Insights into matrix compressibility of coals by mercury intrusion porosimetry and N2 adsorption

Cai, Yidong; Li, Qian; Liu, Dameng; Zhou, Yingfang; Lv, Dawei

doi:10.1016/j.coal.2018.11.007

Cited by 131 publications

(88 citation statements)

References 49 publications

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“…By using this method, Guo et al [23] calculated the coal matrix compressibility coefficients and found it emerges as a "U-shaped" trend with coal ranks. Cai et al [24] found the coal matrix compressibility coefficients are in the range of 0.24−13.56 × 10 −10 m 2 /N, and then they revealed the influence factors of compressibility in differently ranked coals.…”

Section: Introductionmentioning

confidence: 99%

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Insights into Multifractal Characterization of Coals by Mercury Intrusion Porosimetry

et al. 2019

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Mercury intrusion porosimetry (MIP) as a practical and effective measurement has been widely used in characterizing the pore size distribution (PSD) for unconventional reservoirs (e.g., coals and shales). However, in the process of MIP experiments, the high mercury intrusion pressure may cause matrix compressibility and result in inaccurate estimations of PSD. To get a deeper understanding of the variability and heterogeneity characteristics of the actual PSD in coals, this study firstly corrected the high mercury intrusion pressure data in combination with low-temperature N 2 adsorption (LTNA) data. The results show that the matrix compressibility was obvious under the pressure over 24.75 MPa, and the calculated matrix compressibility coefficients of bituminous and anthracite coals range from 0.82 to 2.47 × 10 −10 m 2 /N. Then, multifractal analysis was introduced to evaluate the heterogeneity characteristics of coals based on the corrected MIP data. The multifractal dimension D min is positively correlated with vitrinite content, but negatively correlated with inertinite content and mercury intrusion saturation. The multifractal dimension D max shows negative relationships with moisture and ash content, and it also emerges as a "U-shaped" trend with efficiency of mercury withdrawal. It is concluded that multifractal analysis can be served as a practical method not only for evaluating the heterogeneity of coal PSDs, but also for other unconventional reservoirs (e.g., shale and tight sandstone).

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Section: Introductionmentioning

confidence: 99%

“…Previous studies have shown that it is a feasible method to evaluate coal matrix compressibility by combining low-temperature N 2 adsorption (LTNA) and MIP data [22][23][24]. By using this method, Guo et al [23] calculated the coal matrix compressibility coefficients and found it emerges as a "U-shaped" trend with coal ranks.…”

Section: Introductionmentioning

confidence: 99%

Insights into Multifractal Characterization of Coals by Mercury Intrusion Porosimetry

et al. 2019

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“…7 Because of the complex structure with a three-dimensional network, it is difficult for microorganisms to degrade and utilize coal. [8][9][10] Small molecular organics are dispersed in the polymer structure of coal. 11 Small and medium molecular organics in lignite and volatile bituminous coal account for approximately 10% to 23% of the total organic matter, and in some coal bodies, they even account for 30%.…”

Section: Introductionmentioning

confidence: 99%

Controlling mechanism of coal chemical structure on biological gas production characteristics

et al. 2020

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Summary To find the effect of coal chemical structure on biogas production, Lignite B was collected and extracted with nitrogen methylpyrrolidone (NMP), acetone and 0.60 mol/L NaOH. Simultaneously, methanogenic bacteria were enriched, and gas production experiments involving solvent extraction from residual coal and secondary gas production experiments involving coal were performed. The characteristics of biogas production, microcrystalline structure and coal chemical structure were analyzed. The results showed that the biogas production capacity of residual coal extracted by different solvents differed. The biogas production capacity of residual coal extracted by 0.60 mol/L NaOH was severely inhibited. The biogas production capacity of residual coal extracted by NMP and acetone was enhanced compared with that of raw coal. In contrast, primary residual coal still exhibits potential for methane production, but the methane production efficiency was reduced. Changes in the microcrystalline structure and functional groups of residual coal showed that solvent extraction increases the spacing and stacking height of the aromatic lamellae of coal, reduces the hydroxyl, methyl, methylene and aromatic hydrocarbon levels in coal, loosens the macromolecular network structure of coal, and enhances the connectivity of pores and fissures, thus allowing methane‐producing bacteria to enter the coal mass and create favorable conditions for gas production through interactions between the two. X‐ray photoelectron spectroscopy measurements showed that the secondary gas production increased the C content on the coal surface, decreased the O content and the O/C ratio, thus promoting the consumption of oxygen‐containing functional groups on the coal surface to further produce gas.

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“…The capillary pressure curve (CPC) experimentally obtained by mercury intrusion (also known as the mercury intrusion capillary pressure) has been found to be among the most effective data for studying the pore structure at a relatively large scale compared with the micron‐sized scanning electron microscopy images. The heterogeneity and anisotropy of pore structures are involved in the CPC; thus, the CPC has been applied to a wide range of natural or synthetic porous media, such as shale, tight sandstone, carbonate rock, packing bed, coal rock, cement slurry, and fine sediment containing natural gas hydrate (Cai et al, ; Lei & Santamarina, ; Sang et al, ; Voigt et al, ; Wyrzykowski et al, ). From the equivalent hydraulic size distribution of the pore‐throat (SDPT) given by the CPC, many critical pore structure parameters, such as the threshold pressure and radius, the maximum displacement pressure P d and its corresponding maximum pore‐throat radius r max , the average pore‐throat radius r mean , the irreducible water saturation S wir , the structural coefficient T , and the pore‐throat radius at any saturation (e.g., r 15 , r 25 , r 50 ), can be directly determined (Nooruddin et al, ).…”

Section: Introductionmentioning

confidence: 99%

Capillary Pressure Curve Determination Based on a 2‐D Cross‐Section Analysis Via Fractal Geometry: A Bridge Between 2‐D and 3‐D Pore Structure of Porous Media

Chen

Yao

Luo³

et al. 2019

JGR Solid Earth

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Pore structure is a crucial attribute in characterizing fluid flow through porous media. However, direct experimental measurements or numerical reconstructions are commonly expensive and not environmentally friendly, with great uncertainty caused by the complex nature of porous media. In this study, we demonstrate that one special bridge function, which is a function of the apparent length and tortuosity fractal dimension, can characterize the relationship of pore structures between two dimensions (2‐D) and three dimensions (3‐D), and it can serve as a conversion bridge of the radius to determine the capillary pressure curve (CPC). We compare estimations by the proposed method with experimental results obtained by mercury intrusion porosimetry in six typical natural sandstones with varying porosities and permeabilities. The result shows that cross sections of the global pore structure, such as thin section, electronic probe, and microcomputed tomography slices, give a reliable estimation of the CPC using the bridge function in porous media with a medium porosity. However, in unconventional porous media with a relatively low porosity (~10%) or extra high porosity (~30%), due to the empirical nature of the equation widely used to calculate the tortuosity fractal dimension, the necessary modification is necessary to obtain the CPC when applying the bridge function in such porous media. This insight can significantly simplify the procedure for obtaining the petrophysical properties of a porous medium, which may shed light on the inherent differences and correlations between the 2‐D and 3‐D pore structures of porous media.

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Insights into matrix compressibility of coals by mercury intrusion porosimetry and N2 adsorption

Cited by 131 publications

References 49 publications

Insights into Multifractal Characterization of Coals by Mercury Intrusion Porosimetry

Insights into Multifractal Characterization of Coals by Mercury Intrusion Porosimetry

Controlling mechanism of coal chemical structure on biological gas production characteristics

Capillary Pressure Curve Determination Based on a 2‐D Cross‐Section Analysis Via Fractal Geometry: A Bridge Between 2‐D and 3‐D Pore Structure of Porous Media

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