The characteristics of coal reservoir pores and coal facies in Liulin district, Hedong coal field of China

Zhang, Songhang; Tang, Shuheng; Tang, Dazhen; Pan, Zhejun; Yang, Fangxing

doi:10.1016/j.coal.2009.11.007

Cited by 163 publications

(70 citation statements)

References 35 publications

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“…Many scholars have used mercury intrusion porosimetry, liquid nitrogen and small-angle neutron scattering to study coal pore structures and its influence factors, and they have also carried out significant discussions on the impact on CH 4 adsorption capacity (Bustin and Clarkson 1998;Prinz et al 2004;Prinz and Littke 2005;Tang et al 2008;Zhou and Wu 2012;Ding et al 2011;Gürdal and Yalçın 2001;Ogawa 2001, 2003;Jiang et al 2011;Xue et al 2012;Qu and Wang 2010;Cai et al 2011;Mastalerz et al 2008;Pan et al 2012;Sakurovs et al 2012;Feng et al 2013;Cai et al 2013;Zhang et al 2012). However, we find that the studies on tectonically deformed coal are not fully addressed, particularly in nanoscale pore level.…”

Section: Introductionmentioning

confidence: 97%

Nanoscale Pores in Coal Related to Coal Rank and Deformation Structures

et al. 2015

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Experimental results show that nanoscale pores in coal are affected by coal rank and deformation structures. In terms of pore volume, the transitional pores occupy the largest proportion, and in terms of specific surface area, the sub-micropores take up the largest proportion. For weak brittle deformed coal (including normal structured coal), when the coal rank increases, the volume and specific surface area of pores in different sizes firstly decrease and then increase. The volume and specific surface area of transitional pores and micropores in coal reach the minimum at about R O,ran = 2.0 %. After that, a slow increasing trend is observed. The volume of sub-micropores reaches the minimum at about R O,ran = 1.5 % and then shows a trend of rapid growth as coal rank increases. As the degree of coal deformation increases, both pore volume and specific surface area have a significant increase. Under strong tectonic deformation, both the volume and total specific surface area of the nanoscale pores and of sub-micropores increase significantly; the volume of transitional pores increases moderately, and their specific surface area shows a decreasing trend; the volume and specific surface area increments of micropores decline rapidly as the degree of metamorphism increases.

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Section: Introductionmentioning

confidence: 97%

Nanoscale Pores in Coal Related to Coal Rank and Deformation Structures

et al. 2015

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“…The development of both transition and micropores is controlled by coalification and as a result they are sensitive to coal rank. The transition pores and micropores are the primary sites of gas adsorption and diffusion (Zhang et al, 2010). Lower-rank coals contain mainly macropores and high rank coals contain mainly micropores (Clarkson and Bustin, 1999).…”

Section: Pore Sturcutre Experiments and Discussionmentioning

confidence: 99%

“…Laxminarayana and Crosdale (1999) have found that coal rank has influence on effective diffusivity and inferred this is likely to be related to pore size distribution. While the pore size distribution of coal was found to be related to coal rank (Gan et al, 1972;Laxminarayana and Crosdale, 1999;Levy et al, 1997;Zhang et al, 2010;Zheng et al, 2012), which is also known as maturity commonly quantified by the parameters of vitrinite reflectance. However, all the above studies have not gone into further discussion about the relationship among diffusivity, pore volume distribution and coal rank in a qualitative and quantitative way.…”

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confidence: 99%

Laboratory and Modeling Study on Gas Diffusion with Pore Structures in Different-Rank Chinese Coals

Zheng

Pan

Tang

et al. 2013

Energy Exploration & Exploitation

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The coalbed methane production rate is mainly controlled by two parameters: diffusivity in the coal matrix and permeability in the cleat system. As one key parameter, diffusion plays an important role in coalbed methane producing process. However, till now there is no systematic study on the relationship of diffusivity, pore size and coal ranks. In this work, three Chinese coal samples which belong to low, middle and high rank, respectively, were studied using experimental and modeling methods. Four gases, H 2 , N 2 , CH 4 and CO 2 , are used to study the diffuse characters at four different pressures steps. The experimental results showed that the adsorption balance time varies with different testing gas type and it is closely related with coal rank. Balance time testing with CO 2 is the longest, and then is CH 4 , while He is the slowest. Moreover, high rank coal takes the longest time to reach balance, while low rank coal takes the least. Generally, the sorption balance time for JCC-01 is about 150-350 S 0.5 , it is about 250-400 S 0.5 for CZ-1, while it is about 900-1200 S 0.5 for JCC-01. Modeling results showed that for all these three ranked Chinese coals, the bidisperse model can be used to model the diffuse process. The β value, which is the ratio of macropore adsorption/desorption to the total adsorption/desorption, increases with the increasing of pore pressure, except for sample JCC-01 when measured using CO 2 . There is no regular law for both micropore and macropore diffusion coefficient. In order to study the relationship of diffusivity, pore structure and coal ranks, the experiments of mercury injection test and low-temperature liquid nitrogen experiment were done to analyse the relationship. The results show that, for the low rank coal sample TCG-1, the mesopore takes the majority while the macropore also takes part of the pore distribution, there are few even no micropore. For middle rank sample CZ-1, the mesopore also takes the majority and the macorpore accounts for a small percentage. While for high rank coal sample JCC-01, micropore takes the majority, and mesopore and macropore take small part of the pore structure distribution. The conclusion drawn from these testing results can be used to explain the adsorption and diffusion laws found before.

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“…The pore structure and porosity of coal, which is a complicated and porous solid, affect not only the migration behavior of coalbed gas but also its storage and adsorption mechanisms [1][2][3][4][5][6][7]. There are several categories of coal pore systems.…”

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confidence: 99%

An atomic force microscopy study of coal nanopore structure

et al. 2011

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Coal nanopore structure is an important factor in understanding the storage and migration of absorbed gas in coal. A new method for studying coal nanopore structures is proposed. This idea is based on the nano-level resolution of atomic force microscopy, which can be employed to observe the structural features of coal nanopores clearly, conduct quantitative three-dimensional measurements and obtain structural parameters. Analysis results show that coal nanopores are mainly metamorphic pores and intermolecular pores. The metamorphic pores are commonly rounded and elliptical, increasing quantitatively with the coalification degree. The forms of intermolecular pores change markedly. The average pore size of low-rank coal is bigger than high-rank coal, and the number of intermolecular pores decreases as the coal rank increases. Section analysis effectively characterizes the coal pore microstructure, bearing analysis is a vital approach to measure microporosity, and grain analysis can be employed to study the pore size distribution. Atomic force microscopy is a tool for the in-depth research of coal pore microstructure and the coal-bed methane adsorption mechanism. coal nanopore, atomic force microscopy, coal-bed methane, pore size distribution, porosity Citation:Yao S P, Jiao K, Zhang K, et al. An atomic force microscopy study of coal nanopore structure.The characteristics of coal pores have attracted wide attention from scholars around the world because of the multiple needs of coal-bed methane exploration and development, and CO 2 injection and underground storage. The pore structure and porosity of coal, which is a complicated and porous solid, affect not only the migration behavior of coalbed gas but also its storage and adsorption mechanisms [1-7]. There are several categories of coal pore systems. Xodot used the diameter to classify pores as micropores (<0.01 μm), small pores (0.010.1 μm), mesopores (0.11 μm) and macropores (>1 μm) [8]. Gan et al. [9] classified coal pores as micropores (0.41.2 nm), transitional pores(1.230 nm) and macropores (>30 nm). Zhang [10] divided coal pores into primary pores, metamorphic pores, epigenetic pores and mineral pores according to scanning electron microscopy (SEM) and found that pore diameters were generally larger than 1000 nm. The features of these macropores are of great importance to free gas storage and migration; however, small pores and micropores, which are difficult to observe under normal microscopes and through SEM because their diameters are smaller than 100 nm, have an important role in adsorbed-gas storage and migration. Nowadays, methods of characterizing coal nanopore structure, pore size distribution, porosity and other fractal properties mainly comprise mercury porosimetry, use of the nitrogen adsorption isotherm, SEM, transmission electron microscopy, small-angle X-ray scattering and neutron scattering analysis. Because of the compressibility of coal and the average pore sizes being of nanoscale, it is difficult to characterize pore size distribution ...

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The characteristics of coal reservoir pores and coal facies in Liulin district, Hedong coal field of China

Cited by 163 publications

References 35 publications

Nanoscale Pores in Coal Related to Coal Rank and Deformation Structures

Nanoscale Pores in Coal Related to Coal Rank and Deformation Structures

Laboratory and Modeling Study on Gas Diffusion with Pore Structures in Different-Rank Chinese Coals

An atomic force microscopy study of coal nanopore structure

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