Micro-Computed Tomography Applications in Coal Characterization

Micro-computed tomography (µ-CT) has emerged as a pivotal tool for non-destructive, high-resolution imaging of coal, enabling three-dimensional visualisation and quantification of internal structures at the micrometre scale. By exploiting variations in X-ray attenuation, µ-CT reveals pore networks, microfractures, mineral inclusions and cleat systems without physically altering the sample. This capability underpins detailed assessments of porosity, permeability pathways and mechanical heterogeneity across coal ranks, from peat to anthracite. Recent advances in segmentation algorithms and data-constrained modelling have enhanced the accuracy of phase discrimination and sub-voxel compositional mapping. Four-dimensional studies now capture fluid-solid coupling, illustrating moisture penetration, gas diffusion and stress-induced deformation over time. Insights drawn from µ-CT analyses inform coalbed methane recovery, reservoir stimulation, carbon storage and rock-burst risk assessment by linking pore morphology to flow simulation and mechanical response under varied pressure and loading conditions.

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A recent study employing µ-CT to investigate moisture infiltration demonstrated how water advances through heterogeneous pore networks during infusion. The work established a density-based equation for moisture distribution and validated CT-derived moisture contents against gravimetric measurements. Four-dimensional imaging quantified spatial-temporal water pathways and revealed preferential flow along larger pores and cleat intersections.

In experiments on coals of differing rank, three-dimensional micro-CT combined with nano-indentation elucidated the evolution of pore systems from meso- to micro-scale. Peat samples exhibited well-developed mesopores, which diminished in bituminous coal, while micro-pores persisted and proliferated in higher ranks. Concurrently, nano-mechanical testing showed a linear increase in indentation modulus with coal rank and carbon content, linking structural transformations to mechanical stiffness.

Another investigation reconstructed the micro-pore geometry of bituminous coal from CT scan data and conducted computational fluid dynamics simulations of low-pressure water seepage. The analysis revealed that seepage velocity and pressure profiles depend strongly on pore radii distribution and channel connectivity. Single-channel flow exhibited directional preferences, while multi-channel networks produced enhanced overall permeability, offering new insights into water-injection strategies for reservoir stimulation.

Micro-Computed Tomography Applications in Coal Characterization publication trend

The graph below shows the total number of articles in micro-computed tomography applications in coal characterization across all publications each year (not limited to Nature Index journals).

Technical terms

Micro-computed tomography (µ-CT): A non-invasive imaging technique that uses X-rays to produce high-resolution, three-dimensional reconstructions of a sample’s internal structure at micrometre scale.

Voxel: The smallest distinguishable box-shaped element in a three-dimensional image, analogous to a pixel in two dimensions, representing a uniform volume of material.

Porosity: The proportion of void space within a material, expressed as a fraction of the total volume, which governs fluid storage capacity.

Cleat: A natural set of orthogonal fractures in coal seams that controls permeability and fluid flow pathways.

Segmentation: The process of classifying and isolating different phases (e.g., pores, matrix, minerals) in CT images based on greyscale values or advanced algorithms.

Anisotropy: The directional dependence of a material’s physical properties, reflecting variations in structure or composition along different axes.

References

1. Moisture penetration and distribution characterization of hard coal: a µ-CT study. International Journal of Coal Science & Technology (2024).
2. Characterization of Coal Micro-Pore Structure and Simulation on the Seepage Rules of Low-Pressure Water Based on CT Scanning Data. Minerals (2016).
3. Nano-mechanical Properties and Pore-Scale Characterization of Different Rank Coals. Natural Resources Research (2019).
4. A synchrotron-based local computed tomography combined with data-constrained modelling approach for quantitative analysis of anthracite coal microstructure. Journal of Synchrotron Radiation (2014).
5. Evaluation of Multiple‐Scale 3D Characterization for Coal Physical Structure with DCM Method and Synchrotron X‐Ray CT. The Scientific World JOURNAL (2015).
6. X‐Ray Computed Tomography Analysis of Sajau Coal, Berau Basin, Indonesia: 3D Imaging of Cleat and Microcleat Characteristics. International Journal of Geophysics (2015).