International Journal of Coal Geology最新文献_第5页

Geochemical and petrological characteristics coupled with stable isotope of the Permian Gondwana coals from Tatapani–Ramkola Coalfield, Son–Mahanadi Basin, India: Insights for paleodepositional and paleoclimate conditions 印度Son-Mahanadi盆地Tatapani-Ramkola煤田二叠系Gondwana煤的地球化学和岩石学特征及稳定同位素特征：古沉积和古气候条件的启示

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-09-16 DOI: 10.1016/j.coal.2025.104882

Neeraj Kumar Upadhayay , Amiya Shankar Naik , Shweta Rai , Prakash K. Singh , Alok Kumar , Afikah Rahim , Mohammed Hail Hakimi , Govind Kumar , Pramod Kumar Rajak

This study aimed to investigate the quality and rank of the Tatapani-Ramkola coal and decipher the paleoclimate and depositional conditions during coal formation, explicitly focusing on vegetation sources, detrital contributions, and paleomire conditions. The studied coals exhibit a moisture between 4.0 % and 12.8 % and a volatile matter yield in the range of 28.8–49.5 wt% (dry ash–free basis), classifying them as subbituminous–A to bituminous in rank. This finding is supported by the vitrinite reflectance (VRo) values between 0.5 and 0.7 %. Maceral compositions reveal the dominance of vitrinite (average 47.8–62.4 %) followed by inertinite (average 13.0–29.9 %) and liptinite (average 8.5–13.1 %). This finding of the maceral characteristics together with the mineral composition (primarily clay, carbonate, and sulfide), show that the Tatapani–Ramkola coals were formed under mildly oxic–to–anoxic conditions in limno–telmatic to telmatic paleomires and contributions from forest and herbaceous vegetation. Geochemical isotope indicators, such as δ¹³C (−24.149 ± 0.825 ‰) and δ¹⁵N (+2.710 ± 0.344 ‰), suggest that the coals formed from C3 land plants under warm and humid climate conditions. Major oxide ratios indicate a moderate to high degree of chemical weathering in the source area, further confirming the prevailing warm and humid climate during the peat accumulation. The detrital/authigenic index (DAI) suggests significant detrital influence and authigenic sediment formation in the Tatapani–Ramkola coals. This study provides critical insights into the depositional history and paleoclimate of the Tatapani–Ramkola Basin, contributing to a deeper understanding of Permian coal formation processes.

本研究旨在研究Tatapani-Ramkola煤的质量和等级，揭示成煤时期的古气候和沉积条件，明确关注植被来源、碎屑贡献和古沉积条件。所研究的煤的水分在4.0% ~ 12.8%之间，挥发物产率在28.8 ~ 49.5 wt%（干无灰基）之间，按等级将其分类为亚沥青- a至沥青。镜质组反射率（VRo）值在0.5 ~ 0.7%之间，支持了这一发现。显微成分以镜质组为主（平均47.8 ~ 62.4%），其次为惰质组（平均13.0 ~ 29.9%）和脂质组（平均8.5 ~ 13.1%）。显微特征和矿物组成（主要是粘土、碳酸盐和硫化物）表明，塔塔帕尼-拉姆科拉煤是在轻度氧-缺氧条件下形成的，并有森林和草本植被的贡献。δ13C（−24.149±0.825‰）和δ15N（+2.710±0.344‰）等地球化学同位素指标表明，煤形成于温暖湿润气候条件下的C3陆生植物。主要氧化比表明源区化学风化程度中等至高度，进一步证实了泥炭堆积时期普遍存在的温暖湿润气候。碎屑/自生指数（DAI）表明Tatapani-Ramkola煤中存在明显的碎屑影响和自生沉积形成。该研究为塔塔帕尼-拉姆科拉盆地的沉积历史和古气候提供了重要的见解，有助于更深入地了解二叠纪煤的形成过程。

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引用次数: 0

CO2 sorption induced mechanical response of Beetaloo shale 二氧化碳吸附诱导的Beetaloo页岩力学响应

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-09-16 DOI: 10.1016/j.coal.2025.104881

Umar Farooq , Klaus Regenauer-Lieb , Abolfazl Hashemi , Linan Su , Hamid Roshan

Understanding the mechanical response of organic-rich shales to CO₂ adsorption is critical for optimising CO₂ sequestration and enhanced gas recovery operations. However, these responses are often highly complex and demand a thorough understanding of the underlying sorptive poromechanical mechanisms involved. This study examines the sorptive poromechanical response of Beetaloo shale to CO₂ adsorption under varying confining stress and pore pressure conditions, with a focus on quantifying strength reduction mechanisms. Through controlled triaxial compression experiments, the effects of CO₂ exposure on shale strength with varying pore pressures under different confining stresses were analysed. A theoretical model was then developed and experimentally validated to predict the peak strength of shale with CO₂ adsorption integrating triaxial response with Langmuir adsorption mechanics. The experimental results showed a strong linear relationship between confining stress and both peak strength and elastic modulus, within the range of confining stress tested (up to 25 MPa). It was also revealed that while variations in adsorption across different confining stress levels were relatively small for low gas pressures, this difference became more pronounced at higher pore pressures. In addition, it was observed that the shale strength reduction due to gas adsorption under lower confining stresses follows a near-linear trend with increasing gas saturation. However, under higher confinement (e.g., 25 MPa), the relationship becomes nonlinear, with a more pronounced drop in strength occurring at the early stages of gas adsorption. Moreover, the developed model aligned well with experimental data across all tested conditions, offering a practical tool for predicting mechanical alterations in CO₂ saturated formations. The findings of this study enhance our understanding of coupled poromechanical-sorption effects in shale rocks and provide critical insights for optimising CO₂ injection strategies, ensuring formation integrity, and improving long-term sequestration security in shale carbon sequestration.

了解富有机质页岩对二氧化碳吸附的力学响应对于优化二氧化碳封存和提高天然气采收率至关重要。然而，这些反应通常非常复杂，需要对所涉及的潜在吸附孔隙力学机制有透彻的了解。本研究考察了不同围应力和孔隙压力条件下Beetaloo页岩对CO2吸附的孔隙力学响应，重点研究了强度降低机制。通过可控三轴压缩实验，分析了不同围应力下不同孔隙压力下CO2暴露对页岩强度的影响。建立了基于Langmuir吸附力学和三轴响应的页岩峰值强度预测理论模型，并进行了实验验证。试验结果表明，在测试围应力范围内（最大为25 MPa），围应力与峰值强度和弹性模量均呈较强的线性关系。研究还表明，在低气压下，不同围压水平下的吸附变化相对较小，但在高孔隙压力下，这种差异变得更加明显。此外，在低围应力条件下，随着含气饱和度的增加，气体吸附对页岩强度的降低呈近线性趋势。然而，在更高的约束条件下（例如，25 MPa），这种关系变成非线性的，在气体吸附的早期阶段强度下降更为明显。此外，开发的模型与所有测试条件下的实验数据吻合良好，为预测二氧化碳饱和地层的力学变化提供了实用工具。该研究结果增强了我们对页岩孔隙力学-吸附耦合效应的理解，并为优化二氧化碳注入策略、确保地层完整性和提高页岩碳封存的长期封存安全性提供了重要见解。

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引用次数: 0

Unraveling hiatuses in black shales: Mechanisms and implications from the Lower Silurian Longmaxi Formation, South China 华南下志留统龙马溪组黑色页岩的断裂机制及启示

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-09-02 DOI: 10.1016/j.coal.2025.104869

Yichen Liu , Benzhong Xian , Qianran Wu , Zhiyong Lu , Haocheng Shi , Mingjin Wu , Zhiyun Yu , Lin Zhao , Junyang Geng , Haiying Chen

Fine-grained successions, traditionally interpreted as continuous archives, contain cryptic hiatuses that are critical for evaluating stratigraphic completeness and paleoenvironmental evolution but remain difficult to resolve, especially in deep-water black shales. This study identifies six hiatuses (H1–H6) in the Lower Silurian Longmaxi Formation through integrated sedimentology, cyclostratigraphy, geochemistry, and Evolutive Spectral Analysis (ESA). A 405 kyr eccentricity-tuned astronomical timescale combined with sedimentary noise modeling yields a third-order relative sea-level (RSL) curve, demonstrating controls from both glacio-eustasy and the Kwangsian Orogeny. Our results demonstrate that hiatuses H1–H4 and H6 align with RSL falls, as evidenced by erosion, oxidation, and enhanced bottom-current/gravity-flow activity under cooler climates. Conversely, H5 formed during a warmer highstand, characterized by intense bioturbation and sediment starvation, indicating a non-depositional hiatus. We propose a classification scheme linking ESA spectral features (spectral bifurcation/shifts) with sedimentary attributes, defining seven hiatus types. The Results highlight sea-level fall-driven bottom-current and gravity-flow erosion as the primary hiatus-forming mechanism in deep-water settings. Third-order RSL fluctuations generate major erosional and non-depositional hiatuses (million-year scale), whereas higher-frequency fluctuations induce more subtle and cryptic hiatuses. These surfaces serve as key sequence boundaries, refining sequence stratigraphic frameworks in fine-grained systems. The integrated approach provides a robust methodology for recognizing hiatuses and advances understanding of sedimentary dynamics in deep-water successions.

细粒层序，传统上被解释为连续的档案，包含对评价地层完整性和古环境演化至关重要的隐裂，但仍然难以解决，特别是在深水黑色页岩中。综合沉积学、旋回地层学、地球化学、演化谱分析等方法，确定了下志留统龙马溪组6个断裂（H1-H6）。一个405kyr偏心率调整的天文时间标度结合沉积噪声建模得到了一个三阶相对海平面（RSL）曲线，显示了冰川-eustasy和光西安造山运动的控制作用。我们的研究结果表明，在较冷的气候条件下，侵蚀、氧化和增强的底流/重力流活动表明，H1-H4和H6断裂与RSL下降一致。相反，H5形成于温暖的高水位，具有强烈的生物扰动和沉积物饥饿特征，表明非沉积间隙。我们提出了一种将ESA光谱特征（光谱分岔/移移）与沉积属性联系起来的分类方案，定义了7种裂谷类型。研究结果表明，海平面下降驱动的底流和重力流侵蚀是深水环境下裂缝形成的主要机制。三阶RSL波动产生主要的侵蚀和非沉积中断（百万年尺度），而高频波动则引起更微妙和隐蔽的中断。这些表面是关键的层序边界，在细粒体系中细化层序地层格架。综合方法为识别裂缝提供了一种强有力的方法，并促进了对深水层序沉积动力学的理解。

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引用次数: 0

Pliensbachian (Early Jurassic) deep-time peatland evolution in Northwest China driven by climate change 气候变化驱动下的西北早侏罗世深世泥炭地演化

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-09-01 DOI: 10.1016/j.coal.2025.104871

Lusheng Yin , Minfang Yang , Jing Lu , Xiaoxuan Wu , Xue Peng , Wanqing Wang , Maoyin Tang , Kai Zhou , Peixin Zhang , Longyi Shao , David P.G. Bond , Jason Hilton

As peat deposits represent significant terrestrial carbon sinks, the processes of peatland initiation, evolution and termination are important components of the global carbon cycle. Research on recent peatlands leaves many questions unanswered concerning peatland evolution and the driving mechanisms for changes in peat forming environments in deep-time. Using a combination of sedimentology, coal petrology and palynology, this study investigates coal seams #B, #C and #D from the Pliensbachian (Early Jurassic) Qaidam Basin in China to elucidate the evolution of mire types and vegetation in their precursor peats, and to evaluate paleoenvironmental conditions during peat formation. Based on ash yield, total sulfur contents and coal maceral proxies, coals #B and #C record rheotrophic swamp forest mires that gradually transitioned to ombrotrophic bog forest mire conditions. Coal #D has a more complex evolution, initially forming under the ombrotrophic bog forest mire conditions that characterized coal #C before transitioning to a rheotrophic mire with initially fen and then wet swamp forest conditions. Finally, coal #D records a reversion to ombrotrophic mire conditions dominated by bog forest. Palynological assemblages and the ratios of hygrophytic (H) to xerophytic (X) plants reveal a remarkable change in peat-forming vegetation and paleoclimate. Coals #B and #C are dominated by woody gymnosperms, while deposition of the precursor peats of coal #D gradually evolved into a mix of woody and herbaceous plants. This floristic transition coincided with intensified climatic oscillations, establishing cyclic dry-wet conditions during the later stages of coal #D deposition. Our results reveal that during the Pliensbachian in the Qaidam Basin, climate forcing on peatland environments was manifested primarily through changes in precipitation and water availability brought on by intensification of seasonality. Peatland evolution was a multi-phase process of changing mire types and an overall vegetation succession from woody to herbaceous and woody plants.

泥炭沉积是重要的陆地碳汇，泥炭地的形成、演化和终止过程是全球碳循环的重要组成部分。对近代泥炭地的研究留下了泥炭地演化和深时泥炭形成环境变化驱动机制等诸多未解之谜。结合沉积学、煤岩学和孢粉学等研究方法，对柴达木盆地早侏罗世B、C、D煤层进行了研究，探讨了泥炭前体泥炭泥沼类型和植被的演化，评价了泥炭形成时期的古环境条件。根据灰分产率、总硫含量和煤组分指标，B煤和C煤记录了流变型沼泽森林泥矿逐渐过渡到营养型沼泽森林泥矿条件。D煤的演化更为复杂，最初形成于以C煤为特征的全营养型沼泽森林沼泽条件下，然后过渡到以沼泽森林为特征的流变型沼泽。最后，煤#D记录了以沼泽林为主的近营养化泥沼条件的恢复。孢粉组合和湿生植物(H)与旱生植物(X)的比例揭示了泥炭形成植被和古气候的显著变化。煤#B和煤#C以木本裸子植物为主，煤#D的前体泥炭沉积逐渐演变为木本和草本植物混合。这种植物区系转变与气候振荡加剧相吻合，在D煤沉积后期形成了干湿循环条件。研究结果表明，柴达木盆地Pliensbachian时期，气候对泥炭地环境的强迫作用主要表现为季节性加剧导致的降水和水分有效性的变化。泥炭地的演变是一个多阶段的沼泽类型变化过程，是一个从木本植物到草本植物和木本植物的整体植被演替过程。

{"title":"Pliensbachian (Early Jurassic) deep-time peatland evolution in Northwest China driven by climate change","authors":"Lusheng Yin , Minfang Yang , Jing Lu , Xiaoxuan Wu , Xue Peng , Wanqing Wang , Maoyin Tang , Kai Zhou , Peixin Zhang , Longyi Shao , David P.G. Bond , Jason Hilton","doi":"10.1016/j.coal.2025.104871","DOIUrl":"10.1016/j.coal.2025.104871","url":null,"abstract":"<div><div>As peat deposits represent significant terrestrial carbon sinks, the processes of peatland initiation, evolution and termination are important components of the global carbon cycle. Research on recent peatlands leaves many questions unanswered concerning peatland evolution and the driving mechanisms for changes in peat forming environments in deep-time. Using a combination of sedimentology, coal petrology and palynology, this study investigates coal seams #B, #C and #D from the Pliensbachian (Early Jurassic) Qaidam Basin in China to elucidate the evolution of mire types and vegetation in their precursor peats, and to evaluate paleoenvironmental conditions during peat formation. Based on ash yield, total sulfur contents and coal maceral proxies, coals #B and #C record rheotrophic swamp forest mires that gradually transitioned to ombrotrophic bog forest mire conditions. Coal #D has a more complex evolution, initially forming under the ombrotrophic bog forest mire conditions that characterized coal #C before transitioning to a rheotrophic mire with initially fen and then wet swamp forest conditions. Finally, coal #D records a reversion to ombrotrophic mire conditions dominated by bog forest. Palynological assemblages and the ratios of hygrophytic (H) to xerophytic (X) plants reveal a remarkable change in peat-forming vegetation and paleoclimate. Coals #B and #C are dominated by woody gymnosperms, while deposition of the precursor peats of coal #D gradually evolved into a mix of woody and herbaceous plants. This floristic transition coincided with intensified climatic oscillations, establishing cyclic dry-wet conditions during the later stages of coal #D deposition. Our results reveal that during the Pliensbachian in the Qaidam Basin, climate forcing on peatland environments was manifested primarily through changes in precipitation and water availability brought on by intensification of seasonality. Peatland evolution was a multi-phase process of changing mire types and an overall vegetation succession from woody to herbaceous and woody plants.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"310 ","pages":"Article 104871"},"PeriodicalIF":5.7,"publicationDate":"2025-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145005080","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}

引用次数: 0

Enhancing coal seam gas recovery through greenzyme-induced relative permeability optimisation: Helium-driven core flooding experiments and field-scale production simulations 通过绿酶诱导的相对渗透率优化提高煤层气采收率：氦驱动岩心驱油实验和现场规模生产模拟

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-09-01 DOI: 10.1016/j.coal.2025.104866

Wen Xi , Kunning Tang , Ying Da Wang , Yu Jing , Joan Esterle , Klaus Regenauer-Lieb , Lucas Evangelista , Ryan T. Armstrong , Peyman Mostaghimi

Coal seam gas (CSG) is an unconventional gas resource in the global energy supply. A key factor in predicting and evaluating methane production in coalbeds is coal relative permeability. This study explores the effects of an enzyme-based surfactant, GreenZyme (GZ), on coal relative permeability through drainage unsteady-state core flooding experiments. Initial measurements of interfacial tension (IFT) between helium and GZ solutions at various concentrations demonstrate a decrease in IFT from approximately 70

mN/m

to 45

mN/m

as GZ concentration increases, with 1.2 wt% identified as the critical concentration for solution preparation. Helium was employed as a substitute for methane to eliminate sorption effects and focus on liquid–gas phase interactions. The relative permeability curves for gas and water were derived using the Johnson–Bossler–Naumann (JBN) method. The results show that GZ improves the displacement of water by approximately 5%, with relative permeability curves for both water and gas moving leftward and upward in the presence of GZ. This enhancement is attributed to the reduction in IFT between the water and gas phases. To assess the impact at the field scale, an Eclipse-developed CSG production model incorporating experimental data was developed. Simulation results show that while the gas production rate based on the original relative permeability curves is initially higher during the first 0.28 years, the rate for the GZ-enhanced case surpasses it for the remainder of the production period. These findings provide valuable insights into the influence of GZ on coal relative permeability and demonstrate its potential to enhance CSG recovery at the field scale.

煤层气是全球能源供应中的一种非常规天然气资源。煤的相对渗透率是预测和评价煤层气产量的关键因素。本研究通过排水非稳态岩心驱油实验，探讨了酶基表面活性剂GreenZyme （GZ）对煤相对渗透率的影响。不同浓度的氦气和GZ溶液之间的界面张力（IFT）的初步测量表明，随着GZ浓度的增加，IFT从大约70 mN/m下降到45 mN/m，其中1.2 wt%被确定为溶液制备的临界浓度。氦气被用作甲烷的替代品，以消除吸附效应，并专注于液气相互作用。采用Johnson-Bossler-Naumann （JBN）方法推导了气、水相对渗透率曲线。结果表明：GZ对水驱替的改善作用约为5%，且在GZ作用下，水、气的相对渗透率曲线均呈左移和上移趋势；这种增强归因于水和气相之间IFT的减少。为了评估油田规模的影响，开发了一个eclipse开发的CSG生产模型，并结合了实验数据。模拟结果表明，虽然基于原始相对渗透率曲线的产气量在前0.28年初始较高，但在剩余的生产期内，gz增强情况的产气量都超过了它。这些发现为GZ对煤相对渗透率的影响提供了有价值的见解，并证明了它在现场规模上提高CSG采收率的潜力。

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引用次数: 0

The modes of occurrence, distribution and enrichment of critical raw materials (Ga, Sr, Zr and Ba) within coal discards of the Witbank Coalfield, South Africa 南非Witbank煤田煤堆中关键原料（Ga、Sr、Zr和Ba）的赋存、分布和富集模式

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-09-01 DOI: 10.1016/j.coal.2025.104870

X. Nkwamza, N. Malumbazo

Coal mineralogy and trace element composition provide vital insights into the geological coal formation processes, depositional environments, and potential resource valorization. However, there is limited knowledge and understanding of the geochemical and mineralogical composition of coal discards from the Witbank Coalfield. Thus, the coal discards remain underexplored, limiting effective management and future utilization strategies. To address this gap, this study investigates the occurrence, distribution and enrichment of CRMs within Permian coal discards of the Witbank Coalfield. An integrated suite of analytical techniques such as TGA, Bomb calorimeter, FTIR, XRD, TIMA, SEM-EDS, XRF and ICP-MS was utilized to determine the dominant mineral assemblages and trace elemental enrichments. Results revealed quartz and kaolinite as the principal minerals, with subordinate carbonate and sulfide phases introduced through diagenetic and hydrothermal processes. The coal discards were enriched in trace elements such as Ga, Sr, Zr and Ba. Ga was associated with kaolinite and organic matter, Sr and Ba predominantly occurred in barite, and Zr was hosted primarily in detrital zircon grains. Their spatial variability reflects depositional and diagenetic controls. Geochemical proxies, such as Sr/Ba and TiO₂/Al₂O₃ ratios, indicate freshwater depositional conditions influenced by volcanic ash input and post-depositional alteration. These findings enhanced the understanding of the geochemical cycling within coal discards, their mineralogical stability, and potential environmental implications. Furthermore, the presence of acid-neutralizing minerals supports the potential use of these coal discards in mitigating acid mine drainage, while the enriched CRMs highlight opportunities for sustainable resource recovery.

煤矿物学和微量元素组成为煤的地质形成过程、沉积环境和潜在的资源价值提供了重要的见解。然而，人们对威特班克煤田废煤的地球化学和矿物组成的认识和理解有限。因此，煤炭弃置物仍未得到充分开发，限制了有效的管理和未来的利用战略。为了解决这一空白，本研究调查了Witbank煤田二叠系煤矸石中CRMs的赋存、分布和富集情况。利用TGA、Bomb量热计、FTIR、XRD、TIMA、SEM-EDS、XRF和ICP-MS等综合分析技术测定了主要矿物组合和微量元素富集程度。结果表明，矿床主要矿物为石英和高岭石，次生矿物为碳酸盐和硫化物，由成岩作用和热液作用引入。煤渣中富含Ga、Sr、Zr、Ba等微量元素。Ga与高岭石和有机质伴生，Sr和Ba主要赋存于重晶石中，Zr主要赋存于碎屑锆石颗粒中。它们的空间变异性反映了沉积和成岩的控制作用。Sr/Ba、TiO2/Al2O3等地球化学指标表明淡水沉积条件受火山灰输入和沉积后蚀变的影响。这些发现增强了对煤的地球化学循环、矿物学稳定性和潜在环境影响的理解。此外，酸中和矿物的存在支持了这些废煤在缓解酸性矿井排水方面的潜在利用，而富集的矿质物质则突出了可持续资源回收的机会。

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引用次数: 0

Effect of temperature on coal maceral dissolution and matrix alteration during NaClO stimulation: Insights from microscopy and Micro-CT 温度对NaClO刺激过程中煤显微组分溶解和基质蚀变的影响：来自显微镜和Micro-CT的观察

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-08-23 DOI: 10.1016/j.coal.2025.104868

Sen Yang , Zhentao Li , Joan Esterle , Karen M. Steel

Oxidant stimulation has emerged as a promising supplementary approach to enhance gas recovery from coal seams, targeting coal organic matter more directly than acid stimulation, which affects mineral components. However, the reactivity of different coal maceral subtypes to oxidants, particularly under reservoir conditions, remains poorly understood. In this study, sodium hypochlorite (NaClO) was used to investigate the maceral-specific reactivity and matrix alteration of bituminous coal samples from the Bowen Basin, Australia, under varying temperature conditions. Microscopic and Micro-CT analyses revealed that higher temperatures significantly enhanced maceral dissolution. The observed reactivity followed the order: semifusinite > vitrinite > fusinite, with collodetrinite within vitrinite displaying notably higher reactivity than collotelinite. These divergences should be ascribed to the differences in aromaticity, functional group composition, and pore structure. Micro-CT results revealed maceral-dependent dissolution depths, ranging from 300 to 500 μm for semifusinite, ∼100 μm for fusinite, and 50–150 μm for vitrinite bands. As a fine-grained heterogeneous host to telovitrinite macerals and other detrital components, coal matrix exhibited strong alteration in directional dependence, with significantly enhanced pore and fracture development along the horizontal (bedding plane) direction. At 60 °C, the reaction depth reached up to 850 μm, accompanied by substantial pore enlargement, particularly within the 30–50 μm range. Mixed maceral zones showed deeper reaction fronts than vitrinite-rich areas, emphasizing the influence of maceral heterogeneity on oxidant penetration. This study highlights that both maceral composition and bedding structure critically govern the extent, directionality, and effectiveness of oxidant-induced matrix alteration. These findings provide important insights into optimizing oxidant stimulation strategies for improved gas recovery in heterogeneous coal reservoirs.

氧化增产已成为提高煤层天然气采收率的一种有希望的补充方法，与影响矿物成分的酸增产相比，氧化增产更直接地针对煤中的有机质。然而，不同煤显微组分亚型对氧化剂的反应性，特别是在储层条件下，仍然知之甚少。本研究采用次氯酸钠（NaClO）研究了澳大利亚Bowen盆地烟煤样品在不同温度条件下的显微反应性和基质蚀变。显微和显微ct分析显示，较高的温度显著增强了显微组分的溶解。观察到的反应活性顺序为：半麻质组→镜质组→镜质组→丝质组，镜质组内的胶泥质反应活性明显高于胶泥质。这些差异应归因于芳香性、官能团组成和孔隙结构的差异。显微ct结果显示，半丝质组溶解深度为300 ~ 500 μm，丝质组溶解深度为~ 100 μm，镜质组溶解深度为50 ~ 150 μm。煤基质为细粒非均质寄主，具有较强的方向依赖性，沿水平（顺层）方向孔隙和裂缝发育显著增强。在60℃时，反应深度可达850 μm，孔隙明显扩大，特别是在30 ~ 50 μm范围内。混合显微组分区反应锋面较镜质组富集区深，突出了显微组分非均质性对氧化剂渗透的影响。该研究强调了氧化诱导的基质蚀变的程度、方向性和有效性受显微成分和层理结构的影响。这些发现为优化氧化增产策略以提高非均质煤储层的采收率提供了重要见解。

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引用次数: 0

Mineralogy and elemental geochemistry of Pennsylvanian high-sulfur coals in the Huanghebei Coalfield, Shandong, Northern China: Implications for the enrichment and controlling factors of U 山东黄河北煤田宾夕法尼亚系高硫煤的矿物学及元素地球化学特征：对U - 2富集及控制因素的启示

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-08-23 DOI: 10.1016/j.coal.2025.104867

Bofei Zhang , Wenfeng Wang , Qingfeng Lu , Wenlong Wang , Xiaozhen Teng , Long Chen

Uranium enrichment in coal is of great significance for understanding metallogenic processes and assessing resource potential. Numerous studies have investigated the geochemical behavior and modes of occurrence of U in super-high-organic‑sulfur coals from Southern China. However, the Huanghebei Coalfield in Shandong, a major high‑sulfur coal-bearing region in North China, yet remains largely unidentified. This study investigates the U enrichment and controlling factors of the Pennsylvanian No.11 coal from Huanghebei Coalfield, Shandong, Northern China. Uranium is enriched in the No. 11 coal (up to 89.3 μg/g), where U, Mo, and V are exclusively concentrated in the topmost coal bench underlying the limestone roof. The enrichment of critical elements, including U, Mo, and V, is attributed to infiltration of marine water from the overlying strata during the early diagenetic stage. Uranium in the coal shows both organic and inorganic associations. Notably, a small portion of U occurs in uraninite, which is more easily reduced and precipitated under anoxic conditions. The relationships of Al₂O₃ vs. TiO₂, Al₂O₃/TiO₂-Nb/Yb and the REY distribution patterns indicate that the sediment-source rocks of the No. 11 coal were the North Qinling Orogenic Belt. The predominant minerals identified in the No. 11 coal are NH₄-illite, calcite, quartz, pyrite, bassanite and kaolinite, with minor amounts of dolomite and siderite. The modes of occurrence of NH₄-illite, kaolinite, calcite, pyrite, and quartz, as well as fluorapatite, indicate that the No. 11 coal was likely influenced by multi-stage injection of hydrothermal fluids. Authigenic NH₄-illite is relatively high abundant, probably formed by the interaction of kaolinite with nitrogen released from organic matter during metamorphism induced by igneous intrusion. The δ¹³C_VPDB and δ¹⁸O_VPDB values of epigenetic carbonates in the coals indicate that the carbon and oxygen in the carbonates are primarily derived from hydrothermal fluid activities. The No. 11 coal has potential for resource development and utilization as raw material for U and deserves further attention.

煤中铀的富集对认识成矿过程和评价资源潜力具有重要意义。大量研究对中国南方超高有机硫煤中铀的地球化学行为和赋存模式进行了研究。然而，作为中国北方主要的高硫含煤地区，山东黄河北煤田在很大程度上仍未被发现。研究了山东黄河北煤田宾夕法尼亚系11号煤铀富集特征及控制因素。铀富集于11号煤中（最高可达89.3 μg/g），其中U、Mo、V均集中在石灰岩顶板下的最上层煤阶中。U、Mo、V等关键元素的富集与上覆地层海水在早期成岩阶段的渗透有关。煤中铀既有有机结合又有无机结合。值得注意的是，小部分铀存在于铀矿中，在缺氧条件下更容易还原和沉淀。Al2O3与TiO2、Al2O3/TiO 2 -Nb/Yb的关系及REY分布模式表明，11号煤的沉积源岩为北秦岭造山带。在11号煤中发现的主要矿物为硫酸铵伊利石、方解石、石英、黄铁矿、玄武岩和高岭石，少量白云石和菱铁矿。nh4 -伊利石、高岭石、方解石、黄铁矿、石英和氟磷灰石的赋存方式表明11号煤可能受到多期热液注入的影响。自生nh4 -伊利石相对丰富，可能是在火成岩侵入变质过程中高岭石与有机质释放的氮相互作用形成的。煤中表观成因碳酸盐的δ13CVPDB和δ18OVPDB值表明，碳酸盐中的碳和氧主要来源于热液活动。11号煤作为铀原料具有资源开发利用潜力，值得进一步重视。

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引用次数: 0

Implications of element enrichment in paralic coals from the Carboniferous in England 英国石炭系近流煤元素富集意义

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-08-14 DOI: 10.1016/j.coal.2025.104865

D.A. Spears

The enrichment of trace elements in coals is of significant economic importance because of the growing demand for the critical elements. Several enrichment processes have been identified and in this paper the role of palaeosalinity is evaluated using published data from the East Pennine Coalfield (UK). The coal and associated mudrocks for which comprehensive ICP- AES and ICP-MS analyses are available is the Parkgate Coal. This is a high volatile bituminous coal of Upper Carboniferous (Pennsylvanian) age with a variable S content mainly due to pyritic S (Total S = 2.34 ± 1.83 %, Pyritic S = 1.17 ± 1.79 %).

Supporting information on the mineralogy of this and other major coals comes from XRD analyses. Although there is an extensive geochemical data base on coals and mudrocks from this Coalfield, most of the analyses were made using XRF with a restricted suite of trace elements (13). Comprehensive analyses of marine shales are not available for this coalfield and to evaluate the marine influence use is made of analyses of samples from the Netherlands. These samples are of comparable age and from the same extensive depositional area. Enrichment values calculated for the Parkgate Coal based on detrital trace elements in the mudrocks show that the chalcophile elements are enriched and pyrite is the major host for many of them. Other elements are enriched including Ge and Be and there is an organic association, possibly reflecting an original plant origin. The importance of a seawater control is demonstrated by close similarities in the enrichment values between the coals and marine shales. Use could be made of the enrichment values determined in this work to identify a seawater influence in coals elsewhere. Elements not enriched, and for which other controls operated, are Ga, Li, Zr and Nb. Although not confirmed for the UK coals the REE are probably in the same category. Alternatives to the control of seawater on the element enrichments in the studied coals are considered and rejected as having little or no effect.

随着煤中微量元素需求量的不断增长，煤中微量元素的富集具有重要的经济意义。本文已确定了几个富集过程，并利用英国东彭宁煤田已发表的数据评估了古盐度的作用。具有全面ICP- AES和ICP- ms分析的煤和伴生泥岩是帕克盖特煤。这是一种上石炭世（宾夕法尼亚）时代的高挥发性烟煤，硫含量变化主要是由于黄铁矿S （Total S = 2.34±1.83%，黄铁矿S = 1.17±1.79%）。该煤和其他主要煤的矿物学支持信息来自XRD分析。尽管该煤田的煤和泥岩有广泛的地球化学数据库，但大多数分析都是使用XRF和有限的微量元素组合进行的（13）。没有对该煤田进行海洋页岩的全面分析，评估海洋影响的使用是对来自荷兰的样品进行分析。这些样品的年龄相当，来自同一广泛的沉积区。根据泥岩碎屑微量元素计算的富集值表明，煤中亲铜元素富集，其中黄铁矿为主要寄主。其他元素如Ge、Be等均富集，且存在有机关联，可能为植物源。煤与海相页岩的富集值非常相似，说明了海水控制的重要性。可以利用在这项工作中确定的富集值来确定海水对其他地方煤的影响。未富集的元素有Ga、Li、Zr和Nb。尽管英国煤炭的稀土元素含量尚未得到证实，但它们可能属于同一类别。考虑了控制海水对所研究煤中元素富集的替代方法，并以影响很小或没有影响而拒绝。

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引用次数: 0

Degradation of organic matter by radioactive radiation in black shales: An overlooked modification of organic molecular structures 黑色页岩中放射性物质的降解：一个被忽视的有机分子结构的修饰

IF 5.7 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-08-09 DOI: 10.1016/j.coal.2025.104864

Leibo Bian , Zhe Zhao , Xiaomei Wang , Hamed Sanei , Anthony Chappaz , Jin Dong , Zhongtian Dong , Linfeng Xie , Niels H. Schovsbo , Fariborz Goodarzi , Shuichang Zhang , Wenzhi Zhao

Natural radioactive radiation emitted by uranium (U) in sedimentary basins continuously transforms organic matter and thus its degrading impact overprints the burial-related thermal maturation process. However, the systematic pathway for irradiated alteration of sedimentary organic matter and its influence remain poorly understood. This omission hinders a comprehensive understanding of organic matter evolution after burial. Our study investigated the artificially and naturally irradiated alteration of organic matter in the U- and organic-rich Cambro-Ordovician Alum Shale of Northern Europe and Triassic Chang 7–3 shale in the Ordos Basin of China. After exposure of samples to a Co-60 source, radiation accelerated the conversion of bitumen to natural gas with a lower gas dryness (C₁/C_1–5 < 0.8), while kerogen is converted to natural gas with a higher gas dryness (>0.8). Moreover, enhanced radiation dose facilitates the transformation from resins and asphaltenes to aromatics and leads to enrichments of carbon-13 isotope, when the radiation dose reaches the thresholds of approximately 100 and 2000 kGy, respectively. Natural radiation exposure in the Chang 7–3 shales, identified by spatial distribution and affiliated phases of U, may have influenced bitumen structures through accelerating transformation of macro- to micro-organic compounds and generation of wet gas that could have enhanced hydrocarbon mobility. Moreover, an addition to the standard model for organic matter burial and transformation is proposed with integration of natural radiation exposure. Based on the calculated Proterozoic-Phanerozoic radiation dose in sedimentary rocks, we hypothesize that the radioactive processes might have consistently modified the characteristics of retained bitumen in uranium-enriched shales, thereby affecting carbon cycle on Earth's surface environments.

沉积盆地中铀(U)释放的天然放射性辐射不断转化有机质，其降解作用覆盖了埋藏相关的热成熟过程。然而，沉积有机质辐照蚀变的系统途径及其影响尚不清楚。这种遗漏妨碍了对埋藏后有机质演化的全面认识。研究了北欧寒武系—奥陶系富铀明矾页岩和鄂尔多斯盆地三叠系长7-3页岩中有机质的人工和自然辐照蚀变。样品暴露于Co-60源后，辐射加速了沥青向天然气的转化，天然气干燥度较低（C1/C1 - 5 < 0.8），而干酪根则转化为天然气，天然气干燥度较高（>0.8）。此外，当辐射剂量分别达到约100和2000 kGy时，增强的辐射剂量有利于树脂和沥青质向芳烃的转化，并导致碳-13同位素的富集。根据U的空间分布和附相特征，长7-3页岩的自然辐射暴露可能通过加速宏观有机化合物向微观有机化合物的转化和湿气的生成来影响沥青结构，从而增强油气的流动性。此外，本文还提出了一个有机物质埋藏和转化的标准模型，并将自然辐射照射纳入其中。基于对沉积岩元古宙-显生宙辐射剂量的计算，我们假设放射性过程可能持续改变了富铀页岩中保留沥青的特征，从而影响了地球表面环境的碳循环。

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引用次数: 0