CHAPTER 3 Petrography of Coal: A tool for evaluation of...

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CHAPTER 3

Petrography of Coal: A tool for evaluation

of CBM potential

3.1 Introduction

Petrography of coal is concerned with the macroscopic and microscopic description of the

coal materials, i.e., macerals or maceral groups (an indicator of coal type), mineral matter,

elemental composition and the vitrinite reflectance is usually considered as rank indicator.

The percentage of vitrinite reflectance, fixed carbon, volatile matter, moisture content and

ash determine the rank of coal. Appreciable volume of methane including other

hydrocarbons is generated during coalification processes which transform woody materials

into coal (Fig. 3.1). Maximum volume of methane obtained from coalbeds are formed by

thermogenic process, where interns are controlled by burial history, maceral composition

and basin hydrodynamics [Berbesi et al., 2009, Scott and Kaiser, 1996]. A part of the

generated gas is retained into the coal in adsorbed condition and remaining escapes from

coalbeds. The petrographic composition, coal rank and the type of organic matter are some

of the main factors controlling the quality and quantity of gaseous hydrocarbons retained by

coal [Gurdal and Yacin, 2000; Quick and Brill, 2002; Mastalerz et al., 2008]. Coal rank

indicates the level of maturation of coal, potential of methane generation, the storage

capacity and development of cleat network in coal/coaly bed. Out of all four ranks of coal

(peat, lignite, sub-bituminous, bituminous and anthracite), bituminous shows the maximum

capacity to adsorb coalbed methane as shown in Fig. 3.2. The methane retention capacity

becomes economical in high volatile bituminous coals and peaks at medium volatile

bituminous coals. Gas holding capacity of coal is related to carbon percentage, moisture

content, ash percentage and volatile matter into the coal. In most of the cases, moisture

content decreases with increasing depth and increasing rank of coal [Sivek et al., 2010].

Theoretically, lower moisture and ash content in coal can provide more sites for methane

adsorption [Bustine and Clarkson, 1998; Crosdale et al., 2008; Joubert et al., 1974; Ozdemir

CHAPTER-3 Petrography of coal

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and Schroeder, 2009], hence gas holding capacity in high rank of coal is more than the

lower one. However, again gas adsorption capacity starts to decrease in low volatile

bituminous to Anthracite because of reduction in porosity. In lignite coal although it has

abundant porosity, the gas retention capacity is less due to presence of higher moisture

content. Mineral matter plays an important role for methane retention capacity into the coal.

Mineral matter in coal acts as an inert component and reduces the number of sorption sites.

So with increasing mineral matter in coal the sorption capacity decreases [Brown et al.,

1996]. Petrological aspect is important for evaluation of rank of coal and it depends upon

the volume of maceral group, i.e., vitrinite, semi-vitrinite, liptinite, inertinite, mineral

matter and the mean vitrinite reflectance into the coalbed. The vitrinite maceral is related to

CBM potentiality because of its methane storage capacity, presence of higher proportion of

micropores which results in more surface area and high adsorption capacity.

Fig. 3.1: Generation of Coal

(Source http://www.uow.edu.au/eng/pillar/images/about/coal_rank.jpg)


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Commercial CBM generating coals have reflectance values between 0.7-2.0% [Chandra,

1997]. Reflectance of vitrinite is the main component for development of natural fracture

and cleats into the coalbeds which are responsible for storage and flow of gases through

coalbeds. The cleats are generated during coalification process. The development of cleat

systems within the coal is controlled by exogenic and endogenic processes [Acosta et al.,

2007]. Ammosov and Eremin [1963] and Pashin et al., [1999] observed that most of the

cleat were generated during the bituminous rank stage while their abundance is decreased at

high rank due to an increase in the thermal maturation with the progress of coalification.

Developments of microcleats are more near the medium volatile bituminous rank of coal

and then start to decrease. Initial increase in the development of cleats takes place upto

vitrinite reflectance Ro~1.3 (medium volatile bituminous rank), thereafter, followed by a

reduction in cleat formation [Laubach et al., 1998, and Su et al., 2001]. Depending upon the

cleat density and opening of cleats, permeability of coal varies which increases with

increasing cleat density and opening. So, studies of coal quality parameters which include

grade, chemical composition, maceral composition, rank and physico-mechanical properties

are important for characterizing CBM reservoir and gas flow potential of coal [Kim, 1977;

Levine, 1993; Lamberson and Bustin, 1993; Bustin and Clarkson, 1998, Paul and

Chatterjee, 2011a, b].

Fig. 3.2: Relation between rank and gas content of coal


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CBM reservoir exploration and its characterization may be complex due to heterogeneity

and spatial variation in maceral composition [Chalmers and Bustin, 2007].

The objectives of this chapter are (i) to evaluate coal chemical properties from proximate

and elemental analysis of coal samples, and (ii) determination of maceral groups present in

coal samples under study, (iii) Measurement of vitrinite reflectance, (iv) SEM study and

FTIR study for identification of functional groups present in the samples. Based on

chemical and petrographic characteristics, an attempt has been made to estimate the rank of

coal and capacity for production of CBM.

3.2 Proximate analysis

Proximate analysis is the study of physico-chemical parameters of coal and can be used to

establish the grade and rank of coals as mentioned earlier. For the present study, Bureau of

Indian Standard procedures [BIS Standard: 1350, Part-1, 2003] were followed to determine

moisture, ash and volatile matter content of coals. Coal proximate analysis was carried out

in the Coalbed Methane Laboratory, Department of Petroleum Engineering, Indian School

of Mines, Dhanbad.

3.2.1 Determination of Moisture

One gm of the powdered air-dried sample was weighed and spread uniformly in a petri-dish

which was pre-heated at 108˚C, cooled and weighed. The uncovered petri-dish containing

the sample was weighed and heated in a drying oven at 108˚C±2˚C for 1.5 hours until there

is no further loss in mass. The petri dish was covered, cooled in a desiccator and weighed

again as soon as the samples have reached room temperature. The loss in mass during

drying is reported as the percentage of moisture content in the sample. Calculate the

moisture percentage in the analysis sample as follows:

Moisture in analysis sample, 2 3% 100

2 1

W W

W W

Where, W1 is the weight of empty glass petri dish with lid, (gm), W2 is the mass of the glass

petri dish with lid and coal sample before heating, (gm) and W3 is the mass of the glass

petri dish with lid and sample after heating.


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3.2.2 Determination of Ash content

Total 0.50 gm of the powdered air dried sample was taken in a clean platinum crucible of

known weight. The uncovered vessel containing the sample was weighed and inserted into

a muffle furnace and heated in air to 500˚C in 30 minutes. The temperature was raised from

500˚C to 815˚C±10˚C for a further 30-60 minutes and maintained at this temperature for

another 60 minutes until there is no further loss in mass. The crucible was covered with a

lid, removed from the muffle furnace and cooled in a desiccator. The cooled vessel was

weighed. The mass of remaining of burnt coal is expressed as a percentage of the total mass

of sample and is reported as the percentage of ash yield in the sample.

Ash in analysis sample, 3 1% 100

2 1

W W

W W

Where, W1 is the weight of empty platinum crucible with lid, (gm), W2 is the mass of the

platinum crucible with lid and coal sample before heating, (gm) and W3 is the mass of the

platinum crucible with lid and sample after heating.

3.2.3 Determination of Volatile matter

Total 0.5 gm of the powdered air dried sample was taken in a clean platinum crucible of

known weight. The covered crucible containing the sample was weighed, inserted into a

muffle furnace and heated out of contact with air at 900˚C ±10˚C for 7 minutes in absence

of air. The covered crucible was then removed from the furnace, cooled in a desiccator and

weighed. The percentage of loss in mass with respect to the total is expressed as percentage

of volatile matter.

Volatile matter in analysis sample, 2 3% 100 %

2 1

W WM

W W

Where, ‘W1’ is the weight of empty platinum crucible with lid, (gm), ‘W2’ is the mass of

the platinum crucible with lid and coal sample before heating, (gm), ‘W3’ is the mass of the

platinum crucible with lid and sample after heating and ‘M’ is the percentage of moisture in

the sample on air dried basis.


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3.2.4 Determination of Fixed Carbon

Percentage of fixed carbon is obtained by difference of the moisture percentage, ash

percentage, and volatile matter percentage from 100.

FC= 100-(% M +% A+% VM)

Where, ‘FC’ is the fixed carbon percentage, ‘%M’ is the moisture percentage, ‘%A’ is the

ash percentage and ‘%VM’ is the percentage of volatile matter.

3.2.5 Dry ash-free basis (daf) calculations

For comparison of the results of proximate analysis of different coals, the results obtained

on air dried coal is recalculated on dry ash free basis or generally known as pure coal basis.

Therefore, for Dry ash free (daf) basis calculation the formulae is as follows:

V.M. (daf), % = {V.M. (air dried) ×100}/ {100-(M+A)}

Where, ‘M’ is the percentage of moisture on air dried basis, ‘A’ is the ash percentage on air

dried coal and ‘VM’ is the volatile matter in air dried basis.

Classification of India coal: The general classification of Indian coals and lignites is given

in Table 3.1.

3.3 Elemental analysis

The elemental analysis (C, H, N, S and O) of coal samples collected from different wells of

Jharia coalfield and Singareni coalfield has been analyzed by elemental analyzer

(ElementarVario EL III- CHNS analyzer) in the Department of Fuel and Mineral

Engineering, Indian School of Mines, Dhanbad. The experimental set-up and schematic

diagram of the setup are shown in Fig 3.3 and Fig. 3.4.

Some features of the instrument are:

I. Small pellets with a pinch of titanium oxide along with the sample are prepared and

used for analysis.


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II. Long time stability of the multipoint calibration of the analyzer allows maintenance

free operation over night.

III. The solid samples vary in weight from micro (< 1mg) to macro (1 g) depending on

sample composition whereas bulky samples of up to 1 ml volume can also be

analyzed.

IV. During quantitative high temperature decomposition, the temperature up to 1200°C

(1800°C during combustion) for analytical accuracy was applied.

V. Gas separation with "purge and trap" technique serves for large concentration range,

detection sensitivity.

VI. Helium is used as the carrier gas.

VII. Jet injection of oxygen supplies high concentration at the place of combustion with

very low total usage.

VIII. Carbon is converted to carbon dioxide, nitrogen to nitric oxide, sulphur to sulphur

dioxide and hydrogen to water vapour. Each of these components is collected in

separate chambers.

IX. Analysis time is automatically optimized.

X. All analytical results are automatically calculated and complete operating conditions

for each sample are stored.

XI. Easy operation and maintenance, low consumable costs and no expensive special

catalysts.

XII. Compact design, easy installation and handling, cost effective operation 230/110 V,

50/60 Hz, approx. 1800 VA.

Fig. 3.3: ElementarVario EL III- CHNS analyzer


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Fig. 3.4: Schematic diagram of CHNS analyzer

3.3.1 Importance of elemental analysis

One of the major parameters for determination of coal ranks are elemental compositions

mainly carbon content of coal. Rank of coal increases with increasing carbon content. The

particular organic matters present in coalbeds are classified based on H/C and O/C atomic

ratios [van Krevelen, 1993]. Three main types of kerogen (Type I, Type II and Type III)

occur which are associated in specific geological settings [Tissot and Welte, 1984]. The

elemental analyses data are used for classification of kerogen type in a van Krevelen

diagram (Fig. 3.5) and this graph commonly demonstrates the path of chemical changes of

kerogen and coal macerals which can associate with coalification process and hydrocarbon

generation. The H/C and O/C atomic ratios decrease with increased thermal maturation of

organic matter along the paths of van Krevelen diagram which indicates the corresponding

kerogen and maceral types.

Type I Kerogen: Type I kerogen formed from proteins and lipids and Alginate is the main

organic constitute. The O/C atomic ratio is less than 0.15 and H/C atomic ratio is greater

than 1.25 for type I kerogen.


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Type II Kerogen: Type II kerogen is formed from lipid deposits under reducing conditions

and sapropelic organic matter (Liptinite) is the main constitutent. In Type II kerogen the

O/C ratio ranges from 0.03 to 0.18 and H/C ratio is less than 1.25.

Type III Kerogen: Vitrinite (humic organic matter) is the main organic component in type

III kerogen. For type III kerogen the H/C ratio is less than 1 and O/C ratio varies from 0.03

to 0.30. Type III kerogen is the product of plant material enriched in vitrinite maceral and

recognized as highly gas prone compared to type I and II kerogen.

Fig. 3.5: A van Krevelen diagram showing different kerogen types and positions of coal

and maceral groups relative to hydrogen-carbon and oxygen-carbon atomic ratios [modified

from Cornelius, 1978]


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3.4 Petrographic analysis of coal in laboratory

Coal petrographic analysis for collected coal samples from different coalfields and different

wells were carried out at the Central Institute for Mining and Fuel Research, Dhanbad.

Identification of various maceral groups and measurements of vitrinite reflectance (VRo) in

oil medium was carried out on polished coal surface in reflectance with white light and

fluorescence illumination using Leica DMRXP-HC advance research polarizing

microscope. Analysis was carried out as per Bureau of Indian Standards [BIS No 9127

part 2 for preparation, grinding and polishing of pellet, part 3 for maceral and mineral

identification and part 5 for VRo measurement].

Preparation of coal samples and its studies (maceral analysis and VRo) are described below:

3.4.1 Preparation of representative coal sample

For the preparation of coal samples following steps were followed:

I. The coal samples were broken at 1/2 to 1/4 inches then 1/8 to 1/16 inches and

reduce the volume by quarter and coning method to the required level, i.e., 50 gm to

100 gm in accordance with ISO 1988.

II. The sample was crushed to 16 mesh (1119 micron or 1.19 mm) by controlled

crushing and was sieved through 16 mesh/18 mesh sieve. The filtered samples were

used for pellet preparation which was retained by 18 mesh sieve.

III. The filtered samples (18+ mesh) were spread on the flat surface/ paper in a circular

fashion and then a representative coal sample (5-10 gm) was prepared for pellet

preparation by lifting the spread sample from all corners and middle by

spoon/spatula.

3.4.2 Pellet preparation from representative coal sample

Pellets used for experimental purposes were prepared as per Indian standard [IS. 9127, Pt. 2,

2002/ISO 7404-2:1985]. The volume of the pellet was 25 mm3

and the size of coal sample

was within 840 micron to 1 mm. The representative sample was very carefully crushed so

that it did not produce too much fines. About 3 gm to 6 gm of the sample was mixed with a


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synthetic resin in a mould of the above size. The pellet when hardened was ground and

polished as per the method laid down in the Indian standard [IS No. 9127, Pt. 2, 2002].

3.4.3 Instrument

Leica DMRX polarised light microscope fitted with a 50X oil immersion objective and 10X

paired oculars and a swift point counting was used for petrographic analysis. One of the

oculars was equipped with an adjustable eye piece in which a micrometer graticule was

placed for maceral analysis and reflectance measurements. The slide of an automatic point

counter capable of holding and moving the polished surface was fixed to the stage of the

microscope. The number of push buttons corresponds to the number of macerals and the

mineral matter was classified.

3.4.4 Analytical procedure

3.4.4a Maceral analysis

The maceral analysis has been carried out as per the method described in IS 9127(Part 3):

2002. The polished pellet was fixed on the holder of the slide in such a position that

measurement began in one corner of the specimen. The initial readings of the point counter

were read off and recorded. The point-to-point and line-to-line distances were chosen

according to the diameter of the largest grain, i.e., for a grain size below 1 mm, both the

maximum point-to-point and line-to-line distances were 0.5 mm. However, the normal

distances for maceral analyses lie between 0.3 mm and 0.5 mm. With 0.5 mm intervals, a

polished surface of 2.5 x 2.5 cm represents 800 to 1000 points so that the required

minimum of 500 points on coal was recorded with certainty.

In each case the maceral coincident with the intersection of the cross hairs was taken into

consideration. The total area of the pellet was examined, because macerals are distributed

irregularly. At the end of the measurement the values indicated in the counter were read off

and recorded. The mineral substances either associated with the macerals or free were

recorded as a total, without subdivision into individual minerals that were, however, made as

and when necessary.


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After completion of the analyses the number of grains counted for each individual maceral,

maceral group or mineral was expressed as a percentage of the total of points recorded.

Thus, the values obtained were looked upon as volume percentages.

3.4.4b Reflectance Measurement

Reflectance measurements were carried out using the same microscope following the Indian

and International standard methods [IS 9127, Part. 5: 2002]. Microscope is attached with

photomultiplier and following the analyses by MSP software and ‘J’ and ‘M’ make control

unit. In all the cases random reflectance (under oil) was measured on vitrinite grains for

rank determination.

3.5 Calculation of Vitrinite Reflectance from empirical equation

Vitrinite reflectance of coal was determined by using empirical equation given by Rice

[1993] and from laboratory studies. The value of vitrinite reflectance (VRo %) gives an idea

about the coal rank. The vitrinite reflectance value of coals is calculated by using the

following formula:

% 2.712 log( ) 5.092oR VM 3.1

Where, ‘Ro’ is reflectance value of vitrinite macerals and ‘VM’ is the dry, ash free volatile

matter of coal. This equation was developed for USA coal samples. Empirical correlation

for the Indian coal has been developed in the present study also and described in this

chapter.

3.6 Results and Discussion

The coal samples have been collected from three different wells (Well J1, Well J2 and Well

J3) of Jharia coalfield, Jharkhand, two different wells (Well R1and Well R2) of Raniganj

coalfield, West Bengal and two different boreholes from Singareni coalfield, Andhra

Pradesh. The rank and CBM potential of collected coal samples from different wells was

evaluated on the basis of chemical analysis and petrographic results.


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3.6.1 Chemical characteristics

3.6.1.1 Jharia coalfield

Total 40 numbers of samples were collected from 3 different wells (well J1, well J2 and

well J3) of Jharia coalfield and characterized in laboratory.

3.6.1.1a Proximate analysis

Ash content: Ash yields, which is an indicative measure of mineral matter, vary from 11.5

wt% to 26.6 wt% for well J1, from 10.26 wt% to 24.17 wt% for well J2 and from 14.50

wt% to 40.06 wt% for well J3. Ash content with respect to depth of seam burial for well J1

is shown in Fig. 3.6. Ash content is relatively higher in the coal samples collected from

deeper depths of well J1.

Fig. 3.6: Variation of ash content with depth (m)

Moisture content: Moisture content of samples varies from 0.50 wt% to 0.73 wt% for well

J1, from 0.17 wt% to 1.80 wt% for well J2 wt% and from 0.20 wt% to 0.32 wt% for well

J3. A cross plot between moisture content and depth exhibits a negative correlation and is

shown in Fig.3.7 and Fig. 3.8 for well J1 and well J2 respectively.


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Fig. 3.7: Variation of moisture content with depth (m) for well J1

Fig. 3.8: Variation of moisture content with depth (m) for well J2


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Volatile matter: Volatile matter on dry-ash free basis ranges from 28.4 wt%. to 16.5 wt%

for well J1, from 9.19 wt% to 24.15 wt% for well J2 and from 15.60 wt% to 26.12 wt% for

well J3. As expected dry, ash free volatile matter values, in general, are found to decrease

with depth. Volatile matter exhibits decreasing trend with sample burial depth as shown in

Fig.3.9, Fig. 3.10 and Fig. 3.11 for well J1, well J2 and well J3 respectively.

Fixed carbon: Fixed carbon of the samples collected from well J1, well J2 and well J3

varies from 71.65 wt%. to 83.53 wt%, 76.24 wt% to 91.05 wt%. and 74.15 wt%. to 84.70

wt%. respectively. Fig. 3.12 Fig. 3.13 and Fig. 3.14 displaying the plots between fixed

carbon percentage and depth of coal samples are found to increase with increasing depth of

the burial.

The fixed carbon percentages are plotted against depth for all the samples of the study area

(well J1, well J2 and well J3) of Jharia coalfield (Fig. 3.15). The overall trend of the fixed

carbon percentage increases linearly with depth, i.e., maturity of coal increases with depth

of coal seams.

Based on the values of volatile matter (daf) and fixed carbon percentage, the rank of most

of the coals recovered from Well J1, well J2 and well J3 are inferred to be medium-volatile

bituminous (mvb) to low-volatile-bituminous (lvb) rank as per classification of Indian coals

and Lignites, their properties and utilization [IS: 770-1977, clause 7.1], (Table 3.1).

Medium volatile bituminous to low volatile bituminous coals are important for prospect of

CBM than anthracite or lower rank coals because of amount of methane retention and

development of cleat network as mentioned earlier. Moisture and volatile matters are driven

off during coalification, subsidence, compaction and indurations of plant materials.

Proximate analysis results show that the volatile matter ranges from low to medium and

moisture content of the samples are < 2%, so due to presence of lower values of moisture

content and volatile percentage the study area may be zone of CBM potential.

Proximate analysis results for well J1, well J2 and well J3 are shown in Table 3.2, Table 3.3

and Table 3.4 respectively.


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Fig. 3.9: Variation of Volatile matter with depth (m) for well J1



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Fig. 3.12: Variation of fixed carbon percentage with depth for well J1


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Fig. 3.15: Relation of fixed carbon percentage against depth for 3 wells in Jharia coalfield

Table 3.2: Proximate analysis result of samples from Well J1 of Jharia coalfield

Sample Interval Mean

Intv.

(m)

Moist

(%) Ash

(%) VM

(%)

VM

(daf)

(%)

FC

(%)

FC

(daf)

(%) from (m) to (m)

680.35 680.66 680.505 0.64 11.54 24.90 28.35 62.92 71.65

682.33 682.7 682.515 0.72 13.00 21.03 24.37 65.25 75.63

684.35 684.68 684.515 0.73 15.25 21.11 25.12 62.91 74.88

769.37 769.69 769.53 0.71 12.00 19.52 22.36 67.77 77.64

771.03 771.33 771.18 0.68 16.21 17.64 21.22 65.47 78.78

908.34 908.94 908.64 0.67 12.42 17.33 19.94 69.58 80.06

973.20 973.50 973.35 0.65 16.26 14.91 17.94 68.18 82.06

1060.17 1060.47 1060.32 0.51 24.85 14.03 18.80 60.61 81.20

1061.81 1062.11 1061.96 0.53 18.81 14.86 18.42 65.8 81.58

1064.07 1064.37 1064.22 0.55 18.92 15.52 19.27 65.01 80.73

1067.03 1067.33 1067.18 0.52 17.51 13.50 16.46 68.47 83.53

1068.94 1069.24 1069.09 0.52 26.63 13.26 18.20 59.59 81.80

1071.53 1071.83 1071.68 0.50 21.02 14.83 18.90 63.65 81.10


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Sample interval Mean

depth

(m)

Moist

(%)

Ash

(%)

VM

(%)

VM

(daf),

%

F.C.

(%)

F.C

(daf),

%

from (m) to (m)

1042.62 1042.94 1042.78 0.35 19.52 16.28 16.69 67.08 83.71

1116.81 1117.13 1116.97 1.00 20.75 8.94 9.19 71.50 91.05

1117.97 1118.29 1118.13 0.79 18.56 10.13 12.56 70.52 87.44

1130.31 1130.63 1130.47 0.42 13.99 20.34 23.76 65.25 76.24

1131.16 1131.48 1131.32 1.55 16.18 16.4 19.93 65.87 80.07

1183.76 1184.03 1183.895 0.49 24.17 12.77 16.94 62.57 83.05

1184.96 1185.26 1185.11 0.17 16.36 14.5 17.37 68.97 82.63

1409.83 1410.15 1409.99 1.36 16.86 10.57 12.92 71.21 87.08

1412.58 1412.90 1412.74 0.34 14.15 10.92 12.77 74.59 87.23

1417.03 1417.35 1417.19 0.24 13.91 10.36 12.06 75.49 87.93

1418.33 1418.64 1418.485 0.71 12.24 10.81 12.41 76.24 87.58

1420.68 1420.99 1420.835 0.57 16.38 11.21 13.50 71.84 86.50

1422.75 1423.07 1422.91 0.43 24.08 10.24 13.56 65.25 86.44

1459.15 1459.47 1459.31 0.34 10.26 9.88 11.05 79.52 88.95

1462.02 1462.33 1462.175 0.31 10.89 10.09 11.36 78.71 88.64


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depth

(m)

Moist

(%)

Ash

(%)

VM

(%)

VM

(daf)

(%)

FC

(%)

FC

(daf)

(%) from (m) to (m)

1073.36 1073.86 1073.61 0.35 30.11 16.64 23.92 52.9 76.07

1074.25 1074.75 1074.5 0.30 15.02 18.20 21.50 66.48 78.51

1127.31 1127.61 1127.46 0.26 14.50 17.54 20.57 67.7 79.42

1127.95 1128.26 1128.10 0.25 23.16 19.80 25.85 56.79 74.15

1128.82 1129.12 1128.97 0.35 16.68 16.80 20.24 66.17 79.75

1186.72 1187.02 1186.87 0.22 21.96 15.83 20.34 61.99 79.66

1187.49 1187.79 1187.64 0.25 40.06 14.55 24.37 45.14 75.62

1132.90 1233.20 1233.10 0.30 16.46 16.33 19.13 68.87 82.74

1233.39 1233.69 1233.54 0.25 23.27 15.63 20.43 60.85 79.56

1234.10 1234.40 1234.25 0.22 27.84 14.28 19.84 57.66 80.15

1451.00 1456.25 1453.62 0.20 16.15 12.80 15.30 70.85 84.70

3.6.1.1b Elemental analysis

Total 26 number of coal samples from 2 different wells namely well J1 and well J2 of

Jharia coalfield have been studied for elemental analysis in the laboratory. The main

chemical constituents for coals are generally carbon, hydrogen, nitrogen, oxygen, sulfur and

a small amount of nitrogen varying from 1 to 1.5% [Chandra et al., 1992]. Elemental

compositions of the samples under study are shown in Table 3.5 and Table 3.6.

Carbon content: Elemental compositions of coal samples vary that the carbon content

varies from 79.64% to 90.23% for well J1 and 84.34% to 88.09% for well J2.


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Hydrogen content: Hydrogen content of the sample from well J1 and well J2 varies from

3.84% to 5.30% and 4.25% to 5.26% respectively.

Nitrogen content: Nitrogen content varies from 0.60% to 2.11% for well J1 and 0.58% to

1.99% for well J2.

Sulfur content: Sulfur content of the samples collected from well J1 and well J2 varies

from 0.49% to 2.10% and 0.56% to 1.72% respectively.

Oxygen content: Oxygen content for samples from well J1 varies from 3.26% to 10.98%

and for well J2 varies from 4.69% to 8.94%.

All analysis data presented here are based on dry ash free basis. The enrichment of

hydrogen in the coal samples is possibly due to the prevalence of anoxic conditions of

bacterial decay. The different researchers like Newman and Newman, 1982; Gentzia and

Goodarzi, 1994; Gurba and Ward, 1998; Petersen and Rosenberg, 1998; and Singh et al.,

2.10a, 2012 have documented that enrichment of hydrogen occurs due to organic matter

deposition in a sedimentary basin where depositional condition was anaerobic conditions.

The figures (Fig. 3.16, Fig. 3.17) show a continuous increase in carbon content with

decreasing trend of oxygen content. The carbon content is a better measure of rank of coal

[Chandra, 1992]. Range of carbon contents in samples again confirms that the samples

under study belong to medium-volatile bituminous (mvb) to low-volatile-bituminous (lvb)

rank.

Table 3.5 and Table 3.6 list the experimental results of elemental composition of coal

samples. The plots (Fig. 3.18 and Fig. 3.19) between H/C and O/C ratio in the van Krevelen

diagram fall in the zone of type III kerogen and rank of coal samples indicate the

bituminous rank which indicates a gas prone zone. The diagram (Fig. 3.20) shows the

overall plot of H/C and O/C atomic ratio in the van Krevelen diagram for study area (well

J1 and well J2) located at Jharia coalfield and fall in the zone of type III kerogen.


41

Fig. 3.16: Relationship between carbon and oxygen content of coal samples from well J1 of

Jharia coalfield

Fig. 3.17: Relationship between carbon and oxygen content of coal samples from well J2


42

Table 3.5: Elemental analysis data of samples from Well J1 of Jharia coalfield

mean depth

(m)

Elemental data (%), daf basis Atomic ratios

C H N S O H/C O/C

680.66 79.64 4.16 2.16 0.80 13.24 0.63 0.03

682.7 82.52 4.06 1.74 0.70 10.99 0.59 0.03

684.68 85.46 4.28 1.55 0.76 7.95 0.60 0.03

769.69 84.58 3.85 1.58 0.62 9.37 0.55 0.02

771.33 82.54 5.17 0.60 2.17 9.52 0.75 0.04

908.94 82.99 4.60 0.58 1.96 9.87 0.67 0.02

973.50 82.56 5.30 0.60 1.44 10.10 0.77 0.03

1060.47 88.29 4.56 1.74 0.80 4.61 0.62 0.02

1062.11 91.52 4.60 1.52 0.50 1.86 0.60 0.02

1064.37 90.03 4.35 1.74 0.62 3.27 0.58 0.02

1067.33 81.37 5.25 1.83 0.73 10.82 0.77 0.02

1069.24 87.71 5.07 2.03 0.52 4.68 0.69 0.02

1071.83 87.16 5.30 2.12 0.59 4.84 0.73 0.04

1074.20 90.24 4.66 1.65 0.69 2.77 0.62 0.02


43

Table 3.6: Elemental analysis data of samples from Well J2 of Jharia coalfield

mean depth

(m)

Elemental data (%), daf basis Atomic Ratios

C H N S O H/C O/C

1116.97 85.30 5.23 1.96 0.88 6.63 0.74 0.03

1118.13 87.04 4.34 1.67 0.87 6.08 0.60 0.02

1130.47 87.04 4.91 1.75 0.58 5.71 0.68 0.03

1183.895 86.81 4.25 1.73 0.80 6.42 0.59 0.02

1185.11 86.86 5.09 1.51 0.77 5.77 0.70 0.04

1409.99 85.74 4.89 1.65 0.56 7.15 0.68 0.04

1412.74 87.12 5.26 1.80 0.58 5.23 0.72 0.03

1417.19 86.90 5.01 0.58 1.63 5.88 0.69 0.03

1418.485 84.50 4.82 0.75 1.72 8.20 0.69 0.03

1420.835 87.72 4.70 0.60 1.57 5.42 0.64 0.03

1422.91 88.09 4.57 1.99 0.66 4.69 0.62 0.01

1459.31 84.34 4.50 1.45 0.77 8.94 0.64 0.03

Fig. 3.18: Variation of Kerogen types & position of coal relative to H/C and O/C atomic

ratios in van Krevelen diagram for well J1


44


ratios in van Krevelen diagram for well J2

3.6.1.2 Samples from Raniganj coalfield

The proximate analysis results of well R1 of Raniganj field indicate that the percentage of

moisture is low whereas ash and volatile matter is quite high. The moisture content varies

from 0.77 wt% to 0.96 wt% (average 0.87 wt%) and ash percentage ranges from 12.07 wt%

to 24.92 wt% (average 17.65 wt%) respectively. The coal samples are generally medium

volatile which varies from 32.4 wt% to 38.89 wt% having an average value of 35.48 wt%


45

(from 41.87 wt% to 46.45 wt% daf basis, average 43.55 wt%) and the fixed carbon

percentage ranges from 41.91 wt% to 50.57 wt%, average 45.99 wt% (from 53.54 wt% to

58.12 wt% as daf basis, average 56.43 wt%).


ratios in van Krevelen diagram for well J1 and well J2.


46

Ash percentage of these samples from well R2 of this field is low and varies from 7.6 wt%

to 8.3 wt%. Coal of this field are generally low to medium volatile (from 19.8wt % to 20.7

wt%) coals, moisture percentage are ~ 2% and fixed carbon percentage varies from 69 wt%

to 70.7 wt% (from 76.92 wt% to 78.12 wt% as daf basis). The proximate analysis results

indicate that the coal samples belong to medium volatile bituminous rank. The proximate

analysis result has been summarized in Table 3.7

Table 3.7: Proximate analysis result of samples from 2 different wells of Raniganj coalfield


Intv.

(m)

Moist

(%)

Ash

(%)

VM

(%)

VM

(daf)

(%)

FC

(%)

FC

(daf)

(%)

from (m) to (m)

WELL R1

662.33 662.63 662.48 0.93 17.23 35.22 43.03 46.62 56.96

662.58 663.88 663.23 0.96 18.55 34.47 42.82 46.02 57.17

708.40 708.70 708.55 0.77 24.92 32.4 43.60 41.91 56.39

711.88 712.18 712.03 0.93 12.07 36.43 41.87 50.57 58.12

1002.03 1002.34 1002.20 0.78 15.5 38.89 46.45 44.83 53.54

WELL R2

972.33 972.83 972.58 2.00 8.30 20.70 23.07 69.00 76.92

973.43 973.90 973.66 1.90 7.60 19.80 21.87 70.70 78.12


47

3.6.1.3 Samples from Singareni coalfield

3.6.1.3a Proximate analysis

Total 12 numbers of coal samples were collected from Dorli-Bellampalli coal belt of

Singareni coalfield, Andhra Pradesh. From the proximate analysis results, it was observed

that the ash content varies from 10.52 wt% to 26.59 wt%. Proximate analysis of the

investigated coal samples revealed that the moisture content (M %) varies from 2.46% to

3.82%, whereas volatile matter ranges from 23.30 wt% to 40.26 wt% and fixed carbon

content varies from 26.01 wt% to 53.21 wt%. It is recognized that the fixed carbon of coal

increases with increase in coal depth which is directly proportional to the coal maturity and

coal rank. The similar trend is observed in the present study as shown in Fig. 3.21.

The proximate analysis results and calculated vitrinite reflectance values are summarized in

Table 3.8.

Fig. 3.21: Variation of fixed carbon percentage with depth


48

3.6.1.3b Elemental analysis results

From the elemental results of coal samples obtained from 2 different bore holes of

Singareni coalfield was found that carbon content varies from 59.93% to 83.84% (daf

basis), hydrogen content varies from 5.11% to 5.87% (daf basis), nitrogen content varies

from 1.92% to 2.87% (daf basis), sulfur content varies from 0.58% to 0.97% (daf basis) and

oxygen content varies from 8.21% to 15.97% (daf basis). The elemental analysis results are

represented in Table 3.9. Carbon content of the samples are plotted against oxygen content

(Fig. 3.22) and it is inferred that carbon content increases with the decrease of oxygen

percentage. Atomic ratio of H/C are plotted against O/C atomic ratio in the van Krevelen

diagram (Fig. 3.23) and observed that the coal samples from this coalfield belongs to

kerogen type III organic matter with a maturity of Lignite and sub-bituminous stage, hence

gas content capacity is low.

Table 3.8: Proximate analysis result of samples from Singareni coalfield


depth

(m)

Moist

(%)

Ash

(%)

VM

(%)

VM

(daf)

(%)

FC

(%)

FC

(daf)

(%) from (m) to (m)

Bore hole No. BPA210

426.95 428.95 427.95 3.76 26.00 32.50 46.27 37.74 53.73

429.43 432.00 430.71 3.01 24.94 32.75 45.45 39.3 54.55

498.23 498.35 498.29 3.04 26.59 26.30 37.37 44.07 62.63

499.61 499.86 499.73 3.38 22.82 31.62 42.85 42.18 57.15

501.72 504.00 502.86 3.12 17.03 30.46 38.15 49.39 61.85

540.17 541.77 540.97 3.53 22.65 23.30 31.56 50.52 68.44

Bore hole No. R1255

368.59 369.19 368.89 2.95 23.00 28.96 39.11 45.09 60.89

370.60 372.40 371.5 2.46 45.99 25.45 49.37 26.1 50.63

434.67 436.57 435.62 3.43 25.17 33.61 47.07 37.79 52.93

438.03 439.57 438.8 3.72 15.39 27.68 34.22 53.21 65.78

442.72 444.02 443.37 3.15 10.52 40.26 46.64 46.07 53.36

455.08 458.12 456.6 3.82 11.15 31.11 36.59 53.92 63.41


49

Table 3.9: Elemental analysis data of samples from 2 wells of Singareni coalfield

mean depth (m) Elemental data (%), daf basis Atomic Ratios

C H N S O H/C O/C


426.95 77.82 5.82 2.51 0.97 12.88 0.90 0.12

429.43 79.79 5.72 2.26 0.92 11.31 0.86 0.11

498.23 81.67 5.39 2.40 0.84 9.71 0.79 0.09

499.61 80.51 5.72 2.34 0.75 10.68 0.85 0.10

501.72 82.87 5.44 1.97 0.71 9.02 0.79 0.08

540.17 83.84 5.82 2.51 0.97 12.88 0.90 0.12

Bore hole No. R1255

368.89 83.84 5.11 2.15 0.58 8.32 0.73 0.15

435.62 74.57 5.65 2.87 0.95 15.97 0.91 0.16

438.8 78.94 5.77 2.34 0.71 12.24 0.88 0.12

443.37 83.67 5.33 2.11 0.68 8.21 0.76 0.07

456.6 81.36 5.87 1.92 0.73 10.11 0.87 0.09

Fig. 3.22: Relationship between carbon and oxygen content of coal samples from 2 wells of

Singareni coalfield


50


ratios in van Krevelen diagram for 2 blocks of Singareni coalfield.

3.6.2 Petrographic study

The petrography of coal samples was determined from laboratory studies and from

empirical equation.

3.6.2.1 Sample from Jharia coalfield

Vitrinite: From petrographic study, it is found that Vitrinite is the dominant maceral group

followed by the Inertinite and Liptinite. The volume of vitrinite ranges from 32.04% to

73.35% for well J1, 41.20% to 74.90% for well J2 and 43.70% to 59.00% for well J3.


51

Semi-vitrinite: Semi-vitrinite ranges from 0.60% to 4.10% for well J1, from 1.80% to

2.60% for well J2 and from 0.60% to 2.00% for well J3.

Inertinite: Inertinite ranges from 15.02% to 51.03% for well J1, from 18.20% to 35.00%

for well J2 and from 20.00% to 45.10% for well J3.

Liptinite: Liptinite value for well J1, well J2 and well J3 ranges from 0.02% to 0.98%,

0.20% and 0.20% to 0.40% respectively.

Visible Mineral matter: Mineral matter ranges from 5.73% to 23.00% for well J1, from

4.60% to 5.80% for well J2 and from 6.20% to 35.10% for well J3.

Mean vitrinite reflectance (VRO): Mean vitrinite reflectance of the samples from well J1,

well J2 and well J3 ranges from 1.23% to 1.65%, 1.58% to 2.03% and 1.42% to 1.79%

respectively.

Empirical correlation

For studied coal samples, Rice equation was modified for the Indian coal and also used to

calculate the value of vitrinite reflectance (Ro%) and compared with the results determined

experimentally in laboratory.

% 2.056 log( ) 4.023oR VM 3.2

Vitrinite reflectance of coal is also determined by using Rice empirical equation (1993) and

modified equation for Jharia coalfield. The plots (Fig. 3.24, Fig. 3.25 and Fig. 3.26) show

the variation of vitrinite reflectance with increasing depth of burial for well J1, well J2 and

well J3 of Jharia coalfield. Mean vitrinite reflectance also depends upon the volatile matter

and with increasing volatile matter percentage of vitrinite decreases (Fig.3.27, Fig. 3.28 and

Fig. 3.29). With increase in depth, the volatile matter decreases as mentioned earlier and the

volume of vitrinite increases in coal. Presence of increased volume of vitrinite reflects more

rays incident on its surface.

Variations in the experimental and calculated data were observed for almost every sample

because Rice equation was developed mainly for USA coal which is different from that of

Indian coal. However, similar trends were observed for both the cases.


52

Fig. 3.24: Variation of vitrinite reflectance with depth for well J1

Fig. 3.25: Variation of vitrinite reflectance (analysis) with depth for well J2


53

Fig. 3.26: Variation of vitrinite reflectance with depth for well J3

Fig. 3.27: Variation of vitrinite reflectance with volatile matter for well J1


54




55

The vitrinite maceral is more favorable for CBM potentiality because of development of

higher proportion of micropores which can enhance the gas storage capacity and adsorption

capacity of coal. At a given rank of coal, vitrinite contains more micropores compared to

inertinite and liptinite [Unsworth et al., 1989; Lamberson and Bustin, 1993; Beamish and

Crosdale, 1995]. Surface area of coal is guided by the pore size distribution of a sample

whereby the surface area progressively increases with decline in pore size (microporosity)

for a given pore volume. Table 3.10 shows the variation of pore volume with rank and

depth of coal seam and also reported the gas content and methane adsorption capacity with

pore volume. Some investigators [Gan et al., 1972; Clarkson and Bustin, 1996; Prinz et al.,

2004; Printz and Littke, 2005] reported that micro porosity increases with higher rank of

coal and this is the reason why methane capacity increases with rank. Table 3.11, Table

3.12 and Table 3.13 lists the variation of Vitrinite reflectance and maceral group obtained

from laboratory analysis and established correlation.

Table 3.10: Variation of pore volume, surface area and gas content with depth and rank of

samples from Well J1 of Jharia coalfield

Parameters Well J1 Well J1 Well J1

Depth (m) 682.50 1130.57 1418.33

Vitrinite (%) 73.35 60.20 51.50

Total gas content (cc/g) 12.28 10.14 8.73

CH4 volume 21.90 20.20 17.10

Micropore volume(cc/g) 0.100 0.024 0.046

Micropore area (m²/g) 189.650 31.747 86.476

External surface area (m²/g) 46.111 37.770 21.468

Surface Area (m²/g ) 235.762 83.944 107.944

Total pore volume (cc/g) 1.900e-01 1.269e-01 1.172e-01

Average pore Radius (Å) 1.61186e+01 3.02376e+01 2.17186e+01


56

Table 3.11: Petrographic analysis result of samples from Well J1 of Jharia coalfield

Mean

Intv. (m)

Maceral (Vol.)%

Mean

Ro%

Ro%

From Rice’s

equation

Vitrinite Semi-

vitrinite

Liptinite Inertinite Visible

Mineral

matter

680.50 73.35 0.70 0.20 20.02 5.73 1.23 1.15

682.51 59.02 0.60 0.98 29.50 9.90 1.34 1.33

684.51 68.20 0.80 0.20 23.80 7.00 1.33 1.29

769.53 70.98 0.85 0.89 15.02 12.26 1.42 1.43

771.18 48.51 1.10 0.71 37.44 12.24 1.40 1.49

908.64 56.45 1.39 0.48 32.05 9.62 1.49 1.57

973.35 32.04 1.40 0.50 43.06 23.00 1.55 1.69

1060.32 32.45 3.98 0.20 51.03 12.34 1.57 1.64

1061.96 36.80 4.10 0.20 42.03 16.87 1.61 1.66

1064.22 45.29 3.30 0.09 42.33 8.99 1.57 1.61

1067.18 36.46 2.20 0.50 39.86 20.98 1.61 1.79

1069.09 63.01 1.82 0.37 27.42 7.38 1.65 1.67

1071.68 55.28 3.60 0.02 34.25 6.85 1.62 1.63

1074.05 38.45 2.20 0.20 50.13 9.02 1.62 1.12


Mean

depth

(m)

Maceral (Vol.)% Mean

Ro%

Ro%

From Rice’s

equation Vitrinite Semi-

vitrinite


Mineral

matter

1116.81 58.2 1.8 0.2 35.00 4.8 1.58 2.81

1130.57 60.2 2.5 0.2 32.1 5.2 1.63 1.54

1185.11 41.2 1.4 0.0 51.4 5.8 1.72 1.94

1418.33 51.5 2.6 0.0 40.1 5.8 2.02 2.39

1459.31 74.9 2.3 0.0 18.2 4.6 2.03 2.29


57


Mean

depth

(m)

Maceral (Vol.)% Mean

Ro%

Ro%

From Rice’s

equation Vitrinite Semi-

vitrinite


Mineral

matter

1073.61 43.7 0.8 0.4 20.0 35.1 1.42 1.35

1127.46 46.7 0.7 0.2 45.1 7.3 1.51 1.53

1128.97 48.2 0.6 0.2 44.2 6.8 1.52 1.55

1233.54 59.0 1.5 0.0 33.3 6.2 1.56 1.54

1451.63 48.0 2.0 0.0 39.6 10.4 1.79 1.88

The vitrinite reflectance ranges between 1.23% to 2.03% and hence it may be concluded

that the study areas are good for CBM potential. Based on chemical analysis and

petrographic analysis results, the coals are inferred to range between medium volatile

bituminous (mvb) to low volatile bituminous (lvb) rank.

Relation of Vitrinite reflectance with depth of burial for Jharia coalfield

The plot between mean vitrinite reflectance and depth of coal samples indicates that with

increasing depth of burial of coal seam vitrinite reflectance increases (Fig. 3.30).

Fig. 3.30: Variation of mean vitrinite reflectance with depth of 3 wells of Jharia coalfield


58

The plot (Fig. 3.31) illustrates that with increase of hydrogen content of coal, vitrinite

reflectance increases. Rajpardi lignite deposit of Gujarat and Kalimantan coals of Indonesia

also show the similar trend [Singh et al., 2010a].

Fig. 3.31: Relationship between hydrogen content (daf) and vitrinite reflectance of coal

samples from 2 wells (well J1 and well J2) of Jharia coalfiled

3.6.2.2 Raniganj coalfield

From the proximate analysis data, calculated vitrinite reflectance value ranges from 0.57%

to 0.69% for well R1and from 1.40% to 1.45% for well R2. Hence the coal samples from

well R1 under study are inferred to be high volatile-C bituminous in rank and for well R2

coal rank are medium volatile bituminous which are good for CBM. Table 3.14 displays the

results of vitrinite reflectance derived from empirical equation.

Table 3.14: Results of Vitrinite reflectance for Raniganj coalfield from empirical equation


59

Sample interval Mean Intv. (m)

VRo %

From Rice’s equation

from

(m) to (m)

WELL R1

662.33 662.63 662.48 0.66

662.58 663.88 663.23 0.66

708.40 708.70 708.55 0.64

711.88 712.18 712.03 0.69

1002.03 1002.34 1002.20 0.57

WELL R2

972.33 972.83 972.58 1.40

973.43 973.90 973.66 1.45

3.6.2.3 Singareni coalfield

The Vitrinite reflectances of samples are determined and value ranges from 0.50% to 1.02%

(Table 3.15).

3.7 Scanning Electron Microscope (SEM) analysis

Scanning electron microscopy is widely used for morphological/surface of the surface

analytical techniques. For SEM analysis, the samples were coated with gold to prevent

charging of the sample [Deydier et al., 2005]. The SEM micrographs at different

magnifications of coal samples from Jharia coalfield are shown in Fig. 3.32, Fig.3.33 and

Fig. 3.34 respectively. The figures indicate the presence of different particle sizes and

granular shapes with irregular hexagonal features.


60

Table 3.15: Results of Vitrinite reflectance for Singareni coalfield from empirical equation

Mean Intv. (m)

VRo %

From Rice’s equation


426.95 0.57

429.43 0.60

498.23 0.82

499.61 0.66

501.72 0.80

540.17 1.02

Bore hole No. R1255

368.89 0.77

435.62 0.50

438.8 0.55

443.37 0.93

456.6 0.56

3.8 FTIR spectroscopic analysis of the samples

The FT-IR spectra obtained from coal samples of different depth intervals (680.50 m,

682.70 m and 908.64 m) from Jharia coalfield are shown in Fig. 3.35, Fig. 3.36 and Fig.

3.37 respectively. The intensity of broad band at 3431 cm-1

and 3436 cm-1

is due to

stretching frequency of OH group. Intensity of the bands at 2900 cm-1

and 2924 cm-1

is

corresponding to the stretching vibration of aromatic and aliphatic C-H bonds. Coal

consists of polycyclic materials. The bands observed at 1603 and 1607 cm-1

can be assigned


61

to skeletal C-C stretching modes. The bands at 1401 cm-1

, 1403 cm-1

and 1439 cm-1

are

assigned to –CH2 scissoring and –OH bending vibration respectively. The bands 1232 cm-1

and 1262 cm-1

are due to C-C stretching vibration. The intensity bands at 1031 cm-1

and

1031 cm-1

are due to C-O-C stretching vibration. Signals related to mineral matter

contained in coal at 800-400 cm-1

was observed in both the samples.

Fig. 3.32: SEM of sample from Jharia coalfield of 680.50 m depth



62


Fig. 3.35: FT-IR spectra of sample from Jharia coalfield of 680.50 m depth


63




64

3.9 Conclusions

Based on the laboratory analysis results, the following conclusions are drawn:

1. Coal samples from different wells of Jharia coalfield have been tested for their

petrological properties to determine their CBM generating potential. It has been

observed that samples from all three wells of Jharia coalfield can be considered

viable as potential for CBM gas resources.

2. Fixed carbon percentage shows an increasing trend with depth, whereas moisture

and volatile matter content decreases with increasing depth which is normal for

maximum coal.

3. Vitrinite reflectance values vary from 1.23% to 2.03% as analysed and increases

with increase of depth. On the basis of proximate and petrographic analysis results,

the rank of coal from three wells of Jharia coalfield can be inferred to be medium-

volatile-bituminous (mvb) to low-volatile-bituminous (lvb) rank. Vitrinite

reflectance values are within the range of 0.7% to 2.0% as demarcated by Chandra

(1997) and these 3 wells (Well J1, Well J2 and Well J3) of Jharia coalfield are

highly prospective for CBM exploration. Petrographically, the coals are dominated

by vitrinite macerals followed by inertinite and liptinite in low concentration and

cleat density can be high due to presence of high values of vitrinite macerals.

4. From the proximate analysis results of the samples collected from well R1 of

Raniganj coalfield, the coal samples are inferred to be high volatile-C bituminous in

rank. High volatile-C bituminous rank of coal is less effective for generation of

methane and development of cleat system. While samples from well R2 of this field

are designated as medium volatile bituminous coal and have comparatively higher

methane generation capacity than the lower rank.

5. SEM, IR and surface area analysis gives the insights of particle size and shapes,

functional groups and pore size distribution of the samples.

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