Vitrinite Macerals Research Articles

Effect of Microlithotype Maceral Distribution on Coke Quality

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.

Organic Geochemical and Petrographic Characteristics of the Coal Measure Source Rocks of Pinghu Formation in the Xihu Sag of the East China Sea Shelf Basin: Implications for Coal Measure Gas Potential

AbstractCoal measure source rocks, located in the Xihu Sag of the East China Sea Shelf Basin, were analyzed to define the hydrocarbon generation potential, organic geochemistry/petrology characteristics, and coal preservation conditions. The Pinghu source rocks in the Xihu Sag are mainly gas‐prone accompany with condensate oil generation. The coals and shales of the Pinghu Formation are classified from “fair” to “excellent” source rocks with total organic carbon (TOC) contents ranging from 25.2% to 77.2% and 1.29% to 20.9%, respectively. The coals are richer in TOC and S1+S2 than the shales, indicating that the coals have more generation potential per unit mass. Moreover, the kerogen type of the organic matter consists of types II‐III and III, which the maturity Ro ranges from 0.59% to 0.83%. Petrographically, the coals and shales are dominated by vitrinite macerals (69.1%–96.8%) with minor proportions of liptinite (2.5%–17.55%) and inertinite (0.2%–6.2%). The correlation between maceral composition and S1+S2 indicates that the main contributor to the generation potential is vitrinite. Therefore, the coals and shales of the Pinghu Formation has good hydrocarbon generation potential, which provided a good foundation for coal measure gas accumulation. Furthermore, coal facies models indicates that the Pinghu coal was deposited in limno‐telmatic environment under high water levels, with low tree density (mainly herbaceous) and with low‐moderate nutrient supply. Fluctuating water levels and intermittent flooding during the deposition of peat resulted in the inter‐layering of coal, shale and sandstone, which potentially providing favorable preservation conditions for coal measure gas.

Petrology and hydrocarbon significance of the coaly source rocks from the Pinghu Formation in the Xihu Sag, East China Sea Shelf Basin

The Xihu Sag in the East China Sea Shelf Basin contains abundant oil and gas reserves and is a focus for hydrocarbon exploration and development. Source rocks are mainly coals and coal-measures mudstones in the Paleogene Pinghu and Huagang formations. Samples from the Pinghu Formation in the Xihu Sag were collected for petrology, total organic carbon, and Rock-Eval analysis for the purpose of investigating macerals component and their contributions to hydrocarbon generation potential. The coaly source rocks from the Pinghu Formation are dominated by vitrinite (average 86.18%) but have an obviously elevated content of liptinite (average 12.59%) and a much lower amount of inertinite (average 1.23%). Liptinite of the samples is mainly composed of resinite, with a small amount of cutinite, sporinite and alginate in descending order. TOC values are 37.55%–65.58% (average 49.16%). Effective HI values are 167–281 mg HC/g TOC (average 223.5 mg HC/g TOC), suggesting the organic matter is type II kerogen. Relatively high HI values and macerals components suggest that the coaly source rocks can generate both oil and gas. Although the liptinite in the coaly source rocks has a content lower than vitrinite values, it makes a significant contribution to both total hydrocarbon and liquid hydrocarbon generation. The contributions of vitrinite, liptinite and inertinite to the total hydrocarbon generation approximately are 63.21%, 36.46% and 0.33%, respectively. The contributions of vitrinite and liptinite to the liquid hydrocarbon generation are approximately 40.95% and 59.05%, respectively. These results demonstrate that the coaly source rocks are dominated by vitrinite macerals with a relatively higher content of liptinite macerals, especially resinite, and these source rocks are more prone to both total hydrocarbon and liquid hydrocarbon generation. Paleogene coaly source rocks from other parts of the world should be considered for their oil-prone nature.

THE EFFECT OF CHANGE IN WATER LEVEL ON THE ABUNDANCE OF LIPTINITE AND VITRINITE MACERALS IN UPPER KELESA FORMATION SHALE IN KUBURAN PANJANG, RIAU

Research on changes in water levels to the abundance of liptnite and vitrinite maceral has focused on Kuburan Panjang area of the Sumai sub-Basin, Central Sumatra Basin. The subject of this research is shale rock from the Eocene-Oligocene Kelesa Formation. Series of rocks from bottom to top shows repetition between shale, sandstone and mudstone strata bounded by conglomerates at the top and bottom. The composition of organic material consists of vitrinite ranging from 0.20 - 5.0%, liptinite 0.60 - 4.70%, pyrite 0.20 - 16.00%, carbonate maceral 0.20 - 24.2%, and clay mineral which is the most dominant component, ranging from 71.60 - 98.00%. Based on the results of TOC analysis, the abundant organic material of the Kelesa Formation shale has a TOC value of 1.18% to 7.17% indicating the ability of shale as a source rock is very good. The presence of organic material in the study area shows that there is a cycle of enrichment of organic material from bottom to top. The smaller the ratio of pristane/phytane (anoxic condition, high water level), the smaller the content of liptinite and the higher the content of vitrinite. Otherwise, the greater the ratio (oxic condition, low water level), the higher the content of liptinite and the lower the content of vitrinite. Change in water level during sedimentation has effect on the quality of shale as a source of unconventional hydrocarbon energy in the Kuburan Panjang area.

Estimation of thermal maturity in the Bakken source rock from a combination of well logs, North Dakota, USA

Numerous attempts have been conducted to construct a reliable model to relate petrophysical and geomechanical characteristics of shale to geochemical properties. In this study, continuous logs were built to predict the thermal maturity of the Bakken Formation from a set of petrophysical logs. First, dynamic modulus (Ed) was created from shear and compressional sonic and, density logs and then converted to Ei (nanoindentation based Young's modulus) using the existing experimental relationship between Ed and Ei. Next, continuous TOC logs were generated for the Bakken Shales based on an empirical relationship between well log derived Ei and TOC contents that were measured in the lab. There was found an acceptable difference between estimated log-based TOC and measured values in three separate wells. Solid bitumen reflectance as a reliable indicator of thermal maturity was measured on all samples from the same wells in the scarcity/absence of vitrinite maceral. The relationships between GR/NPHI/RHOZ wireline logs versus solid bitumen reflectance (BRO%) as the maturity index was then investigated in twelve wells. Based on the strength or weight of the relationship between each log and BRO%, a new parameter “Ʈ” was defined to represent thermal maturity from well logs. A good agreement between parameter Ʈ and BRO% values was observed which provided an empirical equation to make the estimation of BRO% values for the whole length of the shale members possible. Ultimately, the continuity of BRO% values, would enable us to establish a relationship between BRO% and measured Tmax values to generate continuous Tmax logs for the Bakken Shale members. Using these newly developed well logs, it would become possible to make a 3D property models for BRO% and Tmax (the thermal maturity property cube) for an accurate petroleum system evaluation based on GR/NPHI/RHOZ logs.

Petrographic controls on phosphorous distribution in coal seams of the Jharia basin, India

In recent years, the international coking coal market is experiencing an acute shortage of coal supply which has caused a fluctuation in its price. Degradation of coke, in the blast furnace, is largely controlled by its inherent mineral matter. Phosphorous occurs in all coals in minor or trace amounts and is an important parameter to coal users, particularly in steel industries. The mode of occurrence and distribution of phosphorous minerals in 17 coal samples of the Jharia coal basin were investigated through petrographic examinations, technological characterisation and phosphorous distribution. The results reveal that the dull bands are eight times more enriched in phosphorous than the bright bands. The macerals of the inertinite group and mineral matter positively correlate with the phosphorous content, whereas vitrinite macerals have an apathetic correlation. The impact of the thermal alterations is localised and diminishes away from the contact of the intrusion. In contrast, the faulting does not appear to have any effect on the phosphorous content.

Raman spectroscopic study of chemical structure and thermal maturity of vitrinite from a suite of Australia coals

The deconvolution and resolution of overlapping bands in the Raman spectra of a suite of coals studied by curve-fitting methods has improved our understanding of the main structural changes in naturally matured coals. Even though much work on deconvolution of Raman spectra has been done, the systematic evolution of chemical structures is not well established. In this study we used a suite of 28 coal samples from Australia with vitrinite reflectance ranging from 0.38 to 3.52%. The micro-Raman spectra of vitrinite macerals from selected coals were acquired using a custom-made Raman spectrometer and supplemented by other Raman spectra previously acquired under the same experimental conditions. In the spectral deconvolution procedure, the second derivative curve-fitting method was used to determine the number of peaks and peak positions of the Raman spectra. Each band was tentatively assigned to a corresponding chemical structure by references to the interpreted major structural changes likely to have taken place during coalification. These parameters included PD (the position of D band), RBS (the distance between G band and D band), FWHMG (full width at half maximum of G band), IG/IGL (the intensity ratio of G band and GL band), and AR/b (the ratio of Raman integrated area and the slope of the spectral background). All of these Raman parameters are found to have a very good correlation with Ro% with R2 higher than 0.90. While five simple equations have been proposed and may be used to estimate thermal maturity of coals, two equations (Eq. (4) for Ro% from 0.38 to 1.5 and Eq. (5) for Ro% from 1.5 to 3.52) are best suitable to predict thermal maturity of coals with the most accuracy.

A hierarchical methane adsorption characterization through a multiscale approach by considering the macromolecular structure and pore size distribution

Abstract Pore structure of coal is known to be strongly heterogeneous in terms of size, shape and occurrence. The underlying sorption mechanisms are expected to be different depending on the type and size of pores. In this study, both experiments and numerical simulation were used to study sorption behavior of coal. Vitrinite maceral was chosen as the study material and the macerals were separated from Yilan subbituminous coals. Pores in vitrinite were categorized into two different types depending on the occurrence mechanisms and they are termed as elemental particle pore (EP pore) and molecular structure pores (MS pore). According to the pore structure and macromolecular structure, pore models of the two types of pores were established and used to numerically estimate the methane adsorption capacity. It was found that gas sorption varies significantly for different types of pores. Methane adsorption capacity of MS micropores is determined by the pore volume, and while that of EP pores is determined by the internal surface area due to the different sorption mechanisms. Methane adsorption in MS pores showed pore volume filling mechanism, and the methane adsorption results can be well modeled by Dubinin and Astakhov (D-A) model. On the contrary, two distinguishable adsorbed layers can be identified for in EP pore sorption, and the methane density of the first layer was much larger than that of the second layer, which is consistent with the BET model. Of the total gas adsorption amount in coal, the amount of absorbed methane in MS pores contributed a relatively large proportion compared to EP pores. With elevated gas pressure, the difference between these two mechanisms decreased, and when the pressure was 10 MPa, the proportion of methane adsorption in EP pores was ∼40%. The overall measured gas adsorption isotherm is a sum of methane adsorption in different types of pores. The combination of simulation and experimental methods can provide more accurate and detailed information and help understand methane adsorption in coal.

Paleoenvironmental reconstruction and hydrocarbon potentials of Upper Cretaceous sediments in the Anambra Basin, southeastern Nigeria

Palynological, organic petrographic, and organic geochemical analyses of the Campanian-Maastrichtian sediments in Akukwa-2 well were carried out to infer their paleoenvironments, origin of the organic matter, and hydrocarbon generation potentials. The TOC values of the analysed sediments range from 0.27–3.02 wt%, while the S2 pyrolysis yield range from 0.55 to 3.35 mg HC/g rock. This indicates that the Nkporo and Mamu sediments possess fair source generative potential. The samples contain Type III-II and Type III kerogen as shown by the present-day HI values between 58 and 292 mg HC/g TOC and pyrolysis-GC data. The organic matter within the sediments is also likely to generate mainly gas. This is in agreement with the petrographic observations, which revealed that the analysed shale samples contain abundant vitrinite macerals, apart from bituminite, alginite, cutinite, and resinite. Also, the sediments are immature to early mature in terms of hydrocarbon generation as indicated by vitrinite reflectance, biomarker maturity, and pyrolysis Tmax data. Biomarker distribution ratios, palynomorphs assemblage, and organic petrographic observations further point out that the organic materials within the sediments were of mixed aquatic and terrigenous origin and were deposited under suboxic paleodepositional conditions. Based on sedimentological, palynological, and biomarker characteristics, the environment of deposition of the analysed sediments was inferred to be a relatively quiet, shallow marine with fluvial incursion, most especially at the upper part of the intervals studied and consequently, it is a delta associated depositional environment with a fluviatile influence. The sediments are therefore suggested to be deposited in a paleogeographic setting close to vegetation source.

Characterization of organic matter from a stratigraphic sequence intercepted by the Nemo-1X well, Mozambique: Potential for hydrocarbon generation

The Mozambique Basin, which occurs onshore and offshore in the central and southern parts of Mozambique, contains a thick sequence of volcanic and sedimentary rocks that range in age from the Jurassic to Cenozoic. This basin, along with the Rovuma basin to the north, has been the main target for hydrocarbon exploration; however, published data on hydrocarbon occurrences do not exist. In this context, the present study aims to contribute to the understanding of the nature of the organic matter of a sedimentary sequence intercepted by the Nemo-1X exploration well located in the offshore area of the Mozambique Basin. The well reached a depth of 4127 m, and 33 samples were collected from a depth of 2219–3676 m ranging in age from early to Late Cretaceous. In this study, petrographic and geochemical analytical methods were applied to assess the level of vitrinite reflectance and the organic matter type as well as the total organic carbon, total sulfur, and CaCO3 contents. The results show that the total organic carbon content ranges from 0.41 to 1.34 wt%, with the highest values determined in the samples from the Lower Domo Shale and Sena Formations, which may be related to the presence of the solid bitumens that occur in the carbonate fraction of those samples. The vitrinite random reflectances range from 0.65 to 0.86%Rrandom, suggesting that the organic matter in all of the samples is in the peak phase of the “oil generation window” (0.65–0.9%Rrandom). The organic matter is mainly composed of vitrinite and inertinite macerals, with a minor contribution of sporinite from the liptinite group, which is typical of kerogen type III. Although all of the samples have vitrinite reflectances corresponding to the oil window, the formation of liquid hydrocarbons is rather limited because the organic matter is dominated by gas-prone kerogen type III.

An Investigation on Floatability Behavior of Coal Macerals In Flotation Process and Reagent Type Optimization at Central Alborz Coal Washing Plant

ABSTRACT In this study, effects of petrographic composition and particle size on flotation process were investigated. Samples were taken from rougher and cleaner cells of central Alborz coal washing plant (Iran). Petrographic study of the feed into flotation circuit with different size fractions showed that an increase in particle size tends to decrease vitrinite and inertinite macerals percentage while increasing that of liptinite. Petrographic analysis of different size fractions of rougher and cleaner cell concentrates showed that, with increasing particle size, vitrinite macerals were reduced but liptinite macerals showed an increase. Evaluation of the cell operation revealed that over 62% of tailings was composed of reactive macerals in coking process, including vitrinite and liptinite. The petrographic study showed that, with the same frother, by applying gasoline as a collector, yield, and total recovery increased by 3.5% and 3%, respectively, as compared to those when kerosene served as collector. Continuing with gasoline as collector, total circuit recovery increased by 2.2% when methyl isobutyl carbinol (MIBC), rather than pine oil, served as frother. Based on petrographic studies and percentages of reactive macerals, the optimal reagents were found to be gasoline (as collector) and MIBC (as frother).

Factors controlling petrographic composition of neogene Tenggarong coals-Kutai basin-East Kalimantan

Petrographic composition of the Neogene Tenggarong coals in the Kutai Basin-East Kalimantan indicates its geological setting. The aim of this study is to obtain an understanding of the geologic aspects controlling the petrographic composition of the coals.Variation of type and rank in the coals was determined by petrographic examination of twenty-two samples. The coals are absolutely dominated by vitrinite, common liptinite and rare inertinite and mineral matter. Vitrinite macerals are dominated by detrovitrinite and telovitrinite. Cutinite and resinite are the dominant liptinite macerals in the coals. The inertinite macerals include semifusinite, inertodetrinite and sclerotinite. Clay and pyrite are the dominant mineral matters in the coals. The type differences largely reflect climatic influence and differences in peat conditions. Rank of the coals, in general, depends largely on the stratigraphic position. Reflectance measurements on the coals indicate that there is a slightly difference in rank. The coals are sub-bituminous rank (R v max of 0.40-0.47%). The change in vitrinite reflectance of the coals is due to the thicker cover/overburden on the high rank coals. Nevertheless, the vitrinite reflectance is higher in some coals in the Loa Kulu area (R v max of 0.48-0.57%) due to its stratigraphic position that is at the bottom of the sequence. The type and rank characteristics of the coals clearly influence the utilization. The coals are suited to utilize for direct combustion and therefore, the major utilization potential would be for power generation.

Self-heating Potential of Coal Inferred from Elemental Data – A Case Study of the Witbank Coalfield of South Africa

Initiation of self-heating is governed by a coal’s ability to oxidize at low temperatures. Aliphatics undergo low-temperature oxidation and are the main constituents of vitrinite. Conversely, the chief constituents of inertinite, aromatics, oxidize at elevated temperatures. In this study, published elemental data for the Witbank Coalfield are used to calculate the H/C ratio and aromatic fraction (fa). The parameters are correlated with petrographic composition. An increased proportion of aliphatics in vitrinite suggests that it has higher heat generating capacity (HG) at low temperatures than inertinite of similar rank. When the heat retention capacity (HR) exceeds HG, self-heating initiates, resulting in oxidation of aromatics. Sustained self-heating, initiated by oxidation of vitrinite macerals, may trigger ignition. Spontaneous combustion in vitrinite-poor coals is indicative of a coal body with high HR. For Witbank coals, the likelihood of self-heating is classed as high- and low-risk corresponding to vitrinite- and inertinite-rich coals, respectively. By implication, spontaneous combustion tests quantify HG.

Flotation production of vitrinite maceral concentrate and its optimization using response surface approach

ABSTRACTIn this paper, an attempt is made to recover vitrinite-rich fraction coal using batch flotation operation. Three important operational variables, viz. collector dose (kg/ton), frother dose (kg/ton), and feed solid concentration, (%) have been changed according to Box–Behnken factorial design and their effect on the response parameter like yield, ash, and vitrinite maceral recovery (vmr) percent has been evaluated. For understanding the influence of interactional effects, response surface methodology (rsm) approach has been adopted. From 69.23 to 99.98 of volume percentage of vitrinite maceral is recovered, when the flotation test is performed without addition of collector with frother level maintained at 0.75 kg/ton of coal keeping feed solid concentration fixed at 5% solid by weight. High value of R2 greater than 90% is obtained for model equations of yield, ash, and vmr. Minitab 16.0 statistical software was used for data analysis.

Assessing thermal maturity beyond the reaches of vitrinite reflectance and Rock-Eval pyrolysis: A case study from the Silurian Qusaiba formation

Thermal maturity assessment in pre-Devonian shales is challenging due to the absence of vitrinite macerals that form the basis for vitrinite reflectance petrography, the most-widely used technique for organic maturity assessment. This paper presents an integrated analysis of thermal maturity on the basis of alternative spectroscopic and geochemical techniques in lieu of conventional organic petrography, applied in four drilled wells in the pre-Devonian (Silurian) Qusaiba Member of the Qalibah Formation in northwestern Saudi Arabia. The techniques comprise both bulk sample (Rock-Eval pyrolysis, infrared and Raman spectroscopy), and kerogen isolate analysis (elemental, density, surface area, and X-ray absorption near edge structure), with each method calibrated to the vitrinite reflectance scale. Rock-Eval pyrolysis, a common alternative to vitrinite reflectance measurements, provided unreliable maturity estimates in the majority of samples because of low S2 signal. In contrast, the other techniques defined a consistent and narrow maturity range within each well, and revealed a wide range of maturity between the wells. On the basis of the spectroscopic and geochemical results, equivalent vitrinite reflectance for the Qusaiba Member in northwestern Saudi Arabia ranges from at least 0.9±0.1 to 2.1±0.2%Ro, demonstrating significant variation in its maturation history. The integrated assessment of maturity across multiple wells provides data that can be used to construct maturity maps for oilfield exploration and appraisal. More generally, the methods and calibrations for thermal maturity presented here can be used to establish vitrinite-reflectance-equivalent maturities in shales as a complement to or especially in the absence of conventional maturity estimates.

Petrological Considerations for the Demineralization of Rajmahal Coals with Pseudomonas mendocina B6-1

ABSTRACT The present study entails the results of the petrological coniderations for demineralization of Rajmahal Gondwana coals with Psudomonas mendocina B6-1. Inertinite group macerals are the dominant constituents of these coals, followed by vitrinite group, while liptinite occurs in low concentration. The amount of Mineral matter is moderately high. The concentration of major, minor and trace elements is high when compared with Clarke values. After the treatment of these coals with Pseudomonas mendocina strain B6-1, a significant reduction in the elemental content of oxygen, hydrogen and sulphur was observed. A gradual reduction of pyrite phase due to bioleaching was identified and its signatures were reflected in the XRD spectra and FTIR absorption bands. Over 5 % reduction in the ash content and decrease of major, minor and trace element to variable degrees were also noticed. Fe, As, and Ca positively correlate with the ash removal percentage indicating that the samples with high concentration of these elements were prone to demineralization with Pseudomonas mendocina strain B6-1 whereas Ni, Zn, Cr and Cu, negatively correlate with the ash removal percentage and shows that their enrichment impeded the process of demineralization. With increasing concentration of vitrinite the removal of major/minor/trace elements also increased which is attributed to the possible association of these elements with the mineral matter occurring as superficial mounting and superficial blanketing over the vitrinite macerals. This could facilitate the bacterial access to the elements to act upon and remove it to the variable extent. Some minerals occur intergrown with inertinites causing restricted bacterial action owing to the non-exposure of the mineral particles and less surface area available to the bacteria for bioleaching. Sulfur removal strongly relates with increase in inertinite content and decrease in liptinite content. This appears that sulfur associated with liptinites have shown difficult removal condition. The maximum removal of the trace elements like Cd, Cu, Co, Zn and Pb was observed from the ‘banded dull coal’ samples of the Rajmahal basin while maximum removal of major/minor elements like Fe, Ca and Mg was noticed from the ‘banded bright coal’ samples. However, maximum removal of Mn and As was also observed in the samples of ‘banded coal’.

Petrographic characteristics of selected tertiary coals from Western Indonesia according to their geological ASPECTS

Selected Tertiary coals from the western part of Indonesia (Sumatera, Kalimantan and Java) indicate similarities and differences in type and rank characteristics. These coals reflect their geological setting, particularly for intrusive and stratigraphic aspects. Type and rank of the coals were assessed by petrographic examination. The coals are mainly dominated by vitrinite, common liptinite and rare inertinite and mineral matter. Vitrinite macerals are dominated detrovitrinite and telovitrinite. Resinite, cutinite and suberinite are the dominant liptinite macerals in the coals. Inertinite macerals in the coals consist of semifusinite, sclerotinite and inertodetrinite. The type differences largely reflect climatic influence and differences in peat conditions. In spite of short geological history, the coals exhibit variable vitrinite reflectances. The high vitrinite reflectance of the coals is a result of higher regional coalification levels in the basins associated with greater cover and effects of igneous intrusions.

Carbon isotope analysis of whole-coal and vitrinite from intruded coals from the Illinois Basin: No isotopic evidence for thermogenic methane generation

Igneous intrusions into coals and organic-rich rocks may have contributed to global warming in the geologic past through the release of greenhouse gases. Evidence for a large release of thermogenic CH4 from the organics would include significant δ13Corg enrichment in the residual organic matter (OM). However, δ13Corg values of thermally altered OM in coals and shales adjacent to intrusions often show negative trends or, in some cases, ambiguous or positive trends. Previous studies have evaluated the δ13Corg of whole-coal samples rather than that of individual organic components, or macerals. As different macerals have different isotopic compositions, maceral-specific trends may be masked by variations in maceral composition of the bulk samples. This study evaluates the hypothesis that, if a large-scale release of 13C-depleted thermogenic CH4 resulted from intrusion of the coal, then it should have produced 13C-enriched coal residuum and, specifically, vitrinite (the most abundant component of the coal) adjacent to the intrusion. This study reports geochemical and petrographic data for whole-coal samples and vitrinite macerals (separated via density-gradient centrifugation, DGC) from a transect of thermally altered Springfield (No. 5) Coal (Pennsylvanian) in the Illinois Basin.Approaching the dike contact, mean vitrinite reflectance (Rr) increases from background levels of 0.55% up to ~4.8% and liptinites become indistinguishable from vitrinite. Isotropic and fine-grained circular mosaic coke is observed in samples within ~1.3m of the coal/intrusion contact. Approaching the intrusion, volatile matter (VM) decreases and fixed carbon (FC) and %C increase, whereas %H decreases. Total organic carbon (TOC) for whole coal decreases from 77% to 34%, whereas TOC for separated vitrinite fractions increases from ~66% to 93% toward the coal/intrusion contact. Density of DGC-separated vitrinites ranges from 1.27g/mL in the unaltered coal to 1.52g/mL in the sample adjacent to the coal/intrusion contact. Vitrinite density increases with increased Rr and %C, and decreases with increased %H and H/C.Despite these marked geochemical and petrographic changes, no significant changes in δ13Corg values of the whole coal (−25.3‰ to −24.9‰) or the separated vitrinites (−25.3‰ to −25.0‰) occur proximal to the intrusion. Changes in the isotopic signatures are not of a magnitude that would be expected if significant quantities of isotopically depleted thermogenic CH4 had been generated by the intrusive event. Moreover, no petrographic evidence supports the occurrence of condensed or immobilized thermal products due to rapid pyrolysis (such as 12C-rich pyrolytic carbon) close to the intrusion that could have moderated any changes in δ13Corg. Geochemical and petrographic results suggest that only minimal loss of CH4 was associated with the rapid heating of the Springfield (No. 5) Coal by the intrusion. These findings have significant implications for models linking past global warming to the intrusion of coals and carbonaceous shales.

Fractal and pore dispositions of coal seams with significance to coalbed methane plays of East Bokaro, Jharkhand, India

In India, much attention has been paid to the Gondwana coals of Permian age of Damodar valley, which comprises the major CBM producing blocks. East Bokaro Coalfield is part of Damodar valley and one of the promising potential CBM plays. In this study, the technological properties, TOC content, thermal maturity (Ro%), low pressure N2 sorption isotherm and SEM analyses were performed to find out the significance of fractal dimension, pore dispositions and associated geological influence on pore structure and fractal dimensions for better understanding of gas adsorption capacities of coal seams of East Bokaro. The micropore and mesopore specific surface area obtained through DR and multi-point BET ranges from 0.18 to 8.86 m2/g and 0.42–7.41 m2/g respectively, signifying dominance of micro and mesopores involvement in specific surface area. The BJH and DFT pore volume varying from 0.002 to 0.007 and 0.001–0.007 cc/g respectively. It is observed that the considerable pore volume contributed by mesopores of the range 3–50 nm and least fractions of macropores ranges from 50 to 278 nm. There is a tremendous increase in pore volume, when the pore size in between 4 and 16 nm, these pores are particularly more suitable for gas storage and associated with carbon rich vitrinite maceral. The pore size distribution obtained through BJH, DFT, DA, DR and average pore diameter values ranges from 2.99 to 10.20, 1.77–3.17, 1.42–2.48, 0.46–3.28 and 4.48–16.43 nm respectively. The opening of the hysteresis loop at lower pressure ∼0.2 (P/P0) and closing of hysteresis loop between 0.6 and 0.8 (P/P0) acutely connects to the adsorption branch is revealing of cavitation and irregularities in pore structures, consequently rapid decline in desorption curve due to the condensation and evaporation characteristics of micro and mesopores, often associated with combined slit and bottle neck pores and bottle-neck open ended shaped mesopores. The variations in correlation coefficients of two separate linear segments of fractal dimensions (D1 and D2), summarizes the suitability of D1, for pore structure analysis. Nevertheless, the low values of fractal dimensions (D1 = 1.1600–2.5450 and D2 = 1.5580–2.8730), signifies the pore surfaces are controlled by heterogeneity of coal composition. However, the correlations of D2 with ash, average pore diameter, specific surface area, Ro%, pore volume and depth accentuated that D2 may be considered for CBM reservoir characterization of East Bokaro Coalfield. The very good correlations between depth with D2, total pore volume and thermal maturity (Ro%) signifies the intensification of fractal dimensions as a function of reduction and variations in pore diameter with increasing degree of coalification. The effects of rank upon fractal dimensions are mainly due to structured variety of micropore and mesopore of coals. SEM studies supports the variations in surface morphology, pore structure and fractal dimension controlled by complex coal compositional parameters like carbon content, volatile matter, thermal maturity and pore size distribution.

Limnic Condition In Rheotrhopic Peat Type As the Origin of Petai Coal, Central Sumatra Basin, Indonesia

Petrographic coal is the study of organic and inorganic components of bearing coal formation. This study aims to determine the composition, depositional facies, type and stage of the genesis of coal in the area of research. This research method using a diagram approach Diessel, 1986, Calder et al., 1991 to determine the depositional facies and peat ecosystems formation of coal carrier. Microscopic observations using Carl Zeiss Microscope and Point Counter Model F was conducted to determine the micro-organic components of coal.&#x0D; Based on microscopic investigation of the overall sample average abundance maceral vitrinite reached 66.3%, 30.32% mineral matter, maceral liptinite 3:26%, and to absent maceral inertinit no indicates oxidation process that occurs during the decomposition of organic matter. Syngenetic depositional pyrite component type spread sporadically on the surface of the coal seam in the form frambiodal and particulates.&#x0D; Facies deposition of coal based on the calculation of tissue prevetion index versus gelification index show faises limnic while the calculation of ground water index versus vegetation index show atmosphere rheotropic mires (correlation +) supported the absence maceral inertinit and funginite, hypothesized water level in stable condition was high watertable during the decomposition process takes place in an atmosphere ph 6-8 and eh balanced. Average rate comparison gelifikasi the preserved tissues of plant cells (tellocolinite) is smaller than the 23.6% plant cell tissue is not preserved (desmocollinite) amounted to 52.6% indicated from plants of the type herbaceous plant.