Rough-walled discrete fracture network modelling for coal characterisation

Jing, Yu; Armstrong, Ryan T.; Mostaghimi, Peyman

doi:10.1016/j.fuel.2016.11.094

Cited by 89 publications

(31 citation statements)

References 62 publications

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“…The measured roughness of the geo-material microfluidics devices was compared against slices of their respective rock types. Roughness is measured based on the arithmetic mean roughness, which indicates the average of the absolute value along the reference length 77 . Eq.…”

Section: Methodsmentioning

confidence: 99%

Functionalisation of Polydimethylsiloxane (PDMS)- Microfluidic Devices coated with Rock Minerals

Alzahid

Mostaghimi

Gerami

et al. 2018

Sci Rep

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Fluid flow in porous rocks is commonly capillary driven and thus, dependent on the surface characteristics of rock grains and in particular the connectivity of corners and crevices in which fluids reside. Traditional microfluidic fabrication techniques do not provide a connected pathway of crevices that are essential to mimic multiphase flow in rocks. Here, geo-material microfluidic devices with connected pathways of corners and crevices were created by functionalising Polydimethylsiloxane (PDMS) with rock minerals. A novel fabrication process that provides attachment of rock minerals onto PDMS was demonstrated. The geo-material microfluidic devices were compared to carbonate and sandstone rocks by using energy dispersive X-ray spectroscopy, scanning electron microscopy (SEM), contact angle measurements, and a surface profilometer. Based on SEM coupled with energy-dispersive X-ray spectrometry (SEM-EDS) analyses, roughness measurements, contact angle, wettability, and roughness were comparable to real rocks. In addition, semivariograms showed that mineral deposition across the different geo-material devices was nearly isotropic. Lastly, important multiphase flow phenomena, such as snap-off and corner flow mechanisms, equivalent to those occurring in reservoir rocks have been visualised. The presented approach can be used to visualise rock-fluid interactions that are relevant to subsurface engineering applications, such as hydrocarbon recovery and CO2 sequestration.

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Section: Methodsmentioning

confidence: 99%

Functionalisation of Polydimethylsiloxane (PDMS)- Microfluidic Devices coated with Rock Minerals

Alzahid

Mostaghimi

Gerami

et al. 2018

Sci Rep

Self Cite

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“…For example, in Figures a and b, both the noise and cleats are shown to be light gray. So during segmentation, noise is unavoidably segmented as void pores (Figures b and e), inducing extra pores that are not void space in reality (Jing et al, ). Therefore, we apply a denoising process to remove the noise from micro‐CT images.…”

Section: Methodsmentioning

confidence: 99%

Topological Characterization of Fractured Coal

et al. 2017

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Coal transport properties are highly dependent on the underlying fractured network, known as cleats, which are characterized by geometrical and topological properties. X‐ray microcomputed tomography (micro‐CT) has been widely applied to obtain 3‐D digital representations of the cleat network. However, segmentation of 3‐D data is often problematic due to image noise, which will result in inaccurate estimation of coal properties (e.g., porosity and specific surface area). To circumvent this issue, a discrete fracture network (DFN) model is proposed. We develop a characterization framework to determine if the developed DFN models can preserve the topological properties of the coal cleat network found in micro‐CT data. We compute the Euler characteristic, fractal dimension, and percolation quantities to analyze the topology locally and globally and compare the results between micro‐CT data (before denoising), filtered micro‐CT data (after denoising), and the DFN model. We find that micro‐CT data with noise have extensive connectivity while filtered micro‐CT data and DFN models have similar topology both globally and locally. It is concluded that the topology of the DFN models are closer to that of the realistic cleat network that do not have segmentation‐induced pores. In addition, micro‐CT imaging always struggles with the trade‐off between sample size and resolution, while the presented DFN models are not restricted by imaging resolution and thus can be constructed with extended domain size. Overall, the presented DFN model is a reliable alternative with realistic cleat topology, extended domain size and favorable data format for direct numerical simulations.

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“…According to rock damage theory, high stresses on the entry wall tend to produce more mining-induced fractures [23][24][25]. The degree of damage differs as the pillar width changes.…”

Section: Model Description At the Laboratorymentioning

confidence: 99%

Analysis and Optimization of Entry Stability in Underground Longwall Mining

et al. 2017

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For sustainable utilization of limited coal resources, it is important to increase the coal recovery rate and reduce mine accidents, especially those occurring in the entry (gateroad). Entry stabilities are vital for ventilation, transportation and other essential services in underground coal mining. In the present study, a finite difference model was built to investigate stress evolutions around the entry, and true triaxial tests were carried out at the laboratory to explore entry wall stabilities under different mining conditions. The modeling and experimental results indicated that a wide coal pillar was favorable for entry stabilities, but oversize pillars caused a serious waste of coal resources. As the width of the entry wall decreased, the integrated vertical stress, induced by two adjacent mining panels, coupled with each other and experienced an increase on the entry wall, which inevitably weakened the stability of the entry. Therefore, mining with coal pillars always involves a tradeoff between economy and safety. To address this problem, an innovative non-pillar mining technique by optimizing the entry surrounding structures was proposed. Numerical simulation showed that the deformation of the entry roof decreased by approximately 66% after adopting the new approach, compared with that using the conventional mining method. Field monitoring indicated that the stress condition of the entry was significantly improved and the average roof pressure decreased by appropriately 60.33% after adopting the new technique. This work provides an economical and effective approach to achieve sustainable exploitation of underground coal resources.

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Rough-walled discrete fracture network modelling for coal characterisation

Cited by 89 publications

References 62 publications

Functionalisation of Polydimethylsiloxane (PDMS)- Microfluidic Devices coated with Rock Minerals

Functionalisation of Polydimethylsiloxane (PDMS)- Microfluidic Devices coated with Rock Minerals

Topological Characterization of Fractured Coal

Analysis and Optimization of Entry Stability in Underground Longwall Mining

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