International Journal of Coal Geology最新文献

Elastic anisotropy and deformation characteristics of Pennsylvania anthracite

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-03-06 DOI: 10.1016/j.coal.2025.104740

Bodhisatwa Hazra , Hem Bahadur Motra , James C. Hower , Maria Mastalerz , Chinmay Sethi , Harold Schobert

The mechanical behavior and elastic anisotropy of coal under stress are critical to understanding its structural integrity and performance in subsurface environments. Despite its significance, limited research has systematically analysed the elastic anisotropic responses of coals under such conditions. This study investigates the elastic anisotropy of three anthracite-rank coals, Primrose, Lattimer, and Mt. Carmel, subjected to conventional triaxial loading. P-wave (V_P) and S-wave (V_S) velocities, along with Thomsen parameters (ε and γ), were evaluated to elucidate the effects of increasing vertical stress on the structural integrity and anisotropy of each coal type. The results reveal that the Primrose coal exhibits the highest structural integrity, maintaining elevated V_P and V_S values and stable Thomsen parameters under stress due to its dense microstructure, higher inertinite content, and low porosity, which resist stress-induced microcracking. In contrast, the Lattimer coal demonstrates a significant reduction in VP and ε beyond 45 MPa, indicating greater susceptibility to microstructural damage and a trend towards isotropy as stress increases. The Mt. Carmel coal shows intermediate behavior, with moderate decreases in VP and ε but relatively stable γ values, reflecting a balanced resistance to structural degradation. S-wave anisotropy, as evidenced by shear wave splitting, remains most prominent in the Primrose coal, suggesting its superior ability to retain directional properties and resist stress-induced deformation. Principal component analysis highlights the role of rank, inertinite-to-vitrinite ratio, and aromaticity in influencing the mechanical responses of the coals, with Primrose coal consistently segregating as the most robust and anisotropically stable sample. These findings underscore the critical influence of compositional and microstructural differences on coal's anisotropic behavior under conventional-triaxial loading. They provide valuable insights for applications in subsurface energy extraction and storage, where understanding the mechanical and anisotropic properties of coal is essential for optimizing performance and mitigating risks.

{"title":"Elastic anisotropy and deformation characteristics of Pennsylvania anthracite","authors":"Bodhisatwa Hazra , Hem Bahadur Motra , James C. Hower , Maria Mastalerz , Chinmay Sethi , Harold Schobert","doi":"10.1016/j.coal.2025.104740","DOIUrl":"10.1016/j.coal.2025.104740","url":null,"abstract":"<div><div>The mechanical behavior and elastic anisotropy of coal under stress are critical to understanding its structural integrity and performance in subsurface environments. Despite its significance, limited research has systematically analysed the elastic anisotropic responses of coals under such conditions. This study investigates the elastic anisotropy of three anthracite-rank coals, Primrose, Lattimer, and Mt. Carmel, subjected to conventional triaxial loading. P-wave (V<sub>P</sub>) and S-wave (V<sub>S</sub>) velocities, along with Thomsen parameters (ε and γ), were evaluated to elucidate the effects of increasing vertical stress on the structural integrity and anisotropy of each coal type. The results reveal that the Primrose coal exhibits the highest structural integrity, maintaining elevated V<sub>P</sub> and V<sub>S</sub> values and stable Thomsen parameters under stress due to its dense microstructure, higher inertinite content, and low porosity, which resist stress-induced microcracking. In contrast, the Lattimer coal demonstrates a significant reduction in VP and ε beyond 45 MPa, indicating greater susceptibility to microstructural damage and a trend towards isotropy as stress increases. The Mt. Carmel coal shows intermediate behavior, with moderate decreases in VP and ε but relatively stable γ values, reflecting a balanced resistance to structural degradation. S-wave anisotropy, as evidenced by shear wave splitting, remains most prominent in the Primrose coal, suggesting its superior ability to retain directional properties and resist stress-induced deformation. Principal component analysis highlights the role of rank, inertinite-to-vitrinite ratio, and aromaticity in influencing the mechanical responses of the coals, with Primrose coal consistently segregating as the most robust and anisotropically stable sample. These findings underscore the critical influence of compositional and microstructural differences on coal's anisotropic behavior under conventional-triaxial loading. They provide valuable insights for applications in subsurface energy extraction and storage, where understanding the mechanical and anisotropic properties of coal is essential for optimizing performance and mitigating risks.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"303 ","pages":"Article 104740"},"PeriodicalIF":5.6,"publicationDate":"2025-03-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143609970","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Origin of chemical structure and pore heterogeneity of over-matured organic matter in the Paleozoic marine shales, China

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-03-05 DOI: 10.1016/j.coal.2025.104742

Yingzhu Wang , Jijin Yang

Organic matter (OM) pores play a leading role in gas storage for many shale formations, and understanding their development mechanism is critical to evaluating the mechanisms of shale gas enrichment. However, an insufficient knowledge of OM compositional and structural complexity makes the origin of pore heterogeneity still unclear. This study correlates high-resolution scanning electron microscopy (SEM) and Raman microscopy to investigate the association of OM molecular structure and pore development in the Cambrian Niutitang shales and Silurian Longmaxi shales, south China. Results show that pyrobitumen, the predominant OM maceral, can be divided into two types (PB1 and PB2) which have differences in petrographic characteristics, Raman parameters, and pore distribution. In the shales with good gas preservation, the pore-filling PB2 shows a lower degree of aromaticity, a higher apparent transformation ratio (15 %–40 %), and larger pore size (peak of 80–90 nm) than that of the less porous PB1. In the poorly-preserved shales, different pyrobitumen exhibit homogeneous molecular structure and smaller pore size (peak of 30–40 nm). The poor development of OM-hosted pores in the Niutitang shale is related to the increased OM graphitization at a Ro > 3.5 %. The heterogeneity of OM structure and porosity in different Longmaxi shales would be originally impacted by a distinction in the degree of oil expulsion under different preservation condition. In the well-preserved shales, a higher retention of aliphatic-rich oil may lead to the more porous and less aromatic pyrobitumen, and thus a higher current gas content. The study provides new insights into the OM chemical controls on nanoscale pore heterogeneity, which is significant for shale gas exploration.

{"title":"Origin of chemical structure and pore heterogeneity of over-matured organic matter in the Paleozoic marine shales, China","authors":"Yingzhu Wang , Jijin Yang","doi":"10.1016/j.coal.2025.104742","DOIUrl":"10.1016/j.coal.2025.104742","url":null,"abstract":"<div><div>Organic matter (OM) pores play a leading role in gas storage for many shale formations, and understanding their development mechanism is critical to evaluating the mechanisms of shale gas enrichment. However, an insufficient knowledge of OM compositional and structural complexity makes the origin of pore heterogeneity still unclear. This study correlates high-resolution scanning electron microscopy (SEM) and Raman microscopy to investigate the association of OM molecular structure and pore development in the Cambrian Niutitang shales and Silurian Longmaxi shales, south China. Results show that pyrobitumen, the predominant OM maceral, can be divided into two types (PB1 and PB2) which have differences in petrographic characteristics, Raman parameters, and pore distribution. In the shales with good gas preservation, the pore-filling PB2 shows a lower degree of aromaticity, a higher apparent transformation ratio (15 %–40 %), and larger pore size (peak of 80–90 nm) than that of the less porous PB1. In the poorly-preserved shales, different pyrobitumen exhibit homogeneous molecular structure and smaller pore size (peak of 30–40 nm). The poor development of OM-hosted pores in the Niutitang shale is related to the increased OM graphitization at a Ro > 3.5 %. The heterogeneity of OM structure and porosity in different Longmaxi shales would be originally impacted by a distinction in the degree of oil expulsion under different preservation condition. In the well-preserved shales, a higher retention of aliphatic-rich oil may lead to the more porous and less aromatic pyrobitumen, and thus a higher current gas content. The study provides new insights into the OM chemical controls on nanoscale pore heterogeneity, which is significant for shale gas exploration.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"303 ","pages":"Article 104742"},"PeriodicalIF":5.6,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143576864","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Restoring the original hydrocarbon-generating potential of deep source rocks: A critical review and a novel method using the Songliao Basin, China, as a case study

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-03-05 DOI: 10.1016/j.coal.2025.104741

Daming Niu , Tianyi Li , Yueyue Bai , Pingchang Sun , Hongliang Dang , Yilin Li , Lianxin Tao , Xingxuan Lei , Sicheng Li , Lixiang Gui , Chunlong Liu

Deep source rocks are typically in a high-to-overmature stage, characterized by lower than original values of total organic carbon. Thus, resource evaluation is significantly influenced by the accuracy of the measured data and the restoration methods of original (pre-thermal maturation) values. Therefore, reliable data for assessing petroleum and natural gas resources generated during the burial process are urgently needed. This study first critically reviews commonly used methods for restoring the original TOC (TOC_o) and hydrocarbon-generating potential (HGP). The principles, advantages, and disadvantages of each method are discussed, and a novel workflow for evaluating the resource is proposed. The workflow involves four steps: (1) selecting a fit for-the-purpose method for original TOC and HGP restoration; (2) establishing original restoration coefficients by weighted TOC and HGP restoration formulas; (3) assessing the remaining resource potential through hydrocarbon generation and expulsion; and (4) validating the assessment results. Using the Permian source rocks in the Songliao Basin as an example, this workflow restores the total remaining resource amount (65.3 × 10⁹ t). Predicted results indicate that high-value areas with remaining resource potential are near the Heyupao Sag (57.7 × 10⁸ t), Chaoyanggou Terrace (73.5 × 10⁸ t), and Binxian-Wangfu Sag (39.0 × 10⁸ t). The advantages of this workflow include: (1) overcoming the limitations of the original TOC and HGP restoration method by selecting the most suitable restoration model; (2) directly identifying the original TOC spatial distribution using recovery coefficient, which overcomes the heterogeneity in the spatial distribution of organic matter types; and (3) accurately verifying the remaining resource potential presence based on tectonic and thermal evolution. The proposed workflow significantly improves the credibility of resource evaluations and is likely applicable to other deep and ultradeep buried source rocks worldwide.

{"title":"Restoring the original hydrocarbon-generating potential of deep source rocks: A critical review and a novel method using the Songliao Basin, China, as a case study","authors":"Daming Niu , Tianyi Li , Yueyue Bai , Pingchang Sun , Hongliang Dang , Yilin Li , Lianxin Tao , Xingxuan Lei , Sicheng Li , Lixiang Gui , Chunlong Liu","doi":"10.1016/j.coal.2025.104741","DOIUrl":"10.1016/j.coal.2025.104741","url":null,"abstract":"<div><div>Deep source rocks are typically in a high-to-overmature stage, characterized by lower than original values of total organic carbon. Thus, resource evaluation is significantly influenced by the accuracy of the measured data and the restoration methods of original (pre-thermal maturation) values. Therefore, reliable data for assessing petroleum and natural gas resources generated during the burial process are urgently needed. This study first critically reviews commonly used methods for restoring the original TOC (TOC<sub>o</sub>) and hydrocarbon-generating potential (HGP). The principles, advantages, and disadvantages of each method are discussed, and a novel workflow for evaluating the resource is proposed. The workflow involves four steps: (1) selecting a fit for-the-purpose method for original TOC and HGP restoration; (2) establishing original restoration coefficients by weighted TOC and HGP restoration formulas; (3) assessing the remaining resource potential through hydrocarbon generation and expulsion; and (4) validating the assessment results. Using the Permian source rocks in the Songliao Basin as an example, this workflow restores the total remaining resource amount (65.3 × 10<sup>9</sup> t). Predicted results indicate that high-value areas with remaining resource potential are near the Heyupao Sag (57.7 × 10<sup>8</sup> t), Chaoyanggou Terrace (73.5 × 10<sup>8</sup> t), and Binxian-Wangfu Sag (39.0 × 10<sup>8</sup> t). The advantages of this workflow include: (1) overcoming the limitations of the original TOC and HGP restoration method by selecting the most suitable restoration model; (2) directly identifying the original TOC spatial distribution using recovery coefficient, which overcomes the heterogeneity in the spatial distribution of organic matter types; and (3) accurately verifying the remaining resource potential presence based on tectonic and thermal evolution. The proposed workflow significantly improves the credibility of resource evaluations and is likely applicable to other deep and ultradeep buried source rocks worldwide.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"303 ","pages":"Article 104741"},"PeriodicalIF":5.6,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143609971","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Rare earth resource in fly ashes from coal power plants of China: Based on machine learning model and unit-based estimation

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-03-05 DOI: 10.1016/j.coal.2025.104743

Chang Liu , Yi Yang , Long Chen , Jiayuan Wu , Yuan Sun , Mingzhe Han , Xingpan Guo , Maoyong He , Zhangdong Jin

Coal fly ashes (CFAs) are an alternative resource of rare earth elements and yttrium (REY). China is the largest producer of CFAs in the world and is likely to hold substantial reserves of CFA-REY resources, while nationwide research on REY resource in Chinese CFAs is lacking. In this work, CFA samples were collected from 118 coal - fired power plants (CFPPs), including eight subjected to long-term monitoring. Based on this, a machine-learned (ML) REY concentration predictive model was developed with a deviation of 16 %, which showed REY concentration and the proportion of air-dried-basis ash yield in coal, and CFPP boiler type were the three governing factors regulating REY concentrations in CFAs. Using this ML model and a unit-based database of Chinese CFPPs, REY concentrations in CFAs from 1062 additional CFPPs were predicted, who accounted for 89.2 % of national coal consumption. Promising CFA-REY resources were defined as those containing ≥300 mg/kg REY in CFA, and were concentrated in North (Inner Mongolia, Shanxi, and Hebei Provinces), East (Shandong, Jiangsu, Zhejiang, and Anhui Provinces), South (Guangdong Province) and Southwest (Guizhou Province) China. Moreover, using a unit-based estimation model, the total amount of rare earth oxides from unutilized CFAs with REY recovery potential in China is estimated to be about 74,300 tons/y, which would meet six months of global demand and have a gross value of US $ 4.2 billion.

{"title":"Rare earth resource in fly ashes from coal power plants of China: Based on machine learning model and unit-based estimation","authors":"Chang Liu , Yi Yang , Long Chen , Jiayuan Wu , Yuan Sun , Mingzhe Han , Xingpan Guo , Maoyong He , Zhangdong Jin","doi":"10.1016/j.coal.2025.104743","DOIUrl":"10.1016/j.coal.2025.104743","url":null,"abstract":"<div><div>Coal fly ashes (CFAs) are an alternative resource of rare earth elements and yttrium (REY). China is the largest producer of CFAs in the world and is likely to hold substantial reserves of CFA-REY resources, while nationwide research on REY resource in Chinese CFAs is lacking. In this work, CFA samples were collected from 118 coal - fired power plants (CFPPs), including eight subjected to long-term monitoring. Based on this, a machine-learned (ML) REY concentration predictive model was developed with a deviation of 16 %, which showed REY concentration and the proportion of air-dried-basis ash yield in coal, and CFPP boiler type were the three governing factors regulating REY concentrations in CFAs. Using this ML model and a unit-based database of Chinese CFPPs, REY concentrations in CFAs from 1062 additional CFPPs were predicted, who accounted for 89.2 % of national coal consumption. Promising CFA-REY resources were defined as those containing ≥300 mg/kg REY in CFA, and were concentrated in North (Inner Mongolia, Shanxi, and Hebei Provinces), East (Shandong, Jiangsu, Zhejiang, and Anhui Provinces), South (Guangdong Province) and Southwest (Guizhou Province) China. Moreover, using a unit-based estimation model, the total amount of rare earth oxides from unutilized CFAs with REY recovery potential in China is estimated to be about 74,300 tons/y, which would meet six months of global demand and have a gross value of US $ 4.2 billion.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"303 ","pages":"Article 104743"},"PeriodicalIF":5.6,"publicationDate":"2025-03-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143576862","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

Implications of solid bitumen association with low- to medium-temperature hydrothermal minerals in hydrocarbon reservoirs of Southwest China: Insights from organic petrology and sulfur isotopes

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-03-04 DOI: 10.1016/j.coal.2025.104739

Wen Sun , Ningning Zhong , Yongli Lu , Dahua Li , Qingyong Luo , Lipeng Yao , Yanan Yang , Chunfang Cai , Zilong Fang

Solid bitumen in Southwest China often coexists with metal deposits, indicating a genetic link between organic matter and ore formation. However, this linkage remains underexplored. This study investigated the relationship between sulfur origin and organic matter maturity through sulfur isotopes of metal sulfides. Organic petrology revealed that solid bitumen associated with minerals exhibited stronger optical anisotropy (ΔBRo >3.32 %) and higher S/C atomic ratios (0.029–0.033) than non-associated bitumen (0.005–0.021). Fluid inclusion analysis showed that ore-stage calcite inclusions have higher homogenization temperatures than those in paleo-oil reservoirs, indicating that ore-forming processes accelerated hydrocarbon thermal evolution. Solid bitumen-mineral associations were classified into Mississippi Valley-type (MVT), stratiform mercury, and disseminated gold deposits. Sulfur isotope compositions identified three sulfur sources: bacterial sulfate reduction (BSR), thermochemical sulfate reduction (TSR), and thermal decomposition of sulfur-containing organic matter (TDS). In the Lanping-Simao Basin, δ³⁴S_CDT values below 0 ‰ suggest sulfur derived from BSR, with hydrocarbons contributing reduced sulfur. In the Xuefeng Mountains Uplift, δ³⁴S_CDT values exceeding 20 ‰ indicate TSR-driven sulfur, with metallogeny enhancing hydrocarbon accumulation and mineralization. In the Kangdian Axis, δ³⁴S_CDT values under 20 ‰ suggest sulfur from TSR and TDS, with mineralization causing oil cracking and reservoir destruction. The findings demonstrate that metallogeny accelerates organic matter maturation, reshapes reservoirs, and drives oil cracking. Simultaneously, organic-inorganic interactions govern metal sulfide formation and precipitation, underscoring their critical role in ore genesis.

{"title":"Implications of solid bitumen association with low- to medium-temperature hydrothermal minerals in hydrocarbon reservoirs of Southwest China: Insights from organic petrology and sulfur isotopes","authors":"Wen Sun , Ningning Zhong , Yongli Lu , Dahua Li , Qingyong Luo , Lipeng Yao , Yanan Yang , Chunfang Cai , Zilong Fang","doi":"10.1016/j.coal.2025.104739","DOIUrl":"10.1016/j.coal.2025.104739","url":null,"abstract":"<div><div>Solid bitumen in Southwest China often coexists with metal deposits, indicating a genetic link between organic matter and ore formation. However, this linkage remains underexplored. This study investigated the relationship between sulfur origin and organic matter maturity through sulfur isotopes of metal sulfides. Organic petrology revealed that solid bitumen associated with minerals exhibited stronger optical anisotropy (ΔBRo >3.32 %) and higher S/C atomic ratios (0.029–0.033) than non-associated bitumen (0.005–0.021). Fluid inclusion analysis showed that ore-stage calcite inclusions have higher homogenization temperatures than those in paleo-oil reservoirs, indicating that ore-forming processes accelerated hydrocarbon thermal evolution. Solid bitumen-mineral associations were classified into Mississippi Valley-type (MVT), stratiform mercury, and disseminated gold deposits. Sulfur isotope compositions identified three sulfur sources: bacterial sulfate reduction (BSR), thermochemical sulfate reduction (TSR), and thermal decomposition of sulfur-containing organic matter (TDS). In the Lanping-Simao Basin, δ<sup>34</sup>S<sub>CDT</sub> values below 0 ‰ suggest sulfur derived from BSR, with hydrocarbons contributing reduced sulfur. In the Xuefeng Mountains Uplift, δ<sup>34</sup>S<sub>CDT</sub> values exceeding 20 ‰ indicate TSR-driven sulfur, with metallogeny enhancing hydrocarbon accumulation and mineralization. In the Kangdian Axis, δ<sup>34</sup>S<sub>CDT</sub> values under 20 ‰ suggest sulfur from TSR and TDS, with mineralization causing oil cracking and reservoir destruction. The findings demonstrate that metallogeny accelerates organic matter maturation, reshapes reservoirs, and drives oil cracking. Simultaneously, organic-inorganic interactions govern metal sulfide formation and precipitation, underscoring their critical role in ore genesis.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"303 ","pages":"Article 104739"},"PeriodicalIF":5.6,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143576865","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

引用次数: 0

The coal-sourced petroleum system in the Barito Basin (S Borneo): Factors controlling quantity and quality of oil from Eocene and Miocene coals

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-03-04 DOI: 10.1016/j.coal.2025.104744

Reinhard F. Sachsenhofer , Stephen Ajuaba , Hafidz Noor Fikri , Brian Horsfield , Nicolaj Mahlstedt , David Misch , Ksenija Stojanović

The Barito Basin in southern Borneo contains large Eocene and Miocene coal deposits as well as a minor petroleum system. Previous authors have distinguished two oil families, termed Tanjung and Warukin. Coal has been discussed as the source for both, but there is no consensus on the lithology of the source rock of the Tanjung family.

Various geochemical parameters including biomarkers, the composition of pyrolysates and carbon isotope ratios were used for oil-source correlation. Biomarker fingerprints (pristane/phytane ratio, abundance of non-hopanoid triterpanes and bicadinanes, predominance of C₂₉ homologues in sterane distribution) and the clear dominance of dibenzofurans over fluorenes and dibenzothiophenes in oils clearly indicated their origin from coal. The excellent agreement between the oil and coal parameters confirms a relation between Tanjung oil and Eocene coals and between Warukin oil and Miocene coals.

The factors controlling the oil potential of marginal mature Eocene coals (0.52–0.59 %Rr) and immature Miocene coals (≤0.40 %Rr) in the Barito Basin were investigated using Rock-Eval pyrolysis of solvent-extracted coals and petrographic and biomarker data that have recently become available in papers investigating the depositional environment of these coals. The study revealed that all coals contain significant amounts of heavy, oxygen-rich bitumen components, which form part of the Rock-Eval S2 peak (S2_bitumen) and showed that the type of oil generated from Eocene (high wax paraffinic oil) and Miocene coals (paraffinic-naphthenic-aromatic mixed oil with moderate wax content) differs significantly. It is concluded that the S2_bitumen is at least partly derived from resins and that the generated oil type is controlled by the prevailing resin producing vegetation, which is palms in Eocene coals and Dipterocarpaceae in Miocene coals. Other liptinite macerals and the mire type do not appear to play a significant role.

{"title":"The coal-sourced petroleum system in the Barito Basin (S Borneo): Factors controlling quantity and quality of oil from Eocene and Miocene coals","authors":"Reinhard F. Sachsenhofer , Stephen Ajuaba , Hafidz Noor Fikri , Brian Horsfield , Nicolaj Mahlstedt , David Misch , Ksenija Stojanović","doi":"10.1016/j.coal.2025.104744","DOIUrl":"10.1016/j.coal.2025.104744","url":null,"abstract":"<div><div>The Barito Basin in southern Borneo contains large Eocene and Miocene coal deposits as well as a minor petroleum system. Previous authors have distinguished two oil families, termed Tanjung and Warukin. Coal has been discussed as the source for both, but there is no consensus on the lithology of the source rock of the Tanjung family.</div><div>Various geochemical parameters including biomarkers, the composition of pyrolysates and carbon isotope ratios were used for oil-source correlation. Biomarker fingerprints (pristane/phytane ratio, abundance of non-hopanoid triterpanes and bicadinanes, predominance of C<sub>29</sub> homologues in sterane distribution) and the clear dominance of dibenzofurans over fluorenes and dibenzothiophenes in oils clearly indicated their origin from coal. The excellent agreement between the oil and coal parameters confirms a relation between Tanjung oil and Eocene coals and between Warukin oil and Miocene coals.</div><div>The factors controlling the oil potential of marginal mature Eocene coals (0.52–0.59 %Rr) and immature Miocene coals (≤0.40 %Rr) in the Barito Basin were investigated using Rock-Eval pyrolysis of solvent-extracted coals and petrographic and biomarker data that have recently become available in papers investigating the depositional environment of these coals. The study revealed that all coals contain significant amounts of heavy, oxygen-rich bitumen components, which form part of the Rock-Eval S2 peak (S2<sub>bitumen</sub>) and showed that the type of oil generated from Eocene (high wax paraffinic oil) and Miocene coals (paraffinic-naphthenic-aromatic mixed oil with moderate wax content) differs significantly. It is concluded that the S2<sub>bitumen</sub> is at least partly derived from resins and that the generated oil type is controlled by the prevailing resin producing vegetation, which is palms in Eocene coals and <em>Dipterocarpaceae</em> in Miocene coals. Other liptinite macerals and the mire type do not appear to play a significant role.</div></div>","PeriodicalId":13864,"journal":{"name":"International Journal of Coal Geology","volume":"303 ","pages":"Article 104744"},"PeriodicalIF":5.6,"publicationDate":"2025-03-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143576863","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}

引用次数: 0

Electron microbeam investigations of the spent ash from the pilot-scale acid extraction of rare earth elements from a beneficiated Kentucky fly ash

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-03-02 DOI: 10.1016/j.coal.2025.104738

Debora Berti , John G. Groppo , Prakash Joshi , Dorin V. Preda , David P. Gamliel , Todd Beers , Michael Schrock , Shelley D. Hopps , Tonya D. Morgan , Bernd Zechmann , James C. Hower

Fly ash derived from the combustion of an eastern Kentucky high volatile bituminous coal blend was, as discussed in previous studies, beneficiated to yield a − 75-μm product with a reduction in the carbon and spinels. The beneficiated fly ash was reacted with a strong acid in a pilot-scale unit to extract rare earth elements (REE) and other major and minor elements. In this study, polished, epoxy-bound pellets of the beneficiated and acid-extracted ashes were examined via scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). Selected slices of the polished section were extracted using a focused ion beam (FIB) technology and further examined via transmission electron microscopy (TEM) and EDS. The bulk chemistry of the original feed ash (not studied by microbeam methods), the beneficiated ash, and the acid-extracted ash exhibit similar Upper Continental Crust-normalized REE patterns. The bulk chemistry indicates that the concentrations of the major oxides (aside from SiO₂), REE, V, Cr, Mn, Ni, As, Rb, Sr, Zr, Ba, and Pb are less in the processed ash compared to the beneficiated ash. The fly ashes have H-type distributions (La_N < Lu_N) with a strong M-type (medium type: La_N/Sm_N < 1, Gd_N/Lu_N > 1) contribution. Among the REE and Y, SEM-EDS and TEM-EDS showed the presence of zircon with Y (and Ce, Nd, and Gd, perhaps from an adjacent monazite); xenotime; a Dy-rich xenotime-structure mineral: and monazite with light REE (La, Ce, Pr, Nd, and Sm), Gd, Dy, Er, and Th. Glassy Al-Si-rich fly ash spheres showed the presence of Ce, Nd, Sm, and Dy but no discernable minerals at the scale of the SEM view. Certain spheres showed 2- to 4-μm amorphous rims surrounding nano-crystalline cores. As with the depletion of elements in the bulk fly ash, the amorphous rims showed a relative increase in Si and a depletion or apparent elimination of other elements, including the REE. It is possible that the apparent absence of 2- to 4-μm particles may mean that these particles were totally or largely dissolved by the acid or as a consequence of multiple wash-filtration cycles to remove leachate from the spent ash. Processing of a combination of a finer size than processed in this pilot-scale investigation and/or more fractured particles, perhaps via a pre-processing step, would permit a greater penetration of the acid into the interior of the fly ash particles, leading to a greater recovery of REE.

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引用次数: 0

Reassessment of the Pennsylvanian bio- and chronostratigraphy of the Saar-Lorraine Basin using high-precision UPb ages of volcanic ashes

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-02-21 DOI: 10.1016/j.coal.2025.104724

Alain Izart , Stanislav Opluštil , Raymond Michels , Sebastian Voigt , Christoph Hartkopf-Fröder , Jocelyn Barbarand , Thomas Blaise , Jiří Laurin , Mark Schmitz , Salim Allouti , Romain Hemelsdael , Jacques Pironon

Chronostratigraphic calibration of the Westphalian and early Stephanian succession in the Saar-Lorraine Basin of Germany and France has been improved using high-precision UPb zircon dating of intercalated tonsteins (volcanic ashes) in coal seams. The clay mineralogy and elemental composition were determined to specify the source of these volcanic ashes and the post-depositional weathering processes. Samples selected for dating were tonsteins with homogeneous zircons without zoning to avoid the inherited ages from the volcanic chamber. Four of them provided concordant ages in agreement with their stratigraphic position. New radiometric ages constrain the hiatus below the Holz Conglomerate approximately between 307.9 and 306.0 Ma, that corresponds to the early and mid-Cantabrian substage as defined in its type area, the NW Spain. The age of T600 tonstein, which corresponds in Saar-Lorraine Basin to the Duckmantian/Bolsovian boundary is fully in agreement with ages of that boundary determined in the Ruhr Basin of the Variscan foreland and in continental basins of the Bohemian Massif. T10 tonstein on top of the Westphalian succession confirms its late Asturian age previously determined from macroflora. T00 tonstein in the Ottweiler Group provided a mid-Barruelian age, which allowed to re-define macrofloral biozones in the lower part of that group from Alethopteris zeilleri of Saberian substage to Crenulopteris lamuriana of Barruelian substage. New UPb ages further improved correlation of local lithostratigraphic units with other basins in Europe and also with global marine-based stages. These new ages allow us to compare radioisotopically constrained Bayesian age model to metronomic age models from Bolsovian to Barruelian and show that the high frequency sequences fall in the range of the precession and obliquity. The sources of the volcanic ashes were probably volcanoes in the Vosges and Black Forest massifs. Considered could be also volcanic centers at a larger distance, e.g., the Teplice-Altenberg volcanic complex for Westphalian, Gothard and Aar massifs in Alps and the Thüringian Forest in Saxony for Stephanian and Autunian tonsteins. The detrital zircons extracted from the sandstones of the Bolsovian deposits and Holz Conglomerate (late Cantabrian) show a wide range of ages from Precambrian to Ordovician that confirms the northward source of these zircons (Rhenohercynian zone) mixed with a local source from the Mid-German Crystalline High.

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引用次数: 0

Evolution of pore structure in the Upper Cretaceous Second White Speckled Shale during thermal maturation: Insights from artificial and naturally matured samples

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-02-19 DOI: 10.1016/j.coal.2025.104728

Haiping Huang , Hong Zhang , Zhongliang Ma , Xiangrong Yang , Yong Ma , Lunju Zheng

The evolution of pore structures in marine shale during thermal maturation was investigated using naturally matured samples (Ro 0.46–1.26 %) from the Upper Cretaceous Second White Speckled Shale and artificially matured samples in a semi-open system (200–450 °C). Analytical techniques, including Rock-Eval pyrolysis, FIB-FESEM, and nitrogen adsorption, revealed key trends in pore volume (PV) and specific surface area (SSA). Immature samples exhibited high PV and SSA, which decreased during early oil generation (Ro ∼0.98 % or 350 °C) due to compaction and oil infill. PV and SSA rose significantly between Ro 0.98 % and 1.26 % (350–400 °C), driven by mesopore development, and remained elevated at higher temperatures. Artificially matured samples showed higher PV and SSA compared to naturally evolved samples, reflecting the absence of compaction and cementation processes in laboratory conditions. Naturally evolved samples demonstrated greater heterogeneity due to expulsion dynamics and geological factors, developing complex pore networks during hydrocarbon generation. Organic matter (OM) composition, dominated by Type II kerogen with terrestrial inputs, played a critical role in pore evolution. Amorphous organic matter (AOM) and solid bitumen were the primary OM components, with liptinite macerals and terrigenous vitrinite and inertinite also contributing. Clay minerals dominated the rock matrix, while pyrite framboids contributed dissolution-induced secondary porosity. SEM imaging identified five pore types, with OM-hosted pores forming predominantly in bitumen rather than kerogen. Mesopores (2–50 nm) were the dominant pore type, while micropores (< 2 nm) were negligible. Fluorescence microscopy and pyrolysis experiments confirmed increasing maturity with depth, accompanied by significant intraparticle pore formation in migrated bitumen at higher temperatures. Artificial maturation studies highlight faster hydrocarbon generation and pore development compared to natural systems but fail to replicate long-term burial effects. PV correlated positively with expelled oil in artificial systems, while bitumen content negatively correlated with PV and SSA in both systems. Advanced imaging techniques and integrated natural and experimental models are essential to further understanding pore evolution, connectivity, and hydrocarbon generation mechanisms in shale reservoirs. This study emphasizes the interplay between OM composition, mineralogy, and thermal processes in shaping shale porosity during natural and artificial maturation.

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引用次数: 0

Extensive accumulation of organic matter in the Late Permian Dalong Formation, Western Hubei Trough, Southern China

IF 5.6 2区工程技术 Q2 ENERGY & FUELS

International Journal of Coal Geology

Pub Date : 2025-02-19 DOI: 10.1016/j.coal.2025.104727

Lulu Xu , Saipeng Huang , Dameng Liu , Zhiwei Liao , Kui Wu , Miankun Chen , Xianghui Zhou , Yanlin Zhang , Bei Liu , Minglong Li

The black shale in the Upper Permian Dalong Formation in the Western Hubei (WH) 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 WH Trough exhibits a higher TOC content (> 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.

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引用次数: 0