Characteristics of microscopic pore structure and fractal dimension of bituminous coal by cyclic gas adsorption/desorption: An experimental study

Pore structure characteristics and the effect of lithotype and maceral on pore for three types of high-volatile bituminous coals from Binchang area were investigated by combined low-temperature nitrogen adsorption/desorption, nuclear magnetic resonance (NMR), scanning electron microscope (SEM) and maceral analysis. The low temperature N2 adsorption/desorption test results show that: micropores are more abundant than transitional pores with high BET surface area; two types of pore structures can be identified by adsorption/desorption isotherms; Pore morphology is mainly represented by well-connected, ink-bottled, cylindrical and parallel plate pores. NMR T2 distributions at full saturated condition are apparent or less obvious trimodal and three types of T2 distributions are identified; Seepage pores are better developed when compared with the middle-high rank coal. Further research found that the three coal lithotypes are featured by remarkably different pore structure characteristics and maceral contents of coal are linearly correlated to some of pore structure parameters.

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Coal Anisotropic Sorption and Permeability: An Experimental Study

Processes ◽

10.3390/pr6080104 ◽

2018 ◽

Vol 6 (8) ◽

pp. 104 ◽

Cited By ~ 7

Author(s):

Yulong Chen ◽

Xuelong Li ◽

Bo Li

Keyword(s):

Experimental Study ◽

Gas Adsorption ◽

Great Influence ◽

Flow Characteristics ◽

Volumetric Strain ◽

Bedding Plane ◽

Gas Production ◽

Desorption Process ◽

Bedding Angle ◽

Adsorption Desorption

Knowledge of the bedding plane properties of coal seams is essential for the coalbed gas production because of their great influence on the inner flow characteristics and sorption features of gas and water. In this study, an experimental study on the anisotropic gas adsorption–desorption and permeability of coal is presented. The results show that during the adsorption–desorption process, an increase in the bedding plane angle of the specimen expands the length and area of the contact surface, thereby increasing the speed and quantity of adsorption and desorption. With an increase in the bedding angle, the number of pores and cracks was found to increase together with the volumetric strain. The evolution of permeability of coal heavily depended on stress–strain stages. The permeability decreased with the increase of stress at the initial compaction and elastic deformation stages, while it increased with the increase of stress at the stages of strain-hardening, softening and residual strength. Initial permeability increased with increasing bedding angle.

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Nano-scale pore structure and fractal dimension of organic-rich Wufeng-Longmaxi shale from Jiaoshiba area, Sichuan Basin: Investigations using FE-SEM, gas adsorption and helium pycnometry

Marine and Petroleum Geology ◽

10.1016/j.marpetgeo.2015.11.019 ◽

2016 ◽

Vol 70 ◽

pp. 27-45 ◽

Cited By ~ 225

Author(s):

Rui Yang ◽

Sheng He ◽

Jizheng Yi ◽

Qinhong Hu

Keyword(s):

Fractal Dimension ◽

Pore Structure ◽

Sichuan Basin ◽

Gas Adsorption ◽

Nano Scale ◽

Longmaxi Shale ◽

Helium Pycnometry

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Corrigendum to “Yang, R., He, S., Yi, J., Hu, Q., 2016. Nano-scale pore structure and fractal dimension of organic-rich Wufeng-Longmaxi shale from Jiaoshiba area, Sichuan Basin: Investigations using FE-SEM, gas adsorption and helium pycnometry” [Mar. Pet. Geol. 70 27–45]

Marine and Petroleum Geology ◽

10.1016/j.marpetgeo.2019.104167 ◽

2020 ◽

Vol 114 ◽

pp. 104167

Author(s):

Rui Yang ◽

Sheng He ◽

Jizheng Yi ◽

Qinhong Hu

Keyword(s):

Fractal Dimension ◽

Pore Structure ◽

Sichuan Basin ◽

Gas Adsorption ◽

Nano Scale ◽

Longmaxi Shale ◽

Helium Pycnometry

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Nano-Scale Pore Structure and Its Multi-Fractal Characteristics of Tight Sandstone by N2 Adsorption/Desorption Analyses: A Case Study of Shihezi Formation from the Sulige Gas Filed, Ordos Basin, China

Minerals ◽

10.3390/min10040377 ◽

2020 ◽

Vol 10 (4) ◽

pp. 377

Author(s):

Zhelin Wang ◽

Xuewei Jiang ◽

Mao Pan ◽

Yongmin Shi

Keyword(s):

Fractal Dimension ◽

Specific Surface ◽

Pore Structure ◽

Surface Area ◽

Mineral Composition ◽

Fractal Dimensions ◽

Contribution Rate ◽

Tight Sandstone ◽

N2 Adsorption ◽

Adsorption Desorption

Fractal dimension is a critical parameter to evaluate the heterogeneity of complex pore structure in tight sandstone gas and other low permeability reservoirs. To quantify the fractal dimension of tight sandstone at various pore size classes and evaluate their implications on mineral composition and nano pore structure parameters, we conducted an integrated approach of N2 adsorption/desorption experiment (N2-GA), X-ray diffraction (X-RD), and field emission scanning electron microscopy (FE-SEM) on Sulige tight sandstone reservoirs. By comparing the nine types of fractal dimensions calculated from N2 adsorption data, we put forward the concept of “concentrated” fractal dimensions and “scattered” fractal dimensions (DN2, DN3, DN5, DN7 and DN8) for the first time according to its concentration extent of distribute in different samples. Result shows that mineral composition has a significant influence of a different level on specific surface area (SSA), pore volume (PV), and fractal dimensions (DN), respectively, where the “scattered” fractal dimension is more sensitive to certain specific property of the reservoir, including mineral content and the specific surface area contribution rate (Sr) of type II mesopores (Mesopore-II: 10~50nm). In addition, three type of hysteresis loops were distinguished corresponding to different pore shape combination of N2-GA isotherm curve, which reveals that pore structure heterogeneity is mainly controlled by inkbottle-shaped pores and the volume contribution rate (Vr) of mesopores in this study area. These findings could contribute to a better understanding of the controlling effect of pore heterogeneity on natural gas storage and adsorption.

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