Pub Date : 2025-05-07DOI: 10.1016/j.coal.2025.104800
Hao Yuan , Maria Mastalerz , Bei Liu , Simon Brassell
The composition of sedimentary organic matter (OM) is an important parameter that determines the hydrocarbon potential and reveals the depositional conditions of organic-rich shales. Several automated analysis methods have been developed to determine the maceral composition of coals, but few studies have applied these techniques to assess the composition of OM in source rocks. This research developed an image evaluation method that combines maceral identification with machine-learning algorithms to quantify OM compositions. Three Devonian shales, two samples of New Albany Shale and one of Marcellus Shale, ranging from marginally mature to overmature were selected to evaluate the thermal evolution of maceral components, including vitrinite, inertinite, liptinite, and secondary products (i.e., solid bitumen and pyrobitumen). The method provides an efficient approach for identifying pyrobitumen and alginite in samples and is superior to automated coal analysis methods. Comparison of traditional point-counting methods with the new approach validates the effectiveness of image analysis in quantifying vitrinite and inertinite contents. However, the challenge of extracting amorphous OM mixed with mineral matter from the background requires further refinement. This methodological advancement provides a new tool for assessing the composition, sources, and thermal evolution of OM, offering valuable data to complement organic geochemical interpretations of depositional environments.
{"title":"Application of image analysis to quantify maceral composition of source rocks: Examples from the Devonian New Albany Shale and Marcellus Shale","authors":"Hao Yuan , Maria Mastalerz , Bei Liu , Simon Brassell","doi":"10.1016/j.coal.2025.104800","DOIUrl":"10.1016/j.coal.2025.104800","url":null,"abstract":"<div><div>The composition of sedimentary organic matter (OM) is an important parameter that determines the hydrocarbon potential and reveals the depositional conditions of organic-rich shales. Several automated analysis methods have been developed to determine the maceral composition of coals, but few studies have applied these techniques to assess the composition of OM in source rocks. This research developed an image evaluation method that combines maceral identification with machine-learning algorithms to quantify OM compositions. Three Devonian shales, two samples of New Albany Shale and one of Marcellus Shale, ranging from marginally mature to overmature were selected to evaluate the thermal evolution of maceral components, including vitrinite, inertinite, liptinite, and secondary products (i.e., solid bitumen and pyrobitumen). The method provides an efficient approach for identifying pyrobitumen and alginite in samples and is superior to automated coal analysis methods. Comparison of traditional point-counting methods with the new approach validates the effectiveness of image analysis in quantifying vitrinite and inertinite contents. However, the challenge of extracting amorphous OM mixed with mineral matter from the background requires further refinement. This methodological advancement provides a new tool for assessing the composition, sources, and thermal evolution of OM, offering valuable data to complement organic geochemical interpretations of depositional environments.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104800"},"PeriodicalIF":5.6,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143931675","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 : 2025-05-06DOI: 10.1016/j.coal.2025.104793
Xiaowei Zheng , Hamed Sanei , Fujie Jiang , Qingyong Luo , Ye Wang , Jennifer L. Nedzweckas , Brett J. Valentine , M. Rebecca Stokes , Liu Cao , Paul C. Hackley
A series of gold tube pyrolysis experiments (72 h, 300–550 °C, 50 MPa) conducted on a graptolite-rich lower Paleozoic marine shale generated pyrolysis residues for a comprehensive evaluation of the molecular and structural variability of three types of graptolite periderm. Organic petrology, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS) were combined to evaluate the thermal evolution process. The three types of graptolite periderm, namely granular, non-granular, and nodular graptolite, were analyzed by Raman spectroscopy wherein point measurements were obtained after the maceral was identified and the location verified by organic petrology. Distinct thermal evolution pathways among non-granular, granular, and nodular graptolite periderms were recorded. The evolution patterns of the Raman parameters, particularly D1 and G bands, highlight the differences in geochemical composition of the graptolite periderm types and the alteration of molecular structure with increasing thermal maturity. Raman parameters D1 (position of the D1 peak), G-FWHM (full width at half maximum of the G peak), and ratios D1-FWHM/G-FWHM (full width at half maximum of the D1 peak ratioed to G-FWHM) and AD1/AG (ratio of D1 and G peak intensities) showed effectiveness in assessing thermal maturity. Bireflectance with increasing gold tube pyrolysis temperature followed a hierarchy: non-granular > granular > nodular, reflecting different molecular alignment intensities. Qualitative FE-SEM evaluation showed that fine-grained mineral inclusions (primarily Fe-sulfide as determined via EDS) were associated with the graptolite populations, with granular graptolite containing greater amounts of coarser-grained (e.g., ∼300–1400 nm) mineral inclusions relative to non-granular and nodular graptolite, which contain finer-grained (e.g., ∼100–200 nm) inclusions difficult to resolve with optical microscopy. These findings are investigated to highlight the mechanisms that drive organic matter evolution within graptolite during thermal maturation, as well as to explore some of the limitations of using spectroscopic parameters as thermal maturity proxies.
{"title":"Relating systematic molecular and textural properties of graptolite pyrolyzed via gold tube hydrous pyrolysis: Implications for thermal proxies in lower Paleozoic marine shales","authors":"Xiaowei Zheng , Hamed Sanei , Fujie Jiang , Qingyong Luo , Ye Wang , Jennifer L. Nedzweckas , Brett J. Valentine , M. Rebecca Stokes , Liu Cao , Paul C. Hackley","doi":"10.1016/j.coal.2025.104793","DOIUrl":"10.1016/j.coal.2025.104793","url":null,"abstract":"<div><div>A series of gold tube pyrolysis experiments (72 h, 300–550 °C, 50 MPa) conducted on a graptolite-rich lower Paleozoic marine shale generated pyrolysis residues for a comprehensive evaluation of the molecular and structural variability of three types of graptolite periderm. Organic petrology, Raman spectroscopy, and field emission scanning electron microscopy (FE-SEM) with energy dispersive spectroscopy (EDS) were combined to evaluate the thermal evolution process. The three types of graptolite periderm, namely granular, non-granular, and nodular graptolite, were analyzed by Raman spectroscopy wherein point measurements were obtained after the maceral was identified and the location verified by organic petrology. Distinct thermal evolution pathways among non-granular, granular, and nodular graptolite periderms were recorded. The evolution patterns of the Raman parameters, particularly D1 and G bands, highlight the differences in geochemical composition of the graptolite periderm types and the alteration of molecular structure with increasing thermal maturity. Raman parameters D1 (position of the D1 peak), G-FWHM (full width at half maximum of the G peak), and ratios D1-FWHM/G-FWHM (full width at half maximum of the D1 peak ratioed to G-FWHM) and A<sub>D1</sub>/A<sub>G</sub> (ratio of D1 and G peak intensities) showed effectiveness in assessing thermal maturity. Bireflectance with increasing gold tube pyrolysis temperature followed a hierarchy: non-granular > granular > nodular, reflecting different molecular alignment intensities. Qualitative FE-SEM evaluation showed that fine-grained mineral inclusions (primarily Fe-sulfide as determined via EDS) were associated with the graptolite populations, with granular graptolite containing greater amounts of coarser-grained (e.g., ∼300–1400 nm) mineral inclusions relative to non-granular and nodular graptolite, which contain finer-grained (e.g., ∼100–200 nm) inclusions difficult to resolve with optical microscopy. These findings are investigated to highlight the mechanisms that drive organic matter evolution within graptolite during thermal maturation, as well as to explore some of the limitations of using spectroscopic parameters as thermal maturity proxies.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104793"},"PeriodicalIF":5.6,"publicationDate":"2025-05-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143935656","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 : 2025-05-01DOI: 10.1016/j.coal.2025.104792
J. Kus, L. Richter, G. Scheeder, C. Ostertag-Henning, M. Blumenberg, M. Mertineit
Hydrocarbon-bearing fluid inclusions (HCFI) in halite from the Gorleben and Morsleben sites (Germany), petroleum from Gorleben, and epoxy resins have been analysed in-situ using a combined approach of confocal laser-scanning microscopy (CLSM), incident light, and transmitted light fluorescence microscopy. The HCFI contain vapour and liquid hydrocarbon phases and their optical appearance varies widely and distinctively. 405 nm based excitation allowed for in-situ CLSM-associated acquisitions and distinction of HCFI emission spectra for both sites. In contrast to transmitted light microscopy equipped with barrier filter >515 nm, the CLSM-related emission >410 nm employed full emission spectra essential for observation of the entire emission spectrum of HCFI. While maximum emission intensity (λmax) of HCFI at the Gorleben site peaks at 455–456 nm, the corresponding λmax at the Morsleben site ranges from 485 to 495 nm, indicating that emission spectra of HCFI at Gorleben site are “blue-shifted” in comparison to those at Morsleben. It is implied that the blue-shift is caused by a shift to a less aromatic/polar composition of the HCFI at Gorleben site. Both, HCFI and petroleum differ noticeably in spectral properties from epoxy resins indicating no contamination of epoxy resin in the examined thick sections. Coarse approximations of °API (a standard for petroleum liquid density), based on red/green coefficient (Qmax) and empirical correlation equation as well as direct measurements of °API, suggested markedly different °API gravities for Gorleben and Morsleben sites with higher °API values, of up to 52.4 for the first. Collectively, the results of this research study demonstrated the applicability and adaptability of CLSM as a well-advanced method to acquire in-situ spectral properties of HCFI in salt rock, as a basis for understanding hydrocarbon generation and migration in sedimentary environments.
{"title":"Characterizing hydrocarbon-bearing fluid inclusions using CLSM-based microspectrometry with application to the Upper Permian rock salt in the Gorleben and Morsleben sites, Germany","authors":"J. Kus, L. Richter, G. Scheeder, C. Ostertag-Henning, M. Blumenberg, M. Mertineit","doi":"10.1016/j.coal.2025.104792","DOIUrl":"10.1016/j.coal.2025.104792","url":null,"abstract":"<div><div>Hydrocarbon-bearing fluid inclusions (HCFI) in halite from the Gorleben and Morsleben sites (Germany), petroleum from Gorleben, and epoxy resins have been analysed in-situ using a combined approach of confocal laser-scanning microscopy (CLSM), incident light, and transmitted light fluorescence microscopy. The HCFI contain vapour and liquid hydrocarbon phases and their optical appearance varies widely and distinctively. 405 nm based excitation allowed for in-situ CLSM-associated acquisitions and distinction of HCFI emission spectra for both sites. In contrast to transmitted light microscopy equipped with barrier filter >515 nm, the CLSM-related emission >410 nm employed full emission spectra essential for observation of the entire emission spectrum of HCFI. While maximum emission intensity (λ<sub>max</sub>) of HCFI at the Gorleben site peaks at 455–456 nm, the corresponding λ<sub>max</sub> at the Morsleben site ranges from 485 to 495 nm, indicating that emission spectra of HCFI at Gorleben site are “blue-shifted” in comparison to those at Morsleben. It is implied that the blue-shift is caused by a shift to a less aromatic/polar composition of the HCFI at Gorleben site. Both, HCFI and petroleum differ noticeably in spectral properties from epoxy resins indicating no contamination of epoxy resin in the examined thick sections. Coarse approximations of °API (a standard for petroleum liquid density), based on red/green coefficient (Q<sub>max</sub>) and empirical correlation equation as well as direct measurements of °API, suggested markedly different °API gravities for Gorleben and Morsleben sites with higher °API values, of up to 52.4 for the first. Collectively, the results of this research study demonstrated the applicability and adaptability of CLSM as a well-advanced method to acquire in-situ spectral properties of HCFI in salt rock, as a basis for understanding hydrocarbon generation and migration in sedimentary environments.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104792"},"PeriodicalIF":5.6,"publicationDate":"2025-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143912502","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 : 2025-04-30DOI: 10.1016/j.coal.2025.104791
M. Wojtaszek-Kalaitzidi , M. Rejdak , M. Książek , S.Y. Larsen , S. Rørvik , R. Muzyka , S. Drewniak
This study presents a pioneering investigation into the behaviour of biocoke, particularly its biogenic component (biochar), during ferromanganese production. Employing μCT scanning, micro-Raman spectrometry, and organic petrology, the research explores the transformation of organic matter throughout different zones of a pilot ferroalloy furnace. The results reveal that the degradation of biocoke and its biocomponent varies significantly depending on the relevant position within the furnace and the temperature conditions. Notably, the biocoke with a 20 % charcoal addition maintained structural integrity and functioned effectively as a reducing agent, contrary to concerns about premature gasification due to the high reactivity of biochar. Microscopic analysis confirmed the presence of partially preserved biochar even at the furnace's lowest levels, indicating active participation in the reduction process. Furthermore, the study provides compelling evidence of partial graphitisation within both the coke matrix and the biogenic component, most likely facilitated by catalytic effects from molten and/or vaporised metals such as iron and manganese at temperatures exceeding 1500 °C. The occurrence of semi-graphitic structures was confirmed by Raman spectroscopy. The work also advocates for a distinct classification of organic inerts of biomass origin, acknowledging their unique gasification and thermal behaviours. This classification should be refined through broader studies involving diverse biochar sources and interlaboratory comparisons. The findings validate the viability of biocoke as a sustainable and economically feasible reductant in ferroalloy production, as demonstrated through the Biocoke4FAI research project.
{"title":"Assessment of biocoke behaviour in a ferromanganese smelting pilot furnace: A petrographic approach","authors":"M. Wojtaszek-Kalaitzidi , M. Rejdak , M. Książek , S.Y. Larsen , S. Rørvik , R. Muzyka , S. Drewniak","doi":"10.1016/j.coal.2025.104791","DOIUrl":"10.1016/j.coal.2025.104791","url":null,"abstract":"<div><div>This study presents a pioneering investigation into the behaviour of biocoke, particularly its biogenic component (biochar), during ferromanganese production. Employing μCT scanning, micro-Raman spectrometry, and organic petrology, the research explores the transformation of organic matter throughout different zones of a pilot ferroalloy furnace. The results reveal that the degradation of biocoke and its biocomponent varies significantly depending on the relevant position within the furnace and the temperature conditions. Notably, the biocoke with a 20 % charcoal addition maintained structural integrity and functioned effectively as a reducing agent, contrary to concerns about premature gasification due to the high reactivity of biochar. Microscopic analysis confirmed the presence of partially preserved biochar even at the furnace's lowest levels, indicating active participation in the reduction process. Furthermore, the study provides compelling evidence of partial graphitisation within both the coke matrix and the biogenic component, most likely facilitated by catalytic effects from molten and/or vaporised metals such as iron and manganese at temperatures exceeding 1500 °C. The occurrence of semi-graphitic structures was confirmed by Raman spectroscopy. The work also advocates for a distinct classification of organic inerts of biomass origin, acknowledging their unique gasification and thermal behaviours. This classification should be refined through broader studies involving diverse biochar sources and interlaboratory comparisons. The findings validate the viability of biocoke as a sustainable and economically feasible reductant in ferroalloy production, as demonstrated through the Biocoke4FAI research project.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104791"},"PeriodicalIF":5.6,"publicationDate":"2025-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143923677","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 : 2025-04-28DOI: 10.1016/j.coal.2025.104790
Eugene Donskoi , Andrei Poliakov , Lauren Williamson , Oliver Scholes
Cokes prepared from Northern Hemisphere (NH) and Australian coals (AU) were characterised by structural/textural parameters obtained using automated optical image analysis. Comparison of matched cokes from NH and AU with similar parent coal rank and amount of vitrinite revealed significant differences between their structural parameters.
The study showed that, NH cokes had coarser structure, including larger porosity pockets, coagulated nodes and connecting walls. However, AU cokes had more connections/walls per unit area which in total were thicker. Inert Maceral Derived Components (IMDC) in NH cokes were smaller, more rounded and less elongated. The IMDC boundary smoothness was higher in NH cokes. There are fewer voids within Reacted Maceral Derived Components on the IMDC boundary in NH cokes, and the average size of these voids is significantly larger. Porosity in AU cokes was more tortuous and there was less fine optically recordable porosity in NH cokes.
For all 26 structural parameters where the difference between NH and AU cokes was significant and where the correlation of each parameter with RMax obtained from a large set of Australian cokes was also significant, the difference was such that the structure of Australian cokes was corresponding to higher RMax than matched NH cokes.
{"title":"Systematic differences in the microstructure of cokes made from medium/high-reflectance Northern hemisphere and Australian coals","authors":"Eugene Donskoi , Andrei Poliakov , Lauren Williamson , Oliver Scholes","doi":"10.1016/j.coal.2025.104790","DOIUrl":"10.1016/j.coal.2025.104790","url":null,"abstract":"<div><div>Cokes prepared from Northern Hemisphere (NH) and Australian coals (AU) were characterised by structural/textural parameters obtained using automated optical image analysis. Comparison of matched cokes from NH and AU with similar parent coal rank and amount of vitrinite revealed significant differences between their structural parameters.</div><div>The study showed that, NH cokes had coarser structure, including larger porosity pockets, coagulated nodes and connecting walls. However, AU cokes had more connections/walls per unit area which in total were thicker. Inert Maceral Derived Components (IMDC) in NH cokes were smaller, more rounded and less elongated. The IMDC boundary smoothness was higher in NH cokes. There are fewer voids within Reacted Maceral Derived Components on the IMDC boundary in NH cokes, and the average size of these voids is significantly larger. Porosity in AU cokes was more tortuous and there was less fine optically recordable porosity in NH cokes.</div><div>For all 26 structural parameters where the difference between NH and AU cokes was significant and where the correlation of each parameter with RMax obtained from a large set of Australian cokes was also significant, the difference was such that the structure of Australian cokes was corresponding to higher RMax than matched NH cokes.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"305 ","pages":"Article 104790"},"PeriodicalIF":5.6,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143902060","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}
Whether the coals in Western Siberia generated commercial volumes of liquid hydrocarbons is an important issue that remains controversial because it has not yet been definitively resolved. Organic petrography and geochemical investigations including Rock-Eval pyrolysis, elemental, isotope, and biomarker analyses were carried out to characterize in detail the hydrocarbon generation potential, type of organic matter, and depositional environment of the Cretaceous and Jurassic coals from the Gyda Peninsula in Western Siberia. The results indicate that the Jurassic coals primarily contain mixed gas-oil-prone Type II-III kerogen. In contrast, the Cretaceous coals exhibit a diverse generation potential with varied proportions of gas- and oil-prone kerogen types. Vitrinite reflectance of the studied coals suggests an immature to early mature stage for the Cretaceous coals and the thermally mature stage for the Jurassic coals, which is supported by maturity-related biomarker parameters and Tmax values. The carbon and nitrogen isotopic signatures in combination with biomarker data and maceral composition predominantly indicate terrestrial input. The presence of retene and simonellite suggests the contribution of conifers. Based on the obtained results, the Jurassic coals were likely to be deposited in limno-telmatic conditions with a rise in the water-level due to the sea expansion. The Cretaceous coals are probably deposited in bogs developed on the lower delta plain in limno-telmatic to telmatic environments with sudden episodes of flooding. Considering the type and thermal maturity of organic matter, the Jurassic coals show strong potential for hydrocarbon generation.
{"title":"Source rock potential and depositional environments of the Jurassic and Cretaceous coals from the Gyda Peninsula, Western Siberia","authors":"Timur Bulatov , Elena Kozlova , Evgenia Leushina , Anastasia Vaitekhovich , Natalia Pronina , Arina Goncharova , Mikhail Kul'kov , Gulmira Salakhidinova , Roman Butyrin , Alina Bazhanova , Ludmila Torshina , Mikhail Spasennykh","doi":"10.1016/j.coal.2025.104789","DOIUrl":"10.1016/j.coal.2025.104789","url":null,"abstract":"<div><div>Whether the coals in Western Siberia generated commercial volumes of liquid hydrocarbons is an important issue that remains controversial because it has not yet been definitively resolved. Organic petrography and geochemical investigations including Rock-Eval pyrolysis, elemental, isotope, and biomarker analyses were carried out to characterize in detail the hydrocarbon generation potential, type of organic matter, and depositional environment of the Cretaceous and Jurassic coals from the Gyda Peninsula in Western Siberia. The results indicate that the Jurassic coals primarily contain mixed gas-oil-prone Type II-III kerogen. In contrast, the Cretaceous coals exhibit a diverse generation potential with varied proportions of gas- and oil-prone kerogen types. Vitrinite reflectance of the studied coals suggests an immature to early mature stage for the Cretaceous coals and the thermally mature stage for the Jurassic coals, which is supported by maturity-related biomarker parameters and T<sub>max</sub> values. The carbon and nitrogen isotopic signatures in combination with biomarker data and maceral composition predominantly indicate terrestrial input. The presence of retene and simonellite suggests the contribution of conifers. Based on the obtained results, the Jurassic coals were likely to be deposited in limno-telmatic conditions with a rise in the water-level due to the sea expansion. The Cretaceous coals are probably deposited in bogs developed on the lower delta plain in limno-telmatic to telmatic environments with sudden episodes of flooding. Considering the type and thermal maturity of organic matter, the Jurassic coals show strong potential for hydrocarbon generation.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"305 ","pages":"Article 104789"},"PeriodicalIF":5.6,"publicationDate":"2025-04-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143899336","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 : 2025-04-27DOI: 10.1016/j.coal.2025.104788
David A. Wood
Characterizing pore-size distributions (PSD) of coals is required to identify optimum zone for gas recovery and suitable sites to store carbon dioxide (CO2) or hydrogen. Micropore and mesopore PSD characteristics vary with differences in thermal maturity, maceral fractions, and as this study novelly identifies, bulk-rock reaction kinetic distributions. Five coal samples from the Damodar Coal Province (India) associated with a wide range of thermal maturity and petrology are evaluated using optical microscopy, N2 and CO2 low pressure gas adsorption analysis, and single-heating rate and multi-heating rate Rock-Eval pyrolysis. The results reveal distinctive relationships between pore volumes, specific surface area (SSA), fractal dimensions, reaction kinetic distributions, and S2 pyrogram features that differ for the micropore and mesopore PSDs. The most thermally mature coals exhibit the highest micropore volumes, SSA and fractal dimensions but the PSD characteristics are also influenced by maceral fractions, particularly liptinite/vitrinite ratio. Difference in PSD characteristics are observed between the micropores and mesopores. The complexity of the kinetic distributions increases with thermal maturity. Clear relationships exist between the weighted average standard deviation of activation energies and micropore fractal dimensions and SSA. Similar but less well-defined relationships exist between single-heating rate transformation fraction temperature ranges and micropore fractal dimensions and SSA. The significance of these results is that it opens the possibility to use Rock-Eval analysis to estimate coal PSD characteristics. Once calibrated with low-pressure gas adsorption (LPGA) analysis, Rock-Eval pyrograms could be generated more rapidly and at lower costs on multiple samples to better delineate the best coal zones for gas recovery and gas storage. No published studies have previously identified or addressed relationships between reaction kinetics distributions and PSD.
{"title":"Complex interactions between coal maceral fractions, thermal maturity, reaction kinetics, fractal dimensions and pore-size distributions: Implications for gas storage","authors":"David A. Wood","doi":"10.1016/j.coal.2025.104788","DOIUrl":"10.1016/j.coal.2025.104788","url":null,"abstract":"<div><div>Characterizing pore-size distributions (PSD) of coals is required to identify optimum zone for gas recovery and suitable sites to store carbon dioxide (CO<sub>2</sub>) or hydrogen. Micropore and mesopore PSD characteristics vary with differences in thermal maturity, maceral fractions, and as this study novelly identifies, bulk-rock reaction kinetic distributions. Five coal samples from the Damodar Coal Province (India) associated with a wide range of thermal maturity and petrology are evaluated using optical microscopy, N<sub>2</sub> and CO<sub>2</sub> low pressure gas adsorption analysis, and single-heating rate and multi-heating rate Rock-Eval pyrolysis. The results reveal distinctive relationships between pore volumes, specific surface area (SSA), fractal dimensions, reaction kinetic distributions, and S2 pyrogram features that differ for the micropore and mesopore PSDs. The most thermally mature coals exhibit the highest micropore volumes, SSA and fractal dimensions but the PSD characteristics are also influenced by maceral fractions, particularly liptinite/vitrinite ratio. Difference in PSD characteristics are observed between the micropores and mesopores. The complexity of the kinetic distributions increases with thermal maturity. Clear relationships exist between the weighted average standard deviation of activation energies and micropore fractal dimensions and SSA. Similar but less well-defined relationships exist between single-heating rate transformation fraction temperature ranges and micropore fractal dimensions and SSA. The significance of these results is that it opens the possibility to use Rock-Eval analysis to estimate coal PSD characteristics. Once calibrated with low-pressure gas adsorption (LPGA) analysis, Rock-Eval pyrograms could be generated more rapidly and at lower costs on multiple samples to better delineate the best coal zones for gas recovery and gas storage. No published studies have previously identified or addressed relationships between reaction kinetics distributions and PSD.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"305 ","pages":"Article 104788"},"PeriodicalIF":5.6,"publicationDate":"2025-04-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143888090","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 : 2025-04-21DOI: 10.1016/j.coal.2025.104777
Ifeanyi Valerian Nwankwo , Morteza Dejam , Scott Austin Quillinan
Flow in shale differs substantially from that in conventional reservoirs due to unfavorable reservoir features such as ultra-low permeability and very poor porosity. Shale also exhibits considerable anisotropy and heterogeneity, with clay laminae and bedding angle being the primary variables influencing anisotropy. As a result, shale is subjected to high stress sensitivity and deformation during depressurization, which affects fluid flow. Furthermore, non-Darcy flow mechanisms exist thereby making flow in shale a complex phenomenon. Nonetheless, many studies have recently focused on the geophysical and geomechanical characterization of shale. Various works have equally examined the complexity of fluid flow. Numerous studies were particularly interested in the influence of non-linear flow parameters and stress sensitivity on apparent permeability, intrinsic permeability, and porosity during pressure depletion. However, relatively few works, mostly theoretical, have been carried out on coupled flow and geomechanical reactions. This review thus includes a report on fluid flow and geomechanical characterization of shale formation, as well as an identification of the factors that influence rock deformation and fluid flow during production. The review showed that flow regimes are predominantly dependent on pore pressure and pore size, whereas flow regimes regulate apparent permeability. For example, at low pressures and pore radius less than 10 nm, flow regims were found to significantly increase the apparent permeability. However, at higher bulk modulus (>10 GPa), pore radius has essentially no impact, hence, pore pressure becomes the dominant factor influencing flow. In addition, the review shows that during depressurization, geophysical metrics are more sensitive to pressure changes than geomechanical properties. Finally, some results in literature revealed that the impact of geomechanical characteristics on cumulative production can be ignored in competent formations with high Young's modulus (about 6 × 106-10 × 106 psi). In conclusion, recovery from shale could be optimized by integrating experimental studies with hydromechanical models during initial reservoir studies.
{"title":"A critical review of experimental and theoretical studies on shale geomechanical and deformation properties, fluid flow behavior, and coupled flow and geomechanics effects during production","authors":"Ifeanyi Valerian Nwankwo , Morteza Dejam , Scott Austin Quillinan","doi":"10.1016/j.coal.2025.104777","DOIUrl":"10.1016/j.coal.2025.104777","url":null,"abstract":"<div><div>Flow in shale differs substantially from that in conventional reservoirs due to unfavorable reservoir features such as ultra-low permeability and very poor porosity. Shale also exhibits considerable anisotropy and heterogeneity, with clay laminae and bedding angle being the primary variables influencing anisotropy. As a result, shale is subjected to high stress sensitivity and deformation during depressurization, which affects fluid flow. Furthermore, non-Darcy flow mechanisms exist thereby making flow in shale a complex phenomenon. Nonetheless, many studies have recently focused on the geophysical and geomechanical characterization of shale. Various works have equally examined the complexity of fluid flow. Numerous studies were particularly interested in the influence of non-linear flow parameters and stress sensitivity on apparent permeability, intrinsic permeability, and porosity during pressure depletion. However, relatively few works, mostly theoretical, have been carried out on coupled flow and geomechanical reactions. This review thus includes a report on fluid flow and geomechanical characterization of shale formation, as well as an identification of the factors that influence rock deformation and fluid flow during production. The review showed that flow regimes are predominantly dependent on pore pressure and pore size, whereas flow regimes regulate apparent permeability. For example, at low pressures and pore radius less than 10 nm, flow regims were found to significantly increase the apparent permeability. However, at higher bulk modulus (>10 GPa), pore radius has essentially no impact, hence, pore pressure becomes the dominant factor influencing flow. In addition, the review shows that during depressurization, geophysical metrics are more sensitive to pressure changes than geomechanical properties. Finally, some results in literature revealed that the impact of geomechanical characteristics on cumulative production can be ignored in competent formations with high Young's modulus (about 6 × 10<sup>6</sup>-10 × 10<sup>6</sup> psi). In conclusion, recovery from shale could be optimized by integrating experimental studies with hydromechanical models during initial reservoir studies.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"306 ","pages":"Article 104777"},"PeriodicalIF":5.6,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143917670","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 : 2025-04-21DOI: 10.1016/j.coal.2025.104776
P.C.S. Carvalho , P.A. Gonçalves , J.G. Mendonça Filho , F. Rocha , J. Silva , D. Flores
A sequence of Upper Ordovician black shales from the Casal de Alge area, Figueiró dos Vinhos, in the Central Iberian Zone, with unusually high organic matter content, is studied for the first time. These black shales rich in organic matter (31.21–41.29 %), also contain quartz (30–61 %) and illite (26–62 %), revealing the contribution of siliciclastic and detrital elements to their composition. The organic matter is composed of well-preserved graptolites and pyrobitumen. The abundance of graptolites supports a marine origin for the black shales, a conclusion further corroborated by the low δ13Corg values (−27.98 and − 27.66 ‰). High graptolite abundance indicates a warm climate and high primary productivity, likely enhanced by nutrient input from continental weathering, as evidenced by the presence of detrital elements in the black shale composition. The unusually high organic matter content in these Upper Ordovician black shales is likely attributable to the graptolite end-Ordovician mass extinction during the Hirnantian glaciation. Additionally, the high clay content in these shales may have further contributed to organic matter preservation, due to clay minerals' strong capacity to absorb.
The equivalent vitrinite reflectance (VReqo) ranges from 4.38 to 5.18 %, indicating that black shales reached the meta-anthracite stage. This high thermal maturation appears to be primarily associated with regional burial; however, circulation of hydrothermal fluids may also have contributed, potentially related to the Figueiró dos Vinhos and Bouçã granitic plutons. Moreover, these fluids likely played a role in the enrichment of K₂O of the black shales and induced the conversion of kaolinite, originally formed under warm and humid climatic conditions, into illite.
首次研究了伊比利亚中部Casal de Alge地区Figueiró dos Vinhos上奥陶统黑色页岩层序，发现其有机质含量异常高。黑色页岩有机质含量丰富（31.21 ~ 41.29%），同时含有石英（30 ~ 61%）和伊利石（26 ~ 62%），显示了硅屑和碎屑元素对其组成的贡献。有机质由保存完好的笔石和焦沥青组成。笔石丰度支持黑色页岩的海相成因，低δ13Corg值（- 27.98‰和- 27.66‰）进一步证实了这一结论。高笔石丰度表明温暖的气候和高初级生产力，可能是由大陆风化的营养输入增强的，黑色页岩组成中存在碎屑元素。上奥陶统黑色页岩有机质含量异常高，可能与希尔南天冰期末奥陶统笔石大灭绝有关。此外，由于粘土矿物的强吸收能力，这些页岩中的高粘土含量可能进一步有助于有机质的保存。等效镜质组反射率（VReqo）在4.38 ~ 5.18%之间，表明黑色页岩进入了变质无烟煤阶段。这种高热成熟似乎主要与区域埋藏有关；然而，热液流体的循环也可能起作用，可能与Figueiró dos Vinhos和Bouçã花岗岩岩体有关。此外，这些流体可能对黑色页岩的K₂O富集起了作用，并促使原本在温暖潮湿气候条件下形成的高岭石转化为伊利石。
{"title":"Unveiling the organic-rich Upper Ordovician black shales of the Foz de Alge region (Central Iberian Zone, Portugal): Insights from geochemistry and organic petrography","authors":"P.C.S. Carvalho , P.A. Gonçalves , J.G. Mendonça Filho , F. Rocha , J. Silva , D. Flores","doi":"10.1016/j.coal.2025.104776","DOIUrl":"10.1016/j.coal.2025.104776","url":null,"abstract":"<div><div>A sequence of Upper Ordovician black shales from the Casal de Alge area, Figueiró dos Vinhos, in the Central Iberian Zone, with unusually high organic matter content, is studied for the first time. These black shales rich in organic matter (31.21–41.29 %), also contain quartz (30–61 %) and illite (26–62 %), revealing the contribution of siliciclastic and detrital elements to their composition. The organic matter is composed of well-preserved graptolites and pyrobitumen. The abundance of graptolites supports a marine origin for the black shales, a conclusion further corroborated by the low δ<sup>13</sup>C<sub>org</sub> values (−27.98 and − 27.66 ‰). High graptolite abundance indicates a warm climate and high primary productivity, likely enhanced by nutrient input from continental weathering, as evidenced by the presence of detrital elements in the black shale composition. The unusually high organic matter content in these Upper Ordovician black shales is likely attributable to the graptolite end-Ordovician mass extinction during the Hirnantian glaciation. Additionally, the high clay content in these shales may have further contributed to organic matter preservation, due to clay minerals' strong capacity to absorb.</div><div>The equivalent vitrinite reflectance (VR<sub>eqo</sub>) ranges from 4.38 to 5.18 %, indicating that black shales reached the meta-anthracite stage. This high thermal maturation appears to be primarily associated with regional burial; however, circulation of hydrothermal fluids may also have contributed, potentially related to the Figueiró dos Vinhos and Bouçã granitic plutons. Moreover, these fluids likely played a role in the enrichment of K₂O of the black shales and induced the conversion of kaolinite, originally formed under warm and humid climatic conditions, into illite.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"305 ","pages":"Article 104776"},"PeriodicalIF":5.6,"publicationDate":"2025-04-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143873982","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 : 2025-04-18DOI: 10.1016/j.coal.2025.104785
Bo Jiu , Zhijun Jin , Huidi Hao , Zhaoguo Wang , Wenhui Huang , Zhenguang Shang , Runchao Liu , Yang Li , Linhao Huang , Binchao Qin , Zixuan Huang , Li Long , Wenzhong Zhang , Yian Wang
Modes of occurrence of rare earth elements (REE; if including Y, REY) in coal have attracted much attention owing to the extraction potential of REY from coal fly ash. Although previous studies have explored the associations of REY in coals with different ranks and the affinities of light, medium, and heavy REY associated with organic matter, challenges remain due to the limitations of indirect or in-situ analytical techniques. This study focused on the in-situ distribution of REY in the selected subbituminous coals from the Jungar Coalfield as well as in their associated mudstone and tonstein partings and the widely distributed calcite veins inside the coal seam, using LA-ICP-MS spot and mapping analysis. The results showed that in the subbituminous coal, La and Ce as well as other light REY (LREY) are concentrated in the minerals such as bastnasite and monazite. Small amounts of Pr, Nd, and Sm can be associated with organic matter including vitrinite and liptinite. Medium REY (MREY) and heavy REY (HREY) are highly enriched in vitrinite in the subbituminous coal. In terrigenous mudstone of the subbituminous coal, La and Ce are concentrated in monazite. Other LREY are present in Ti-oxides, while HREY tend to occur in zircon. MREY can be associated with both Ti-oxides and zircon. The calcite veins in the coal seam are classified into three types based on their morphology and occurrence features: bedding calcite veins in the upper part of the coal, vertical calcite veins in the middle, and vertical calcite veins with a high Sr value in the lower part of the coal. Polarization and crystal size of calcite crystals in these veins exhibit multistage growth. LA-ICP-MS spot analysis shows that the bedding and vertical calcite veins are characterized by positive Y and Gd anomalies, suggesting their formation under meteoric water leaching. The vertical calcite vein in the lower part of the coal seam displays a positive Gd anomaly and high Sr concentrations, indicating formation under seawater injection. The concentration of REY in all epigenetic calcite veins increases with depth. For calcite veins with multi-stage growth, the REY content in the late-stage calcite is consistently higher than in the early stages. It is proposed that leaching of meteoric water and seawater on the coal seams is the key factor for the association of REY with organic matter, influenced by the chemical composition and pH value of the leaching fluids. In particular, MREY and HREY are preferentially associated with organic matter, mainly vitrinite, and the over-leached MREY and HREY in coal were concentrated in epigenetic minerals, with calcite being the primary phase in this study.
{"title":"Modes of occurrence of rare earth elements and yttrium in the subbituminous coal of the Jungar Coalfield, Ordos Basin, North China","authors":"Bo Jiu , Zhijun Jin , Huidi Hao , Zhaoguo Wang , Wenhui Huang , Zhenguang Shang , Runchao Liu , Yang Li , Linhao Huang , Binchao Qin , Zixuan Huang , Li Long , Wenzhong Zhang , Yian Wang","doi":"10.1016/j.coal.2025.104785","DOIUrl":"10.1016/j.coal.2025.104785","url":null,"abstract":"<div><div>Modes of occurrence of rare earth elements (REE; if including Y, REY) in coal have attracted much attention owing to the extraction potential of REY from coal fly ash. Although previous studies have explored the associations of REY in coals with different ranks and the affinities of light, medium, and heavy REY associated with organic matter, challenges remain due to the limitations of indirect or in-situ analytical techniques. This study focused on the in-situ distribution of REY in the selected subbituminous coals from the Jungar Coalfield as well as in their associated mudstone and tonstein partings and the widely distributed calcite veins inside the coal seam, using LA-ICP-MS spot and mapping analysis. The results showed that in the subbituminous coal, La and Ce as well as other light REY (LREY) are concentrated in the minerals such as bastnasite and monazite. Small amounts of Pr, Nd, and Sm can be associated with organic matter including vitrinite and liptinite. Medium REY (MREY) and heavy REY (HREY) are highly enriched in vitrinite in the subbituminous coal. In terrigenous mudstone of the subbituminous coal, La and Ce are concentrated in monazite. Other LREY are present in Ti-oxides, while HREY tend to occur in zircon. MREY can be associated with both Ti-oxides and zircon. The calcite veins in the coal seam are classified into three types based on their morphology and occurrence features: bedding calcite veins in the upper part of the coal, vertical calcite veins in the middle, and vertical calcite veins with a high Sr value in the lower part of the coal. Polarization and crystal size of calcite crystals in these veins exhibit multistage growth. LA-ICP-MS spot analysis shows that the bedding and vertical calcite veins are characterized by positive Y and Gd anomalies, suggesting their formation under meteoric water leaching. The vertical calcite vein in the lower part of the coal seam displays a positive Gd anomaly and high Sr concentrations, indicating formation under seawater injection. The concentration of REY in all epigenetic calcite veins increases with depth. For calcite veins with multi-stage growth, the REY content in the late-stage calcite is consistently higher than in the early stages. It is proposed that leaching of meteoric water and seawater on the coal seams is the key factor for the association of REY with organic matter, influenced by the chemical composition and pH value of the leaching fluids. In particular, MREY and HREY are preferentially associated with organic matter, mainly vitrinite, and the over-leached MREY and HREY in coal were concentrated in epigenetic minerals, with calcite being the primary phase in this study.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"305 ","pages":"Article 104785"},"PeriodicalIF":5.6,"publicationDate":"2025-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143855308","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号