nitrogen to Ammonia as

shown below:

N2 + 8H+ + 8e- 2NH3 + H2

Enzymes are defined as a biocatalysts synthesized by living cells. Usually, enzyme is

protein in nature, colloidal and specific in their action. They increase the activity and improve

rate of reaction. Enzymes are best catalyst due to its great specifity and high turnover rates. The

mechanism in ECBM using Nitrogenase enzyme is outlined as follows:

1. Extraction of Nitrogenase enzyme from nitrogen fixing bacteria.

6. Nitrogen is converted into Ammonia in presence of Nitrogenase enzyme.

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The proposed set for the ECBM is shown as below in Figure 3.4:

Figure 3.4: Basic Setup on the ECBM using Nitrogenase Enzyme

From the literature, it is found that the adsorptivity of Ammonia is higher than Nitrogen, Carbon

Dioxide and Methane. Considering the ammonia solubility in water at reservoir condition, it is

determined that the amount of ammonia dissolved in water will be minor.

The basic flow path equation for ECBM using Nitrogenase enzyme are:

N2 + 8H+ + 8e- 2NH3 + H2

N2 + Nitrogenase enzyme NH3

Figure 3.5 shows the molecular structure of Nitrogenase enzyme. In coal cleat, ammonia

distributes into two phases; first ammonia dissolved in water. Then ammonia adsorbed in coal

surface. Using the data calculated, it is found that more 70% of Ammonia adsorbed on the coal

surface. Figure 3.6 shows ammonia in coal seam.

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Figure 3.5: Molecular structure of Nitrogenase enzyme

Figure 3.6: Explanation of Ammonia in coal seam

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3.2.2 Enhanced Coal Bed Methane using Microorganism

There are two principle methods of ECBM recovery using microorganism. The first is

use of nitrogen injection and the second one through displacement desorption employing carbon

dioxide injection. Nitrogen is chosen as an injection gas due to its availability while carbon

dioxide gives benefit of green house sequestration. Injection of N2 – CO2 mixtures rich in N2

lead to fast recovery of methane, while mixtures rich in CO2 gives slower initial recovery

increases breakthrough time and decreases the injection to sweep out the coal bed. Based on

M.V.Jadhav paper, it more focuses on fixation of nitrogen and carbon dioxide with help of

bacteria.

Bacteria are unicellular and prokaryotes (organism that have false nucleus). Some of

classification of bacteria are cryophilic, thermophilic and hyperthermophilic. The thermophiles

bacteria can sustain and reproduce at temperature as high as 700C. Prokaryotes and free living

bacteria only responsible for fixing nitrogen and carbon dioxide. These bacteria should be strictly

anaerobic or facultative anaerobes where in coal seam, it is oxygen free.

Bacteria can be reproduced by binary fission. The main advantage of binary fission is that

one cell divides producing two cells. There are four phases where bacteria can be present at

various interval of time:

Lag Phase – the addition of inoculums to a new medium. Then, double the

population while bacteria grow in size.

Log Phase – the cells divide steadily at a constant rate. The generation time of

bacteria can be calculated using special log formula.

Stationary Phase – the growth begins to taper off after several hours.

Decline Phase – the bacteria die in this phase.

The conversion of molecular nitrogen into ammonia is known as nitrogen fixation. Some

examples of Nitrogen – Fixing bacteria are Azospirilum lipoferum, Tricodesmium and

Methylomonas methanitrificans. For Carbon dioxide fixation, these archaebacteria generated to

reduce CO2 with the formation of methane gas. Some examples of Carbon dioxide – Fixing

bacteria are Carboxydotrotrophic, Arthobacter and Methanobacterium.

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From the experiment done, the optimum growth conditions are scored by measuring

methane concentrations after 48 hours inoculation. The methane production rate is determined

from consecutive methane concentration measurements. In inoculation, microbes are injected

followed by injection of N2 and CO2. This ensure that time for bacteria to settle down on coal

matrix is quite sufficient. After settling down, the bacteria fix nitrogen in to the form of ammonia

while carbon dioxide fixing bacteria use the glucose and CO2 to release methane.

The adsorption/ desorption of the components to/from coal bed surface is approximated

by an extended Langmuir isotherm and the gas phase behavior is predicted by Van der Waal’s

interaction forces. Figure 3.7 represent the Langmuir isotherm and break through curve for the

ammonia.

Figure 3.7: The Langmuir isotherm and break through curve for ammonia

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As a conclusion, the conversion of nitrogen to ammonia may lead to more recovery. The

methane production can be enhanced by 8 – 10% by using the microorganism to increase the

methane recovery in coal seam, which is more ecofriendly and save to the environment.

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CHAPTER 4

THE CHALLENGES OF OIL AND GAS INDUSTRY IS FACING IN SOURCING THE HYDROCARBON

4.1 Introduction

There are several challenges has been facing by the oil and gas industry in sourcing the

hydrocarbon from coal bed methane (CBM). The first challenge is the development of CBM was

produce large amount of water and this water improperly managed. This is occurs as a result of

the large amount of water being pumped from coal seam aquifers. Besides that, the effect of

carbon dioxide produce from methane recovery plant on environment is concerned. To reduce

the effect of this gas, carbon dioxide will be used back to enhance the CBM recovery by

injecting back to the CBM reservoir.

4.2 CBM product water management

4.2.1 CBM development reduce flow to streams, springs and wells

Large amount of water being pumped from coal seam aquifers, cause the impact to

springs and streams and to the level of water in drinking and livestock wells. This happens at

very specific location. If a spring or stream is fed by a coal seam aquifer (the coal seam surfaces

and discharges water into a stream or spring), CBM development in the local area may decrease

flow to those water bodies. And if a spring or stream is not fed by a coal seam aquifer, decreases

in flow would be minimal. However, if CBM product water is land applied or impounded in a

holding pond (most often these ponds are not lined and discharge to the subsurface), streams

down slope may have increased flow during development due to subsurface flow. If a drinking

water or livestock well gets water directly from a coal seam, then CBM development in the local

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area may decrease the water level in that well. Duration of impacts to spring flow and water

available from wells will depend on the total area developed and timing.

4.2.2 The quantity of the CBM product water

Extraction of CBM involves pumping large volumes of water from the saturated coal

seam in order to release the water pressure holding the gas in the coal seam. Each well produces

5 to 20 gallons of water per minute. At 12 gallons per minute, one well produces a total of

17,280 gallons of water per day. It is common to have one well every 80 acres, and in the

Powder River Basin, there are up to three methane-bearing coal seams. Therefore, there may be

up to three wells per 80 acres.

4.2.3 The quality of CBM product water and its effects on soil

CBM product water has a moderately high salinity hazard and often a very high sodium

hazard based on standards used for irrigation suitability. Irrigation with water of CBM product

water quality on range or crop lands should be done with great care and managed closely. With

time, salts from the product water can accumulate in the root zone to concentrations which will

affect plant growth. Saline conditions stunt plant growth because plants must work harder to

extract water from the soil. The sodium hazard of CBM product water poses additional threats to

certain soil resources.

Sodic irrigation water causes soil crusting and impairs soil hydraulic conductivity,

adversely affecting water availability and aeration and subsequent crop growth and yield. Upon

wetting of soils containing swelling clay, sodium causes the degree of swelling in the clay to

increase, leading to dispersion and migration of clay particles. Current research at Montana State

University shows that water with sodium levels equal to typical Montana CBM product water

can degrade the physical and chemical properties of heavier, clay soils, making such soils

completely unsuitable for plant growth.

The risk of sodium degradation has been observed in other soil textures. Jim Oster

(personal com.) observed crusting, poor soil tilth, hardsetting and aggregate failure on a sandy

loam soil irrigated with water with EC ~ 1 and sodium adsorption ratio (SAR) ~ 7. Minhaus

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(1994) saw irreversible and severe reduction in infiltration on sandy loam soil with long term

irrigation under high SAR water followed by monsoon rain.

There are many factors in addition to soil textures that affect infiltration rates.

Mineralogy, lime, sesquiozides, organic matter content, cultivation, irrigation method, wetting

rate, antecedent water content and time since cultivation all play a role in infiltration. The only

way to be certain of the impacts of sodic irrigation water on the soil is to periodically sample and

test the irrigation water and the soil.

4.2.4 The quality of CBM product water and its effect on plants

Disposal of the quantities of CBM product water into stream channels and on the

landscape poses a risk to the health and condition of existing riparian and wetland areas. High

salinity and sodium levels in product water may alter riparian and wetland plant communities by

causing replacement of salt intolerant species with more salt tolerant species. It is well

recognized that encroachment of such noxious species as salt cedar, Russian olive, and leafy

spurge is enhanced by saline conditions.

Impounded CBM discharge in an ephemeral channel. Encroachment of halophytic weed Die-off of plants within weeks of release. species within one season.

Figure 4.1: Left: An example of soils of eastern Montana that are high in swelling (montmorillonitic) clay. Right: Complete dispersion of the same soil following a season of exposure to high saline/sodic water.

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4.2.5 Managing CBM product water

Currently, CBM product water in the Powder River Basin is managed by the following

methods:

a. Discharged into a stream channel - Although direct stream discharge is

no longer

permitted on new wells, existing operations were "grandfathered" and are still

discharging directly into streams. Also, proposals are being advanced to allow

regulated discharges during certain flow conditions.

b. Impounded - This method involves constructing a pond in which CBM product

water is stored or allowed to infiltrate to the subsurface. There are several terms

for these impoundments: "holding ponds", "zero discharge ponds" or "infiltration

ponds". Although they do not directly discharge water on the land surface, most

impoundments are not lined and do discharge to the subsurface. Some percentage

of seepage flow from impoundments is likely to reach stream channels via

subsurface flow.

c. Land applied to crop or rangeland - through some form of irrigation equipment.

d. Other uses - CBM product water is also used for dust control and, in some cases,

is being used by coal mines.

Another option proposed for disposal of CBM product water in eastern Wyoming and

Montana is to reinject the CBM product water back into an aquifer(s). This practice occurs in the

southwest U.S., where CBM product water is injected into formations below CBM-bearing coal.

This approach avoids surface discharge.

4.3 Carbon Dioxide (CO2) Sequestration with Enhanced CBM Recovery

There is a growing concern in the international community that CO2 emissions from

burning fossil fuels may play an important role in global climate change. Recent efforts in

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reducing the carbon content in fuels and improving the energy efficiency can certainly help in

reducing the amount of CO2 released into the atmosphere.

The first large-scale opportunities for carbon dioxide sequestration are likely to be

associated with storage in geologic formations. These geologic formations include oil and natural

gas reservoirs, saline aquifers, and coal beds. In some instances, the recovery of a saleable

commodity will offset the cost of sequestration. Included within this category are CO2 injection

for enhanced oil recovery, reassure maintenance of oil or gas reservoirs, and enhanced methane

production from coal seams. Of the sequestration options available, geologic sequestration of

CO2 in coal formations to enhance coal bed methane production is considered one of the methods

with the greatest short term potential. Figure 2 shows the CO2 sequestration process at BP’s

Tiffany field. CO2 from methane recovery plant is injected back to CBM reservoir in order to

enhance CBM recovery.

Figure 4.2: CO2 sequestration with enhanced coal bed methane recovery at BP’s Tiffany Field.

Current research activities focus on addressing the risks involved in geologic

sequestration of CO2 in coal seams. The actual CO2 sequestration capacity of coal is largely

36

dictated by how effectively injected gases contact and interact with the reservoir over the active

project lifetime and also defined as the economic limit for methane recovery and CO2 storage.

Usually this is dictated by CO2 breakthrough, poor injectivity or a variety of other factors that

make further operation economically prohibitive.

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CHAPTER 5

CONCLUSION

Coal plays an important role as an alternative energy source. The methane content of the

coal is usually referred to as coal-bed methane (CBM). A spectrum of geology factors including

stratigraphy, sedimentology, structural geology, hydrogeology, geochemistry and coal petrology

will determines the properties of coal as a source and reservoir rocks. Worldwide CBM reserve

and resources are in Australia, China, Europe, Canada and Indonesia. Two methods to produce

methane from coal bed are by using conventional techniques and Enhanced Coal Bed Methane

Recovery.

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REFERENCES:

Chapter 1

[1] Energy Information Administration, 2008. www.eia.doe.gov .

[2] Koplow.D, “Bio fuels At What Cost? International Institute for Sustainable

Development”, October 2006,

[3] Wood, D.A., 2009a. Global LNG Report: Uncertain supply and demand outlook for

LNG, World Oil”, February 2009

[4] Larry Thomas, “Coal Geology”, John Wiley & Sons, LTD, 2002

Chapter 2

[1] D.K. Luo*, Y.J. Dai, L.Y. Xia, Economic evaluation based policy analysis for coalbed

methane industry in China, Elsevier, 2010

[2] Ali S. Ziarani, Roberto Aguilera, Chris R. Clarkson, Investigating the effect of sorption

time on coalbed methane recovery through numerical simulation, Elsevier, 2011

[3] Alex Chakhmakhchev, IHS, Worldwide Coalbed Methane Overview, Society of

Petroleum Engineers, 2007

Chapter 3

[1] J.N. Vishnukumar, “Enhanced Coal Bed Methane Recovery Using Nitrogenase Enzyme”, SPE-113033-STU, November 2007

[2] D.W.Moore, J.F.Lea, J.cox, “Coal bed Methane Production Facilities: A Case History,SPE 20668,Arco Oil & Gas Co, September 1990”

[3] D.A.Sampson, J.F.Lea, J.C.Fox, “Coal Bed Methane Production”, SPE 80900, BP America and Texas Tech University, March 2003

[4] J.F.Manrique, B.D.Poe Jr, K.England, “Production Optimization and Practical Reservoir Management of Coal Bed Methane,”SPE 67315, Schlumberger, March 2001

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[5] M.V.Jadhav, “Enhanced Coalbed Methane Recovery Using Microorganisms” SPE 105117, Maharashtra Inst.of Technology, March 2007

Chapter 4

[1] Kristin Keith and Jim Bauder, “ Coal Bed Methane” Montana State University-Bozeman John Wheaton, Montana Bureau of Mines and Geology, 2003

[2] http://en.wikipedia.org/wiki/Coalbed_methane

[3] http://en.wikipedia.org/wiki/Coal_bed_methane_extraction

[4] http://waterquality.montana.edu/docs/methane/cbmfaq.shtml

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