Experimental Study on Fractal Characteristics of Surface Roughness of Briquettes and their Effect on Wettability of Coal Samples

Yan, Min; Luo, Hanxi; Yang, Tao; Yan, Dongjie; Wei, Jianing; Lin, Haifei; Li, Shugang

doi:10.1007/s11053-023-10174-8

Cited by 7 publications

(4 citation statements)

References 31 publications

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“…Generally speaking, the core of acidification technology is to inject acid solution into seams to dissolve minerals in a reservoir and react with the active organic components so as to change the physical and chemical properties and realize the extraction enhancement of CBM. Wettability is a comprehensive reflection of the hydrophilic/hydrophobic ability of coal which could reflect the gas–water competition adsorption and gas migration in seams and is also closely related to the pore and fissure structure of coal. , Therefore, the effects of acidification can be evaluated by analyzing the changes of wettability of coal samples before and after acidification. In this paper, the wettability of coal is picked up as the basis for optimization, and then the optimal scheme was selected from nine acidification modification schemes by the AHP–TOPSIS method.…”

Section: Resultsmentioning

confidence: 99%

“…Wettability is a comprehensive reflection of the hydrophilic/hydrophobic ability of coal which could reflect the gas–water competition adsorption and gas migration in seams and is also closely related to the pore and fissure structure of coal. 49 , 50 Therefore, the effects of acidification can be evaluated by analyzing the changes of wettability of coal samples before and after acidification. In this paper, the wettability of coal is picked up as the basis for optimization, and then the optimal scheme was selected from nine acidification modification schemes by the AHP–TOPSIS method.…”

Section: Resultsmentioning

confidence: 99%

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Research on the Optimization for Acidification Modification Scheme Considering Coal’s Wettability Based on the AHP–TOPSIS Method

He,

Yuan,

et al. 2023

ACS Omega

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Acidification technology is an important measure for enhancing the extraction of coalbed methane from seams with low permeability and abundant minerals, and the acidification scheme is the key to the success of acidification treatment. To determine the optimal acidification modification scheme, an improved AHP−TOPSIS method is proposed to decide on the optimal conditions for wettability modification. This method constructs an evaluation index system, taking the wettability of coal as the target layer and the pro/hydrophobic functional groups in coal as the index layer. Meanwhile, it innovatively takes the adsorption energy of each functional group when absorbing a single water molecule as the basis for assigning weights to the evaluation indexes. Then, nine acidification modification schemes are evaluated and selected by the improved AHP−TOPSIS method based on the test results of different schemes to get the optimal one. The optimal scheme selected by the AHP−TOPSIS method is validated by water adsorption tests and isothermal adsorption tests. The results showed that the significance of each evaluation index is ranked as follows: aromatic structures > hydroxyl groups > aliphatic functional groups > oxygen-containing functional groups. The optimal acidification modification scheme is selected by the AHP−TOPSIS method with a HF concentration of 4% and a reaction time of 6 h. The ranking of acidification modification schemes obtained by the AHP−TOPSIS method is in high agreement with the ranking of water adsorption tests. When compared with raw coal, the coal samples treated with the optimal scheme have lower adsorption capacity for gas, which indicates that the aforementioned method could be used to evaluate and select the optimal acidification modification scheme, and the selected optimal scheme has the potential to increase the output of coalbed methane.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Research on the Optimization for Acidification Modification Scheme Considering Coal’s Wettability Based on the AHP–TOPSIS Method

He,

Yuan,

et al. 2023

ACS Omega

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“…The surface roughness of coal (a solid property) is another factor determining the coal-water contact angle [21][22][23]. Shojai Kaveh et al [24] investigated the wettability and surface roughness of hvbB coal under different CO 2 pressure atmospheres and found that, with an increase in CO 2 pressure, the surface roughness of coal increased because of the expansion of the coal matrix as a result of the diffusion of CO 2 into the coal matrix.…”

Section: Introductionmentioning

confidence: 99%

The Wetting Characteristics and Microscopic Wetting Mechanism of Coal under High-Pressure Nitrogen Environment

Long,

Shi,

Cao

et al. 2024

Processes

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The wettability of coal is an important factor influencing hydraulic stimulation. Field-trial data has proven that high-pressure N2 injection plays a positive role in increasing the coalbed methane (CBM) production rate. For the purpose of investigating the mechanism by which N2 promotes the gas rate, multiple experiments were conducted sequentially on the wettability of anthracite under different N2 pressures. Testing of the coal surface contact angle was conducted under 0.1–8 MPa nitrogen pressure using a newly built contact angle measuring device. The coal samples were collected from the Xinjing Coal Mine in the Qinshui Basin, China. The test results revealed that the contact angle increased with increasing N2 pressure. That is, the contact angle was 77.9° at an N2 pressure of 0.1 MPa and gradually increased to 101.4° at an infinite N2 pressure. In contrast, the capillary pressure decreased with an increasing N2 pressure, from 0.298 MPa to −0.281 MPa. The relationship between the contact angle and N2 pressure indicates a reversal of the wettability, at 5.26 MPa, with a contact angle of 90° and a capillary pressure of 0 MPa. The capillary pressure reversed to a negative value as the N2 pressure increased. At the microlevel, a high N2 pressure increases the surface roughness of coal, which improves the ability of the coal matrix to adsorb N2, forming the gas wall that hinders the intrusion of water into the pores of the coal matrix. The results of this study provide laboratory evidence that high-pressure N2 injection can prevent water contamination and reduce the capillary pressure, thus benefiting coalbed methane production.

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“…D S decreased with increasing hydrocarbon content and decreasing ash content. Yan et al [29] investigated the relationship between the fractal dimension of different roughness coal samples and their water content using electron microscope image processing and analyzed the mechanism of the effect of roughness on the wettability properties. The fractal dimension of coal samples was shown to gradually increase with increasing surface roughness.…”

Section: Introductionmentioning

confidence: 99%

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

Chen

et al. 2023

Fractal Fract

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As a non-homogeneous porous medium, the structural complexity of coal directly affects pore structure parameters and gas percolation characteristics, which in turn determine the fractal dimension of coal samples. Among them, the specific surface area of coal largely determines the complexity of the pore structure and is closely related to coal and gas protrusion hazards. To investigate the relationship between the fractal dimension of coal and its specific surface area, we analyzed the pore structure of coal samples using low-temperature nitrogen adsorption, the mercury pressure method, and X-ray micro-computed tomography (CT) experiments. By calculating the fractal dimension of coal and reconstructing it in three dimensions, the morphological characteristics and distribution of pores can be described qualitatively and quantitatively. The fractal dimension of coal samples was found to increase exponentially with the specific surface area based on measurements of large pores and mesopores via the mercury pressure method and those of small pores and micropores using the nitrogen adsorption method. X-ray micro-CT experiments revealed that the fractal dimension of large pores (i.e., >2 μm) conformed to this pattern.

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Experimental Study on Fractal Characteristics of Surface Roughness of Briquettes and their Effect on Wettability of Coal Samples

Cited by 7 publications

References 31 publications

Research on the Optimization for Acidification Modification Scheme Considering Coal’s Wettability Based on the AHP–TOPSIS Method

Research on the Optimization for Acidification Modification Scheme Considering Coal’s Wettability Based on the AHP–TOPSIS Method

The Wetting Characteristics and Microscopic Wetting Mechanism of Coal under High-Pressure Nitrogen Environment

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

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