Effects of Rapid Thermal Exposure from Igneous Intrusions on the Pore Structure, Thermal Maturity, and Nanomechanical Properties of Coal and Shale
Bibliographic record
Abstract
High Resolution Image Download MS PowerPoint Slide Rising energy demands and concerns about global warming have made coal and shale increasingly important not only as unconventional energy sources but also as potential storage sites for CO 2 sequestration. However, selecting these formations for either energy extraction or carbon storage requires comprehensive geological and petrophysical assessments. This is particularly important because, in some cases, localized thermal metamorphism from igneous intrusions can significantly alter their organic and structural properties, beyond natural thermal gradients, potentially making them unsuitable. Despite this, studies investigating the effects of igneous intrusions on the pore structure, geochemical attributes, and mechanical behavior at the micro- and nanoscale remain limited, especially in the Indian geological context. To address this gap, the present study offers the first integrated comparison of thermally altered and unaltered Indian coals and shales from the Raniganj Basin, with a focus on evaluating their suitability for CO 2 sequestration. A range of analytical techniques was applied, including Rock–Eval pyrolysis, petrography, X-ray diffraction (XRD), N 2 and CO 2 low-pressure gas adsorption, and nanoindentation, to assess the influence of igneous intrusion on the chemical, mineralogical, pore structural, and nanomechanical characteristics of both shale and coal. The results indicate a reduction in the hydrogen index, increased thermal maturity, higher quartz content, finer pore structures, elevated pore volumes and adsorption capacities, and significantly greater Young’s moduli in the heat-altered samples compared to unaltered ones. The increased stiffness observed in the thermally altered samples is attributed to the elevated thermal maturity of organic matter, marked by a higher proportion of aromatic carbon. This transformation, driven by aliphatic chain cracking and hydrocarbon expulsion, leads to the formation of devolatilization vacuoles and the development of finer micropores. Additionally, mineral transformations documented by XRD analysis, particularly the reduction of kaolinite and the enrichment of quartz, contribute to the enhanced mechanical stiffness. These changes result from abrupt, short-duration thermal exposure at high temperatures associated with igneous activity, which contrasts with gradual burial-related maturation processes. Overall, the findings provide new insights into the transformative effects of igneous intrusions on coal and shale properties, extending beyond conventional burial histories. They highlight the implications for hydrocarbon recovery, CO 2 sequestration potential, and geomechanical stability in thermally altered basins and support the need for further targeted studies.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".