International Journal of Coal Geology最新文献

{"title":"Extensive accumulation of organic matter in the Late Permian Dalong Formation, Western Hubei Trough, Southern China","authors":"Lulu Xu ,&nbsp;Saipeng Huang ,&nbsp;Dameng Liu ,&nbsp;Zhiwei Liao ,&nbsp;Kui Wu ,&nbsp;Miankun Chen ,&nbsp;Xianghui Zhou ,&nbsp;Yanlin Zhang ,&nbsp;Bei Liu ,&nbsp;Minglong Li","doi":"10.1016/j.coal.2025.104727","DOIUrl":"10.1016/j.coal.2025.104727","url":null,"abstract":"<div><div>The black shale in the Upper Permian Dalong Formation in the Western Hubei (W<img>H) Trough is characterized by its extreme organic matter accumulation (OMA), and its vertical heterogeneity necessitates more nuanced research. The characteristics of the lithology, conodont, total organic carbon (TOC), mineral composition, silica origin, palaeoenvironmental evolution, and the OMA mechanisms of the Dalong Formation were systematically studied. The results indicate that the Dalong Formation can be subdivided into six distinct members, primarily composed of argillaceous siliceous rocks, siliceous dolomite, siliceous shales, calcareous siliceous rocks, and siliceous limestone, respectively. The silica in the organic-rich shale is predominantly of mixed biogenic and terrigenous origin, with localized contributions from hydrothermal sources. The organic-rich shale (ORS) is primarily distributing below the Wuchiapingian and Changhsingian boundary (WCB), which is deposited under moderate terrigenous input, semi-humid to semi-arid climate, euxinic conditions in a semi-open to the semi-restricted basin, and high palaeoproductivity caused by the upwelling setting and high-frequency volcanic ash layers. The WCB is characterized by the arid climate, oxic conditions in a strongly restricted basin, and low palaeoproductivity. Palaeoproductivity is identified as the principal controlling factor for the OMA. Additionally, the hydrothermal silica is commonly deposited under euxinic conditions, which are conducive to the preservation of organic matter. Evidence suggesting that thicker volcanic ash layer during the Changhsingian Stage may be one of the reasons for the mass extinction in the Late Permian. The north-central of the W<img>H Trough exhibits a higher TOC content (&gt; 4 %), overmature source rock with the vitrinite reflectance (R_o) ranging from 2 % to 3 %, and an euxinic conditions, suggesting more beneficial to shale gas enrichment.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"302 ","pages":"Article 104727"},"PeriodicalIF":5.6,"publicationDate":"2025-02-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143474638","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}

{"title":"Isotopic and hydrochemical evidence for the origins of unconventional gases in the Middle and Lower Jurassic coal measures in the Fukang area of Junggar Basin, NW China","authors":"Jie Xiang ,&nbsp;Jiandong Li ,&nbsp;Xianqing Li ,&nbsp;Xiaomin Ma ,&nbsp;Jie Sun ,&nbsp;Zhuo Zou ,&nbsp;Yuling Qin","doi":"10.1016/j.coal.2025.104726","DOIUrl":"10.1016/j.coal.2025.104726","url":null,"abstract":"<div><div>Extensive coalbed gas exploration has been conducted in the Fukang area of the Junggar Basin in China, but no significant breakthroughs have yet to be achieved, partly due to the unclear origin of coalbed gas. In this study, the compositions and isotopes of coalbed, shale, and tight sandstone gases, along with the chemical characteristics of formation water are reported. The results indicate that the coalbed, shale, and tight sandstone gases are dominated by CH₄. Based on the carbon isotopes of CH₄ and CO₂, the coalbed gas in the Fukang area is primarily biogenic gas via CO₂ reduction pathway, whereas the shale and tight sandstone gases are mainly biogenic gas via acetate (methyl-type) fermentation pathway. The formation water is chiefly derived from glacial meltwater with the chemical type of Na-HCO₃. High concentrations of Na⁺, Cl⁻, and HCO₃⁻ and low concentrations of Mg²⁺, Ca²⁺, and SO₄²⁻ indicate that the study area is distant from the water recharge area. In the contact area between the recharge runoff and the stagnant area, microbial modification of thermogenic gas is enhanced, leading to an enrichment of secondary biogenic gas. The findings of this study contribute to the geological understanding of coalbed, shale, and tight sandstone gases, providing valuable insights for future exploration efforts in the Fukang area.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"302 ","pages":"Article 104726"},"PeriodicalIF":5.6,"publicationDate":"2025-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143479070","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}

{"title":"Spatial and temporal variation in coal fire emissions: Examples from two eastern Kentucky coal fires","authors":"Donald R. Blake ,&nbsp;Jennifer M.K. O'Keefe ,&nbsp;Trent Garrison ,&nbsp;Gregory C. Copley ,&nbsp;James C. Hower","doi":"10.1016/j.coal.2025.104725","DOIUrl":"10.1016/j.coal.2025.104725","url":null,"abstract":"<div><div>Organic gases were collected at the Truman Shepherd and Lotts Creek coal fires, both developed in high volatile A bituminous coals, several times over the course of five to six months. Carbon dioxide and CO, exceeding 102,800 ppmv and 11,000 ppmv, respectively, at two of the vents studied, dominate the gas chemistry. Methane, ethane, and propane dominate the aliphatic gases and benzene dominates the aromatic gases. The aliphatic gases, exclusive of the latter three gases vary between vents and between months at both sites, with the Lotts Creek vents exhibiting a greater variation. At both fires, there was a tendency for decrease in methane/(methane + ethane + propane + butane) and an increase in benzene/(Σ BTEX [benzene + toluene + ethylbenzene + xylene]) across the sampling times.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"302 ","pages":"Article 104725"},"PeriodicalIF":5.6,"publicationDate":"2025-02-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453434","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}

{"title":"Correlations between metapelitic zones and graptolite reflectance in Ordovician successions from northwestern Argentina depicting a complex postdepositional history","authors":"Nexxys C. Herrera Sánchez ,&nbsp;Margarita Do Campo ,&nbsp;Blanca A. Toro ,&nbsp;Fernando Nieto García","doi":"10.1016/j.coal.2025.104723","DOIUrl":"10.1016/j.coal.2025.104723","url":null,"abstract":"<div><div>Correlations between metapelitic zones and organic proxies of thermal maturity, like coal rank, vitrinite reflectance and color alteration index in conodonts, were developed several decades ago and have been widely applied with satisfactory results. In contrast, comparisons between graptolite reflectance and metapelitic zones defined by Kübler Index values, clay mineral assemblages and chlorite geothermometry are scarce. In this study, samples from Ordovician successions in northwestern Argentina, where graptolite reflectance had been previously measured, were analyzed for clay mineral assemblages using X-ray diffraction, Scanning Electron Microscopy with Backscattered Electrons, and Electron Probe. Additionally, the Kübler Index was determined, and a chlorite geothermometer was applied to compare the response of these proxies for diagenetic-metamorphic temperatures and thermal maturity. The studied material was selected from two sections: Los Colorados, in the western part of the Cordillera Oriental, which mainly comprises the Acoite Formation (Early-Middle Ordovician), and Muñayoc, in the eastern part of the Puna highland, corresponding to the Cochinoca-Escaya Magmatic-Sedimentary Complex (Early-Middle Ordovician). The samples coming from the Los Colorados section reveal a clay mineral assemblage consisting of dioctahedral mica, kaolinite, along with scarce chlorite-bearing mixed-layers and chlorite in few cases, exhibiting Kübler Index values indicative of diagenesis (≥ 0.52 Δ°2θ), and corresponding temperatures between 109 and 282 °C. In contrast, samples from the Muñayoc section present a clay mineral assemblage, comprising mainly dioctahedral mica illite, subordinate kaolinite and smectite, associated with chlorite in few samples; Kübler Index values agree with the epizonal zone (≤ 0.32 Δ°2θ), and temperatures ranging from 177 to 321 °C. Notably, these findings show improved correlation with the temperatures derived from graptolite reflectance when considering updated equations between graptolite and vitrinite reflectance. On the other hand, most of the samples from Muñayoc show non equilibrium clay assemblages, as smectite and kaolinite are not stable in the epizone. This fact, along with the absence of chlorite in several samples, is probably a consequence of the hydrothermal alteration that affected the Ordovician rocks in several localities of the Puna region. As any of these approaches has its own limitation factors and sources of uncertainty, the combination of inorganic and organic proxies provide a more robust methodology to outline low-temperature burial pathways. Moreover, the correlation between Kübler Index and equivalent vitrinite reflectance revealed higher geothermal gradients in Puna than in Cordillera Oriental.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"302 ","pages":"Article 104723"},"PeriodicalIF":5.6,"publicationDate":"2025-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143453435","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}

{"title":"Petrological, mineralogical, and geochemical compositions of the Eocene coals from Senakin Peninsula, South Kalimantan, Indonesia","authors":"Ferian Anggara ,&nbsp;Donatus Hendra Amijaya ,&nbsp;Tim A. Moore ,&nbsp;Azmii Nanda Fadhillah ,&nbsp;Aulia Agus Patria","doi":"10.1016/j.coal.2025.104722","DOIUrl":"10.1016/j.coal.2025.104722","url":null,"abstract":"<div><div>Samples from the Senakin coal bed (Eocene age, Pasir Sub-basin) were analyzed to study the concentration of critical elements and investigate genetic types and enrichment processes. Of particular interest was to determine if an overlying mafic volcanic unit dated to the same age as the overlying Eocene sediments and tonstein layers withing the coal, affected the geochemical composition of the coal bed. Five partings were identified as being mafic-alkali tonsteins. The lower and upper tonsteins are interpreted to originate both from volcanic ash-fall material intermingled with water-borne detrital sediments. The middle tonstein is thought to have originated primarily as an ash-fall. A consistent feature of all partings, however, is that they are characterized by a graupen texture with additional vermicular and vitroclastic textures. The coal samples from the Senakin coal bed are dominated by vitrinite (64 vol%) with subordinate proportions of liptinite (29 vol%), and inertinite (7 vol%). Optical and SEM-EDX measurements of the coal samples showed that the inorganic material is dominantly pyrite, marcasite, quartz, kaolinite, illite, apatite, calcite, Ti oxides, Ti-V-bearing minerals, and a Mo-bearing mineral. Some coal samples from the Senakin coal bed have total rare earth element and yttrium (REY) concentrations up to 283.53 ppm. Furthermore, coals are enriched in REY and some trace elements (e.g., Zr (Hf), Nb (Ta), Ga, Sr, and V). It is hypothesized that the critical enrichments of the Senakin coal bed may be controlled primarily by three factors: (1) mafic-intermediate volcaniclastic rocks whose provenance are possibly from the Pitap and Haruyan Formations, (2) marine water infiltration from overlying sediments into recently buried peat, and/or (3) the occurrence mafic-alkali tonstein layers.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"301 ","pages":"Article 104722"},"PeriodicalIF":5.6,"publicationDate":"2025-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422165","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}

{"title":"Organic matter content and its role in shale porosity development with maturity: Insights from Baltic Basin Silurian shales","authors":"Grzegorz P. Lis ,&nbsp;Tomasz Topór ,&nbsp;Maria Mastalerz","doi":"10.1016/j.coal.2025.104713","DOIUrl":"10.1016/j.coal.2025.104713","url":null,"abstract":"<div><div>Porosity, pore size distribution, and surface area are the main petrophysical characteristics indicative of gas storage capacity in shales. This paper investigates the influence of organic matter (OM) content on the evolution of these parameters at different stages of thermal maturity. Ninety-six samples of Silurian shales from the Baltic Basin ranging in maturity from immature to overmature were selected for this study. Porosity evolution was evaluated using N₂ and CO₂ low-pressure gas adsorption. At the immature stage, the samples with high OM content are characterized by lower porosity than the organic-matter-lean samples. At this stage, high OM content leads to the disruption of stiffer mineral framework; mixed organic-mineral framework is more prone to mechanical compaction than mineral framework. At the oil window stage, porosity of OM-rich samples declines due to pore-throat plugging and pore filling by bitumen. At the wet and dry gas generation stage, porosity of OM-rich samples increases mainly due to pore-throats unplugging. Absent or weak correlation between porosity and OM content at the wet and dry gas stages indicates poor development of OM-hosted secondary porosity. High contents of clay minerals in the studied samples fail to provide the rigid mineral framework and pressure shadows necessary for OM-hosted secondary porosity development.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"301 ","pages":"Article 104713"},"PeriodicalIF":5.6,"publicationDate":"2025-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143387891","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}

{"title":"Characteristics of in-situ stress field of coalbed methane reservoir in the eastern margin of Ordos basin","authors":"Kaichao Zhang ,&nbsp;Song Li ,&nbsp;Guanghao Zhong ,&nbsp;Peng Feng ,&nbsp;Chuang Chang ,&nbsp;Hao Li","doi":"10.1016/j.coal.2025.104715","DOIUrl":"10.1016/j.coal.2025.104715","url":null,"abstract":"<div><div>The eastern margin of the Ordos Basin in China holds substantial coalbed methane resources. Nevertheless, coalbed methane production in this region is significantly constrained due to the unclear characteristics of the in-situ stress field within the coal reservoirs. Drawing on extensive coal seam test data, including well testing and hydraulic fracturing, and uses hydraulic fracturing calculation methods, this study conducts a comparative analysis of the in-situ stress characteristics across various CBM blocks in the region. Results indicate that the in-situ stress of the coal reservoirs along the eastern margin of the Ordos Basin predominantly exhibits medium-high stress, with stress levels higher in the south and lower in the north. The stress field is dominated by the inverse fault stress field (<span><math><msub><mi>σ</mi><mi>H</mi></msub><mo>&gt;</mo><msub><mi>σ</mi><mi>V</mi></msub><mo>&gt;</mo><msub><mi>σ</mi><mi>h</mi></msub></math></span>) in the north while in the south, it is characterized by a normal fault stress field (<span><math><msub><mi>σ</mi><mi>V</mi></msub><mo>&gt;</mo><msub><mi>σ</mi><mi>H</mi></msub><mo>&gt;</mo><msub><mi>σ</mi><mi>h</mi></msub></math></span>). The in-situ stress characteristics of the coal seams are primarily governed by burial depth and local structural factors, with the three principal stresses showing a strong linear positive correlation with burial depth. The vertical stress field distinctly exhibits a “three-zoned” distribution. At a depth of 750 m, the in-situ stress relationship is <span><math><msub><mi>σ</mi><mi>H</mi></msub><mo>&gt;</mo><msub><mi>σ</mi><mi>V</mi></msub><mo>&gt;</mo><msub><mi>σ</mi><mi>h</mi></msub></math></span>, indicating that the coal reservoir is predominantly under compressive stress. At depths between 750 and 1500 m, the coal seam stress state follows the relationship <span><math><msub><mi>σ</mi><mi>H</mi></msub><mo>≈</mo><msub><mi>σ</mi><mi>V</mi></msub><mo>&gt;</mo><msub><mi>σ</mi><mi>h</mi></msub></math></span>, transitioning into a stress regime characteristic of a transition zone. At a depth of 1500 m, the in-situ stress relationship is <span><math><msub><mi>σ</mi><mi>V</mi></msub><mo>&gt;</mo><msub><mi>σ</mi><mi>H</mi></msub><mo>&gt;</mo><msub><mi>σ</mi><mi>h</mi></msub></math></span>, and the coal reservoir is predominantly characterized by tensile stress. Despite the relatively deep burial depth of the coal seams in the Hancheng block, its location within the Tongchuan-Hancheng fault zone, where north-south faulting is significantly developed, causes substantial local structural effects. As a result, the coal seam stress field in this area remains dominated by reverse faulting.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"301 ","pages":"Article 104715"},"PeriodicalIF":5.6,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143422164","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}

{"title":"Chemistry imaging and distribution analysis of rare earth elements in coal using LIBS and LA-ICP-MS instruments","authors":"Chet R. Bhatt ,&nbsp;Jinesh C. Jain ,&nbsp;Alexander A. Bol'shakov ,&nbsp;Dustin L. McIntyre","doi":"10.1016/j.coal.2025.104710","DOIUrl":"10.1016/j.coal.2025.104710","url":null,"abstract":"<div><div>Currently, demand for rare earth elements (REEs) increased significantly. Coal is actively evaluated as potential economic sources for extraction of REEs. In this work, laser-induced breakdown spectroscopy (LIBS) was evaluated for rapid estimation of REEs content and their distribution in the natural coal samples. The results were compared with similar laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) measurements. Thirteen coal samples (nine standard samples and five natural samples) were used in this study. Powder samples were pressed into pellets while coal chunks were directly ablated for data recording. Pellets of the powder standard samples were used to optimize the data acquisition system and then data recorded with this optimized system was used to identify the proper data acquisition and analysis models. After establishing the proper data acquisition system and analysis model using the standard samples, natural coal samples in powder form and their chunks were utilized to record LIBS and LA-ICP-MS spectra. Multivariate calibration models were developed using four of the natural samples, which were evaluated by predicting the REE content in the fifth sample. Principal component analysis was performed on the LIBS data obtained from the natural samples and it classified all the samples with high accuracy. Two-dimensional (2D) elemental mapping on coal chunk samples was also performed using both LIBS and LA-ICP-MS to study the distribution of REEs in the samples. The resulting elemental images and their correlations can be used to infer mineral distributions.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"301 ","pages":"Article 104710"},"PeriodicalIF":5.6,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143427996","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}

{"title":"Nanomechanical properties of anthracite and graphite: The role of heteroatom functional groups and structural evolution","authors":"Yuhui Wang ,&nbsp;Suping Yao ,&nbsp;Hanlin Zheng ,&nbsp;Zhaoxi Zuo ,&nbsp;Yang Liu","doi":"10.1016/j.coal.2025.104714","DOIUrl":"10.1016/j.coal.2025.104714","url":null,"abstract":"<div><div>This study investigates the anthracite and graphite samples from the Hanpoao mining area in Hunan Province, China, to understand their structural deformation characteristics in relation to tectonic stress and magmatic intrusion. Despite previous research highlighting the influence of tectonic stress on the microcrystalline structure of organic matter, there remains a gap in comprehensively understanding how these factors interact and affect the mechanical properties of coal and graphite. To address this, the research employed a combination of optical microscopy, reflectance measurements, Raman spectroscopy, and high-resolution atomic force microscopy, along with powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses. Studies have shown that the Young's modulus of anthracite and graphite exhibits a certain correlation with both coal rank and the degree of graphitization. Notably, the presence of heteroatom functional groups, particularly sulfur-containing groups, plays a crucial role in modulating the Young's modulus. The study reveals an inverse correlation between thiophene sulfur content and Young's modulus, and a positive correlation with sulfone and sulfoxide sulfur content, suggesting that these groups significantly influence the mechanical properties of anthracite and graphite. We have done comprehensive investigation of the interplay between coal rank, microcrystalline structure, and heteroatom functional groups on the nanomechanical properties of anthracite and graphite. These studies provide a novel perspective for the assessment of the mechanical properties of coal and coal-based graphite, while also offering important theoretical foundations for the efficient utilization and advanced processing technologies of coal resources.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"301 ","pages":"Article 104714"},"PeriodicalIF":5.6,"publicationDate":"2025-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143377574","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}

{"title":"Intelligent identification of coal macerals using improved semi-supervised semantic segmentation methods","authors":"Na Xu ,&nbsp;Qingfeng Wang ,&nbsp;Pengfei Li ,&nbsp;Jiapei Kong ,&nbsp;Qing Li ,&nbsp;Mark A. Engle ,&nbsp;James C. Hower ,&nbsp;Wei Zhu","doi":"10.1016/j.coal.2025.104712","DOIUrl":"10.1016/j.coal.2025.104712","url":null,"abstract":"<div><div>Recently, the demand for automatic coal maceral identification has gradually received much attention, and hence deep learning has been applied to the identification of coal macerals. However, a large number of labels are necessary for supervised learning, which imposes challenges for automatic coal maceral identification. In this study, the methods for identifying coal macerals were fully reviewed. Considering the limited data and the complexity of annotation, a semi-supervised semantic segmentation model combined with conditional random fields (CRF) algorithm was suggested for pixel-level identification of coal macerals. Initially, a new dataset of coal macerals was established. The dataset contains many different coal maceral images collected from the USA and China, as well as the corresponding labeled images. Then the model was trained through adversarial loss, and the prediction results were evaluated through pixel accuracy (PA) and intersection over union (IoU). The results are compared with other three existing unsupervised image segmentation methods. The semi-supervised model achieved, on average, PA and IoU of 84 % and 74 %, respectively. The results show that semi-supervised semantic segmentation can achieve high-precision identification of coal macerals. The CRF algorithm is then employed on the predictions of the model, and the accuracies for the three coal maceral groups achieved 81 %, 84 %, and 88 %, respectively. Finally, the application results of the model on the testing dataset are discussed to compare the differences between artificial intelligence and manual identification. This study demonstrates that semi-supervised semantic segmentation combined with CRF algorithm can be successfully applied to automatic coal maceral identification.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"300 ","pages":"Article 104712"},"PeriodicalIF":5.6,"publicationDate":"2025-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143238665","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}