Atul Varma
Indian School of Mines, Dhanbad, Applied Geology, Faculty Member
- Prof. Varma has contributed significantly in different fields of coal and lignite geology, petroleum geology, coal an... moreProf. Varma has contributed significantly in different fields of coal and lignite geology, petroleum geology, coal and organic petrology, coal bed methane, shale gas, coal conversion, coke petrography, hydrogenation residue petrography, coal combustion, trace elements and rare earth distribution in coal.edit
Mishra S, Mendhe VA, Kamble AD, Bannerjee M, Varma AK, Singh BD & Pandey JK 2016. Prospects of shale gas exploitation in Lower Gondwana of Raniganj Coalfield (West Bengal), India. The Palaeobotanist 65(1): 31–46. Geochemical analyses such... more
Mishra S, Mendhe VA, Kamble AD, Bannerjee M, Varma AK, Singh BD & Pandey JK 2016. Prospects of shale gas exploitation in Lower Gondwana of Raniganj Coalfield (West Bengal), India. The Palaeobotanist 65(1): 31–46. Geochemical analyses such as proximate, pyrolysis, TOC and FTIR, and other analyses like surface area, pore size, pore volume (using low–pressure N 2 physisorption measurements) and SEM were performed on the shale samples derived from Early Permian Barakar and Late Permian Barren Measures formations of the Raniganj Coalfield, West Bengal. Rock–Eval pyrolysis and TOC data indicated that the heterogeneity of Barren Measures and Barakar shales is laterally varying, but in general, factors which support the occurrence of shale gas accumulations include a moderate to high TOC content (3.38–7.87 wt.%) with sufficient thermal maturity and type III–IV organic matters (kerogens). FTIR spectra indicate the presence of quartz and kaolinite with absorbance bandwidth between 1200–800 cm −1 and 3750–3400 cm −1 , respectively. Abundance of quartz, as compared to clay, points towards the brittle characteristics of shales favourable for good fracability. Besides, mesopores and macropores are well–developed and the capacity of gas generation and adsorption are significant. On the basis of SEM, the pores are classified into four types– (i) inter–granular pores, (ii) dissolve pores, (iii) composite inter–granular pores, and (iv) hair line micro–fractures. The BET multipoint surface area varies from 8.104 to 16.937 m 2 /g and 17.376 to 29.675 m 2 /g for Barakar and Barren Measures shales, respectively. Size of the pores varies from 3.072 to 3.728 nm for the Barakar shales and 2.984 to 3.521 nm for the Barren Measures shales, as measured by BJH method. Overall, it is observed that mesopores, macropores, micro–fractures and micropores are adequate in the samples and the studied shales are having interconnected networks of natural cracks and pores system, which may control the storage and migration of shale gas in the reservoir. jkuhxa t dks ;yk{ks =k ¼if'pe ca xky½] Hkkjr ds v/kks xks a Mokuk es a 'ks y xS l LokFkZ lk/ku dh la Hkkouk,a lq HkkJh feJ] fouks n ,-es a <+ s ] vYkdk Mh-dka cys ] ekW fYydk cS uthZ ] vrq y ds-oekZ ] Hkxoku Mh-fla g ,oa t; ds-ika Ms s lkjka 'k jkuhxa t dks ;yk{ks =k] if'pe ca xky ds iz kja fHkd ifeZ ;u cjkdkj ,oa foya fcr ifeZ ;u vuq Riknd 'kS y&la Lrj 'kS ylew gks a ls O;q RiUu 'ks y uew uks a ij Hkw &jklk;fud fo'ys "k.k tS ls ?kVd&oxZ ] rkika 'ku] Vh vks lh ,oa ,Q Vh vkbZ vkj rFkk i` "Bh; {ks =k] fNfnz y vkdkj] fNfnz y vk;ru ¼vYi ncko N 2 HkkS frd 'kks "k.k ekiu iz ;q Dr djrs gq ,½ vkS j Øeoh{k.k bys DVª ku lw {en'khZ tS ls vU; fo'ys "k.k fd, x,A 'kS y&ew Y;ka du rkika 'ku ,oa Vh vks lh vka dMs + us la ds r fn;k fd vuq Riknd 'kS y&la Lrjks a ,oa cjkdkj 'ks yks a dh fotkrh;rk ik'oZ :i ls ifjofrZ r gS fda rq O;kid :i ls ] i;kZ Ir rkih; ifjiDork ,oa III-IV iz dkj dkcZ fud inkFkks Z a ¼dS jks tu½ lfgr e/;e ls mPp Vh vks lh va roZ Lrq ¼3.38-7.87 Hkkj %½ lekfo"V 'ks y xS l la p;u leFkZ u iz nku djrs gS a A ,Q Vh vkbZ vkj Lis DVª k Øe'k% 1200-800 ls eh-1 ,oa 3750-3400 ls eh
Spontaneous combustion is an inherent problem to the coal mining industry. The paper describes an electro-chemical method called wet oxidation potential technique for determining the susceptibility of coal to spontaneous combustion.... more
Spontaneous combustion is an inherent problem to the coal mining industry. The paper describes an electro-chemical method called wet oxidation potential technique for determining the susceptibility of coal to spontaneous combustion. Altogether 78 coal samples collected from thirteen mining companies spreading over most of the Indian Coalfields have been used for this experimental investigation and 936 experiments have been carried out by varying different experimental conditions to standardize wet oxidation potential method for wider application. The results of wet oxidation potential (WOP) method have been correlated with the intrinsic properties of coal by carrying out proximate, ultimate and petrographic analyses of the coal samples. Experimental results are first analyzed with principal components analysis and then by multiple regression analysis. Results obtained from this method have been compared with one of the widely used method, i.e. crossing point temperature (CPT) in India. The experimental investigation clearly indicates that WOP method with 0.2 N KMnO 4 in 1 N KOH solution at 45 °C (susceptibility index PD12) should be used for finding out the susceptibility of coal to spontaneous combustion. PD12 results are well corroborated with CPT results.
Keywords: Total organic carbon fraction of conversion methane sorption Langmuir volume vitrinite reflectance FTIR Shale gas has strikingly altered the international energy landscape and consequently research on shale gas systems has... more
Keywords: Total organic carbon fraction of conversion methane sorption Langmuir volume vitrinite reflectance FTIR Shale gas has strikingly altered the international energy landscape and consequently research on shale gas systems has increased many folds in recent years. For the purpose of assessing hydrocarbon generation potential, methane sorption capacity and degree of conversion of organic matter, thirty nine borehole shale samples from different parts of Raniganj basin, India were studied. All the samples of the Barakar and Barren Measures Formations have excellent (N4 wt.%) total organic carbon (TOC) content, while the Raniganj Formation shales show good to excellent TOC (3.13–29.74 wt.%) content. Relationship between hydrogen index (HI) and T max values of rock eval pyrolysis indicates that depending upon kerogen type, conversion of kerogen to hydrocarbons takes place at different maturities and typifying kerogen type based on HI values alone can be misleading. Petro-graphically calculated fraction of conversion (f) of kerogen also substantiates the above observation. Good positive correlations were observed between TOC and sorption amount [methane sorption capacity (MSC) and Langmuir volume (V L)] and hence indicate that organic matter abundance is a significant factor in controlling methane sorption for the studied shale samples. However, the results also indicate the role of mineral matter on methane sorption capacity of the samples. Fourier Transform Infrared (FTIR) analysis indicates the presence of kaolinite and quartz within the studied samples. The sample showing the maximum MSC, V L , T max , mean vitrinite reflectance (Romv), f and fixed carbon (FC) content, had a forty centimeter thick lamprophyre intrusion occurring immediately above it which might have resulted in cooking and maturing the sample. The FTIR spectra of this sample also show the partial removal of aliphatics and disordering of kaolinite due to the impact of heat.
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The emergence of shale gas as potential hydrocarbon resource has changed the global energy landscape. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), X-ray florescence (XRF) and Scanning Electron Microscope (SEM)... more
The emergence of shale gas as potential hydrocarbon resource has changed the global energy landscape. Fourier Transform Infrared (FTIR), X-ray diffraction (XRD), X-ray florescence (XRF) and Scanning Electron Microscope (SEM) characteristics of thirty nine borehole shale samples belonging to the Barakar (Lower Permian), Barren Measures (Upper Permian) and Raniganj (Upper Permian) Formations from different parts of Raniganj basin, India were studied. FTIR analysis indicates the presence of aromatic hydrogen, aromatic carbon, aliphatic CeH stretching, aliphatic CeH bending, OH functional group within the organic matter and presence of kaolinite, quartz and carbonates within the studied samples. XRF studies indicate that the shales have undergone intermediate to strong weathering condition, and are marked by presence of clay minerals mainly illite and kaolinite. In addition to illite, kaolinite and quartz, alkali feldspar, siderite and calcite were identified within the shales through XRD. Marked development of amorphous character was noted in the XRD plot of one heat affected shale sample. FTIR analysis of this sample also indicates removal of aliphatics and disordering of kaolinite within the sample due to the impact of heat. Through SEM studies different types of surface morphologies, different types of pores and pore shapes in organic matter were identified. SEM studies also indicate intimate mixing of organic matter and mineral matter in shales even at submicroscopic levels. This intimate association appears to have impact on the retention of hydrocarbons by the mineral matrix during Rock Eval pyrolysis. The various micropores, microcracks, fracture traces, macropores and vacuoles may play significant role in diffusion and flow of hydrocarbons.
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For the purpose of assessing methane sorption capacity, degree of conversion of organic matter and hydrocarbon prospectivity, twenty one borehole shale samples of the Lower Permian Barakar Formation were studied from the West Bokaro and... more
For the purpose of assessing methane sorption capacity, degree of conversion of organic matter and hydrocarbon prospectivity, twenty one borehole shale samples of the Lower Permian Barakar Formation were studied from the West Bokaro and Raniganj basins in India. Positive correlation between total organic carbon (TOC) content and sorption amount [methane sorption capacity (MSC) and Langmuir volume (VL)] was observed and indicates that organic matter abundance is a significant factor in controlling methane sorption in the studied shale samples. TOC-normalized MSC and VL shows polynomial relationship with ash yield and clay and hence point towards the importance of mineral matter on methane sorption capacity. Shales from the West Bokaro and Raniganj basin are marked by 'good' to 'excellent' TOC content, input of type III-II/III admixed organic matter and are capable of generating oil and thermogenic gas upon thermal cracking. Tmax (thermal maturity) value of shales from West Bokaro basin varies between 444 and 454 C, while those from Raniganj basin vary between 438 and 464 C. The sample showing highest MSC, VL and Tmax value, had a forty centimeter thick lamprophyre intrusion occurring immediately above it which might have resulted in increasing its maturity (Tmax value), cooking and thus increasing its MSC and VL. This sample also shows maximum fraction of conversion (f ¼ 0.70; i.e. 70% of the hydrocarbon generation process has been completed).
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Shale gas has strikingly altered the international energy landscape and consequently research on shale gas systems has increased many folds in recent years. For the purpose of assessing hydrocarbon generation potential, methane sorption... more
Shale gas has strikingly altered the international energy landscape and consequently research on shale gas systems
has increased many folds in recent years. For the purpose of assessing hydrocarbon generation potential, methane sorption capacity and degree of conversion of organic matter, thirty nine borehole shale samples from different parts of Raniganj basin, India were studied. All the samples of the Barakar and Barren Measures Formations have excellent (N4 wt.%) total organic carbon (TOC) content, while the Raniganj Formation shales
show good to excellent TOC (3.13–29.74 wt.%) content. Relationship between hydrogen index (HI) and Tmax
values of rock eval pyrolysis indicates that depending upon kerogen type, conversion of kerogen to hydrocarbons takes place at different maturities and typifying kerogen type based on HI values alone can be misleading. Petrographically calculated fraction of conversion (f) of kerogen also substantiates the above observation. Good positive correlations were observed between TOC and sorption amount [methane sorption capacity (MSC) and Langmuir volume (VL)] and hence indicate that organic matter abundance is a significant factor in controlling methane sorption for the studied shale samples. However, the results also indicate the role of mineral matter
on methane sorption capacity of the samples. Fourier Transform Infrared (FTIR) analysis indicates the presence
of kaolinite and quartz within the studied samples. The sample showing the maximum MSC, VL, Tmax, mean vitrinite reflectance (Romv), f and fixed carbon (FC) content, had a forty centimeter thick lamprophyre intrusion occurring immediately above itwhich might have resulted in cooking and maturing the sample. The FTIR spectra of this sample also show the partial removal of aliphatics and disordering of kaolinite due to the impact of heat.
has increased many folds in recent years. For the purpose of assessing hydrocarbon generation potential, methane sorption capacity and degree of conversion of organic matter, thirty nine borehole shale samples from different parts of Raniganj basin, India were studied. All the samples of the Barakar and Barren Measures Formations have excellent (N4 wt.%) total organic carbon (TOC) content, while the Raniganj Formation shales
show good to excellent TOC (3.13–29.74 wt.%) content. Relationship between hydrogen index (HI) and Tmax
values of rock eval pyrolysis indicates that depending upon kerogen type, conversion of kerogen to hydrocarbons takes place at different maturities and typifying kerogen type based on HI values alone can be misleading. Petrographically calculated fraction of conversion (f) of kerogen also substantiates the above observation. Good positive correlations were observed between TOC and sorption amount [methane sorption capacity (MSC) and Langmuir volume (VL)] and hence indicate that organic matter abundance is a significant factor in controlling methane sorption for the studied shale samples. However, the results also indicate the role of mineral matter
on methane sorption capacity of the samples. Fourier Transform Infrared (FTIR) analysis indicates the presence
of kaolinite and quartz within the studied samples. The sample showing the maximum MSC, VL, Tmax, mean vitrinite reflectance (Romv), f and fixed carbon (FC) content, had a forty centimeter thick lamprophyre intrusion occurring immediately above itwhich might have resulted in cooking and maturing the sample. The FTIR spectra of this sample also show the partial removal of aliphatics and disordering of kaolinite due to the impact of heat.
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High energy prices and severe energy shortage has led shale gas to become the focus of study and exploration in many countries. India, like many other countries around the world with shale gas potential recognizes the strategic importance... more
High energy prices and severe energy shortage has led shale gas to become the focus of study and exploration in many countries. India, like many other countries around the world with shale gas potential recognizes the strategic importance of developing its shale gas resources. For the purpose of shale gas
assessment, the authors have selected sixty six borehole shale samples of different formations from different parts of Raniganj basin, West Bengal, India. Rock eval pyrolysis and total organic carbon (TOC) analysis and petrographic characterization of the shales were carried out. Shales from Barakar (Lower Permian), Barren Measures (Upper Permian) and Raniganj Formation (Upper Permian) are marked by ‘good’ to ‘excellent’ TOC content, input of type III organic matter and are capable of generating oil and thermogenic gas upon thermal cracking. Igneous intrusives (dykes and sills) in the formations occurring
in and around the areas of Sitarampur (Si) and Kulti (Ku) in western part of the basin might have resulted in cooking of the shales, increasing their maturities (estimated vitrinite reflectance, VRo) as indicated by the Barren Measures shales of shallow depths from the above mentioned areas. Majority of the samples are marked by low oxygen index (OI) values.
assessment, the authors have selected sixty six borehole shale samples of different formations from different parts of Raniganj basin, West Bengal, India. Rock eval pyrolysis and total organic carbon (TOC) analysis and petrographic characterization of the shales were carried out. Shales from Barakar (Lower Permian), Barren Measures (Upper Permian) and Raniganj Formation (Upper Permian) are marked by ‘good’ to ‘excellent’ TOC content, input of type III organic matter and are capable of generating oil and thermogenic gas upon thermal cracking. Igneous intrusives (dykes and sills) in the formations occurring
in and around the areas of Sitarampur (Si) and Kulti (Ku) in western part of the basin might have resulted in cooking of the shales, increasing their maturities (estimated vitrinite reflectance, VRo) as indicated by the Barren Measures shales of shallow depths from the above mentioned areas. Majority of the samples are marked by low oxygen index (OI) values.
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For the purpose of assessing methane sorption capacity, degree of conversion of organic matter and hydrocarbon prospectivity, twenty one borehole shale samples of the Lower Permian Barakar Formation were studied from the West Bokaro and... more
For the purpose of assessing methane sorption capacity, degree of conversion of organic matter and hydrocarbon prospectivity, twenty one borehole shale samples of the Lower Permian Barakar Formation were studied from the West Bokaro and Raniganj basins in India. Positive correlation between total
organic carbon (TOC) content and sorption amount [methane sorption capacity (MSC) and Langmuir volume (VL)] was observed and indicates that organic matter abundance is a significant factor in controlling methane sorption in the studied shale samples. TOC-normalized MSC and VL shows polynomial
relationship with ash yield and clay and hence point towards the importance of mineral matter on methane sorption capacity. Shales from the West Bokaro and Raniganj basin are marked by 'good' to 'excellent' TOC content, input of type III- II/III admixed organic matter and are capable of generating oil
and thermogenic gas upon thermal cracking. Tmax (thermal maturity) value of shales from West Bokaro basin varies between 444 and 454 C, while those from Raniganj basin vary between 438 and 464 C. The sample showing highest MSC, VL and Tmax value, had a forty centimeter thick lamprophyre intrusion occurring immediately above it which might have resulted in increasing its maturity (Tmax value), cooking and thus increasing its MSC and VL. This sample also shows maximum fraction of conversion (f ¼ 0.70; i.e. 70% of the hydrocarbon generation process has been completed).
organic carbon (TOC) content and sorption amount [methane sorption capacity (MSC) and Langmuir volume (VL)] was observed and indicates that organic matter abundance is a significant factor in controlling methane sorption in the studied shale samples. TOC-normalized MSC and VL shows polynomial
relationship with ash yield and clay and hence point towards the importance of mineral matter on methane sorption capacity. Shales from the West Bokaro and Raniganj basin are marked by 'good' to 'excellent' TOC content, input of type III- II/III admixed organic matter and are capable of generating oil
and thermogenic gas upon thermal cracking. Tmax (thermal maturity) value of shales from West Bokaro basin varies between 444 and 454 C, while those from Raniganj basin vary between 438 and 464 C. The sample showing highest MSC, VL and Tmax value, had a forty centimeter thick lamprophyre intrusion occurring immediately above it which might have resulted in increasing its maturity (Tmax value), cooking and thus increasing its MSC and VL. This sample also shows maximum fraction of conversion (f ¼ 0.70; i.e. 70% of the hydrocarbon generation process has been completed).
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Publisher Summary This chapter discusses the influence of petrographical factors on the hydrogenation of inertinite rich coals from the Upper Silesian Coal Basin of Poland. Various workers found the fair correlation between the sum of... more
Publisher Summary This chapter discusses the influence of petrographical factors on the hydrogenation of inertinite rich coals from the Upper Silesian Coal Basin of Poland. Various workers found the fair correlation between the sum of preassumed reactive macerals (vitrinite and exinite) and hydrogenation of coals. The hydrogenation of the coals depends on the ranks of the coal. The proposed index of hydrogenation of coal appears to be directly proportional to the degree of conversion. It seems that the reactivity of duroclarite, vitrinertoliptite, and trimacerite is greater than clarite and vitrinertite, which is greater than vitrite during coal liquefaction. The effect of sedimentary facial conditions is not visible and needs to be interpreted after the study of hydrogenation residues.
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Abstract The present study investigates the molecular ratio and stable carbon isotopic compositions of gas samples from the Lower to Middle Eocene lignite deposits of the Lower to Middle Tharad Formation in the Sanchor Sub-Basin, Gujarat,... more
Abstract The present study investigates the molecular ratio and stable carbon isotopic compositions of gas samples from the Lower to Middle Eocene lignite deposits of the Lower to Middle Tharad Formation in the Sanchor Sub-Basin, Gujarat, India, which were understudied, hitherto. The stable carbon isotopic composition of methane (-69.30 to -57.20 ‰ in BK-5 and from -67.40 to -64.50 ‰ in BK-7 well) may imply the generation of primary microbial gas through the hydrogenotrophic methanogenesis, which was mixed with the early mature thermogenic gas, and this is a novel finding from this study area. The relation between the gas molecular ratio [methane/(ethane + propane)] and the stable carbon isotopic composition of methane confirms the mixing trend (∼90 to ∼40 %) of the primary microbial methane with the early mature thermogenic gas sourced from hydrogen-rich macerals either in situ or at a higher depth that subsequently migrated upwards. Further, the studied gas samples comprise a large amount of carbon dioxide (16.95 to 32.32 vol.% and from 18.91 to 28.60 vol.% in BK-5 and BK-7 wells, respectively). The relation between the carbon dioxide content and its stable carbon isotopic composition (-21.30 to -11.80 ‰ and from -11.20 to -9.40 ‰ in BK-5 and BK-7 wells, respectively) may suggest the origin of carbon dioxide from volcanic degassing from the Deccan Trap basaltic magma as well as from coalification through decarboxylation and decarbonylation reactions. So, the mixed origins of carbon dioxide (inorganic + organic) and methane (primary microbial and early mature thermogenic) would have influenced the carbon isotopic difference between carbon dioxide and methane as well as the isotopic discrimination factor, which is also reported for the first time from this investigation. Finally, the relation between the gas molecular ratio and the carbon isotopic difference between carbon dioxide and methane compliments the gas mixing effects. Hence, the novelty of this investigation lies in elucidating the influences of the early mature thermogenic gas on the gas molecular and stable carbon isotopic signatures of primary microbial gas originated through the hydrogenotrophic pathway as depicted by the gas molecular ratio and stable carbon isotopic compositions of methane and carbon dioxide.
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The present investigation aims to elucidate the roles of the functional group chemistry on coal carbonization. Seventeen coal samples were collected from the Barakar and the Raniganj Formations of the West Bokaro, Giridih, and Jharia... more
The present investigation aims to elucidate the roles of the functional group chemistry on coal carbonization. Seventeen coal samples were collected from the Barakar and the Raniganj Formations of the West Bokaro, Giridih, and Jharia Basins of India. Fourier transform infrared (FTIR) spectroscopy was conducted to manifest the functional groups present in these coal samples, and the crucible swelling number was determined to assess their caking ability. From the FTIR spectra, the chain length, areal concentrations of the oxygenated functional groups (1650–1800 cm−1), and the pyrrolic–NH functionality (a heterocyclic aromatic compound where the nitrogen atom contributes a pair of unhybridized p-electrons to the aromatic π-electron system and is bonded with a hydrogen atom in the plane of the aromatic ring; 3330–3470 cm−1) are determined. The crucible swelling number shows positive relation (r = 0.87) with the pyrrolic–NH concentration, but inverse correlations with the chain length and the oxygenated functional group concentrations (r = − 0.91 and − 0.86, respectively). Furthermore, the multiple regression analyses may suggest that a high degree of aliphatic branching provides a large amount of aliphatic bridge bonds that thermally rupture to produce free radicals during coal carbonization. Moreover, large amounts of pyrrolic–NH moieties may source an ample amount of transferrable hydrogen that can stabilize the free radicals to form the thermoplastic mass. Besides, low amounts of oxygenated functional groups may not consume large amounts of the transferrable hydrogen during their thermal decomposition. Hence, sufficient amounts of transferrable hydrogen remain available for capping or stabilizing the free radicals. The ample availability of transferrable hydrogen may also prevent the cross-linking of the free radicals and thereby enhance the duration of thermoplasticity. Hence, the results suggest that the properties of the studied coal samples are advantageous for transforming the metaplast into semicoke and subsequently for producing good quality coke.
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Multi-scale pores, spatial distributions, and their connectivity have been investigated in shale deposits of the Barakar Formation in the Mand-Raigarh Basin, India, through imaging skills, i.e., x-ray tomography (μ-CT), scanning electron... more
Multi-scale pores, spatial distributions, and their connectivity have been investigated in shale deposits of the Barakar Formation in the Mand-Raigarh Basin, India, through imaging skills, i.e., x-ray tomography (μ-CT), scanning electron microscopy (SEM) images, and sample photographs. Additionally, geochemical analyses, ash yield, total organic carbon (TOC), X-ray diffraction (XRD), low-pressure nitrogen gas adsorption (N2), and porosity analyses were executed to account for the organo-inorganic controls on the development of pores in shale. Shale lithology, X-ray tomography, and SEM images spell out various types of multi-scale pores categorized as grain edge-pores, fracture-pores, interlayered, inter-particle, and inter-crystalline pores predominantly controlled by fissile nature, stress conditions, and organo-inorganic mineral compositions. The results of geochemical analyses, viz, ash yield, TOC, and mean vitrinite reflectance (RO%) ranging from 69.33 to 89.26 wt%, 1.88 to 6.99 wt%, and 0.64 to 0.96%, respectively, assign fair to good source rock budding for hydrocarbon generation. XRD analysis displays clay mineral richness (30.50 to 71.10 wt%) comprised mainly of kaolinite and illite with non-clays (26.30 to 60.50 wt%) influencing pore shapes and spatial distributions owing to the alteration and fissile nature. The pore sizes through Barrett-Joyner-Halenda (BJH) and density functional theory (DFT) range 2.98 to 4.19 nm and 0.79 to 12.79 nm and points at mesoscale pores standing out in fine-grained shale deposits carrying an ample space for gas storage. The cylindrical pores and bottle-neck pores were distinguished through the vicissitudes in the hysteresis curves. The clay minerals, non-clay minerals, and the total organic carbon content participate significantly in the development of various pores in shale formations.
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Abstract The East Bokaro Basin of the Damodar valley is a potentially prospective CBM (coalbed methane) play having significant cumulative coal seam thickness, in-situ gas content, vitrinite percentage, and adequate thermal maturity.... more
Abstract The East Bokaro Basin of the Damodar valley is a potentially prospective CBM (coalbed methane) play having significant cumulative coal seam thickness, in-situ gas content, vitrinite percentage, and adequate thermal maturity. Successful CBM recovery needs a detailed understanding of the organic content, pore structures/networks, storage properties and gas flow mechanism. The present work attempts to systematically investigate East Bokaro coal for organo-petrographic controls on gas content and generation, variations in sorption capacity and saturation, pore mechanisms, cleat intensity, cleat aperture distribution and spacing. The values of in-situ gas, sorption capacity and methane concentration (C1) vary from 3.52 to 30.93 cc/g (dry ash-free basis), 15.40–32.40 cc/g (dry ash-free basis), and 66–93 vol%, respectively. The atomic ratios H/C and O/C indicate that thermally matured coal seams contain type III-IV kerogen positioned in the dry gas window. The decrease of hydrogen-containing liptinite with increasing depth reveals the function of thermal gradient on the cracking of liptinitic compounds with successive evolution of hydrocarbons and the development of a carbon-rich pore matrix. The H/C ratio is also influenced by the increasing content of vitrinite and reflectance values of deeper coal. More than 63 % of desorbed gas was determined from desorption measurement and low sorption time (τ, mainly
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The coking behavior of coal is an important facet in utilization of coal in metallurgy and in other industries. The carbonization behavior of coal mainly depends on coal rank, petrographic composition, ultimate composition and rheology of... more
The coking behavior of coal is an important facet in utilization of coal in metallurgy and in other industries. The carbonization behavior of coal mainly depends on coal rank, petrographic composition, ultimate composition and rheology of coal. Coal petrography has become very useful technique for establishment between formulation of coal blend composition and coke quality prediction. It is generally established that blend containing optimal reactives produces the coke of maximum strength. The coking properties of coal not depend only on the macerals composition, but also on the way in which the macerals are distributed among one another, forming preferential associations called microlithotypes. The measurements of relative proportion of microlithotypes are called microlithotype analysis. In present work, distribution of macerals (microlithotype) in coal samples were studied and correlated with the coke quality. Beneficiation by wet method were carried out (only indigenous coal) by washing media of specific gravity 1.30 to 1.40 to achieve <10% ash level. Coal microlithotypes plays an important role on coke quality. Bi-maceral and tri-macerals microlithotype distribution (vitrinertite and duroclarite and clarodurite) in coal samples act as a vital role for coke quality. Inter-growth of internite within vitrinite macerals has also significant role on coke quality. Therefore, the combined analysis of maceral and microlithotype distribution is important for coke quality. Distribution of bi-maceral and tri- maceral in coal improved coke quality (M40 and M10 indices). The microlithotype distribution measurement by petrography analysis gave considerable correlations with M40, M10, Coke Reactivity Index (CRI) and Coke Strength after Reaction (CSR) parameters. It gave details the adaptability of Indian coke quality in favor of macerals assemblages in coal.
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The supercritical carbon dioxide marks as one of the most important step-ups toward green chemistry in order to develop sustainability in the chemical industries. Being a green medium, this proves as a potential substitute of the... more
The supercritical carbon dioxide marks as one of the most important step-ups toward green chemistry in order to develop sustainability in the chemical industries. Being a green medium, this proves as a potential substitute of the traditional toxic organic solvents and volatile organic compounds that are extremely hazardous to the environment. Owing to its inflammability, non-toxicity, minimum expenses, and easy availability, the supercritical carbon dioxide makes itself highly valuable to the modern industrial protocols.
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The carbon content of different types of coal determines its utility in industries and thermal power generation. The most popular and widely used is the conventional method (ultimate analysis) to determine coal’s carbon content (C, wt.%),... more
The carbon content of different types of coal determines its utility in industries and thermal power generation. The most popular and widely used is the conventional method (ultimate analysis) to determine coal’s carbon content (C, wt.%), along with H, N, and S. In the present study, the authors attempted to analyze the carbon content (C in %) in coals via data from Fourier-transform infrared (FTIR) spectroscopy, which can be a promising alternative. As a reference, the carbon content in the coal samples, referred to as CCHNS (in wt.%), was determined from the ultimate analysis. The mid-infrared FTIR spectroscopic data were used to investigate the response of functional groups associated with carbon or its compounds, which were used to model and estimate the carbon content in coal samples (referred to as CFTIR, in wt.%). FTIR spectral signatures were utilized in specific zones (between wavenumbers 4000 and 400 cm−1) from a total of 18 coal samples from the Johilla coalfield, Umaria ...
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The organo-lithotype properties of Barakar and Raniganj Formation coal seams have been investigated to assess the process of cleat origin, occurrence, and their influence on strength properties. Coal cleats have wide applications in... more
The organo-lithotype properties of Barakar and Raniganj Formation coal seams have been investigated to assess the process of cleat origin, occurrence, and their influence on strength properties. Coal cleats have wide applications in coalbed methane gas recovery, underground mine strata mechanics, beneficiation, and pulverization. However, there is very limited information available on the cleat occurrence and controlling parameters of Indian coals. In this view, a total of 31 coal samples were retrieved from eight exploratory boreholes intersecting coal-bearing formations like Barakar and Raniganj in the Raniganj Coalfield. We identified four distinct lithotypes in coal seams: (i) B, bright coal; (ii) Db, dull banded coal; (iii) Bb, bright banded coal; and (iv) Bd, banded coal. The abundance of bright-band-associated lithotype indicates organic matter that attained the early anoxic conditions after deposition. The cleat system in Barakar coal is comparatively better than in Raniganj coal controlled by the lithotype, type of organic matter, thermal maturity, and gelification extent. The carbon enrichment process in coal mainly controls the megascopic cleat genesis pattern. The positive trend of cleat intensities with the depth of coal seams as determined by megascopic, microscopic, and scanning electron microscope (SEM) studies postulates that the macro- to nanocleats are interdependent and developed during devolatilization due to loss of plasticity. The field emission scanning electron microscopy (FE-SEM) photographs have shown intricate microfractures and pore structures owing to the epigenetic characteristics. Vitrinite bands indicate that it comprises the partially deformed planer cleat system. The resistance to quartz weathering nature attributed to coal brittleness properties also contributed to cleat genesis. The total clay content exhibits an inverse relationship with different cleat intensities, suggesting that hydrous clay swells due to its inherent ultrafine characteristics, thus not supporting the cleat construction. However, it ropes the development of the irregular crack when organo–inorganic matter achieves the dry thermal conditions. The microfractures linked with different pore structures in studied coals can be classified into seven types: (i) vitrite-associated regular open-slit pores, (ii) vitriinertite-char allied irregular pores, (iii) irregular fracture-pore partially filled with clay, (iv) fissile pores along bedding planes of clay, (v) organic pores evolved due to external heat received from intrusives, (vi) deep organic pores evolved during compaction and thermal transformation, and (vii) pore fractures blocked by boghead algae. The clay content showed a positive relationship with physicomechanical properties, signifying the cementing characteristics of clay holding fractures and pores. There is significant variation in the strength properties of Barakar and Marren measures coal influenced by thermal maturity, lithotype characteristics, and organo–inorganic content.
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Cleat attributes and coal quality have been evaluated through field observation, SEM images analysis and proximate-ultimate analyses on representative coal samples collected from four different underground coal mines of Son-Valley coal... more
Cleat attributes and coal quality have been evaluated through field observation, SEM images analysis and proximate-ultimate analyses on representative coal samples collected from four different underground coal mines of Son-Valley coal Basin of central India for the characterization of coal bed methane prospective. The coal samples were characterized as durainic-clarodurainic-vitrainic type to durocalrainic-clarainic type based on litho-type composition. Cleats were identified as face cleat and butt cleat range 5-10 cm-1 to 2–3 cm-1 depending on the litho-types whereas, cleat density ranges 7-16 cm-2 revealed that cleat development is influenced by litho-types. The cleat orientation shows two main strikes almost NW-SE to NNW-SSE and NE-SW to ENE-WSW elucidates the face cleat and butt cleats are perpendicular to each other. SEM images for coal samples were analysed to validate the cleat geometry at micro-scale, illustrates that face cleat and butt cleats are orthogonal to each other....
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The well-developed coal and shale bearing sequence belong to the Tikak Parbat Formation (Oligocene) of the Makum Coalfield have been studied to understand the paleoclimate and depositional conditions through organic petrography,... more
The well-developed coal and shale bearing sequence belong to the Tikak Parbat Formation (Oligocene) of the Makum Coalfield have been studied to understand the paleoclimate and depositional conditions through organic petrography, palynofacies, and mineralogy. The depositional settings of the studied formation range from mildly oxic-to-anoxic deltaic forest to limnic swamp environmental conditions. Both are marked by high vitrinite (~ 66.86 vol. %), with significant liptinites (7.26–34.46 vol. %) and low inertinite (≤ 4.77 vol. %). Similarly, palynofacies indicate high phytoclasts, with amorphous organic matter and few palynomorphs (mostly spores and pollens). These suggest dependence of higher plant organic matter (OM) on floral precursors likely controlled by the combination of depositional conditions, i.e., water level, temperature, salinity, etc. The dominance of terrestrial land plants as major OM source indicates high water level in the peat. In addition, the geochemical plot of MgO/Al2O3 and K2O/Al2O3 and occurrences of framboidal pyrite and other carbonate mineral phase point towards non-marine to marine environment. The high K2O and MgO in shales indicate periodic marine water incursion, perhaps due to sea-level rise. Samples mostly having 1–10 salinity and some have > 10 also specifies transitional environment. The inorganic matters (IM) within the sediments were mostly derived from mixed felsic igneous rocks of granodiorite and granite compositions and had experienced moderate-to-strong weathering which reveals change in climatic conditions during the Oligocene epoch. This study suggests existing of multiple phase environmental transformations during the deposition of coal and shale bearing sequence and further leads to the accumulation of diversified plant species and with sufficient basinal thermal maturity.
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Abstract The Palaeocene-Eocene organic sedimentary archives comprising lignites, carbonaceous shales, and shales from the Palana Formation of the Bikaner-Nagaur Basin, Rajasthan, India, are investigated in this study using elemental and... more
Abstract The Palaeocene-Eocene organic sedimentary archives comprising lignites, carbonaceous shales, and shales from the Palana Formation of the Bikaner-Nagaur Basin, Rajasthan, India, are investigated in this study using elemental and biogeochemical proxies. The objectives of this investigation are to elucidate the sources of organic matter and their responses to palaeoredox and palaeoclimatic conditions, as well as to reconstruct the palaeoenvironment of the organic matter deposition. Elemental distributions, Rock Eval pyrolysis, stable carbon isotope, n-alkane and its ratios, acyclic isoprenoids and terpenoid biomarkers are employed as the tools to carry out this research. The hydrogen index shows that the samples contain type III, admixed type II-III and type II kerogen. The presence of admixed type II-III kerogen in the samples may indicate mixing of terrestrial plant-derived organic matter with autochthonous organic matter in a coastal depositional setting. Deposition in a coastal setting may also raise the possibility of organic matter supply from coastal vegetation. The large HI values (>300 mg HC/g TOC) may result from selective preservation of hydrogen-rich biomolecules derived from terrestrial and coastal vegetation. The stable carbon isotopic composition of bulk organic matter (−30.66 to −25.51‰) and total carbon to organic nitrogen ratio (26.62–131.12) may suggest that the organic matter was sourced primarily from C3 plants. The integration of these two parameters may also indicate that mangroves supplied significant amount of organic matter to the coastal peatland. The n-alkane distributions and carbon preference indices show the derivation of organic matter from waxy terrestrial plants, aquatic submerged vegetation, and microbial communities. The palaeohydrological proxies, i.e., proxy-aqueous ratio (0.24–0.86), proxy-wax ratio (0.33–0.84), and average chain length (26.32–28.30) may illustrate intermittent changes in organic matter sources (mangrove-dominated emergent vegetation and waxy plants to aquatic submergent plants and vice-versa) and their relations with shifts in palaeohydrological conditions of mire and associated palaeoclimatic oscillations between wet (high rainfall) and dry spells (low rainfall). Additionally, terpenoid distributions reveal organic matter input from angiosperms (including mangroves) (olean-12-ene, de-A-olean-13(18)-ene, de-A-lupane, and other de-A-triterpenoids), conifers (C18 diterpane, abietane, and ent-beyerane) and microbial sources (hopanoids). Besides, regarding the palaeodepositional environment, acyclic isoprenoid distributions (pristane and phytane), relative hydrocarbon potential, and the newly introduced palaeoredox factor may put forward mostly suboxic to oxic redox conditions of organic matter deposition. The total organic carbon and sulfur contents may further imply deposition of organic matter in topogenous-transitional mire conditions under a marginal marine/coastal environment. In complementary, the ranges of production index (0.01–0.19), Tmax (388–422 °C) and the presence of 17β(H),21β(H)-hopanes (ββ hopanes), 17α(H),21β(H)-homohopane, hop-17(21)-ene, ββ-hopanes, norhopanes and angiosperm-derived unsaturated triterpenoids may suggest thermal immaturity of organic matter in the studied samples.
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Abstract The present study portraits the organic petrological, geochemical and microstructural characters of twenty borehole shale samples for assessing the hydrocarbon generation proficiency of the shales from the Barren Measures... more
Abstract The present study portraits the organic petrological, geochemical and microstructural characters of twenty borehole shale samples for assessing the hydrocarbon generation proficiency of the shales from the Barren Measures Formation (a stratigraphic unit of the Gondwana that is devoid of any workable coal seam) of the Jharia Basin, India, which was underinvestigated until now. The samples consist of vitrinite grains ranging from 5.41 to 20.57 vol%, the dominance of which compared to the inertinite and liptinites may reflect the lignocellulosic organic matter (type-III kerogen) input from the terrestrial plants. The range of the mean random vitrinite reflectance values (0.93–1.27%) may suggest the gas generation potential of the shale samples. The peak palaeotemperature values, may, in addition, suggest wet gas generation from these shales in complementary to some shale samples having efficiency to generate dry gas. The total organic carbon in these samples ranging between 3.87 and 15.99 wt% may imply good to excellent hydrocarbon generation capability. Rock Eval pyrolysis suggests the input of type-III kerogen within the mire and the correlations of the pyrolysis parameters exhibit that the shale samples possess significant potential to generate gaseous hydrocarbons (shale gas). The factor of kerogen conversion (f) of many shales suggests almost 20–30% transformation of kerogen to hydrocarbons. On attaining sufficient thermal maturity, the remaining large amount of labile chemical moieties may convert to hydrocarbons. The positive relation of the present-day hydrogen index (HIpd) with the A-factor would suggest the depletion of hydrogen containing functional groups for generating the gaseous hydrocarbons (shale gas). The Raman spectra of the samples reveal poorly organized microstructure, possibly, due to the presence of labile aliphatic compounds that would yet to generate hydrocarbons on attaining relevant thermal maturity as well as because of partially condensed aromatic system containing heteroatoms. The correlations of the Raman data with the mean random vitrinite reflectance data reveal generation of wet and dry gas from these shale samples based on the maturity level. The scientific content of this present study lies in suggesting a set of new equations from the relations obtained between of the Raman spectral parameters and the Rock Eval data in order to suggest the applicability of the Raman spectroscopy in elucidating the shale gas potential. These may be considered as the addendum to the applications of the existing techniques to elucidate the hydrocarbon potential of the organic-rich source rocks, which also add the novelty of this investigation. The new equations and the relations may be tested in the samples of different thermal maturity from other basins for substantiating their world-wide applications.
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Research Interests: Geology and Geophysics
Research Interests: Geology, Geochemistry, Geophysics, Sedimentology, Paleoecology, and 14 moreStable Isotope Geochemistry, Coal, Paleoenvironmental Change, Petrology and Geochemistry, Sedimentary geology and stratigraphy, Coal Geology, Nitrogen, Nitrogen Isotopes, Elsevier, Bituminous Coal, Organic Matter, Stable Isotope Applied to Paleoclimate and Paleoenvironment, Anthracite, and Stable nitrogen isotope of coal
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Research Interests: Geology, Geochemistry, Oil Shale, Permian, Petrography, and 5 moreBiogeosciences, Shale gas, Earth Science, Maceral, and vitrinite
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Research Interests: Geology, Geochemistry, Petrophysics, Oil Shale, Permian, and 4 moreCoal Geology, Shale gas, Feldspar, and Source Rock
Statement of Retraction We, the Editor and the Publisher of the Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, have retracted the following article: Saroj Kumar Sahoo, Nikkam Suresh & A. K.... more
Statement of Retraction We, the Editor and the Publisher of the Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, have retracted the following article: Saroj Kumar Sahoo, Nikkam Suresh & A. K. Varma (2017) Correlation between Average Gray Value (AGV) of coal froth image with its ash and vitrinite content, Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 39:9, 893-898, DOI: 10.1080/15567036.2016.1273280 It was brought our attention that the manuscript contains significant overlap with a previously published source: Jiakun Tan, Long Liang, Yaoli Peng, Guangyuan Xie, (2016). “The concentrate ash content analysis of coal flotation based on froth images”, Minerals Engineering, 92, 9-20, DOI: 10.1016/j.mineng.2016.02.006. Following notification, we investigated in accordance with the Committee on Publication Ethics (COPE) guidelines on plagiarism. Overlap includes general rephrasing of the introduction, the experimental section (2.5. Gray value), the results and discussion, and conclusion. Attribution was not made to the original source, Tan et al., 2016. This article is therefore not deemed to be an original contribution, and we have informed the author of this decision. The authors do not agree with the retraction. We have been informed in our decision-making by our policy on publishing ethics and integrity and the COPE guidelines on retractions. The retracted article will remain online to maintain the scholarly record, but it will be digitally watermarked on each page as “Retracted”.
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Abstract Utilisation of any coal primarily depends on its organic constituents. However, the inorganic constituents i.e., mineral matter present in the coal can decide its end uses. Therefore, the study of mineral matter in coal is an... more
Abstract Utilisation of any coal primarily depends on its organic constituents. However, the inorganic constituents i.e., mineral matter present in the coal can decide its end uses. Therefore, the study of mineral matter in coal is an inevitable and such type of studies in India is very scanty. In this paper, we present the characters of a relatively low-ash non-coking coal from Kathara mines, East Bokaro coalfield, India with emphasis on its inorganic constituents and mineral matter. The coal is characterised by 22.56 wt% ash (dry basis), 28.78 wt% volatile matter (dry basis), and 48.66 wt% fixed carbon (dry basis). Modal analysis by optical microscopy revealed 53.6 vol% vitrinite, 38.3 vol% inertinite, 8.1 vol% liptinite on the mineral matter free basis (mmf), and 25.1 vol% mineral matter. The minerals present in this coal are dominantly clay, quartz and siderite with a minor quantity of hematite, magnetite, goethite and pyrite. Electron micro-probe studies revealed trace presence of sphalerite, baddeleyite, and some altered magnesium silicate. The total sulphur content of this coal is found to be 1.16 wt% on dry ash free basis (daf). Since the majority of the minerals, although fine in size, occur as independent phases with distinct and weak grain boundaries with the macerals, the coal shall be susceptible for beneficiation and the cleaner product can find applications in metallurgical industries for partial substitution in coke making because the mean vitrinite reflectance of this coal is 0.70%.