International Journal of Coal Geology最新文献

{"title":"Enrichment mechanisms of Nb, Zr, and REY in the Late Permian coal-bearing strata in western Guizhou, SW China","authors":"Wei Deng ,&nbsp;Hanjie Wen ,&nbsp;Kunyue Ling ,&nbsp;Shengjiang Du ,&nbsp;Chongguang Luo ,&nbsp;Yang Yang","doi":"10.1016/j.coal.2024.104517","DOIUrl":"10.1016/j.coal.2024.104517","url":null,"abstract":"<div><p>Niobium, Zr, REE, and Y are widely enriched in the Upper Permian coal-bearing strata in southwestern China and are regarded as a substantial resource. To better understand the occurrence modes and enrichment mechanisms of these rare metals, comprehensive heavy-mineral separation, Micro-Raman spectroscopy, EPMA, and LA-ICP-MS analyses of primary and secondary metal minerals were conducted in the polymetallic beds in western Guizhou. In addition, the XRD, XRF, and ICP-MS analyses of bulk rocks were carried out. Our results suggest that Nb is primarily hosted in secondary TiO₂ polymorphs which converted from primary Nb-rich rutile, and occurs as minor ilmenorutile and columbite-(Fe). The Zr is sequestered in both detrital zircon and secondary microcrystalline zircon. REE and Y (REY) are mainly incorporated into secondary florencite-(Ce), rhabdophane-(Ce), churchite-(Y), and zircon, also partially adsorbed by clay minerals. The assemblage of detrital zircon, Nb-rich rutile, and discrete Nb minerals reveals that rare metals are preconcentrated during the waning-stage Emeishan alkaline magmatisms. Complex zonings in rutile crystals may result from the diffusion of Nb⁵⁺ and Fe²⁺, and these grains are further overprinted by magmatic-hydrothermal and enveloped by ilmenorutile and columbite-(Fe). Furthermore, magmatic rutile is commonly converted into anatase, brookite, and leucoxene under supergene conditions, and then persisted as stable phases. Authigenic REY-rich (Al)-phosphates and zircon are sourced from the leaching, even decomposition of primary REY-phosphates and zircons. Their colloidal aggregates are precipitated from the acidic and oxidizing low-temperature fluids, which are superposed onto clay matrix. The mineralogical and geochemical features suggest that the polymetallic beds are enriched by both alkaline magmatic-hydrothermal processes in source rocks and supergene fluid alterations in sediments. This study gives new insights into the enrichment processes and conditions, and further extraction of critical metals in the coeval coal-bearing strata in southwestern China.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"287 ","pages":"Article 104517"},"PeriodicalIF":5.6,"publicationDate":"2024-04-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140778758","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 characteristics and formation mechanism of organic-rich source rocks of mixed sedimentary strata in continental saline lacustrine basin: A case study of Permian Pingdiquan formation in the Shishugou Sag, Junggar Basin, Northwest China","authors":"Wenren Zeng ,&nbsp;Boran Wang ,&nbsp;Xuan Chen ,&nbsp;Guobin Fu ,&nbsp;Zhihuan Zhang ,&nbsp;Zhilong Huang","doi":"10.1016/j.coal.2024.104508","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104508","url":null,"abstract":"<div><p>The Permian Pingdiquan Formation (P₂p) in Shishugou Sag, Junggar Basin, Northwest China, is a typical example of mixed sedimentary strata formed in a saline lacustrine environment, characterized by complex lithological assemblages and extensive distribution of organic-rich source rocks. To further investigate the differences in oil-source contribution and hydrocarbon generation characteristics of source rocks with different lithologies, studying the difference of their geochemical characteristics and the formation mechanism of organic-rich source rocks is the top priority. Based on a comprehensive analysis of lithologic types, geochemical characteristics, and hydrocarbon generation potential of source rocks using organic petrology, molecular geochemistry and element geochemistry, this paper reveals the formation background and organic matter enrichment mechanism of the P₂p organic-rich source rocks. The results show that the mixed sedimentary rocks of the P₂p were deposited under relatively arid and saline lacustrine conditions. Paleoclimatic conditions tended to be more arid and hydrothermal activity became more frequent during the sedimentation process from mudstone, dolomitic mudstone to argillaceous dolomite. Consequently, the water column salinity elevated, leading to an increased proportion of salt-tolerant green algae and slight salt-tolerant cyanobacteria compared to salt-intolerant algae. Frequent changes in paleoclimate and hydrothermal activity control the interbedding deposition of mudstone, dolomitic mudstone and argillaceous dolomite, and the resulting salinity fluctuations contribute to variations in the proportion of salt-tolerant and intolerant algae in source rocks with different lithologies. Furthermore, the source rocks within the mixed sedimentary strata (mudstone, dolomitic mudstone and argillaceous dolomite) all exhibit substantial hydrocarbon generation potential, and there exists heterogeneity among source rocks of the same lithology. The key factor influencing the development of these organic-rich source rocks is the enhancement of palaeoproductivity driven by volcanic activity. Additionally, the water stratification caused by saline water promotes anoxic water columns, also contributing to organic matter enrichment in the source rocks.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"287 ","pages":"Article 104508"},"PeriodicalIF":5.6,"publicationDate":"2024-04-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140558101","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":"Petrology and organic geochemistry of the Middle Devonian cutinitic liptobioliths from Luquan region, Yunnan Province, China","authors":"Daofu Song ,&nbsp;Tieguan Wang ,&nbsp;Hao Wang ,&nbsp;Honghe Xu ,&nbsp;Zhengang Lu ,&nbsp;Yue Liu","doi":"10.1016/j.coal.2024.104507","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104507","url":null,"abstract":"<div><p>The majority of Middle Devonian coal samples from Wujing (WJ), Damo (DM), and Batang (BT) areas in the Luquan region of China have cutinite content exceeding 50%, classifying them as typical cutinitic liptobioliths. These coals are notable for their thinly-bedded texture, which allows them to split readily into leaf-like laminae. However, coals from these areas display distinct macroscopic, microscopic, and geochemical features. The split laminae from WJ and DM coals are black and ribbon-like, with those from WJ being notably longer and wider. In contrast, BT coal laminae are irregular, small fragments with golden or brown hues. Correspondingly, the cutinite in WJ coals is predominantly thick-walled, DM coals primarily contain a medium-walled type, and BT coals are characterized by a thin-walled type. Additionally, BT coals are rich in sporinite, with some classified as sporinite-rich durain or sporinitic liptobiolith. Abundant tetracyclic diterpenoids were detected in the maltene fraction of all the coal extracts. The concentration and composition of these diterpenoids are influenced by the content and type of cutinite present in the coals. The presence of tetracyclic diterpenoids, with beyerane, atisane and kaurane skeletons, had already evolved in early land plants. This implies that the precursors of these compounds were likely significant components of the cuticles of early land plants or, at least coexisted alongside plant cuticles. The spore assemblages in coals and the microscopic features of cutinite suggest that the coal-forming plants of the Luquan cutinitic liptobioliths were early land plants, predominantly herbaceous lycopsids, rhyniopsids, <em>Orestovia</em> and <em>Spongiophyton</em>. However, it is important to note that the specific types of these coal-forming plants may vary by areas. This variation leads to the distinctive macroscopic and microscopic characteristics observed in coals from different locations.</p><p>Cutinitic liptobiolith appears to have been exclusive to the Middle Devonian period, especially during the Givetian. The emergence of this distinct coal type is likely due to the unique structure of Devonian land plants. Specifically, the combination of well-developed cuticles and less developed woody tissues in these early land plants might have played a key role in the formation of cutinitic liptobioliths.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"286 ","pages":"Article 104507"},"PeriodicalIF":5.6,"publicationDate":"2024-03-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140342284","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":"Genesis and accumulation mechanism of external gas in deep coal seams of the Baijiahai Uplift, Junggar Basin, China","authors":"Bin Zhang ,&nbsp;Shu Tao ,&nbsp;Bin Sun ,&nbsp;Shuling Tang ,&nbsp;Shida Chen ,&nbsp;Yijie Wen ,&nbsp;Jincheng Ye","doi":"10.1016/j.coal.2024.104506","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104506","url":null,"abstract":"<div><p>Coal seams are typically self-sourced reservoirs. However, in certain special cases, the coal seams also contain large amounts of external gas from other source rocks. Successful development strategies in relation to Jurassic coalbed methane (CBM) in recent years have confirmed the presence of large amounts of external gas within the coal seams of the Baijiahai Uplift, Junggar Basin, China, which has important exploration and development prospects. However, the genesis and source of Jurassic CBM in the area remain unclear, limiting our understanding of its formation and accumulation as well as the planning of further development strategies. Based on a comprehensive analysis of the geochemical characteristics of Jurassic CBM, combined with research on the burial and thermal evolution history of the Jurassic coal seams, this study discusses the production curves of typical wells as well as regional tectonic styles, genesis, source, and accumulation of Jurassic CBM in the Baijiahai Uplift. Depending on the genesis, Jurassic CBM in the study area is divided mainly into coal-type (humic-type) gas, oil-type (sapropelic-type) gas, and mixtures of them, all of which are thermogenic gases of medium to high maturity. There are two main sources of Jurassic CBM in the Baijiahai Uplift. On the one hand, it comes from the vertical migration of gas generated by Permian and Carboniferous source rocks in the Baijiahai Uplift directly. On the other hand, it comes from the regional lateral migration from the Dongdaohaizi and Fukang Sags. Gas generated by source rocks in the Dongdaohaizi and Fukang Sags is driven by pressure, migrates towards the Baijiahai Uplift through sandstone channels, and accumulates in the Jurassic coal seams through faults. Compared with common self-sourced coal seams, enrichment of the coal seams with large amounts of external gases requires two necessary conditions: (1) Other layers of gas-generating source rocks are present at levels deeper than those of the coal seams, constituting additional gas sources for the coal seams, and (2) an open fault system is developed regionally, providing pathways for gas from other layers to enter the coal seams.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"286 ","pages":"Article 104506"},"PeriodicalIF":5.6,"publicationDate":"2024-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140330623","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":"Pyrolysis of macroalgae: Insight into product yields and biochar morphology and stability","authors":"H.I. Petersen ,&nbsp;H. Deskur ,&nbsp;A. Rudra ,&nbsp;S.B. Ørberg ,&nbsp;D. Krause-Jensen ,&nbsp;H. Sanei","doi":"10.1016/j.coal.2024.104498","DOIUrl":"https://doi.org/10.1016/j.coal.2024.104498","url":null,"abstract":"<div><p>Pyrolysis of biomass residues into biochar is seen as a feasible way to mitigate climate change by biological carbon storage (carbon dioxide removal, CDR) and to substitute fossil fuel with sustainable biofuel. This study applies a combination of flash and ramp heating pyrolysis, and organic petrography to investigate the hydrocarbon (biofuel) potential and biochar stability and morphotypes of eight brown, red, and green macroalgal species of different tissue complexity. The carbon stability of biochar derived from macroalgae has not previously been assessed using organic petrography (reflectance measurements) and evaluated in the context of the geological carbon cycle. The biochar, hydrocarbon, and CO + CO₂ yields vary due to different chemical composition of the macroalgal species, but the product yield variations are not related to the brown, red, or green macroalgal groups. The total biofuel yield shows an inverse trend with biochar yield. A slower heating rate produces more biochar and higher CO + CO₂ and lower biofuel yields than the combined flash pyrolysis and faster heating rate. The morphotype composition of the biochar was qualitatively examined by reflected light microscopy while carbon stability was assessed by random reflectance (R_o) measurements. The diverse morphotype compositions observed in biochar formed under similar pyrolysis conditions likely stem from variations in the original algal composition. While some biochar samples show morphologies resembling the original macroalgal structure, porous morphotypes predominantly characterize the biochar samples overall. Despite a maximum pyrolysis production temperature (PT) of 650 °C, the highest mean R_o value among all biochar samples is 2.91%, corresponding to a carbonization temperature (CT) of 526 °C. This observation is tentatively related to the less lignocellulosic structure of the macroalgae compared to terrigenous biomass. Four biochar samples have their entire R_o distribution range above the inertinite benchmark (IBR_o2%) of R_o = 2% indicating high carbon stability. Conversely, the remaining four biochar samples exhibit R_o distributions extending below IBR_o2%, indicating the presence of a carbon fraction with lower long-term stability in soil. The statistically significant inverse relationship observed between the mean R_o values and the peak hydrocarbon generation temperature (T_max) can be attributed to the behavior of residual macromolecules within the biochar. When these macromolecules reach peak biofuel generation at a lower temperature, they undergo carbonization over a more extended time interval during pyrolysis. Consequently, this prolonged exposure to the pyrolysis process leads to higher degrees of carbonization, as reflected by higher R_o values. In conclusion, the findings from pyrolysis and organic petrography reveal: (1) Macr","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"286 ","pages":"Article 104498"},"PeriodicalIF":5.6,"publicationDate":"2024-03-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000557/pdfft?md5=0d65373d62f36defcafced7d9787f013&pid=1-s2.0-S0166516224000557-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140321530","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":"High-cellulose content of in-situ Miocene fossil tree stumps and trunks from Lusatia lignite mining district, Federal Republic of Germany","authors":"J. Kus ,&nbsp;M. Dolezych ,&nbsp;W. Schneider ,&nbsp;J.C. Hower ,&nbsp;T. Hofmann ,&nbsp;E. Visiné Rajczi ,&nbsp;A. Bidló ,&nbsp;B. Bolodár-Varga ,&nbsp;R.F. Sachsenhofer ,&nbsp;A. Bechtel ,&nbsp;K. Stojanović ,&nbsp;D. Životić ,&nbsp;I. Kojić ,&nbsp;M. Mastalerz ,&nbsp;T. Graupner ,&nbsp;W.E. Lukens ,&nbsp;L. Donaldson","doi":"10.1016/j.coal.2024.104494","DOIUrl":"10.1016/j.coal.2024.104494","url":null,"abstract":"<div><p>Second Miocene Seam Complex (2nd MFK; <em>germ.:</em> 2. Miozäner Flözkomplex) holds many <em>in-situ,</em> not permineralised fossil tree stumps and trunks with high-cellulose contents. The state of preservation of a set of <em>in-situ</em> fossil trees (<em>Taxodioxylon cryptomerioides</em>, <em>Sciadopityoxylon wettsteinii</em>, and <em>Quasisequoioxylon piskowitzense</em>) collected from three open-cast mines (Welzow-Süd, Meuro, and Piskowitz) in Lusatia lignite mining district, Federal Republic of Germany was investigated using a multi-method research schema.</p><p>Examination of preservation state of thermally immature fossil woods revealed: (1) well-preserved (non-deformed, non-degraded, and non-flattened) textinite, (2) a retained structural integrity represented by multilayered (multi-zoned) cells with primary, secondary cell wall, and middle lamella, (3) microfracturing restricted to secondary walls only, (4) preservation of polyphenolic parenchyma cells (PP cells), (5) excellent preservation of pits in ray tracheids, (6) presence of amorphous silica (opal-A) coating, and (7) crystalline silica (opal-CT) fillings of small-bladed crystals.</p><p>Thermogravimetric analysis results showed dissimilar gelification status of fossil samples, supporting chlorite holocellulose assay results. The latter indicated anomalously high-cellulose values (15.6–37.6% holocellulose). The micro-FTIR data obtained revealed an excellent preservation of both hemicellulose (bands at 1740 and 1245 cm⁻¹) and cellulose (bands at 1110 and 1040 cm⁻¹). Micro-FTIR spectrometry indicated lack of preferential hydrolytic removal of polysaccharides in examined samples.</p><p>Biomarker patterns in lignite revealed forested and prevailing reed-mire vegetation. The results indicated lower contribution of Cupressaceae and emergent macrophyta to precursor organic matter of Welzow-Süd in comparison to Piskowitz lignite. Piskowitz lignite formed in permanent mire with stable water table under reducing, mesotrophic conditions. In contrast, more pronounced water level fluctuations (reducing to slightly oxic settings) and/or post-depositional events are postulated for Welzow-Süd samples.</p><p>Biomarker assemblages obtained from fossil wood show a distinct dominance of diterpenoids and δ¹³C values (−24.6 ‰ to −20.3 ‰) that clearly confirm gymnosperm sources. Distributions of diteprenoids and sesquiterpenoids, as well as fatty acids indicate the higher amount of saturated diterpenoids (pimarane, abietane) in fossil than in modern wood. This indicates reducing conditions promoting hydrogenation reactions. In addition to low Eh, preservation of cellulose in fossil wood was also favored by acidic conditions, very low degrees of aerobic fungal degradation, and protection of wood by Cupressaceae-derived resins.</p><p>While δ¹³C values of fossil wood are generally consistent with stratigraphic trends and chemotaxonomical classification, ","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"286 ","pages":"Article 104494"},"PeriodicalIF":5.6,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S016651622400051X/pdfft?md5=7962ebc6d65adfe24913c93fee7a4a1d&pid=1-s2.0-S016651622400051X-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140270566","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":"Origin and nature of pores in the Toolebuc Formation, a potential unconventional target in Australia","authors":"Xiaoxiao Mao ,&nbsp;Grant K.W. Dawson ,&nbsp;Victor Rudolph ,&nbsp;Sandra Rodrigues ,&nbsp;Suzanne D. Golding","doi":"10.1016/j.coal.2024.104497","DOIUrl":"10.1016/j.coal.2024.104497","url":null,"abstract":"<div><p>The Toolebuc Formation of Australia, a potential unconventional hydrocarbon resource, has limited studies on its pore structure and sorption characteristics. In this study, shale samples covering the lower mixed argillaceous mudstone (MAM) lithofacies, the middle interbedded calcareous mudstone and shelly thin beds (CM-STB) lithofacies, and the upper interbedded calcareous mudstone and shelly horizons (CM-SH) lithofacies of the Toolebuc Formation were collected. These samples were analysed for pore structure using a combination of scanning electron microscopy, X-ray diffraction, helium pycnometry, mercury intrusion porosimetry, and N₂ physisorption techniques. Additionally, methane sorption isotherms were measured under in-situ conditions. The results reveal that most pores are mineral-related intraparticle (intraP) and interparticle pores, with slit, equant and elongated shapes. Organic matter (OM) pores are rare. Porosity, total pore volume and BET specific surface area (SSA) are 3.25–8.26%, 1.32–3.55 cm³/100 g, and 1.26–9.65 m²/g, respectively. Pore volume is dominated by mesopores and macropores while specific surface area is dominated by fine mesopores and micropores. The porosity of the organic matter is significantly low due to the rarity of OM pores in the stage of early oil-window thermal maturity; organic matter consequently occludes pore space and also negatively impacts the average porosity. Clay by contrast is positively correlated to the average porosity. Carbonate provides intraP pores in fecal pellets, but also fills in other pore spaces as occlusion. Methane isotherms exhibit linear shapes, suggesting that a portion of the gas is stored in solution. The lower MAM lithofacies, characterised by rich clay, high porosity and BET SSA, was measured to have an in-situ methane sorption capacity of 4.32 cm³/g; the middle CM-STB lithofacies has intermediate porosity, but exhibits excellent gas generation potential and high in-situ methane sorption capacity (4.12–5.5 cm³/g). Within the CM-STB lithofacies, porosity declines with depth. The upper CM-SH lithofacies is carbonate-rich, exhibiting the lowest porosity and in-situ methane sorption capacity (2.56 cm³/g), but may act as an intraformational seal. The combination and vertical stacking pattern of the three lithofacies provided a favourable setting for gas storage.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"286 ","pages":"Article 104497"},"PeriodicalIF":5.6,"publicationDate":"2024-03-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000545/pdfft?md5=cf98cdb7f41de7d62bb00c9eb59b7312&pid=1-s2.0-S0166516224000545-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140272232","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":"From abandoned mines to carbon sinks: Assessing the CO2 storage capacity of Austrian low-rank coal deposits","authors":"Majid Safaei-Farouji ,&nbsp;David Misch ,&nbsp;Reinhard F. Sachsenhofer ,&nbsp;Max Rauscher ,&nbsp;Nikolaos Kostoglou","doi":"10.1016/j.coal.2024.104495","DOIUrl":"10.1016/j.coal.2024.104495","url":null,"abstract":"<div><p>This study represents the first assessment of CO₂ storage potential in Austrian coal seams. Coal samples were taken from Fohnsdorf and Leoben abandoned coal mines, with particular emphasis on the Fohnsdorf coal since Leoben coal reserves were largely mined during previous coal production. Several methods were used to compare coal characteristics, including Rock-Eval pyrolysis (RE), organic petrography, and low-pressure N₂ and CO₂ sorption measurements. Both Fohnsdorf and Leoben coal samples show low sulfur and ash yields, as well as correspondingly high total organic carbon (TOC) contents. The pyrolysis T_max and vitrinite reflectance values agree with a low coal rank for both sites. According to the N₂ adsorption measurements at 77 K, low-lying mire coals from Fohnsdorf show a higher BET-specific surface area (BET-SSA) and BJH pore volume compared to raised-mire coals from Leoben. However, sapropelic shales and high-ash coals from Leoben show the highest BET-SSA and BJH pore volumes of all investigated samples and considerably exceed the N₂ adsorption volumes of pure coals from both locations (N₂ uptake up to 16 cm³/g; avg. for all samples 5.4 cm³/g). In contrast, the mean adsorbed CO₂ uptake measured at 273 K and ∼ 1 bar followed the order of Fohnsdorf low-lying mire coals &gt; Leoben raised-mire coals &gt; Leoben sapropelic coals and shales, ranging at ∼0.8 mmol/g, ∼0.7 mmol/g, and ∼ 0.2 mmol/g, respectively. This shows that BET-SSA and BJH equations did not allow for adequate estimation of CO₂ adsorption capacity trends in the investigated sample set. Furthermore, based on the existence of a hysteresis loop between CO₂ adsorption and desorption branches for all investigated samples, the occurrence of weak chemisorption phenomena during CO₂ adsorption is indicated. This effect helps to increase CO₂ uptake and storage safety since the chemisorption process is not fully reversible upon pressure decrease. Ultimately, the theoretical CO₂ sequestration potential of the remaining unmined Fohnsdorf coal reserves was estimated at 4.65 million tons, with an additional potential for enhanced coal bed methane production due to the gas-rich nature of Fohnsdorf coals with an estimated 1.2 billion m³ of CH₄ in place.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"286 ","pages":"Article 104495"},"PeriodicalIF":5.6,"publicationDate":"2024-03-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000521/pdfft?md5=5c56313ec144f9edbe6b12d09c45dc7d&pid=1-s2.0-S0166516224000521-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140278981","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":"A complex case of thermal maturity assessment in a terrigenous sedimentary system: The Northwestern Black Sea basin","authors":"Hamed Sanei ,&nbsp;Oskar Hagelskjær ,&nbsp;Henrik I. Petersen ,&nbsp;Arka Rudra ,&nbsp;Søren B. Nielsen ,&nbsp;François Lorant ,&nbsp;François Gelin","doi":"10.1016/j.coal.2024.104496","DOIUrl":"10.1016/j.coal.2024.104496","url":null,"abstract":"<div><p>An integrated approach combining fluorescence spectrometry, pyrolysis geochemistry, and dispersed organic matter (DOM) maceral analysis has been used to determine the thermal maturity of Oligocene source rocks in two neighboring offshore wells within the complex deep-sea system of the Northwestern Black Sea. The samples contain predominantly immature Type II kerogen, including a mixture of marine liptinite (alginite, liptodetrinite), degraded liptinite, primary vitrinite, and reworked vitrinitic macerals. The occurrence of several vitrinite reflectance (VR_o) populations in the samples is attributed to a high influx of reworked vitrinite transported to the marine basin from multiple terrestrial sources with diverse degrees of degradation. The presence of multiple VR_o populations complicates the application of VR_o for determining the thermal maturity of the organic matter. Further, the VRo measurements on the primary vitrinite population show only a subtle increasing trend with depth. A significantly improved thermal maturity resolution was obtained using the red to green quotient (R/G). R/G was measured on the autochthonous unicellular <em>Tasmanites</em>-type alginite under UV-excitation. In contrast to VR_o the results show a significant correlation between increasing R/G values with increasing depth. This indicates that the R/G quotient is a better maturity proxy for the studied low maturity marine system with a large influx of sediments. The beginning of the downward declining trend in the temporal variation of liptinite is regarded as the onset of catagenesis. This occurs at a burial depth of 2.5 km and a R/G value of 0.50, corresponding to a VR_o equivalent (VR_{o Eq}) of 0.44%. At a burial depth of 3.2 km and a R/G value of 0.57 (VR_{o Eq} = 0.57%), the onset of the oil window is marked by an increase in the amount of solid bitumen (initial oil solid bitumen). The observed alterations in maceral composition with burial depth align with the thermal maturity of the wells. However, the data suggest that the thermal evolution of the organic matter is out of sync with the surrounding formation temperature, possibly due to rapid burial induced by a high sedimentation rate.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"286 ","pages":"Article 104496"},"PeriodicalIF":5.6,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S0166516224000533/pdfft?md5=c25dfaa5878aa022d98e07e9e6b20c57&pid=1-s2.0-S0166516224000533-main.pdf","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140205789","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":"Solid bitumen as an indicator of petroleum migration, thermal maturity, and contact metamorphism: A case study in the Barrandian Basin (Silurian - Devonian), Czech Republic","authors":"Václav Suchý ,&nbsp;Ivana Sýkorová ,&nbsp;Jiří Zachariáš ,&nbsp;Kateřina Pachnerová Brabcová ,&nbsp;Petr Dobeš ,&nbsp;Martina Havelcová ,&nbsp;Ivan Rozkošný ,&nbsp;Qingyong Luo ,&nbsp;Weixun Cao ,&nbsp;Jin Wu ,&nbsp;Petra Mácová ,&nbsp;Alberto Viani ,&nbsp;Ivo Svetlik ,&nbsp;Daniel Maxa","doi":"10.1016/j.coal.2024.104493","DOIUrl":"10.1016/j.coal.2024.104493","url":null,"abstract":"<div><p>Silurian and Devonian marine shales and limestones of the Barrandian Basin host abundant black solid, non-fluorescing bitumens that fill tectonic fractures and veins, and occlude fossil moulds and diagenetic concretions. Solid bitumen, interpreted as thermally degraded petroleum, entered the rocks during several successive episodes of fracture-bound petroleum migration that occurred during deeper burial of the strata. Regional distribution of bitumen reflectance values that range between ∼0.9–2.3% R_r, correlate with variations of its FT-IR and Raman spectroscopic characteristics and aromatic hydrocarbon composition, and collectively evidence the maturity trend increasing across the basin from the southwest to the northeast. The reflectance of chitinozoans and graptolites (∼0.8–1.9% R_r) in the country rocks and homogenization temperatures of hydrocarbon fluid inclusions document palaeotemperatures ranging between ∼90–150 °C, characteristic of the oil window zone grading into the gas/condensate zone. Although in a basin-wide perspective the averaged values of solid bitumen and zooclast optical reflectance converge and indicate the same northeastern-increasing regional diagenetic trend, solid bitumen reflectance values vary considerably at individual localities and even within some bitumen samples. The wide scatter of optical reflectance values and the heterogeneity of optical properties, which were attributed to the presence of multiple source rocks in the basin, the variable lithology of bitumen host rocks, or other variables, hamper the use of solid bitumen as a simple alternative to zooclast/vitrinite reflectance palaeothermometers in a given basin. On the other hand, the highly anisotropic domain and the mesophase “coking” textures of the solid bitumen that were recognized in the NE part of the basin provide unique evidence on an anomalous, hitherto unrecognized, geologically short-lasting thermal event that affected the Palaeozoic rocks. A line of indirect evidence suggests that the coking of the bitumen was caused by a cryptic intrusion, possibly a concealed branch of the Central Bohemian Pluton, which intruded into the strata during the Variscan orogeny. More rarely occurring semi-solid, vividly yellow fluorescing waxy bitumen, that postdates solid bitumen in some fractures and voids, does not reveal a regional thermal maturation trend. It precipitated from relict waxy oils that migrated through the strata during a post-Neogene uplift of the Barrandian region.</p></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"286 ","pages":"Article 104493"},"PeriodicalIF":5.6,"publicationDate":"2024-03-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"140205786","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}