Coal Petrology Effect on Nanopore Structure of Lignite: Case Study of No. 5 Coal Seam, Shengli Coalfield, Erlian Basin, China

Zhao, Jincheng; Shen, Jian; Qin, Yong; Wang, Jinyue; Zhao, Jiaxin; Li, Chao

doi:10.1007/s11053-020-09743-y

Cited by 10 publications

(3 citation statements)

References 39 publications

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“…Therefore, there is a positive correlation between the filling degree of mineral and the proportion of dull material. Furthermore, the characteristic of pores and fractures is affected by the coal lithotype. , On the one hand, minerals have a bad influence on the fracture network conductively, leading to the decrease of permeability. On the other hand, the artificial fractures propagate along the boundary of minerals and the organic coal matrix easily …”

Section: Results and Discussionmentioning

confidence: 99%

Characteristics of a Multi-scale Fracture Network and Its Contributions to Flow Properties in Anthracite

Han

Shen

et al. 2021

Energy Fuels

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Fractures are the main flow channels in the coal and play a significant role in coalbed methane (CBM) production. For a comprehensive understanding of the importance of multi-scale fractures in coal, an integrated approach of laboratory experiments and numerical simulation was used to analyze the characteristics of coal fracture networks in the samples collected from the southern Qinshui Basin, China. X-ray micro-computed tomography (micro-CT) was conducted to study the geometrical and topological parameters of multi-scale fractures in samples of different sizes. The fracture parameters, including fracture equivalent diameter, angle, orientation, spacing, fracture porosity, fractal dimension, and intersection point density, were quantitatively measured from micro-CT images of the coal samples. These micro-CT data were used to generate the multi-scale discrete fracture networks (DFNs), followed by the simulation of the gas flow behavior in coal fractures using COMSOL modeling software. The results show that the fracture equivalent diameter, fracture porosity, fractal dimension, and intersection point density are higher in the bright coal lithotype, indicating the heterogeneity distribution of the fractures in different coal lithotypes. The results depict a decline in the fracture equivalent diameter, fracture angle, fracture spacing, fracture porosity, and fractal dimension with the decrease in the sample size. However, the intersection point density of fractures shows the opposite trend. According to the fracture parameters, the fracture network development degree decreases, while the relation between different fractures (connectively) increases with the decrease of the fracture scale. The DFN simulation illustrates that the permeability increases from semi-dull coal (0.02 mD) to bright coal (0.025 mD). The long fractures contribute to the fracture connectivity network by connecting to smaller fractures and might show high-flow velocity in coal seams. Overall, the results indicate that the semi-bright coal and bright coal are beneficial to the production of CBM for the development of fractures. The findings of this study can help for a better understanding of the distribution of fractures in different coal lithotypes and will be favorable for enhancing CBM production.

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Section: Results and Discussionmentioning

confidence: 99%

Characteristics of a Multi-scale Fracture Network and Its Contributions to Flow Properties in Anthracite

Han

Shen

et al. 2021

Energy Fuels

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“…There is an internal relationship between the pore structure and petrology characteristics. The petrological characteristics are the material and spatial framework basis of the pore structure [62,63]. The size of debris particles directly determines the size of the primary pore particles; generally, the larger the debris particles, the larger the intergranular pores.…”

Section: Sedimentation and Pore Structurementioning

confidence: 99%

Pore Structure Characteristics and Main Control Factors of Sandstone in the Jurassic Zhiluo Formation in the Northern Ordos Basin

Liu,

Guo,

Hong

et al. 2023

Minerals

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The Jurassic Yan’an Formation in the Ordos Basin is one of the main coal seams mined in the basin, and the enrichment of water bodies in the upper part of this coal seam is closely related to the sand bodies in the Zhiluo Formation. This study is based on the use of core observations in the northern part of the Ordos Basin for studying the pore characteristics of the permeable sand layer of the Zhiluo Formation in the study area through testing methods such as ordinary thin sections, cast thin sections, scanning electron microscopy (SEM), mercury intrusions, and physical property analysis. The results indicate that the primary pores of the Zhiluo Formation sandstone in the study area include primary intergranular pores, residual intergranular pores, and interstitial micropores. The secondary pores are mainly intergranular pores, feldspar dissolution pores, and rock debris dissolution pores. The throat-type pores are mainly variable fault contractions, sheets, curved sheets, and bundle-shaped throats. The pore structures of the Zhiluo Formation sandstone in the research area are complex, and the permeability is influenced by the throat characteristics. The main controlling factors of the pore structure characteristics of the Zhiluo Formation sandstone in the study area are sedimentation and diagenesis. Compaction and cementation are the main factors that destroy the sandstone pore structure, while later dissolution plays a certain role in the improvement of the pores. Section 1 of the Zhiluo Formation is greatly affected by diagenesis, and section 2 is greatly affected by sedimentation.

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“…Previous research in the Erlian Basin has primarily focused on the structural and sedimentary geological characteristics of coal-bearing strata (Bonnetti et al, 2014; Ding et al, 2015) and on the CBM genetic types, biogas generation influencing factors, nanopore structure characteristics and feasibility studies of biogas recovery in the Jiergalangtu sag (Chen H et al, 2019; Sun B et al, 2018; Sun F et al, 2017; Sun QP et al, 2018; Tao JJ et al, 2019; Zhao et al, 2021). The Bayanhua sag is the key sag with low-rank CBM exploration potential in the Erlian Basin.…”

Section: Introductionmentioning

confidence: 99%

Coalbed methane geology and exploration potential in large, thick, low-rank seams in the Bayanhua Sag of the Erlian Basin, northern China

Tang

Tao

et al. 2022

Energy Exploration & Exploitation

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The Erlian Basin may be one of the most promising areas for low-rank coalbed methane (CBM) in China. The Cretaceous coal-bearing strata in the Bayanhua sag contain abundant low-rank CBM resources with suitable depths and large coal thicknesses (1.00–78.85 m, avg.22.53 m). However, the research on CBM geology and exploration potential is still lacking, which severely hinders its exploration and development. This paper presents an integrated study of CBM geology in terms of gas reservoir properties, gas-bearing characteristics and controlling factors. The results of the analysis show that lignite and subbituminous coals are the main coal types present in the study area, with medium porosity (7.3–27.8%, avg.20.77%) and low permeability (0.05–21.8 mD, avg.5.54 mD) being dominant. The pores are dominantly transition pores with inkpot shapes, which is beneficial to the adsorption of CBM. The gas content of the coal seams is 1.66–4.45 m3/t and most coal reservoirs are oversaturated. The CBM is primarily of secondary microbial origin, mostly carbon dioxide reduction. The accumulation of CBM is mainly influenced by the structure type, roof lithology and hydrogeology in the study area. According to the integrated analysis of the vertical changes in the physical properties and gas-bearing characteristics, the dominant horizon tends to be the No. 6-7 coal seam, followed by the No. 6-4 coal seam. Based upon the CBM geology and the factors controlling enrichment, the prospecting potential in the Bayanhua sag was appraised, and two favorable areas are proposed for CBM exploitation.

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Coal Petrology Effect on Nanopore Structure of Lignite: Case Study of No. 5 Coal Seam, Shengli Coalfield, Erlian Basin, China

Cited by 10 publications

References 39 publications

Characteristics of a Multi-scale Fracture Network and Its Contributions to Flow Properties in Anthracite

Characteristics of a Multi-scale Fracture Network and Its Contributions to Flow Properties in Anthracite

Pore Structure Characteristics and Main Control Factors of Sandstone in the Jurassic Zhiluo Formation in the Northern Ordos Basin

Coalbed methane geology and exploration potential in large, thick, low-rank seams in the Bayanhua Sag of the Erlian Basin, northern China

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