An atomic force microscopy study of coal nanopore structure

Yao, Shuchun; Jiao, Kun; Zhang, Ke; Hu, Wenxuan; Ding, Hai; Li, MiaoChun; Pei, Wenming

doi:10.1007/s11434-011-4623-8

Cited by 68 publications

(20 citation statements)

References 25 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, traditional methods do little to connectivity analyses of pores in coal. Recently, new techniques such as Focused Ion Beam-Scanning Electron Microscopy (FIB-SEM) and X-ray Computed Tomography (X-ray CT) have been successfully applied to study the pores in conventional reservoir and gas shale (Clarkson et al, 2013;Radliński et al, 2009;Yao et al, 2011). While X-ray CT has been applied to study the pores in coal seams (Ramandi et al, 2016;Pant et al, 2015;Golab et al, 2013;Yao et al, 2009;), FIB-SEM has not been widely used in coal seams.…”

Section: Introductionmentioning

confidence: 99%

FIB-SEM and X-ray CT characterization of interconnected pores in high-rank coal formed from regional metamorphism

Liu¹,

Sang

Wang

et al. 2017

Journal of Petroleum Science and Engineering

139

View full text Add to dashboard Cite

Pores in coal and their connectivity are important properties of coal, providing network or channels for gas storage and migration within coal, e.g. during the coalbed methane (CBM) recovery. To investigate the growth characteristics and genetic types of pores in coal in terms of macropore and mesopore, the pores of a high-rank coal were measured by various techniques such as the mercury intrusion method, nitrogen adsorption, focused ion beam scanning electron microscopy (FIB-SEM), and X-ray micro-CT (Computed Tomography). Two high-rank coals formed from regional metamorphism collected from the southern Qinshui basin were selected. The FIB-SEM and X-ray micro-CT provides detailed experimental information for development of a three dimensional (3D) pore network model, which was further used to characterize the pore connectivity. Volume percent of pores of these high-rank coals are dominated by mesopores of approximately 10-50 nm in width, and then followed by micropores, along with the smallest volume percent of macropores. The connectivity within this high-rank coal was mesopore-dominated pore network. Electron microscopy observations further revealed there are coalification-related pores and mineral-related pores in the high-rank coal. The coalification-related pores can be classified as secondary gas pores in organic matter and shrinkage-induced pores around quartz and clay minerals; and the mineral-related pores are developed within minerals, and can be classified as dissolution-created pores and intercrystalline pores. The secondary gas pores are macropores and have poor connectivity. The mineral-related pores can be both macropores and mesopores, and have little influence on pore connectivity due to small content of carbonate minerals in these samples. Under electron microscopy, the shrinkage-induced pores are mainly mesopores. The regional metamorphism, with a high abnormal old thermal field in the research area, is the precondition of the formation of the shrinkage-induced pores. The quartz and clay minerals in the coal provide different formation conditions and hence form different shapes of the shrinkage-induced pores. The coal samples include a large number of shrinkage-induced pores that act as the interconnected pores in the coal and exhibit good connectivity. The quartz and clay minerals play a significant role in developing the interconnected pores in the high-rank coal formed from regional metamorphism.

show abstract

Section: Introductionmentioning

confidence: 99%

FIB-SEM and X-ray CT characterization of interconnected pores in high-rank coal formed from regional metamorphism

Liu¹,

Sang

Wang

et al. 2017

Journal of Petroleum Science and Engineering

139

View full text Add to dashboard Cite

show abstract

“…The AFM research to date has focused on coal maceral [36,37] or coal surface pore characteristics of surface topography [38]. Here, we use combined multimodal micro-Raman and functional AFM imaging through band excitation-atomic force acoustic microscopy (BE-AFAM) to resolve chemical, mechanical and structural components of coal on the micron-nanometer scale.…”

Section: Introductionmentioning

confidence: 99%

Breaking the limits of structural and mechanical imaging of the heterogeneous structure of coal macerals

et al. 2014

View full text Add to dashboard Cite

The correlation between local mechanical (elasto-plastic) and structural (composition) properties of coal presents significant fundamental and practical interest for coal processing and for the development of rheological models of coal to coke transformations. Here, we explore the relationship between the local structural, chemical composition, and mechanical properties of coal using a combination of confocal micro-Raman imaging and band excitation atomic force acoustic microscopy for a bituminous coal. This allows high resolution imaging (10s of nm) of mechanical properties of the heterogeneous (banded) architecture of coal and correlating them to the optical gap, average crystallite size, the bond-bending disorder of sp 2 aromatic double bonds, and the defect density. This methodology allows the structural and mechanical properties of coal components (lithotypes, microlithotypes, and macerals) to be understood, and related to local chemical structure, potentially allowing for knowledge-based modeling and optimization of coal utilization processes.2

show abstract

“…They concluded that pore volume and frequency are controlled by rank [37]. The average pore size of low-rank coals is larger than that of high-rank coals [39]. A report by Rodrigues and Lemos de Sousa (2002) indicated that high-volatile bituminous A and higher rank coals are dominated by micropores.…”

Section: Pores In Coalmentioning

confidence: 98%

“…In terms of the relationship between porosity and the maceral composition, the research results conducted by different researchers are not consistent due to the difference of the studied samples, the different measuring methods and sometimes even the different coal size classification standards. For example, Mastalerz (2008) reported that vitrinite maceral predominantly contains micropores and inertinite mostly contains mesopores and macropores [39,40]. But Harris and Yust (1976) reported that vitrinite is mainly composed of micropores and mesopores, inertinite of mesopores, and liptinite of macropores.…”

Section: Pores In Coalmentioning

confidence: 99%

“…These researchers concluded that inertinite is the most porous (predominant macropores) maceral group and liptinite is the least porous [41]. However, it is generally accepted that Vitrinite content is the most important maceral composition because of high internal surface area due to the abundant microporosity [39]. Gan et al (1972) described coal porosity in a series of coal samples from lignite to anthracite coals.…”

Section: Pores In Coalmentioning

confidence: 99%

See 1 more Smart Citation

Oxidant stimulation of coal seams to increase coal seam permeability

Jing¹

View full text Add to dashboard Cite

Low permeability renders a significant fraction of coal seam gas (CSG) resources subeconomic. An effective permeability enhancement strategy is thereby crucial in monetising low permeability CSG resources. Though employed in a number of coal basins, conventional low permeability stimulation treatments have not been ubiquitously successful. The natural cleat system of coal is the primary conduit for gas flow and low permeability is in many cases attributed to low cleat porosity and connectivity. Cleat demineralisation by acid has been addressed previously with mixed results. This thesis explores the possibility that coal cleats could be etched and the cleat aperture could be widened by use of oxidants. It could have high potential to increase the cleat porosity and connectivity, thus enhancing the coal permeability in the near well bore region where high permeability is critical. Two coal samples, from the Bowen (coal B) and Surat (coal S) basins in Queensland, Australia were selected. A screening method was designed based on time-lapse photography to assess the extent of coal particle size change immersed in potential oxidants, including sodium hypochlorite (NaClO), potassium permanganate (KMnO4), hydrogen peroxide (H2O2), and potassium persulfate (K2S2O8). Results show coal solubilisation and the propensity to swell in all the oxidants as well as coal breakage in specific oxidants (NaClO and KMnO4). Both coals react vigorously with NaClO and KMnO4, where massive coal solubilisation occurs, but react only slightly with K2S2O8 and H2O2. Given the solid products of the KMnO4 reaction (MnO2), NaClO is selected as the most promising oxidant stimulant. After NaClO treatment, the total accessible pore volume of both coals increases. Pore size distributions indicate that oxidation can enlarge the pores, particularly for coal S, which was confirmed by scanning electron microscopy (SEM). A microfluidic cleat flow cell (CFC) was used to inject NaClO into artificial channels scribed on polished coal samples, and measured an increase in the widths of the channels after NaClO treatment. The channel aperture increase indicates that coal solubilisation/etching is a more dominant mechanism than coal swelling when coal is confined in coal cleats. The channel aperture of coal S increases more than coal B.

show abstract

An atomic force microscopy study of coal nanopore structure

Cited by 68 publications

References 25 publications

FIB-SEM and X-ray CT characterization of interconnected pores in high-rank coal formed from regional metamorphism

FIB-SEM and X-ray CT characterization of interconnected pores in high-rank coal formed from regional metamorphism

Breaking the limits of structural and mechanical imaging of the heterogeneous structure of coal macerals

Oxidant stimulation of coal seams to increase coal seam permeability

Contact Info

Product

Resources

About