International Journal of Coal Geology最新文献

{"title":"Geomechanical characterization and mineralogical correlation of compositionally diverse world-class Kazakhstani source rocks: Insights from nanoindentation testing","authors":"Riza Nurbekova ,&nbsp;Xiangyun Shi ,&nbsp;Randy Hazlett ,&nbsp;David Misch ,&nbsp;Milovan Fustic ,&nbsp;Reinhard F. Sachsenhofer","doi":"10.1016/j.coal.2024.104545","DOIUrl":"10.1016/j.coal.2024.104545","url":null,"abstract":"<div><p>Extensive nanoindentation testing over a range of deflection depths of up to 4 μm yielded a large dataset, providing a viable framework for the statistical assessment of the mechanical properties, specifically elastic modulus (<em>E</em>) and hardness (<em>H</em>), of compositionally diverse organic-rich mudstone samples. The data from indentations as shallow as 300–400 nm were clustered using the <em>k</em>-means algorithm to identify three mechanical categories in the samples: a soft pseudophase (e.g., organic matter, gypsum, and clay minerals), a stiff pseudophase (e.g., quartz and feldspar), and a transitional composite-like pseudophase bridging the soft and hard minerals. The initially diverse values of <em>E</em> and <em>H</em> for the mechanical pseudophases were observed to converge to a constant value at indentations beyond 2–2.5 μm (varying between different samples), implying the existence of a minimal probing depth for assessing the bulk <em>E</em> and <em>H</em> of heterogeneous mudstone samples. The obtained bulk <em>E</em> and <em>H</em> values (8–21 GPa and 0.3–0.9 GPa, respectively) demonstrated a strong correlation with the mineralogical composition of the indented samples. Despite containing a notable proportion of mechanically stiff components (&gt;45 vol%), the bulk mechanical parameters determined in this study were significantly lower than those reported for major shale formations such as the Barnett and Longmaxi Shale. This discrepancy is primarily due to the presence of organic matter with low thermal maturity (R_o &lt; 0.6%), which constitutes &lt;36 vol% of the samples, and a significant gypsum content, accounting for &lt;15 vol%.</p><p>The employed approach not only demonstrated the importance of choosing the proper indentation depths for investigating the mechanical properties of highly heterogeneous mudstone rocks and their constituent minerals, but it also illustrated the capability of examining various volumes of investigation using nanoindentation, approaching macroscopic values, and identifying a representative element volume (REV). The findings also provided crucial insights into the fracability and overall producibility of the investigated formations, thereby enhancing our understanding of their extraction potential.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"289 ","pages":"Article 104545"},"PeriodicalIF":5.6,"publicationDate":"2024-06-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141277094","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":"Geochemical tracers associated with methane in aquifers overlying a coal seam gas reservoir","authors":"J.K. Pearce ,&nbsp;H. Hofmann ,&nbsp;K. Baublys ,&nbsp;D.I. Cendón ,&nbsp;S.D. Golding ,&nbsp;S.J. Herbert ,&nbsp;Z. Bhebhe ,&nbsp;A. Nguyen ,&nbsp;P. Hayes","doi":"10.1016/j.coal.2024.104535","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104535","url":null,"abstract":"<div><p>Understanding inter-aquifer connectivity or leakage of greenhouse gases and groundwater to aquifers overlying gas reservoirs is important for environmental protection and social licence to operate. Australia's Great Artesian Basin (GAB) is the largest artesian groundwater system in the world with groundwater extracted for agriculture, livestock, mines, energy, private or town water supply. Microbial coal seam gas (CSG) and production water are also extracted from the GAB. Here a range of groundwater tracers is used to investigate the potential for gas and groundwater connectivity between the CSG reservoir and aquifers.</p><p>The GAB aquifer and alluvium contained a range of methane concentrations (0.001 to 2100 mg/L) that exhibit an increase with depth and δ¹³C-CH₄. Aquifer and alluvium groundwater ⁸⁷Sr/⁸⁶Sr were in the range 0.7042 to 0.7082. CSG production waters however had non-radiogenic, distinctive ⁸⁷Sr/⁸⁶Sr signatures &lt;0.7036, indicating a lack of significant groundwater leakage. One gassy aquifer bore with 160 mg/L methane conversely has ⁸⁷Sr/⁸⁶Sr, δ¹³C-CH₄, δ²H-CH₄ and δ¹³C-DIC values overlapping the CSG waters. In several aquifers δ³⁴S-SO₄ and δ¹⁸O-SO₄ are sourced from windblown surface salts of inland Australian playa lakes in recharge waters. Bacterial sulphate reduction is additionally occurring in a regional aquifer. Cosmogenic isotopes and tritium show recent recharge and mixing with older groundwaters in several shallow aquifers.</p><p>Groundwater and gas signatures indicate that leakage of groundwater and methane from the CSG reservoir was not occurring in the majority of areas investigated here. Methane was consistent with in situ generation in shallow GAB aquifers by primary microbial CO₂ reduction or acetate fermentation. Connectivity of one alluvial bore and the underlying GAB aquifer could not be completely ruled out. Separately, one gassy Springbok GAB aquifer bore is either connected to the underlying CSG gas reservoir, or has in situ secondary microbial CO₂ reduction producing methane from interbedded coal within the aquifer. This study is relevant to other basins in Australia and internationally where gas is observed in aquifers that overly conventional, unconventional or coal seam gas reservoirs.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"289 ","pages":"Article 104535"},"PeriodicalIF":5.6,"publicationDate":"2024-05-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000922/pdfft?md5=79a21be44647689570498e729acffea5&pid=1-s2.0-S0166516224000922-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141290912","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Palynostratigraphy of the Mississippian-Pennsylvanian boundary in the Tyler Formation, Williston Basin, USA: Implications for organic matter-rich source rocks and paleoenvironmental reconstruction","authors":"Ahmed Mansour ,&nbsp;Thomas Gentzis ,&nbsp;Timothy O. Nesheim ,&nbsp;Jian Wang ,&nbsp;Xiugen Fu ,&nbsp;Mohamed S. Ahmed ,&nbsp;Humberto Carvajal-Ortiz","doi":"10.1016/j.coal.2024.104533","DOIUrl":"10.1016/j.coal.2024.104533","url":null,"abstract":"<div><p>The Carboniferous was a period of intense environmental perturbations, climate changes between greenhouse and icehouse, eustatic sea level change, and accumulation of organic carbon-rich sediments. At this time, the Tyler Formation was deposited in the midcontinent USA. A detailed palynological analysis of the Tyler Formation revealed a highly diverse assemblage of spores with minor pollen content, represented by 100 species belonging to 51 genera. Stratigraphically constrained spores and pollen grains were used to construct three interval zones of middle-late Chesterian (late Viséan-Serpukhovian) to early Morrowan (middle Bashkirian) ages. The stratigraphic position of the Mississippian-Pennsylvanian boundary was determined in the lower Tyler Formation based on the last appearance of typical forms of the late Chesterian, including <em>Tripartites vetustus</em>, <em>Knoxisporites triradiatus</em>, <em>Knoxisporites stephanephorus</em>, <em>Densosporites diatretus</em>, and <em>Schopfipollenites acadiensis</em>, compared to the first appearance of early Morrowan <em>Crassispora kosankei</em>, <em>Cirratriradites saturnii</em>, <em>Radiizonates aligerens</em>, and <em>Raistrickia saetosa</em>. Palynofacies analysis and statistical clustering of the Tyler Formation showed three palynofacies assemblages. PFA-1 showed moderate relative abundances of phytoclasts and AOM, suggesting deposition close to fluvio-deltaic and shallow marine environments, while PFA-2 exhibited high abundances of phytoclasts, mostly of opaque wood, reflecting deposition in active river-dominated delta plains. PFA-3 showed the highest abundances of AOM, suggesting deposition in a shallow marine environment. Organic petrography and geochemistry data indicate that the Tyler Formation is one of the best source rock intervals throughout the midcontinent USA. Based on organic matter richness, the Tyler Formation is subdivided into three groups. The first group has TOC contents higher than 10 wt% of kerogen Types III, mixed II/III, and II with excellent hydrocarbon generation potential. The second group has TOC content in the range of 2–10 wt% of kerogen Types III, mixed II/III, and II, and fair to excellent hydrocarbon generation potential. The third group shows organic matter richness with TOC content below 2 wt% with good organic matter richness and kerogen Types III to IV, and poor to fair hydrocarbon generation potential. The organic matter thermal maturity is evaluated based on T_max and VRo% values, suggesting that all samples of Tyler Formation are in the early to late stages of the oil window. However, care should be considered when assessing a mature source rock because the kerogen typing and generation is based on present-day TOC, S₂, and HI rather than their original values.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"288 ","pages":"Article 104533"},"PeriodicalIF":5.6,"publicationDate":"2024-05-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141187741","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 petrology, palynology, and geochemistry of soils from serpentine barrens, Chester and Lancaster counties, Pennsylvania: Notes on maceral development","authors":"James C. Hower ,&nbsp;Jennifer M.K. O'Keefe ,&nbsp;Roger Earl Latham ,&nbsp;Shifeng Dai ,&nbsp;Luis F.O. Silva ,&nbsp;Kevin R. Henke ,&nbsp;Jon S. Thorson","doi":"10.1016/j.coal.2024.104532","DOIUrl":"10.1016/j.coal.2024.104532","url":null,"abstract":"<div><p>An investigation of the soils developed on ultramafic rocks in the State Line Serpentinite Belt in southeastern Pennsylvania demonstrated that the mineral assemblages are dominated by quartz, with lesser amounts of the serpentine group minerals lizardite and antigorite, and clinochlore, among other minerals. The samples have up to 39.91% MgO, 22,500 μg/g Cr, and 3300 μg/g Ni (ash basis). The light rare earth elements have a significant correlation to MgO/(MgO + SiO₂) while the distribution of Cr is random. The organic matter in the soil bears a strong similarity to lignite and subbituminous macerals. Wood-derived macerals showed variations from relatively pristine wood to degraded and attrital forms with evidence of fungal and faunal activity. Macrinite ranged from coprolitic forms to amorphous masses with little or no recognizable structure. The pollen assemblages were dominated by <em>Pinus</em> sp., <em>Quercus</em> sp., and <em>Ribes</em> sp. Analysis of the fungal assemblages and guild structures suggests that the Goat Hill Barrens assemblage differed from the New Texas Barrens and Nottingham Barrens assemblages and that the guild structures encountered are both similar to those encountered in peatlands while also very different, especially in the proportion of arbuscular mycorrhizal fungal remains.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"289 ","pages":"Article 104532"},"PeriodicalIF":5.6,"publicationDate":"2024-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141187738","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":"Raman Spectroscopy for the characterization of the macromolecular structure of Highveld coals (South Africa)","authors":"Itumeleng V. Matlala ,&nbsp;Ofentse M. Moroeng ,&nbsp;Stavros Kalaitzidis ,&nbsp;Nicola J. Wagner","doi":"10.1016/j.coal.2024.104531","DOIUrl":"10.1016/j.coal.2024.104531","url":null,"abstract":"<div><p>Industrial applications of coal rely on understanding its macromolecular structure, which is primarily controlled by coal type and rank. The present study assessed five (5) samples from different collieries extracting coal from the No. 4 Seam of the Highveld Coalfield and their float products, produced at relative densities (RD) of 1.7 and 1.9 g/cm³. The aim was to assess changes in maceral composition and coal quality following the density fractionation, and to use Raman Spectroscopy to compare differences in macromolecular structures between the parent samples and the float products. Raman parameters were also determined for specific macerals, i.e., semifusinite and collotelinite. Mean random vitrinite reflectance (%RoV) values for the studied coals range between 0.57 and 0.60% (medium rank D/C bituminous) and the parent coals are inertinite-rich (70.3 to 88.7 vol% mmf), enriched in semifusinite and inertodetrinite. Following density fractionation, reactive macerals (a combination of liptinite, vitrinite, and reactive semifusinite) are enriched in the float products (designated by “F”), specifically in the products obtained at the 1.7 RD. In comparison, the proportion of inert macerals is higher in the F1.9 samples. These differences in maceral composition are reflected in the Raman spectra and parameters. Although the G and D1 bands for the parent coals and F1.9 samples are similar, these bands are narrower than for the F1.7 samples, indicative of greater aromaticity. The G FWHM values for the F1.9 samples are comparable to those for the parent coal samples, and lower than for the F1.7 samples. This reflects larger differences in maceral composition between the parent coals and the F1.7 samples. In contrast, the D1 FWHM values for the float products, particularly the F1.7 samples, are slightly higher than the parent coals, reflecting a disordered aromatic character mainly related to the presence of aliphatic chains. The Raman spectra for the F1.7 samples are more like that for collotelinite. In contrast, the Raman spectra and parameters (G and D1 FWHM) for the F1.9 samples are more comparable to semifusinite. Thus, the increased aliphaticity for the F1.7 samples is attributed to the relative enrichment of reactive macerals, whereas higher aromaticity for the F1.9 samples reflects a larger proportion of inert macerals<strong>.</strong> Raman spectroscopy expanded on the petrographic data by interrogating the macromolecular structure of the isorank Highveld coals and their float products. This may assist in predicting the behaviour of the coals during industrial applications (i.e., liquefaction, gasification, combustion, and carbon fibre production).</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"288 ","pages":"Article 104531"},"PeriodicalIF":5.6,"publicationDate":"2024-05-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000880/pdfft?md5=0f0d6ad7ecf7e2e6f30b2aeac9a5c94d&pid=1-s2.0-S0166516224000880-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141134850","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ranking the oil contribution of individual layers in a lacustrine shale oil system based on non-hydrocarbon analysis by FT-ICR MS","authors":"Ming Yuan ,&nbsp;Caineng Zou ,&nbsp;Songqi Pan ,&nbsp;Guosheng Zhang ,&nbsp;Quan Shi ,&nbsp;Lingyuan Xie ,&nbsp;Zhengfu Zhao ,&nbsp;Yating Shen ,&nbsp;Zhenhua Jing","doi":"10.1016/j.coal.2024.104528","DOIUrl":"10.1016/j.coal.2024.104528","url":null,"abstract":"<div><p>Identifying the dominating oil-producing layer(s) within a shaly system, typically characterized by multiple layers with similar properties, is always a critical yet formidable task, as the oil component disparities among these closely adjacent layers are too minor to be resolved by the traditional geochemical fingerprints. This challenge is now likely addressed by high-resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR MS), which can resolve thousands of non-hydrocarbons that could serve as new fingerprints. Taking a typical shaly system in the Ordos Basin in China as an example, the specific proportions of non-hydrocarbon compounds from the retained petroleum of different source rock layers (rock extracts) and the produced oil at the wellhead were identified by FT-ICR MS. Their compositional similarity was calculated using a multidimensional scaling (MDS) method, and the layers hosting the retained petroleum with higher compositional similarity to the produced oils are considered to be the main contributors to oil production. The results show that the main producing layers identified by FT-ICR MS differ from those proposed based on traditional fingerprints like the Rock-Eval parameters. A typical example is that the thick low-TOC shales, conventionally proposed to be unessential to oil production, seem to have a similar contribution, if not higher, to their thick silty counterparts. This divergence may be attributed to the fact that the conventional fingerprints primarily rely on the rock extracts from a vertical well section, which may only represent a limited lateral area, while the non-hydrocarbon similarity approach involving the produced oil appears to be more realistic, as it can consider the engineering processes, like the horizontal well track and the hydraulic fracturing effects. The current approach provides a novel route for identifying the dominating producing layer(s) in a shale oil system, which may have extensive potential for optimizing the production strategy of shale oil wells.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"288 ","pages":"Article 104528"},"PeriodicalIF":5.6,"publicationDate":"2024-05-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141033487","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":"Corrigendum to “From abandoned mines to carbon sinks: Assessing the CO2 storage capacity of Austrian low-rank coal deposits” [International Journal of Coal Geology 286 (2024) 1–13/104495]","authors":"Majid Safaei-Farouji ,&nbsp;David Misch ,&nbsp;Reinhard F. Sachsenhofer ,&nbsp;Max Rauscher ,&nbsp;Nikolaos Kostoglou","doi":"10.1016/j.coal.2024.104520","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104520","url":null,"abstract":"","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"287 ","pages":"Article 104520"},"PeriodicalIF":5.6,"publicationDate":"2024-05-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000776/pdfft?md5=5cb227760ddf2b50eacf2fc4ff0ec435&pid=1-s2.0-S0166516224000776-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140825708","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Structure and morphology of chars and activated carbons obtained from thermal treatment of coal and biomass origin materials, including their wastes: Results from the ICCP Microscopy of Carbon Materials Working Group","authors":"G. Predeanu ,&nbsp;M. Wojtaszek-Kalaitzidi ,&nbsp;I. Suárez Ruiz ,&nbsp;M.N Bălănescu ,&nbsp;A. Gómez Borrego ,&nbsp;M.D. Ghiran ,&nbsp;P.C. Hackley ,&nbsp;S. Kalaitzidis ,&nbsp;J. Kus ,&nbsp;M. Mastalerz ,&nbsp;M. Misz-Kennan ,&nbsp;S. Pusz ,&nbsp;S. Rodrigues ,&nbsp;G. Siavalas ,&nbsp;A. Varma ,&nbsp;A. Zdravkov ,&nbsp;D. Životić","doi":"10.1016/j.coal.2024.104519","DOIUrl":"10.1016/j.coal.2024.104519","url":null,"abstract":"<div><p>This paper describes the evaluation of petrographic textures in char and activated carbon derived from coal, coal by-products and biomass, formed during carbonization and activation processes. This work represents the results of interlaboratory exercises from 2016 to 2022 of the Microscopy of Carbon Materials Working Group in Commission III of the International Committee for Coal and Organic Petrology. The interlaboratory exercises were run on photomicrograph samples. For textural characterization of carbon materials, the existing American Society for Testing and Materials (ASTM) classification system for metallurgical coke was applied. Morphological differences were evaluated in 29 carbon material types, including 22 char samples, and 7 activated carbon (AC) samples obtained experimentally using conventional direct/indirect and microwave heating technologies. This approach gives an extended view on the identification of microporous carbons, and how a certain heat treatment develops a certain optical texture and structure in a raw material. The requested evaluation of carbon materials was related to their porosity, origin, extent, and characteristics, which are particular to each carbon material type. Because carbon matrices can form a wide range of optical textures during heat treatment it is important to demonstrate which carbon occurrences will have a crucial role in industrial applications dominated by adsorption phenomena.</p><p>The interlaboratory exercises included 17 participants from 14 laboratories. Four sets of digital black and white and colour photomicrographs were distributed, which in total comprised 184 fields of different types of carbon material. The results were evaluated based on four levels: (i) optical texture (isotropic/anisotropic), (ii) optical type and size (punctiform, mosaic, fiber, ribbon, domain), iii) morphology (porous, non-porous/massive), and (iv) particle origin (precursor type).</p><p>The statistical method applied to evaluate the results was based on “raw agreement indices”. Comparative analyses of the average values of the level of overall agreement showed homogeneity in the results, the mean value was 89%, with a minimum value of 87% and a maximum value of 91% for those who participated in at least three out of four exercises.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"288 ","pages":"Article 104519"},"PeriodicalIF":5.6,"publicationDate":"2024-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141058217","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":"Methane diffusion in coal matrix considering heterogeneity of micromechanical properties by nanoindentation","authors":"Yidong Cai ,&nbsp;Ding Jia ,&nbsp;Dameng Liu ,&nbsp;Ranjith Pathegama Gamage ,&nbsp;Qian Li ,&nbsp;Yingfang Zhou ,&nbsp;Zhentao Li","doi":"10.1016/j.coal.2024.104518","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104518","url":null,"abstract":"<div><p>The coal matrix exhibits significant heterogeneity at the micro-scale. In this study, a heterogeneous mechanical model of coal matrix from different coal ranks was constructed by using nanoindentation. Additionally, a fluid-solid coupling model was developed to consider matrix shrinkage and stress sensitivity, enabling the incorporation of porosity changes during methane diffusion. The methane concentration and matrix deformation characteristics in the simulation area at different times was obtained. The effects of matrix shrinkage and stress sensitivity on porosity changes and matrix deformation were compared. And the deformation of the matrix under different micromechanical properties was compared. The findings indicate that the nanoindentation method effectively characterizes the micromechanical heterogeneity of coal matrices. Furthermore, during the diffusion process, we observed an initial increase followed by a decrease in matrix deformation, with matrix shrinkage leading to more pronounced deformation. Notably, harder coal matrices exhibited reduced deformation. This study enhances the understanding of the dynamic changes in the matrix during coalbed methane extraction.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"287 ","pages":"Article 104518"},"PeriodicalIF":5.6,"publicationDate":"2024-04-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140822814","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":"Depositional setting and sequence stratigraphy of Upper Mississippian coal-bearing paralic cyclothems in Upper Silesian foreland","authors":"S. Opluštil ,&nbsp;J. Laurin ,&nbsp;J. Jureczka ,&nbsp;W. Nadłonek ,&nbsp;B. Naglik ,&nbsp;J. Horák ,&nbsp;A. Kędzior ,&nbsp;R. Lojka ,&nbsp;R. Nádaskay ,&nbsp;M. Sivek","doi":"10.1016/j.coal.2024.104516","DOIUrl":"10.1016/j.coal.2024.104516","url":null,"abstract":"<div><p>The upper Serpukhovian Poruba Member (c. 325–324 Ma) is a coal-bearing “paralic” succession deposited in the Upper Silesian Coal Basin located along the eastern foreland of the Moravo-Silesian segment of the Variscan fold and thrust belt. The basin formed an &gt;150 km long, tectonically controlled embayment open to the north and northeast, with estuarine circulation, predominance of fluvial discharge and a limited tidal influence. A high-accommodation depocentre (possibly up to 1100 m/Myr) was filled by shallowing-upward successions related to the progradation of river dominated (bay-head) deltas, with subordinate fluvial and marine sediments. These strata form two orders of transgressive-regressive cycles, or genetic sequences, both overlapping with the Milankovitch band. Intervals of maximum transgression, marked by marine or brackish faunal horizons, immediately overlie coal beds, suggesting non-accretionary transgression in a low energy setting. Six medium-term genetic sequences (cyclothems) are recognized, each consisting of 4 to 6 elementary sequences and a number of smaller scale units of possible autocyclic origin. The medium-term sequences are attributed to a combined influence of relative sea-level change and changes in sediment input, both possibly as a far field response to Gondwanan glaciation through glacioeustasy and attendant changes in climatic seasonality.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"287 ","pages":"Article 104516"},"PeriodicalIF":5.6,"publicationDate":"2024-04-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140756311","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}