Pub Date : 2025-06-06DOI: 10.1016/j.coal.2025.104825
Katalin Sári , Mária Hámor-Vidó , Ernő Takács , Márton Bauer , Richard William McIntosh , Zoltán Püspöki
An intriguing problem of the Upper Miocene stratigraphy in the Pannonian Basin is the correlation of marginal lignite-bearing units to the thick siliciclastic succession in the basin centre; however, it is inevitable in the stratigraphic investigation of the Jászság Basin, necessitated by a regional scale hydrogeological study. An essential precondition of this investigation is integrating data from lignite and hydrocarbon research of very different scales. The Tiszapalkonya-1 long core traversing the lignite-bearing succession across 1300 m enabled this data integration, as (i) it was measured by wireline logs, (ii) its lignite samples were subjected to laboratory and coal petrological analyses and (iii) the logs can be correlated with seismic sections.
Three lignite-bearing units were identified in the section. According to lithological and organic petrological data, the lower represents mostly floodplain conditions with intermediate complex and marsh. The middle indicates a change from aquatic to unbalanced wet forest swamp, floodplain. In the upper unit more stable, balanced accumulation could develop. The density log proved to be a reliable proxy on the occurrence and ash content of peat-forming environments, and the lignite-bearing units occur as autonomous seismic facies based on their higher seismic amplitude. These enable the basin-scale tracking of the identified lignite-bearing units. A log-based multi-proxy time-series analysis revealed regular cycles in the succession but raised some necessity of re-consideration of the existing magnetostratigraphy of the section. The density log gained eminent cyclostratigraphic potential due to the sensitivity of the “coal window” to climate changes.
{"title":"Integrated stratigraphy of an upper miocene lignite-bearing succession based on wireline log, seismic and organic petrographic data in the Tiszapalkonya-1 core section, NE Hungary","authors":"Katalin Sári , Mária Hámor-Vidó , Ernő Takács , Márton Bauer , Richard William McIntosh , Zoltán Püspöki","doi":"10.1016/j.coal.2025.104825","DOIUrl":"10.1016/j.coal.2025.104825","url":null,"abstract":"<div><div>An intriguing problem of the Upper Miocene stratigraphy in the Pannonian Basin is the correlation of marginal lignite-bearing units to the thick siliciclastic succession in the basin centre; however, it is inevitable in the stratigraphic investigation of the Jászság Basin, necessitated by a regional scale hydrogeological study. An essential precondition of this investigation is integrating data from lignite and hydrocarbon research of very different scales. The Tiszapalkonya-1 long core traversing the lignite-bearing succession across 1300 m enabled this data integration, as (i) it was measured by wireline logs, (ii) its lignite samples were subjected to laboratory and coal petrological analyses and (iii) the logs can be correlated with seismic sections.</div><div>Three lignite-bearing units were identified in the section. According to lithological and organic petrological data, the lower represents mostly floodplain conditions with intermediate complex and marsh. The middle indicates a change from aquatic to unbalanced wet forest swamp, floodplain. In the upper unit more stable, balanced accumulation could develop. The density log proved to be a reliable proxy on the occurrence and ash content of peat-forming environments, and the lignite-bearing units occur as autonomous seismic facies based on their higher seismic amplitude. These enable the basin-scale tracking of the identified lignite-bearing units. A log-based multi-proxy time-series analysis revealed regular cycles in the succession but raised some necessity of re-consideration of the existing magnetostratigraphy of the section. The density log gained eminent cyclostratigraphic potential due to the sensitivity of the “coal window” to climate changes.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"307 ","pages":"Article 104825"},"PeriodicalIF":5.6,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144263080","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-06DOI: 10.1016/j.coal.2025.104816
Rafał Morga , Roman Wrzalik
To date, the pore system of graptolite periderm in shales with thermal maturity at the transition phase from the oil to the gas window has been poorly researched and understood. It was also not clear whether the graptolite periderm develops secondary pores. Therefore, porosity, pore characteristics, and surface roughness of the graptolite periderm (graptolite reflectance GR = 1.30–1.83 %; vitrinite reflectance equivalent VRE = 1.11–1.50 %) in the Silurian shales of the Baltic Basin (northern Poland) were investigated by atomic force microscopy (AFM). The size of the 200 × 200 nm measurement area was chosen to allow observation of pores with diameters ≥1.4 nm. The graptolite periderm shows a very low porosity (0.16–0.28 %), which increases with increasing thermal maturity and decreases the mean equivalent pore diameter and surface roughness. With the onset of the gas window (at GR ≥ 1.58 %; VRE ≥ 1.31 %), limited secondary porosity develops, and percentage of pores <5 nm in size significantly increases. Elliptical or roundish micropores appear within the granular fragments, and sparse pores <5 nm in size emerge within the non-granular fabric. The ability of the graptolite periderm to generate gaseous hydrocarbons at the beginning of the gas window is poor. Granular type is more generative compared to non-granular type. The ratio between the two types of fabric is not significant for the overall source and reservoir potential of the host formation at the maturity level considered in this study. However, it can be important at higher maturities. Changes in the pore system and roughness parameters align with the alteration of the chemistry and microstructure of graptolite periderm. The development of secondary porosity can depend on thermal degradation of the graptolite periderm during and after burial.
{"title":"Nanoporosity of graptolite periderm by atomic force microscopy (AFM): A case study from the Baltic Basin, Poland","authors":"Rafał Morga , Roman Wrzalik","doi":"10.1016/j.coal.2025.104816","DOIUrl":"10.1016/j.coal.2025.104816","url":null,"abstract":"<div><div>To date, the pore system of graptolite periderm in shales with thermal maturity at the transition phase from the oil to the gas window has been poorly researched and understood. It was also not clear whether the graptolite periderm develops secondary pores. Therefore, porosity, pore characteristics, and surface roughness of the graptolite periderm (graptolite reflectance GR = 1.30–1.83 %; vitrinite reflectance equivalent VRE = 1.11–1.50 %) in the Silurian shales of the Baltic Basin (northern Poland) were investigated by atomic force microscopy (AFM). The size of the 200 × 200 nm measurement area was chosen to allow observation of pores with diameters ≥1.4 nm. The graptolite periderm shows a very low porosity (0.16–0.28 %), which increases with increasing thermal maturity and decreases the mean equivalent pore diameter and surface roughness. With the onset of the gas window (at GR ≥ 1.58 %; VRE ≥ 1.31 %), limited secondary porosity develops, and percentage of pores <5 nm in size significantly increases. Elliptical or roundish micropores appear within the granular fragments, and sparse pores <5 nm in size emerge within the non-granular fabric. The ability of the graptolite periderm to generate gaseous hydrocarbons at the beginning of the gas window is poor. Granular type is more generative compared to non-granular type. The ratio between the two types of fabric is not significant for the overall source and reservoir potential of the host formation at the maturity level considered in this study. However, it can be important at higher maturities. Changes in the pore system and roughness parameters align with the alteration of the chemistry and microstructure of graptolite periderm. The development of secondary porosity can depend on thermal degradation of the graptolite periderm during and after burial.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"307 ","pages":"Article 104816"},"PeriodicalIF":5.6,"publicationDate":"2025-06-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144243228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-03DOI: 10.1016/j.coal.2025.104818
Zhiheng Zhou, Hamed Sanei
Point counting is a widely used quantitative technique in microscopic analysis for estimating the volume percentage of target constituents within a sample. Its application in coal petrography has been standardized through international guidelines such as ISO 7404 and ASTM D2797/D2799, which were primarily developed for the analysis of carbonaceous materials such as coal and peat. These standards have governed sample preparation, maceral identification, and point counting procedures since the 1980s. However, modern applications of coal petrography point counting to dispersed organic matter (DOM), particularly in low-TOC samples, have revealed methodological incompatibilities. As a result, significant procedural modifications have been implemented across laboratories, but no universally adopted approach has been established.
To address these challenges, this study proposes and evaluates a point counting method for dispersed organic matter (DOM) using a 21-crosshair grid reticle. The method embeds 21 crosshairs within a 60-μm-diameter region (under 500× magnification) in the microscope system and requires counting at least 300 suitable microscopic fields where all crosshairs fall on sample particles. The use of 21-crosshair grid increases the probability of intersecting DOM in sample particles within pellets. This results in a 68 % reduction in analysis time (from 2.5 h to 1.0 h per sample) compared to when traditional coal petrography point counting is applied to DOM. Furthermore, the use of a denser grid in the 21-crosshair DOM point counting method improves measurement accuracy by more effectively capturing the areas of constituents within sample particles. By requiring the counting of at least 300 suitable microscopic fields, it generates a robust dataset of over 6300 points, achieving strong correlations (R2 > 0.80) between the volume percentage of maceral assemblage and TOC in case studies. The method has been validated in applications such as hydrocarbon potential assessment, solid bitumen characterization, thermal maturity analysis, and depositional environment reconstruction. This paper bridges the gap between traditional standards and modern analytical needs by proposing a standardized, efficient, and reliable method for DOM point counting.
{"title":"Maceral point counting for dispersed organic matter (DOM)","authors":"Zhiheng Zhou, Hamed Sanei","doi":"10.1016/j.coal.2025.104818","DOIUrl":"10.1016/j.coal.2025.104818","url":null,"abstract":"<div><div>Point counting is a widely used quantitative technique in microscopic analysis for estimating the volume percentage of target constituents within a sample. Its application in coal petrography has been standardized through international guidelines such as ISO 7404 and ASTM D2797/D2799, which were primarily developed for the analysis of carbonaceous materials such as coal and peat. These standards have governed sample preparation, maceral identification, and point counting procedures since the 1980s. However, modern applications of coal petrography point counting to dispersed organic matter (DOM), particularly in low-TOC samples, have revealed methodological incompatibilities. As a result, significant procedural modifications have been implemented across laboratories, but no universally adopted approach has been established.</div><div>To address these challenges, this study proposes and evaluates a point counting method for dispersed organic matter (DOM) using a 21-crosshair grid reticle. The method embeds 21 crosshairs within a 60-μm-diameter region (under 500× magnification) in the microscope system and requires counting at least 300 suitable microscopic fields where all crosshairs fall on sample particles. The use of 21-crosshair grid increases the probability of intersecting DOM in sample particles within pellets. This results in a 68 % reduction in analysis time (from 2.5 h to 1.0 h per sample) compared to when traditional coal petrography point counting is applied to DOM. Furthermore, the use of a denser grid in the 21-crosshair DOM point counting method improves measurement accuracy by more effectively capturing the areas of constituents within sample particles. By requiring the counting of at least 300 suitable microscopic fields, it generates a robust dataset of over 6300 points, achieving strong correlations (R<sup>2</sup> > 0.80) between the volume percentage of maceral assemblage and TOC in case studies. The method has been validated in applications such as hydrocarbon potential assessment, solid bitumen characterization, thermal maturity analysis, and depositional environment reconstruction. This paper bridges the gap between traditional standards and modern analytical needs by proposing a standardized, efficient, and reliable method for DOM point counting.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"307 ","pages":"Article 104818"},"PeriodicalIF":5.6,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144221678","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-06-03DOI: 10.1016/j.coal.2025.104817
Yueguo Li , Haijiao Fu , Xianbo Su , Detian Yan , Gang Wang , Shuguang Yang , Xing Chen , Jianzhang Liu , Jintao Kong
The benefits of coalbed gas (CBG) development are directly affected by the production capacity level. Previous studies of CBG productivity response have mainly focused on the hydrogeochemical characteristics of produced water, and paid less attention to the correlation between microbial communities and productivity. This study focuses on nine CBG wells in the Liulin Block of the eastern Ordos Basin, systematically analyzing the CBG genesis, as well as the relationships between hydrogeochemical parameters, microbial community characteristics and CBG productivity. The results show that the CBG in Liulin Block is a mixture of secondary biogenic gas and thermogenic gas, and the proportion of biogenic methane is 48.0 % to 49.7 %. The total dissolved solids (TDS) content is positively correlated with the average daily production of CBG, and the concentration of HCO3− is negatively correlated with the average daily gas production. The concentration of elemental Sn in the produced water is significantly correlated with average daily gas production. Positive δ13CDIC values indicate the occurrence of microbial methanogenesis. Analysis of the microbial community shows that the bacterial community exhibits significant functional diversity, with Hydrogenophaga having the highest relative abundance and a positive correlation with average daily production of CBG. The archaeal community is dominated by methanogenic archaea. From the perspective of community diversity, the Operational Taxonomic Units (OTU) number, Chao1 and Ace indexes of the archaeal community show a positive correlation with average daily gas production. This study provides a novel perspective for research on microbial indicators of CBG production.
{"title":"Investigating coalbed gas productivity response from hydrogeochemical and microbial perspectives: A case study of the Liulin block, eastern Ordos Basin, China","authors":"Yueguo Li , Haijiao Fu , Xianbo Su , Detian Yan , Gang Wang , Shuguang Yang , Xing Chen , Jianzhang Liu , Jintao Kong","doi":"10.1016/j.coal.2025.104817","DOIUrl":"10.1016/j.coal.2025.104817","url":null,"abstract":"<div><div>The benefits of coalbed gas (CBG) development are directly affected by the production capacity level. Previous studies of CBG productivity response have mainly focused on the hydrogeochemical characteristics of produced water, and paid less attention to the correlation between microbial communities and productivity. This study focuses on nine CBG wells in the Liulin Block of the eastern Ordos Basin, systematically analyzing the CBG genesis, as well as the relationships between hydrogeochemical parameters, microbial community characteristics and CBG productivity. The results show that the CBG in Liulin Block is a mixture of secondary biogenic gas and thermogenic gas, and the proportion of biogenic methane is 48.0 % to 49.7 %. The total dissolved solids (TDS) content is positively correlated with the average daily production of CBG, and the concentration of HCO<sub>3</sub><sup>−</sup> is negatively correlated with the average daily gas production. The concentration of elemental Sn in the produced water is significantly correlated with average daily gas production. Positive δ<sup>13</sup>C<sub>DIC</sub> values indicate the occurrence of microbial methanogenesis. Analysis of the microbial community shows that the bacterial community exhibits significant functional diversity, with <em>Hydrogenophaga</em> having the highest relative abundance and a positive correlation with average daily production of CBG. The archaeal community is dominated by methanogenic archaea. From the perspective of community diversity, the Operational Taxonomic Units (OTU) number, Chao1 and Ace indexes of the archaeal community show a positive correlation with average daily gas production. This study provides a novel perspective for research on microbial indicators of CBG production.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"307 ","pages":"Article 104817"},"PeriodicalIF":5.6,"publicationDate":"2025-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144212711","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-30DOI: 10.1016/j.coal.2025.104811
Stavros Kalaitzidis, Kimon Christanis
{"title":"Editorial of the special issue: The 2023 joint 74th ICCP and 39th TSOP meeting: Organic petrology in the energy transition era: Challenges ahead","authors":"Stavros Kalaitzidis, Kimon Christanis","doi":"10.1016/j.coal.2025.104811","DOIUrl":"10.1016/j.coal.2025.104811","url":null,"abstract":"","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"307 ","pages":"Article 104811"},"PeriodicalIF":5.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144237512","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-30DOI: 10.1016/j.coal.2025.104815
Jia Song , Beilei Sun , Sandra Rodrigues , Chao Liu , Zhanming Guo , David French
Lithium (Li) enrichment in coal has attracted significant attention due to its economic potential and complex geochemical behavior during coal formation. This study investigates the concentration and isotopic composition of Li in kaolinite and organic matter from three high-Li coals from North China using Secondary Ion Mass Spectrometry (SIMS), complemented by TESCAN Integrated Mineral Analyzer (TIMA), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), Fourier Transform-Infrared Spectroscopy (FTIR), and Confocal Raman Microscopy (Raman). Results reveal that kaolinite is the primary host of Li, with concentrations exceeding 1516 μg/g. Lithium isotopic compositions (δ7Li) in kaolinite from high-rank coals exhibit narrow ranges, suggesting Li isotopic homogenization as a result of the elevated paleotemperature. In contrast, δ7Li values in lower-rank coals show greater variability, influenced by pore fluids and depth-dependent fractionation processes. Organic material, characterized by lower lithium concentrations (mostly <100 μg/g) and highly variable δ7Li values, exhibits a heavier lithium isotopic composition in high-rank coal compared to δ7Li values in low-rank coal. These findings highlight the role of kaolinite in this isotopic fractionation. and emphasize the role of kaolinite as a major Li carrier. This study provides critical insights into Li enrichment mechanisms and isotopic fractionation during coalification, contributing to a better understanding of Li sources and mobility in coal-bearing strata.
{"title":"Li concentration and isotopes in kaolinite and organic of coals determined by secondary ion mass spectrometry","authors":"Jia Song , Beilei Sun , Sandra Rodrigues , Chao Liu , Zhanming Guo , David French","doi":"10.1016/j.coal.2025.104815","DOIUrl":"10.1016/j.coal.2025.104815","url":null,"abstract":"<div><div>Lithium (Li) enrichment in coal has attracted significant attention due to its economic potential and complex geochemical behavior during coal formation. This study investigates the concentration and isotopic composition of Li in kaolinite and organic matter from three high-Li coals from North China using Secondary Ion Mass Spectrometry (SIMS), complemented by TESCAN Integrated Mineral Analyzer (TIMA), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), Fourier Transform-Infrared Spectroscopy (FTIR), and Confocal Raman Microscopy (Raman). Results reveal that kaolinite is the primary host of Li, with concentrations exceeding 1516 μg/g. Lithium isotopic compositions (δ<sup>7</sup>Li) in kaolinite from high-rank coals exhibit narrow ranges, suggesting Li isotopic homogenization as a result of the elevated paleotemperature. In contrast, δ<sup>7</sup>Li values in lower-rank coals show greater variability, influenced by pore fluids and depth-dependent fractionation processes. Organic material, characterized by lower lithium concentrations (mostly <100 μg/g) and highly variable δ<sup>7</sup>Li values, exhibits a heavier lithium isotopic composition in high-rank coal compared to δ<sup>7</sup>Li values in low-rank coal. These findings highlight the role of kaolinite in this isotopic fractionation. and emphasize the role of kaolinite as a major Li carrier. This study provides critical insights into Li enrichment mechanisms and isotopic fractionation during coalification, contributing to a better understanding of Li sources and mobility in coal-bearing strata.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104815"},"PeriodicalIF":5.6,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144184395","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-28DOI: 10.1016/j.coal.2025.104814
Agnieszka Drobniak , Maria Mastalerz , Zbigniew Jelonek , Iwona Jelonek , Menandro N. Acda , Tushar Adsul , Neža Malenšek Andolšek , Lorenzo Animali , Omid H. Ardakani , Telma Ataide , Demberelsuren Batbold , Mohd Younus Bhat , Tara Congo , Bryon S. Donohoe , Olugbenga A. Ehinola , Deolinda Flores , Carolina Fonseca , Santanu Ghosh , Paula Gonçalves , Paul C. Hackley , Konrad Ziemianin
As nations transition toward sustainable energy systems, biomass has become a vital component of global energy portfolios. Derived from organic materials such as wood, agricultural residues, forestry byproducts, and organic waste, biomass is a renewable energy source with significant environmental and economic benefits. Responsible biomass energy production can improve waste management, reduce emissions of greenhouse gases, and mitigate environmental pollution. However, as the diversity of biomass-derived fuels increases, robust quality assessment methods are essential to ensure their efficiency, safety, and minimal environmental impact.
Reflected light microscopy (RLM) is one such technique with the potential to complement conventional physico-chemical analyses by enabling a rapid identification of material constituents and impurities. To refine this methodology and evaluate the reproducibility of solid biomass component identification using RLM, an interlaboratory study (ILS) was conducted. The study involved the recognition of 58 components across 45 photomicrographs, with the participation of 65 scientists and students from 25 countries.
The participants faced high difficulty identifying some of the marked components, and as a result, the percentage of correct answers ranged from 19.0 % to 98.3 %, with an average correct identification rate of 62.7 %. The most challenging aspects of the identification process included distinguishing between woody and non-woody (agro) biomass, accurately identifying petroleum-derived materials, and differentiating agro biomass from inorganic matter.
The results suggest that while RLM is an important tool for characterizing solid biomass, further development of methodology guidelines and training are necessary to enhance its effectiveness. Future research should prioritize preparing detailed, image-rich, microscopic morphological descriptions of biomass fuel components, which could improve the accuracy and reliability of using RLM in biomass fuel characterization.
{"title":"Component identification of solid biomass fuels using reflected light microscopy: Interlaboratory study 2","authors":"Agnieszka Drobniak , Maria Mastalerz , Zbigniew Jelonek , Iwona Jelonek , Menandro N. Acda , Tushar Adsul , Neža Malenšek Andolšek , Lorenzo Animali , Omid H. Ardakani , Telma Ataide , Demberelsuren Batbold , Mohd Younus Bhat , Tara Congo , Bryon S. Donohoe , Olugbenga A. Ehinola , Deolinda Flores , Carolina Fonseca , Santanu Ghosh , Paula Gonçalves , Paul C. Hackley , Konrad Ziemianin","doi":"10.1016/j.coal.2025.104814","DOIUrl":"10.1016/j.coal.2025.104814","url":null,"abstract":"<div><div>As nations transition toward sustainable energy systems, biomass has become a vital component of global energy portfolios. Derived from organic materials such as wood, agricultural residues, forestry byproducts, and organic waste, biomass is a renewable energy source with significant environmental and economic benefits. Responsible biomass energy production can improve waste management, reduce emissions of greenhouse gases, and mitigate environmental pollution. However, as the diversity of biomass-derived fuels increases, robust quality assessment methods are essential to ensure their efficiency, safety, and minimal environmental impact.</div><div>Reflected light microscopy (RLM) is one such technique with the potential to complement conventional physico-chemical analyses by enabling a rapid identification of material constituents and impurities. To refine this methodology and evaluate the reproducibility of solid biomass component identification using RLM, an interlaboratory study (ILS) was conducted. The study involved the recognition of 58 components across 45 photomicrographs, with the participation of 65 scientists and students from 25 countries.</div><div>The participants faced high difficulty identifying some of the marked components, and as a result, the percentage of correct answers ranged from 19.0 % to 98.3 %, with an average correct identification rate of 62.7 %. The most challenging aspects of the identification process included distinguishing between woody and non-woody (agro) biomass, accurately identifying petroleum-derived materials, and differentiating agro biomass from inorganic matter.</div><div>The results suggest that while RLM is an important tool for characterizing solid biomass, further development of methodology guidelines and training are necessary to enhance its effectiveness. Future research should prioritize preparing detailed, image-rich, microscopic morphological descriptions of biomass fuel components, which could improve the accuracy and reliability of using RLM in biomass fuel characterization.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"307 ","pages":"Article 104814"},"PeriodicalIF":5.6,"publicationDate":"2025-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144212712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-27DOI: 10.1016/j.coal.2025.104813
Majid Safaei-Farouji , David Misch , Reinhard F. Sachsenhofer , Johannes Weitz , Ivan Kojic , Ksenija Stojanović , Serik Tursyngaliyev , Medet Junussov , Milovan Fustic
The Bogatyr Komin open-pit mine in the Ekibastuz Basin, located in north-east Kazakhstan, is one of the largest coal mines in the world. It is based on three Lower Carboniferous seams (from bottom to top: seams 3, 2, and 1), which together form a 150 m thick, uniform seam complex. At the study site on the western basin edge, the seams dip steeply. Organic petrological and geochemical investigations have been performed to determine the maturity and depositional environment of these exceptionally thick seams.
Vitrinite reflectance (0.8–1.1 %Rr) classifies the coal as high-volatile bituminous A coal, which is also supported by Tmax values and maturity-related biomarker ratios. Vitrinite reflectance patterns prove pre-deformational coalification and a relatively high paleo-heat flow, likely caused by magmatic activity.
High ash yields and relatively low sulfur contents indicate that the coal accumulated in low-lying mires without marine influence. The input of detrital minerals decreased during peat accumulation. Relatively high concentrations of sulfur-bearing aromatic compounds, particularly in the lower part of seam 3, may reflect volcanic activity, which is also evidenced by the presence of distinct ash layers (“kaolinitic beds”) and kaolinite in coal samples.
Thick wood-forming plants were rare in the peat-forming vegetation. However, samples from seams 1 and 3 contain higher concentrations of aromatic compounds derived from lignin-bearing arborescent cordiaite-conifer-pteridosperm vegetation. Enhanced bacterial activity during deposition of the upper part of seam 2 and seam 1 is indicated by elevated hopane concentrations.
The exceptional thickness of the coal complex indicates a geodynamic setting with high subsidence rates.
{"title":"Organic petrography and geochemistry of the Lower-Carboniferous coals from the Ekibastuz Basin, Kazakhstan","authors":"Majid Safaei-Farouji , David Misch , Reinhard F. Sachsenhofer , Johannes Weitz , Ivan Kojic , Ksenija Stojanović , Serik Tursyngaliyev , Medet Junussov , Milovan Fustic","doi":"10.1016/j.coal.2025.104813","DOIUrl":"10.1016/j.coal.2025.104813","url":null,"abstract":"<div><div>The Bogatyr Komin open-pit mine in the Ekibastuz Basin, located in north-east Kazakhstan, is one of the largest coal mines in the world. It is based on three Lower Carboniferous seams (from bottom to top: seams 3, 2, and 1), which together form a 150 m thick, uniform seam complex. At the study site on the western basin edge, the seams dip steeply. Organic petrological and geochemical investigations have been performed to determine the maturity and depositional environment of these exceptionally thick seams.</div><div>Vitrinite reflectance (0.8–1.1 %Rr) classifies the coal as high-volatile bituminous A coal, which is also supported by Tmax values and maturity-related biomarker ratios. Vitrinite reflectance patterns prove pre-deformational coalification and a relatively high paleo-heat flow, likely caused by magmatic activity.</div><div>High ash yields and relatively low sulfur contents indicate that the coal accumulated in low-lying mires without marine influence. The input of detrital minerals decreased during peat accumulation. Relatively high concentrations of sulfur-bearing aromatic compounds, particularly in the lower part of seam 3, may reflect volcanic activity, which is also evidenced by the presence of distinct ash layers (“kaolinitic beds”) and kaolinite in coal samples.</div><div>Thick wood-forming plants were rare in the peat-forming vegetation. However, samples from seams 1 and 3 contain higher concentrations of aromatic compounds derived from lignin-bearing arborescent cordiaite-conifer-pteridosperm vegetation. Enhanced bacterial activity during deposition of the upper part of seam 2 and seam 1 is indicated by elevated hopane concentrations.</div><div>The exceptional thickness of the coal complex indicates a geodynamic setting with high subsidence rates.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104813"},"PeriodicalIF":5.6,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144170243","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-23DOI: 10.1016/j.coal.2025.104812
Ji Chen , Jingwen Zheng , Daxiang He , Peng Cheng , Qin Zhou , Tengfei Li , Haifeng Gai
Solid bitumen constitutes a predominant organic component in thermally mature source rocks, yet its role in shale reservoirs remains poorly constrained. This study integrated hydrocarbon expulsion simulation via sequential solvent extraction with isothermal pyrolysis experiments conducted on an early mature bituminite-rich shale sample from the Mesoproterozoic Xiamaling Formation in North China. Organic petrography and gas adsorption were applied to characterize the solid bitumen and pore structure in pyrolysis residues, respectively. The primary objective was to advance the understanding of the solid bitumen formation and its influence on the porosity development of shales within the dry gas window. Quantitative petrographic evidence confirms that the composition of retained extractable organic matter exerts fundamental control over the yield and properties of solid bitumen. Notably, the polar fraction (e.g., asphaltene component) exhibits superior solid bitumen-generating capacity, indicating that expulsion-driven compositional fractionation of residual hydrocarbons serves as the primary determinant of intraformational solid bitumen heterogeneity. Furthermore, empirical data demonstrate an inverse relationship between solid bitumen content and porosity development of shales across the investigated maturity spectrum (vitrinite reflectance 1.02 %–3.62 %), manifested through depressed specific surface area and diminished pore volume metrics. Our findings suggest that provenance-controlled variations in solid bitumen occurrence and subsequent pore architecture may induce complex reservoir quality modifications, potentially accounting for divergent porosity trends observed in natural shale systems. While this investigation provides fundamental insights into organo-petrophysical relationships, the general applicability of these conclusions warrants further validation through subsequent research.
{"title":"Solid bitumen formation and resulting differential porosity development in the Mesoproterozoic Xiamaling shale during artificial thermal maturation","authors":"Ji Chen , Jingwen Zheng , Daxiang He , Peng Cheng , Qin Zhou , Tengfei Li , Haifeng Gai","doi":"10.1016/j.coal.2025.104812","DOIUrl":"10.1016/j.coal.2025.104812","url":null,"abstract":"<div><div>Solid bitumen constitutes a predominant organic component in thermally mature source rocks, yet its role in shale reservoirs remains poorly constrained. This study integrated hydrocarbon expulsion simulation via sequential solvent extraction with isothermal pyrolysis experiments conducted on an early mature bituminite-rich shale sample from the Mesoproterozoic Xiamaling Formation in North China. Organic petrography and gas adsorption were applied to characterize the solid bitumen and pore structure in pyrolysis residues, respectively. The primary objective was to advance the understanding of the solid bitumen formation and its influence on the porosity development of shales within the dry gas window. Quantitative petrographic evidence confirms that the composition of retained extractable organic matter exerts fundamental control over the yield and properties of solid bitumen. Notably, the polar fraction (e.g., asphaltene component) exhibits superior solid bitumen-generating capacity, indicating that expulsion-driven compositional fractionation of residual hydrocarbons serves as the primary determinant of intraformational solid bitumen heterogeneity. Furthermore, empirical data demonstrate an inverse relationship between solid bitumen content and porosity development of shales across the investigated maturity spectrum (vitrinite reflectance 1.02 %–3.62 %), manifested through depressed specific surface area and diminished pore volume metrics. Our findings suggest that provenance-controlled variations in solid bitumen occurrence and subsequent pore architecture may induce complex reservoir quality modifications, potentially accounting for divergent porosity trends observed in natural shale systems. While this investigation provides fundamental insights into organo-petrophysical relationships, the general applicability of these conclusions warrants further validation through subsequent research.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104812"},"PeriodicalIF":5.6,"publicationDate":"2025-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144170242","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-05-15DOI: 10.1016/j.coal.2025.104810
M.M. Bicca , W. Kalkreuth , T.F. Silva , M. Guerra-Sommer , I. Degani-Schmidt , C.M. Felix , D.R. Boardman , P.A. Souza
Coals from southern Brazil are preserved in the Lower Permian postglacial Rio Bonito Formation of the Paraná Basin. Previous studies on the Candiota Coalfield have shown intervals with significant accumulations of inertinite macerals in the Banco Louco and S9 coal seams. Aiming to understand the causes of these anomalous inertinite accumulations, this study analyzed coal samples from the anomalous inertinite-rich interval and underlying carbonaceous siltites from the top of the Candiota Coal Superior (CCS), Banco Louco (BL), S9, and overlying S8 seams (post-anomalous) obtained from two borehole cores. The samples were analyzed using organic petrology, SEM, palynology, and biomarker (PAH) techniques. The results indicate that inertinite macerals accumulated in the paleoswamp in alternating small cycles, with general inertinite enrichment (fusinite, semifusinite, and inertodetrinite) towards the top of each coal seam analyzed. Macrocharcoal was present in all coal seams as charred wood, leaf fragments, and one reproductive structure. The peak of the inertinite-rich interval occurs at the S9 seam with the dominance of microcharcoal dispersed in fine-grained sediments and completely black palynomorphs, suggesting a significant wildfire event affecting the interval. Inertinite reflectance measurements indicated the predominance of ground and surface fire events with the rare occurrence of crown fires. Combustion of organic matter is also marked by the dominant presence of 3–5 ring PAHs and local occurrence of 6-ring PAHs (including coronene). The peatland flora was mainly composed of hygrophilous lycopsids and filicopsids, with subordinate elements represented by sphenopsids, mesophilous glossopterids, and meso-xerophilous conifers. The frequent oscillations in the vegetation composition were potentially related to climate changes and related environmental conditions, varying from hygrophilous to meso-hygrophilous and mesophilous, indicating that the vegetation composition adapted to environmental/climate changes as recognized by the alteration in the pollen-spore-producing flora towards the top of BL seam and their expansion in the overlying seams at the top of the anomalous interval. In the middle of the S9 seam, the completely dark palynomorphs and phytoclasts, plus a high abundance of pyrogenic biomarkers including 6-ring PAHs, point to significant fire events linked to the peak of the inertinite-rich interval during drier, warming intervals, which contributed to modifying the paleoecological patterns of the peatland. The paleo-wildfires of the Asselian age (ca. 298 Ma) Candiota Coalfield are the oldest record of wildfires in peat-forming environments of southern Brazil, being coeval with a warming period at the end of the Late Paleozoic Ice Age in Western Gondwana.
来自巴西南部的煤被保存在帕拉南盆地的下二叠世冰期后里约热内卢Bonito组中。以往对坎迪奥塔煤田的研究表明，Banco Louco和S9煤层具有明显的惰性矿物聚集。为了了解这些异常惰质岩聚集的原因，本研究分析了来自candota coal Superior （CCS）、Banco Louco （BL）、S9和上覆S8煤层（异常后）顶部的异常富惰质层和下伏碳质粉砂岩的煤样。利用有机岩石学、扫描电镜、孢粉学和生物标志物（PAH）技术对样品进行了分析。结果表明，古沼泽中惰质组以交替小旋回的方式富集，各煤层顶部均有普遍富集的惰质组（云母组、半云母组和惰质组）。大炭在所有煤层中以烧焦的木材、叶片碎片和一个生殖结构的形式存在。富贫质层段的峰值出现在S9煤层，微炭主要分布在细粒沉积物中，呈全黑色，表明该层段受野火事件影响较大。惯性反射率测量表明，地面和地面火灾事件占主导地位，很少发生树冠火灾。有机质的燃烧也以3-5环多环芳烃为主，局部出现6环多环芳烃（包括冠烯）。泥炭地植物区系主要由喜湿石松类和丝松类组成，次要成分以喜湿石松类、中湿石松类和中湿针叶树类为代表。植被组成的频繁振荡可能与气候变化和相关环境条件有关，从亲湿型到中亲湿型再到中亲湿型，表明植被组成适应环境/气候变化，这主要表现在产花粉菌群向BL层顶部的变化及其在异常区间顶部的上覆层中的扩张。在S9煤层中部，全暗的孢岩和植物碎屑，加上6环多环芳烃等高丰度的热生生物标志物，表明在干燥、变暖时期，泥炭地富惰质层的峰值与显著的火灾事件有关，这有助于改变泥炭地的古生态模式。阿塞利亚时代（约298 Ma）坎迪奥塔煤田的古野火是巴西南部泥炭形成环境中最古老的野火记录，与冈瓦纳西部晚古生代冰期结束时的一个变暖期同期。
{"title":"Multiproxy-based evidence of wildfire occurrence in the Lower Permian coal-bearing Rio Bonito Formation, Paraná Basin, Brazil","authors":"M.M. Bicca , W. Kalkreuth , T.F. Silva , M. Guerra-Sommer , I. Degani-Schmidt , C.M. Felix , D.R. Boardman , P.A. Souza","doi":"10.1016/j.coal.2025.104810","DOIUrl":"10.1016/j.coal.2025.104810","url":null,"abstract":"<div><div>Coals from southern Brazil are preserved in the Lower Permian postglacial Rio Bonito Formation of the Paraná Basin. Previous studies on the Candiota Coalfield have shown intervals with significant accumulations of inertinite macerals in the Banco Louco and S9 coal seams. Aiming to understand the causes of these anomalous inertinite accumulations, this study analyzed coal samples from the anomalous inertinite-rich interval and underlying carbonaceous siltites from the top of the Candiota Coal Superior (CCS), Banco Louco (BL), S9, and overlying S8 seams (post-anomalous) obtained from two borehole cores. The samples were analyzed using organic petrology, SEM, palynology, and biomarker (PAH) techniques. The results indicate that inertinite macerals accumulated in the paleoswamp in alternating small cycles, with general inertinite enrichment (fusinite, semifusinite, and inertodetrinite) towards the top of each coal seam analyzed. Macrocharcoal was present in all coal seams as charred wood, leaf fragments, and one reproductive structure. The peak of the inertinite-rich interval occurs at the S9 seam with the dominance of microcharcoal dispersed in fine-grained sediments and completely black palynomorphs, suggesting a significant wildfire event affecting the interval. Inertinite reflectance measurements indicated the predominance of ground and surface fire events with the rare occurrence of crown fires. Combustion of organic matter is also marked by the dominant presence of 3–5 ring PAHs and local occurrence of 6-ring PAHs (including coronene). The peatland flora was mainly composed of hygrophilous lycopsids and filicopsids, with subordinate elements represented by sphenopsids, mesophilous glossopterids, and meso-xerophilous conifers. The frequent oscillations in the vegetation composition were potentially related to climate changes and related environmental conditions, varying from hygrophilous to meso-hygrophilous and mesophilous, indicating that the vegetation composition adapted to environmental/climate changes as recognized by the alteration in the pollen-spore-producing flora towards the top of BL seam and their expansion in the overlying seams at the top of the anomalous interval. In the middle of the S9 seam, the completely dark palynomorphs and phytoclasts, plus a high abundance of pyrogenic biomarkers including 6-ring PAHs, point to significant fire events linked to the peak of the inertinite-rich interval during drier, warming intervals, which contributed to modifying the paleoecological patterns of the peatland. The paleo-wildfires of the Asselian age (ca. 298 Ma) Candiota Coalfield are the oldest record of wildfires in peat-forming environments of southern Brazil, being coeval with a warming period at the end of the Late Paleozoic Ice Age in Western Gondwana.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104810"},"PeriodicalIF":5.6,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144069774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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