When predicting coke quality or coking behaviour, the more accurate models typically include vitrinite content in addition to rank. This work explores how the two most abundant vitrinite macerals (collotelinite and collodetrinite) behave during carbonisation. The insights gained highlight important differences, paving the way for more sophisticated coke quality prediction models and enhanced blending/processing strategies.Australian bituminous coals from Bowen Basin with random vitrinite reflectance (%Ro) ranging 0.81–1.18% were cut and polished into coal blocks having a 15 mm × 15 mm face running perpendicular to the bedding plane. Following petrographic analysis, these blocks were carbonised at 3 °C/min to 525 °C, set in resin, and repolished to examine coking behaviour of identified macerals. Vitrinite concentrates (VCs) were prepared alongside “whole coal” samples to measure viscosity using rheometry. Collotelinite underwent considerably more expansion than collodetrinite with the extent of collotelinite expansion greater for the lower reflectance bituminous coals; characterised by large pores and thin pore walls, while higher reflectance coals gave rise to smaller pores and thicker pore walls. Separated VCs were rich in collotelinite and generated significant fluidity, i.e. low viscosity. For whole coals, viscosities were higher due to the presence of inertinite, however, this work suggests that higher viscosities are also due to increased collodetrinite. The maceral picking process for one coal led to a situation where the VC and the whole coal had similar levels of vitrinite, however, the VC was richer in collotelinite and exhibited a significantly lower viscosity. This result suggests that fluidity development and expansion behaviour for these two vitrinite macerals is different, and aligns with visual observations.It is proposed that volatile release behaviour is different for collotelinite and collodetrinite due to the differences in microstructure. More specifically, volatiles are better retained in collotelinite which contributes to its greater fluidity development and expansion behaviour. The process of geochemical gelification that gives rise to collotelinite may enable it to have no, or very few, defects and therefore limited pathways for volatiles to leave. Instead, volatiles are trapped and contribute to both the liquid development and bubble expansion. With no inclusions and defects to destabilise bubble interfaces, significant expansion occurs. In contrast, whilst collodetrinite arises via a similar process, it is less than 10 μm in size and co-occurs with other macerals and minerals, held together physically owing to its detrital origin and/or its mechanical degradation within the palaeomires. Accordingly, there are defects and grain boundaries between components through which volatiles may diffuse out, preventing fluid development and expansion. Overall, the outcome of this study shows that the vitrinite size and relative ease of volatile release for different maceral types may play a crucial role in a coal's fluidity development, and consequently its coking behaviour.
Three round robin exercises (RRE) aimed at characterizing bituminite and testing the reproducibility of random vitrinite (VRo %) and bituminite (BitRo %) reflectance measurements on samples of dispersed organic matter from organic‑carbon rich shale intervals of Kimmeridge Clay Formation were conducted in 2016, 2018, and 2020. This work was conducted by the Identification of Dispersed Organic Matter Working Group (IDOM WG) of the International Committee for Coal and Organic Petrology (ICCP). The Kimmeridge Clay Formation represents the major marine source rock for the North Sea hydrocarbon province. Samples collected from Kimmeridge Bay, Dorset, England, United Kingdom and Filey Bay, North Yorkshire, England, United Kingdom outcrops and the 16/17–14 well in the Tiffany oil field, Viking Graben, North Sea, were analyzed by 19 to 23 participants in 15 to 17 laboratories from 14 to 15 countries. Samples contain moderate to high organic matter content [5.32 to 12.10 wt% total organic carbon (TOC) content] with thermal maturity ranging from immature to thermally mature (Tmax 418 to 445 °C).Participants used a standard description sheet to record bituminite morphological characteristics, including its form, size, mode of appearance, and impurities, for use in the revision of the bituminite definition. The usage of previously published classifications of bituminite types (e.g., bituminite I sensu Teichmüller and Ottenjann, 1977) in the RRE was not found to be helpful. The indistinct, amorphous character of boundaries of bituminite, and the poor preparation of whole rock pellets for the 2018 and 2020 RRE hampered identification of bituminite. Mean random BitRo %, including outlying values, varied in all three RRE from 0.19 to 0.35% and is reported here for the first time. Application of the criterion standard deviation (SD) < 0.15 × BitRo % to exclude outlying BitRo % values showed virtually no change in modified BitRo % in immature samples (2016 and 2018 RRE) and an unexpected increase to 0.43% BitRo in the thermally mature sample (2020 RRE).Mean VRo values, including outliers in the three RRE, range from 0.47 to 0.71%, confirming the immature to thermally mature nature of samples of the Kimmeridge Clay Formation used in this study. Application of the criterion SD < 0.15 × VRo to exclude outlying values results in a comparable range of modified VRo values and a decrease in group standard deviation. Precision of VRo values (including outlying values) evaluated via the averaged unsigned multiple of the standard deviation rule (< 1.5) showed moderate to high precision comparable to historical values from similar RRE. An average reproducibility limit (RL) of 0.29% (including outlying values) showed an improvement in reproducibility relative to similar historical RRE (0.35%), which was attributed to the application of a common methodology (ASTM D7708, 2014b, 2023) to enhance the quality of data from the reflectance test method.
We respond to Segit's Discussion concerning lithological terminology, sampling strategy, stratigraphic interpretation, palaeo‑oxygenation, and the tectono-sedimentary context of Middle Jurassic organic-matter-bearing deposits of the Szlachtowa Formation in the Pieniny Klippen Belt. We clarify that our study deliberately examined lithologically variable, dark, organic-bearing siliciclastic deposits within a heterolithic turbiditic succession, and that the term “black shale deposits” was not intended as a strict classification of all analysed samples. The lithology of each sample was explicitly reported, and additional field documentation is provided to clarify the sedimentological context of the sampled material.We further emphasize that tectonic fragmentation and discontinuous exposure within the Pieniny Klippen Belt limit the possibility of geographically uniform sampling and broad basin-scale extrapolation. The assignment of sample 50SL from Vršatské Podhradie to the Szlachtowa Formation remains plausible, although the structurally complex setting of this locality requires caution and further independent verification.The dinoflagellate cyst assemblages support a broad Middle Jurassic affinity for the analysed material, with a well-supported Lower Bajocian component and evidence that some horizons may extend into the Bathonian. The proposed Toarcian–Aalenian affinity of selected samples is retained only as a tentative interpretation requiring further biostratigraphic confirmation.We also clarify that our palaeoenvironmental interpretation did not imply persistent basin-wide anoxia or a Toarcian Oceanic Anoxic Event-type euxinic system. Rather, the integrated organic-petrological, palynofacies, Rock-Eval, and biomarker dataset indicates a terrigenously influenced, heterolithic depositional system characterized predominantly by dysoxic to suboxic conditions, with local and potentially episodic shifts towards more reducing conditions. Overall, the discussion concerns the scope and wording of selected interpretations rather than the validity of the underlying analytical dataset.
Biochar carbon permanence remains difficult to quantify because multiyear soil incubation experiments reproduce biological decay but commonly measure only 1–2% carbon loss from highly carbonized biochars, leaving long-term decay constants poorly constrained. Accelerated thermochemical oxidation resolves the full carbon reactivity spectrum and supports kinetic extrapolation, but it does not directly represent biological decay in soil. This study links the two approaches using raw biomass as a common reference. Multipool kinetic models were fitted to accelerated oxidation data for raw wood, two intermediate biochars, inertinite-rich biochar, and synthetic graphite, and to five published soil incubation datasets for raw biomass. The biological reference rate, defined as the geometric mean of the effective rate constants derived from the incubation datasets, was 51.3-fold, or 1.71 orders of magnitude, faster than the thermochemical decay rate of raw wood. Thermochemical rate constants were therefore uniformly increased by this factor to generate a conservative biologically anchored persistence scenario. After calibration, effective half-lives were 2.06 years for raw wood, 4.38 × 103 and 9.15 × 103 years for the two intermediate biochars, and 1.25 × 105 years for inertinite-rich biochar. At 1000 years, the corresponding modeled fractions of carbon remaining were 0%, 76%, 78%, and 99%, respectively. Permanence increased strongly and nonlinearly with mean random reflectance and was best represented by a double logistic function, consistent with two transitions in carbon stability during progressive structural condensation. This method bridges the limitations of soil incubation and thermochemical oxidation and provides conservative lower-bound estimates of long-term biochar carbon persistence across the carbonization continuum.
The Guaduas Formation, which spans from the Upper Maastrichtian to the Lower Paleocene, is the primary source of thermal and coking coal in the Eastern Cordillera of Colombia. This study analyzed 64 coal samples collected from the southern (Sutatausa), central (Guachetá), and northern (Samacá) sections of the Checua-Lenguazaque Syncline (CLS) coalfield, where this coal-bearing unit reaches approximately 1100 meters at its deepest point. Mean random vitrinite reflectance (VRr%) was integrated with numerical modeling of thermal histories, subsidence analysis, and estimations of eroded section thickness. The results reveal significant variation in VRr% values, which can be attributed to complex and contrasting tectonic and thermal histories, as well as prolonged residence times near the oil and gas generation window. The minimum estimated thickness of the eroded sedimentary succession is approximately 1000-1300 m, consistent with the maximum depth of the decompacted Guaduas Formation. In the Samacá section (northwards), two distinct VRr% populations were identified: one ranging from 0.8 to 1.0, and another from 1.2 to 1.5. These populations correspond to two different thermal residence periods, occurring at temperatures of approximately 120°C and 160°C, respectively, between 70 and 40 Ma. In the Guachetá section, thermal modeling of 18 samples indicates a rapid cooling phase between 70 and 55 Ma, followed by a reheating phase between 55 and 30 Ma. This was succeeded by a prolonged residence or slow cooling period at temperatures near 160°C, with VRr% values ranging from 1.4 to 1.8. For the Sutatausa section (southwards), a cooling pulse occurred between 70 and 58 Ma, followed by a heating event between 60 and 45 Ma. Subsequently, a prolonged residence period at temperatures close to 120°C was observed, resulting in VRr% values ranging from 0.6 to 1.0. The reheating phases of the organic matter align with periods of subsidence previously reported for the study area and the adjacent sedimentary basins (Middle Magdalena Valley and Llanos). At the same time, the most recent cooling pulse is associated with the post-Miocene exhumation of the Eastern Cordillera during the Andean Orogeny.
Magmatic intrusion into coal seams substantially alters mineral composition, pore structure, and methane adsorption capacity. However, the effects of magmatic–hydrothermal-induced epigenetic mineral infilling on both pore structure and adsorption capacity remain poorly understood, limiting accurate evaluation of coalbed methane potential in intrusion-affected coal seams. The Carboniferous–Permian coal-bearing strata of the Tashan Coal Mine, Datong Coalfield, North China, contain extensive diabase and lamprophyre intrusions. Fourteen coal samples were collected at varying distances from a diabase intrusion in the No. 3–5 seams of the Taiyuan Formation, and their mineralogy, maceral composition, pore structure, and methane adsorption properties were systematically analyzed. Maximum vitrinite reflectance (Ro, max), mineral content, and ash yield increase with proximity to the intrusion. Coal samples were classified into unaffected, slightly thermally affected, and highly thermally affected groups. Magmatic heating promotes gas pore formation, but pores and fractures in highly affected coal are commonly infilled by epigenetic minerals (carbonates and clays), producing distinct pore genetic types across categories. Unaffected coal is dominated by plant tissue and intergranular pores, slightly affected coal by gas and plant tissue pores, and highly affected coal by mineral-filled residual gas pores and intercrystalline pores. Volumes and surface areas of macropore, mesopore, and micropore, as well as the hysteresis loop coefficient, show strong negative correlations with ash yield, highlighting the role of mineral infilling. Langmuir volumes (12.31–22.67 cm3/g) decrease near intrusions and correlate negatively with coal rank, as epigenetic mineral infilling blocks adsorption sites. The results suggest that epigenetic mineral infilling may partly offset, or locally exceed, the positive effect of increased coal rank on methane adsorption capacity. These findings imply that hydrothermal processes may be a major factor in controlling coalbed methane potential in intrusion-affected coal.
The production of biochar and its incorporation into soils have recently gained attention as a carbon dioxide sequestration pathway within negative emissions strategies. The long-term persistence of biochar in soil is governed by its intrinsic material properties, which are controlled by pyrolysis conditions and feedstock type, as well as by environmental factors. This study investigates the evolution of biochar structural properties derived from three biomass feedstocks—peanut shells, sycamore wood, and wheat straw—across a range of pyrolysis temperatures (300–700 °C) using a combined reflectance and Raman spectroscopic approach.Raman spectra were analyzed using two deconvolution approaches: a two-band model (D and G bands) and a four-band model (D1, D3, D4, and G bands). The resulting Raman parameters effectively capture structural transformations in biochar as functions of pyrolysis temperature and biochar reflectance. Across all samples, consistent trends were observed, including systematic shifts in band positions, increasing band separation, and progressive band narrowing with increasing temperature. Several Raman parameters—specifically the D and D1 band positions, D-band full width at half maximum (FWHM), and Raman band separation—exhibit near-linear relationships with biochar reflectance, indicating their potential as spectroscopic proxies for reflectance.Notably, several Raman parameters display inflection points near 500 °C and at reflectance values of approximately 2.0–2.5%, marking a transition from biomass decomposition-dominated reactions to the growth and coalescence of polyaromatic clusters. This convergence of Raman-derived inflection points with reflectance thresholds closely corresponds to the stage at which biochar acquires substantially enhanced permanence in soil. Overall, the strong agreement between Raman and reflectance trends demonstrates that Raman spectroscopy provides a valuable complementary tool for biochar characterization, offering molecular-scale insights that enhance assessments of biochar stability and carbon sequestration potential.
Deciphering the coupled controls of salinity, redox dynamics, and climate on coal depositional settings remains a key challenge in palaeoenvironmental reconstruction, particularly within Indian Gondwana basins, where integrated geochemical frameworks are limited. The present study adopts a multiproxy outlook by combining organic petrography, stable isotopes (S13C and S15N), as well as major, trace, and rare earth element geochemistry to understand the depositional conditions of coal and shaly coal from the Rajmahal Basin. The samples are of subbituminous to high-volatile bituminous rank (VRo = 0.41-0.63%) and are dominated by vitrinite-rich assemblages, indicating well-preserved terrestrial organic matter. Isotopic compositions (S13C = -22.6 to -23.8%o; S15N = +2.1 to +4.0%o) and elevated TOC/TN ratios (42.31-57.7) indicate a vascular land plant source, with isotopic variability reflecting microbial reworking and depositional controls. Maceral composition and indices support peat accumulation under fluctuating water table conditions within a forested mire. Redox-sensitive elemental proxies and S15N values record oscillatory redox regimes, ranging from oxic to suboxic conditions, with evidence for episodic anoxia. Salinity proxies indicate a dominantly freshwater system punctuated by marginal brackish incursions. Correlative relationships among palaeo-redox and salinity proxies demonstrate that their variability is closely associated with climate-driven weathering and hydrological fluctuations. Enhanced chemical weathering under warm-humid conditions is likely to increase solute fluxes, thereby promoting water-column stratification and transient oxygen depletion. These results support a process-based palaeoenvironmental model in which climate-controlled weathering and hydrological variability appear to have influenced salinity gradients, which are closely linked to redox conditions and organic matter preservation.
Shale oil has emerged as an increasingly important unconventional resource in the global oil and gas market. It is defined as hydrocarbons retained within the nano- to micro-scale pore-throat networks of shale, comprising a complex mixture of multi-component hydrocarbons, non-hydrocarbons, and semi-solid to solid organic matter. Despite its substantial resource potential, the efficiency of enhanced oil recovery (EOR) remains limited in shale due to highly variable fluid mobility and complex nano- to micro-scale pore-throat networks. Therefore, it is crucial to improve EOR efficiency by unraveling the factors controlling shale oil mobility, referred to herein as the mechanism of Component Flow (CF). In this study, we combined geochemical experiments and molecular dynamics simulations to investigate the behavior of different oil components and identify the factors governing shale oil mobility. Our results demonstrate that the variations in organic matter composition, in conjunction with complex mineralogical characteristics, result in a highly heterogeneous distribution of pore-throat structures that affects the mobility of shale oil. The shale oil formed in freshwater lacustrine environments is enriched in light-to-medium hydrocarbons that exhibit favorable fluid mobility. These hydrocarbons are preferentially retained in fine pore-throat structures in shale reservoirs and are subject to strong adsorption effects due to high clay mineral abundance. In contrast, the oil formed in saline lacustrine settings contains a higher proportion of heavy and non-hydrocarbon fractions, which are retained in larger pore-throat structures and have a weaker adsorption owing to relatively low clay mineral contents. Furthermore, molecular simulations and experimental results show that with increasing formation temperature and pressure, light hydrocarbons act as natural solvents to dilute heavy fractions and disaggregate asphaltenes. This process reduces oil viscosity and enhances the miscible flow of shale oil. Based on case studies from the Permian Lucaogou Formation in the Junggar Basin, the Paleogene Kongdian Formation in the Bohai Bay Basin, and the Cretaceous Qingshankou Formation in the Songliao Basin, we conclude that exploiting the CF mechanism can effectively enhance cumulative per-well production. Our study underscores the significance of the CF mechanism in deciphering the critical factors and conditions for optimizing EOR in shale oil systems.
Depositional conditions, thermal evolution, and post-depositional alteration processes control organic geochemical signatures preserved in sedimentary rocks. This study investigates the geochemical variability of organic matter and hydrocarbon composition in shale, marlstone, and siltstone influenced by the thermal effects of igneous intrusions within the Permian succession of the Paran & aacute; Basin, Brazil. This interval corresponds to the most significant anoxic event recorded in the basin and represents an important organic-rich succession within the Gondwana stratigraphic record. The study area is located along the southeastern margin of the basin, near the rifted South Atlantic margin. Core samples from borehole CBM-003-ST-RS were collected at varying distances from an approximately 18-m-thick diabase sill and analyzed using an integrated approach that combined random vitrinite reflectance (VRr), open-system pyrolysis, and molecular biomarker analyses. Based on lithology, organic matter characteristics, and distance from the intrusion, four sample zones (A, B, C, and D) were defined. The results reveal a clear thermal gradient consistent with conductive heat transfer from the sill. Zones A and B, located within the first 17 m from the contact, exhibit strong thermal alteration of organic matter, with VRr values of 1.02-3.11% and T-max values of 437-470 degrees C. These samples display low Total Organic Carbon (TOC) contents (< 1 wt%) and very low S-1 and S-2 values (< 0.5 mg HC/g rock), indicating severe depletion of hydrocarbon-generating potential. Molecular parameters also indicate intense thermal stress, including the absence of pristane and phytane, marked alterations in biomarker ratios, and significant changes in polycyclic aromatic hydrocarbon (PAH) distributions, characterized by the predominance of fluoranthene and pyrene. Variations in phenanthrene and methylphenanthrene isomers further indicate advanced thermal maturity. In contrast, samples located 17.65-33.35 m from the intrusion (Zones C and D) show limited thermal influence. These intervals display VRr values of 0.7-0.8%, consistent with the onset of the hydrocarbon generation window, and preserve relatively stable biomarker ratios and PAH distributions. Sterane distributions (C-2(7)-C-2(9)) and the presence of gammacerane indicate a predominantly marine-transitional depositional environment under moderate salinity conditions. Elevated GAM/C-3(0) hopane in some samples from Zone C suggests deposition in relatively shallow-water environments where carbonates were interbedded with organic-rich shales. These results are consistent with biomarker data reported from other sectors of the basin where equivalent strata were not affected by igneous heating, indicating that key depositional signals may remain preserved despite localized thermal overprinting. The Irati Formation, therefore, represents an example of molecular resilience in organic-rich sediments affected by magmatic activity. Unlike other volcanic-influenced basins, such as the Karoo Basin (South Africa), Raton Basin (USA), and Newark Basin (USA), where magmatic heating commonly has destroyed primary geochemical signatures, the Irati Formation succession preserves diagnostic proxies, such as gammacerane, even under moderate thermal stress. These observations support a "dual control" model in which original depositional signals can be distinguished from the thermal overprint generated by igneous intrusions.
The western Shandong region, a component of the North China Craton (NCC), is a major coal-producing area extensively affected by magmatic-hydrothermal activities, which also hosts abundant coal-associated mineral resources. However, the relationships between magmatic intrusion and the mineralogical/geochemical compositions of Early Permian coals and associated rocks in the Huanghebei Coalfield (HHBC), alongside sediment source shifts and the redistribution of critical elements, remain poorly understood. To address these gaps, coal, mudstone and sandstone samples from drillhole ZK12 were analyzed via XRD, ICP-OES, ICP-MS, and TIMA. Results show that the sediments are primarily derived from the Yinshan paleoland. Distinct geochemical variations in Al2O3/TiO2 ratios among samples suggest rapid provenance shifts during the Early Permian, indicating a tectonically active and unstable basin setting. Hydrothermal minerals such as vein-like hematite and kaolinite provide robust evidence for magmatic-hydrothermal overprinting. This hydrothermal activity significantly elevated coal rank and promoted the redistribution of some critical elements, without causing their pronounced overall enrichment. Thermal decomposition of dolomite and ankerite and magmatically induced carbon redeposition artificially elevate volatile matter contents, leading to biased estimates of volatile yield and coal rank; thus, vitrinite reflectance serves as the most reliable coal-rank indicator for magmatic-hydrothermally altered coal. Given that this study only analyzed six samples from a single drillhole, thus expanded sampling and further research are required to verify and consolidate these conclusions.
High chlorine contents in coal pose significant challenges for industrial utilization, yet the enrichment mechanisms in non-marine settings remain poorly understood. This study investigates the modes of occurrence, sources, and enrichment pathways of chlorine in Middle Jurassic high-chlorine coals (0.56-1.57 wt%) from the Luxin mine, Turpan Basin, NW China. An integrated approach combining cryo-scanning electron microscopy (Cryo-SEM), sequential chemical extraction with high-temperature combustion hydrolysis (SCEP-HTCH), mineralogical and elemental geochemistry, and chlorine stable isotopes (delta 37Cl) was employed. Sequential extraction results indicate that water-soluble chlorine is overwhelmingly dominant, accounting for 75-85% of total chlorine, and exhibits a strong positive correlation with moisture content (R2 = 0.774). Cryo-SEM provides indirect evidence that chlorine predominantly occurs as dissolved Cl- in pore water, based on the observation of sporadic, irregular Na-Cl aggregates interpreted as recrystallization artifacts, though the presence of minor readily soluble microcrystalline salts cannot be entirely ruled out. Mineralogical features (fracture-filling kaolinite, calcite, barite) and geochemical indicators (elevated Na2O, CaO, MgO; high Sr/Ba; low Rb/Sr; elevated Cl/Br and Sr/Cu) collectively point to the introduction of chloride-rich saline fluids under arid to semi-arid paleoclimatic conditions. The narrow delta 37Cl range (-0.56%o to +0.96%o) is suggestive of a relatively homogeneous fluid source, constraining the origin of chlorine. Chlorine enrichment is interpreted as the cumulative result of: (1) evaporative concentration of surface waters generating saline fluids; (2) fracture-controlled migration of these fluids into peat swamps and coal seams; and (3) retention of dissolved chloride ions in coal pore water. This occurrence-process-source framework elucidates the formation of high-chlorine coal in nonmarine basins and highlights the key role of saline fluid interactions that post-dated the main peat-forming period.
Robust assessment of thermal maturity is critical for accurate petroleum system characterization and unconventional resource evaluation, particularly in geologically complex rift basins. Vitrinite reflectance (VRo) remains the benchmark for evaluating organic matter (OM) transformation, while Tmax derived from Rock-Eval pyrolysis is commonly used as a supplementary proxy. However, their interrelationship is frequently complicated by sedimentary organic matter (kerogen) heterogeneity, mineral matrix effects, and post-depositional alteration, leading to potential misclassification of hydrocarbon windows. This study presents an integrated thermal maturity analysis of the Visean Rudov Beds (V-23 horizon) within the South Flank play of the Dnieper-Donets basin (Eastern Ukraine), an emerging unconventional shale gas target. Over 500 core and drilling cutting samples from 16 wells were analyzed using TOC measurements, Rock-Eval pyrolysis (S1, S2, HI, PI, Tmax), and optical vitrinite reflectance. The Rudov Beds comprise organic-rich shales with mixed type II-III kerogen, deposited under anoxic to dysoxic marine conditions, exhibiting substantial lateral and vertical heterogeneity in maturity due to complex burial, tectonic evolution, and salt-related thermal anomalies. Analysis of S2-Tmax, HI, PI, and VRo highlights significant scatter in Tmax, particularly within the peak oil window, emphasizing the need for integrated interpretation. Application of global Tmax-VRo correlations results in systematic over- or underestimation of maturity. A locally derived regression (VRo = 0.0141 & sdot;Tmax - 5.31; R2 = 0.87), constrained by PIfiltered pyrolysis and optical VRo, provides a reliable, basin-specific calibration that captures spatial variability, improves predictive accuracy for hydrocarbon generation, and reduces uncertainty in unconventional resource evaluation. These findings demonstrate the critical importance of basin-specific, integrated approaches for interpreting thermal maturity in structurally complex, mixed-organic matter systems and offer a transferable framework applicable to other Paleozoic rift basins.
Achieving rapid and accurate prediction of coal calorific value is of great significance for coal utilization. This study compiled three representative large-sample coal datasets: 6375 samples from the United States, 64,419 and 5323 samples from Chinese coal-fired power plants. Four typical machine learning algorithms were employed to develop lower heating value (LHV) prediction models based on proximate analysis parameters. Each algorithm was trained independently on each of the three datasets. All models achieved R2 values exceeding 0.95 on their respective training datasets. However, when evaluated on unseen datasets, model performance deteriorated markedly, revealing that conventional data-driven models suffer from dataset dependence and insufficient generalization capability. To address these limitations, this study proposes a transfer learning framework based on a fully connected neural network (FCNN) using a "Pre-training and Fine-tuning" approach. The effects of different transfer strategies on model performance were systematically investigated. The results indicate that the performance of the transfer model improves with increasing the amount of fine-tuning data, and 300 samples are recommended as the minimum reliable size for fine-tuning. At this sample size, the root mean square error (RMSE) is reduced by up to 45.10% compared to direct cross-sample dataset prediction without transfer learning. Fine-tuning samples that adequately represent the target domain further improve transfer performance. Furthermore, freezing one hidden layer is optimal, whereas freezing two layers hinders adaptation to the target domain. Finally, a DeepCoal system was developed for early warning and prediction of calorific value. Independent data tests reveal that, under the recommended transfer strategy, RMSE is reduced by approximately 32.66% and 11.67% compared to direct cross-sample dataset prediction and retraining, respectively. These results demonstrate that the proposed transfer learning framework enables knowledge transfer across datasets and improves cross-sample dataset applicability.
Global demand for bauxite is rising steadily with ongoing industrialization, prompting increasing attention to resources buried within coal-bearing successions. Deeply buried bauxite horizons within coal measures are emerging as important exploration frontiers, not only as potential Al sources but also as unconventional gas reservoirs. However, the depositional controls and spatial distribution of such deep bauxite systems remain insufficiently constrained. To address this issue, this study investigates the Benxi Formation in the ShenmuJiaxian Block on the eastern margin of the Ordos Basin. Based on 254 well profiles and paleogeomorphic reconstruction using the impression method, a tripartite geomorphic framework comprising the Karst Highland, Karst Slope, and Karst Depression is recognized, and it exerts fundamental control on the sedimentary architecture of the coal-bauxite system. Seven lithofacies associations are identified. The deep bauxite formed under a persistently warm-humid climate in a continental-marine transitional setting characterized by suboxic to anoxic conditions. A four-stage genetic model is proposed, encompassing karst weathering, transport and deposition, reworking, and burial diagenesis. The central-southern Shenmu-Jiaxian Block is delineated as the most favorable zone for exploration, highlighting the dual potential of deep bauxite horizons as both a strategic Al resource and a target for unconventional gas. These findings deepen understanding of the depositional and diagenetic controls on deep bauxite formation and provide a predictive framework for integrated resource evaluation in the Ordos Basin and analogous coal-bearing basins worldwide.
Biogenic gas constitutes a significant component of global natural gas resources. Coalbed gas (CBG), as an important type of unconventional natural gas, holds significant importance in terms of the contribution from its biogenic gas. Conventional understanding suggests that biogenic CBG is primarily generated and preserved in shallow coal seams (< 1000 m). Because exploration and development have been limited mainly to shallow coal-bearing basins, the genetic mechanisms of CBG at greater burial depths remain poorly understood. This study investigates CBG and associated coalbed water from the Fukang area, southern Junggar Basin, with burial depths ranging from 665.85 m to 1607.18 m. By systematically analyzing the geochemical characteristics of gas composition, stable isotopes, and hydrochemistry, combined with 16S rRNA sequencing and metagenomic analysis, this study further explores the structural characteristics of microbial communities related to biogenic methane generation and their methanogenic functional potential. The results demonstrate that the CBG in the Fukang area is biodegraded thermogenic gas. The CO2 in CBG exhibits distinct biogenic characteristics. The hydrochemical features of coalbed water indicate a Na-HCO3-Cl water type with high total dissolved solids (TDS) content, suggesting stagnant hydrodynamic conditions and a highly confined formation water environment. Hydrogen isotopic fractionation between coalbed water and methane reveals that CO2 reduction serves as the predominant methanogenic pathway. The anomalously positive delta C-13-DIC values coupled with extremely high HCO3- concentrations indicate intense microbial methanogenesis. In the microbial community structure, bacterial communities are dominated by groups involved in the carbon cycle, forming a complex synergistic metabolic network together with groups participating in nitrogen and sulfur cycles. Archaeal communities are predominantly hydrogenotrophic methanogens, while various methanogens also possess metabolic capabilities for methylotrophic and acetoclastic pathways. Additionally, the presence of both aerobic and anaerobic methanotrophs was detected. Microbial gene function analysis reveals that the microbial communities in the study area possess diverse methanogenic functional potential, including acetoclastic and hydrogenotrophic pathways. Moreover, the widespread detection of the signature mcrA gene supports the presence of methanogenic communities and their methane-producing potential. Despite the wide range of burial depths, geochemical and microbial characteristics do not show significant differences between shallow and deep samples, indicating that microbial methanogenesis can extend to coal seam environments over a thousand meters deep in the study area. This study holds important theoretical value and practical significance for accurately assessing the resource potential of deep CBG and expanding the depth limit for CBG exploration and development.
Lightweight structural design with enhanced mechanical properties is considered a significant requirement in the field of advanced manufacturing industries such as aerospace engineering, biomedical engineering, and automotive engineering. Lattice structures have been considered as potential solutions to obtain structures with enhanced mechanical properties such as strength to weight ratio and energy absorption capacity. This research aims to carry out a comparative analysis of eleven different lattice structures inspired by nature using Fused Deposition Modelling with PLA as the chosen material. FEA analysis was conducted to analyse the mechanical behaviour of the lattice structures with respect to stress-strain behaviour, displacement, reaction force, structural efficiency, and energy absorption capacity. The results indicate the significance of lattice structures with different topologies to obtain enhanced mechanical properties. The lattice structure with the highest energy absorption capacity was the Truncated Cube lattice structure with 539.08 N.mm energy absorption capacity while maintaining the highest structural efficiency.
The trends of mass customization and personalized production lead to increased manufacturing complexity, requiring human involvement for flexibility, particularly in High-Mix, Low-Volume (HMLV) assembly. These production systems impose challenges on operators, highlighting the growing importance of providing cognitive support. Digital assembly instructions have emerged as a solution, offering step-by-step guidance to operators. However, creating and maintaining these instructions is labor-intensive, especially in HMLV contexts, due to numerous product variants and frequent design changes. This study introduces a framework for integrating product variability in digital assembly instructions and streamlining the instruction authoring process. A semantic model based on the industrial standard ISA-95 is proposed to integrate engineering information into assembly instructions. Additionally, a methodology is presented that incorporates a 150% workflow for managing instructions for a product family, from which specific variant configurations can be derived. The system suggests relevant instruction content during the authoring process of a new product variant to enhance the reuse of previously written instructions. A methodology to handle engineering changes within the assembly instructions has also been developed to warrant consistency with the product design. Initial testing has demonstrated promising results, including substantial time savings and improved consistency.
