Fractal Analysis of Coal Pore Structure Based on Computed Tomography and Fluid Intrusions

Chen, Xuexi; Ma, Rupeng; Wu, Jinsui; Sun, Jihong

doi:10.3390/fractalfract7060439

Cited by 3 publications

(2 citation statements)

References 44 publications

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“…However, the fractal dimension D 2 is negatively correlated with the average pore diameter (Figure 10d), indicating that the smaller the average pore diameter, the more complex the pore structure, which is also supported by other investigations. 45,46 Based on this phenomenon, we can infer that deformed coals with smaller pore sizes should correspond to a more complex pore structure compared with primary coals. 47 In addition, D 2 is positively correlated with the micropore volume percentage and total pore volume of coal samples, and the correlation coefficients (R 2 ) are 0.95 and 0.70, respectively (Figure 10f,h), which indicates that the micropore content and total pore volume have a great influence on the pore structure and further confirms that the fractal dimension D 2 represents the pore structure characteristics of coal.…”

Section: Relationships Between Fractal Dimension and Coalmentioning

confidence: 93%

Investigation on Adsorption Pore and Fractal Analyses of Low-Rank Coals in the Northern Qaidam Basin

Zhou,

He,

Hou

2024

ACS Omega

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The northern Qaidam Basin has abundant coal and coalbed methane (CBM) resources, and quantitative evaluation of adsorption pore characteristics has great significance for optimum selection of CBM-favorable areas. Based on vitrinite reflectance, coal maceral, proximate analysis, low-temperature N 2 adsorption, and methane isothermal adsorption experiments, the heterogeneities of adsorption pores (pore diameter <100 nm) were quantitatively characterized, and relationships between fractal dimensions and physical parameters of low-ranked coal reservoirs were revealed. The results show that the micropore volume percentage ranges between 33.70 and 86.44% with an average of 64.94%. Based on N 2 adsorption/desorption curves and pore diameter distribution characteristics, the adsorption pore structures of low-ranked coals were divided into 3 types. According to the FHH model, fractal dimension D 1 (relative pressure between 0 and 0.5) and D 2 (relative pressure between 0.5 and 1) were calculated. Fractal dimension D 1 , representing adsorption pore surface area, ranges from 2.001 to 2.345, with lower values. Fractal dimension D 2 (adsorption pore structure) is from 2.641 to 2.917, with relatively high values, which has a decreasing tendency from west to east in the study area. There are positive relationships between fractal dimension D 1 and Langmuir volume and specific surface area, whereas negative correlations are found between fractal dimension D 2 and Langmuir pressure, ash yield, moisture content, volatile content, and average pore diameter. Combined with the related data for middle-and high-rank coals, the characteristics of pore surface and methane adsorption capacity can be analyzed based on the variation of vitrinite reflectance. Furthermore, the complexity of pore structure can also be predicted according to the averaged pore size and micropore content to some degree.

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Section: Relationships Between Fractal Dimension and Coalmentioning

confidence: 93%

Investigation on Adsorption Pore and Fractal Analyses of Low-Rank Coals in the Northern Qaidam Basin

Zhou,

He,

Hou

2024

ACS Omega

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“…The main current research methods for coal reservoir pores and fractures include the traditional low-temperature liquid nitrogen method and mercury injection method, , high-resolution scanning electron microscopy, , CT scanning, nuclear magnetic resonance, other photo electromagnetic observation methods , and X-ray microcomputed tomography (CT). CT is a widely used nondestructive testing method for analyzing the pore and fracture structure of reducing coal. − Previous scholars have used CT technology to analyze different aspects of the coal reservoir pore and fracture structure.…”

Section: Introductionmentioning

confidence: 99%

Comprehensive Analysis of Connectivity and Permeability of a Pore-Fracture Structure in Low Permeability Seam of Huainan–Huaibei Coalfield

Wang,

Fang,

Sang

et al. 2024

ACS Omega

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The connectivity and permeability of the coal seam pore structures control the occurrence and migration of coalbed methane. Coal samples were used from Huainan−Huaibei to reconstruct three-dimensional models of the pores and an equivalent pore network model, Statistical pore structure characteristic parameters. The pore structure of the coal reservoir was analyzed from the direction of multidimensional and multiangle. It shows that based on quantitative analysis, the representative Elementary volume of 500 × 500 × 500 was the most suitable experimental volume. The Y-axis direction of the Renlou sample had poor pore connectivity compared to that of other samples. Large volume connected pores dominated their pore systems. In terms of coal sample pore connectivity, the coal samples from the Liuzhuang and Qidong regions had pore connectivity better than those from the other regions. The pore connectivity of the Liuzhuang coal samples was the best. In terms of coal permeability, the Liuzhuang sample had better permeability than the other three samples, and the permeability was the best in the Y-axis direction. For all the combinations of the different types of throats, the shorter the throat, the greater the equivalent radius and the better the permeability. Conversely, the worse the permeability. During gas injection production, the closer the gas injection area was to the gas injection well, the poorer the connectivity and the lower the permeability over time. Near the production area, where the CO 2 did not reach the production area, the fracture porosity and effective connected porosity of the coal reservoir increased over time. When CO 2 reached the production area, the change in its connected pore structure was consistent with the change in the connected pores in the gas injection area. With this study, the coal seam pore structure on a microscale was characterized. A comprehensive analysis of the coal reservoir pore connectivity and permeability was completed. The study results are significant for the exploration and development of coalbed methane in the Huainan−Huaibei coalfield.

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Multifractal Characteristics of Low-Field Nuclear Magnetic Resonance of Different Rank Coals and Its Permeability Predicting Method

Yu,

Meng,

et al. 2024

Langmuir

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Fractal Analysis of Coal Pore Structure Based on Computed Tomography and Fluid Intrusions

Cited by 3 publications

References 44 publications

Investigation on Adsorption Pore and Fractal Analyses of Low-Rank Coals in the Northern Qaidam Basin

Investigation on Adsorption Pore and Fractal Analyses of Low-Rank Coals in the Northern Qaidam Basin

Comprehensive Analysis of Connectivity and Permeability of a Pore-Fracture Structure in Low Permeability Seam of Huainan–Huaibei Coalfield

Multifractal Characteristics of Low-Field Nuclear Magnetic Resonance of Different Rank Coals and Its Permeability Predicting Method

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