Quantitative characterization of water transport and wetting patterns in coal using LF-NMR and FTIR techniques

Cai, Yuliang; Zhai, Cheng; Yu, Xu; Sun, Yong; Xu, Jizhao; Zheng, Yangfeng; Cong, Yuzhou; Li, Yujie; Chen, Aikun; Xu, Hexiang; Wang, Shuai; Wu, Xizhuo

doi:10.1016/j.fuel.2023.128790

Cited by 25 publications

(4 citation statements)

References 59 publications

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“…The low-field NMR technology inverts pore size information from the relaxation process (nuclei transitioning from high-energy nonequilibrium states to low-energy equilibrium states) of 1 H fluids (water) in porous media under an applied magnetic field. , It features nondestructive, rapid, and accurate measurements. Rock porosity is an important parameter for evaluating the internal damage of rock .…”

Section: Resultsmentioning

confidence: 99%

Study on Damage Characteristics of Hot Dry Rock by Liquid Nitrogen Cyclic Cold Shocks Based on Ultrasonic Testing

Lai,

Zhai,

Sun

et al. 2023

Energy Fuels

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Efficient exploitation of hot dry rock resources can alleviate global energy supply pressure. However, the “low-porosity, low-permeability” occurrence characteristics of hot dry rock severely restrict the exploitation efficiency. To achieve efficient exploitation of hot dry rock resources, artificial fracturing and permeability-enhancing measures must be taken to transform the reservoir and improve the heat-exchange efficiency. Liquid nitrogen cyclic cold shock is an effective fracturing method for geothermal reservoirs. The huge temperature difference between liquid nitrogen and hot rock can cause uneven contraction between mineral particles, inducing fracture networks. It is crucial to study the damage characteristics of hot dry rock under liquid nitrogen cyclic cold shock. Therefore, this paper carries out liquid nitrogen cold shock experiments on high-temperature granite. Granite samples heated to different temperatures (200, 300, 400, 500, and 600 °C) were subjected to cyclic cold shocks (five times) using liquid nitrogen. NMR testing and ultrasonic testing were performed on the treated samples to study the damage characteristics of hot dry rock. The results show that with the increase of heating temperature and the number of cold shocks, the porosity of the cores increases continuously. After five cold shocks, the porosity of the cores heated at 200–600 °C increases by 1.108, 1.154, 1.158, 3.080, and 6.896%, respectively. The wave velocity decreases continuously, and the time delay and distortion of the waveforms become more obvious. The frequency distribution gradually shifts toward lower frequencies, the wavelet packet energy distribution transfers to lower-frequency sub-bands, the total energy of the Hilbert energy spectrum decreases continuously, the duration of high instantaneous energy becomes shorter, and the frequency distribution interval shifts toward lower frequencies. The quality factor Q decreases with increasing heating temperature and the number of liquid nitrogen cold shocks and has a good linear relationship with the core porosity.

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Section: Resultsmentioning

confidence: 99%

Study on Damage Characteristics of Hot Dry Rock by Liquid Nitrogen Cyclic Cold Shocks Based on Ultrasonic Testing

Lai,

Zhai,

Sun

et al. 2023

Energy Fuels

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“…Zhu et al studied the difference in wetting behavior between graphite and montmorillonite based on the microscopic method and investigated the relationship between particles and wetting behavior. Cai et al explained the macroscopic wetting matrix between coal and water based on low-field NMR methods and further summarized a variety of interpore wetting patterns. Tao et al investigated the interaction law between micro properties and the wettability relationship by adding surfactants, and the results showed that the wettability of coal showed enhanced hydrophilicity in the presence of surfactants.…”

Section: Introductionmentioning

confidence: 99%

Changes in the Microstructure and Wettability of Water-Containing Coal after Hot Flue Gas (CO₂–N₂) Injection

Liu,

Zha,

Lin

et al. 2024

Energy Fuels

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This study aims to explore changes in the microstructure and wettability of water-containing coal after hot flue gas (CO 2 −N 2 ) injection. To achieve this aim, thermal modification was conducted on Wulan anthracite with the aid of an experimental platform for coal modification by hot flue gas injection, and changes in the microscopic characteristics before and after the modification were investigated by means of Fouriertransform infrared spectroscopy (FT-IR) and carbon-13 nuclear magnetic resonance ( 13 C NMR). The results demonstrate that affected by acidic and hydrothermal environments, some oxygencontaining functional groups and aliphatic side chains in the molecular structure become detached. To be specific, the coefficient of oxygen-containing functional groups I O declines by 19.3%, and the aliphatic carbon content f al decreases by 32.7%. With the obtained microscopic data, the coal macromolecular structure models before and after the modification were established and verified by inverting the 13 C NMR spectra, and the coal matrix models with a projection area of 100 nm 2 were also generated. Subsequently, the wetting behavior of a water cluster on the coal matrix model was simulated by a molecular dynamics method. Based on the simulation results, a method of characterizing the microscopic wettability according to the maximum spreading area H and the maximum height D was put forward. The results are pretty consistent with the experimentally measured wettability. These results can lay a foundation for researching the microscopic control mechanism of water-containing coal seam modification by hot flue gas injection.

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“…3,7 According to its storage form, water can also be divided into free water, adsorbed water, and chemically bound water. 8 Free water is stored in the fracture and macropores in a free state, while adsorbed water is retained in the microporous surface by physical adsorption. CBM is mainly divided into free gas and adsorbed gas, and its occurrence characteristics are similar to those of free water and adsorbed water.…”

Section: Introductionmentioning

confidence: 99%

“…Coalbed methane (CBM) is a new type of clean energy that can fill the energy gap in China. − Water and methane coexist in coal seams, and water has a significant effect on the pore structure and gas adsorption capacity of coal. − During the formation of coal, a large amount of water will be produced. , According to its storage form, water can also be divided into free water, adsorbed water, and chemically bound water . Free water is stored in the fracture and macropores in a free state, while adsorbed water is retained in the microporous surface by physical adsorption.…”

Section: Introductionmentioning

confidence: 99%

Effect of Water on Effective Pore Structures for Medium-Rank Coal: Based on the Prefreezing Nitrogen Adsorption–Desorption Experiment

Li,

Wang,

Lou

et al. 2023

ACS Omega

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Water is ubiquitous in coal reservoirs, and its distribution can have a remarkable influence on the effective pore space of methane. This study conducted the combination experiments of moisture equilibrium and prefreezing nitrogen adsorption–desorption to explore the adsorption behavior of water in coal pores and thus to reveal the distribution characteristics of water in pores with different scales as well as the influence of water on pore structures. The results showed that the adsorption mechanism of water vapor undergoes a transition from monolayer to multilayer to condensation with the increase in relative humidity (RH). The occurrence characteristics of adsorbed water in coal pores are controlled by the RH and pore size. When the RH is increased from 0 to 98%, the nitrogen adsorption capacity, specific surface area, and effective pore volume of the samples were all decreased significantly due to the different adsorption modes of water, which is more significant in pores with d < 10 nm. Additionally, the relative pressure corresponding to the branching position of the nitrogen adsorption-desorption curve will be changed with the increase in moisture content. Based on this, it is calculated that the adsorbed water will change the smoothness of the pore wall and the complexity of the pore structure.

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Quantitative characterization of water transport and wetting patterns in coal using LF-NMR and FTIR techniques

Cited by 25 publications

References 59 publications

Study on Damage Characteristics of Hot Dry Rock by Liquid Nitrogen Cyclic Cold Shocks Based on Ultrasonic Testing

Study on Damage Characteristics of Hot Dry Rock by Liquid Nitrogen Cyclic Cold Shocks Based on Ultrasonic Testing

Changes in the Microstructure and Wettability of Water-Containing Coal after Hot Flue Gas (CO₂–N₂) Injection

Effect of Water on Effective Pore Structures for Medium-Rank Coal: Based on the Prefreezing Nitrogen Adsorption–Desorption Experiment

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Quantitative characterization of water transport and wetting patterns in coal using LF-NMR and FTIR techniques

Cited by 25 publications

References 59 publications

Study on Damage Characteristics of Hot Dry Rock by Liquid Nitrogen Cyclic Cold Shocks Based on Ultrasonic Testing

Study on Damage Characteristics of Hot Dry Rock by Liquid Nitrogen Cyclic Cold Shocks Based on Ultrasonic Testing

Changes in the Microstructure and Wettability of Water-Containing Coal after Hot Flue Gas (CO2–N2) Injection

Effect of Water on Effective Pore Structures for Medium-Rank Coal: Based on the Prefreezing Nitrogen Adsorption–Desorption Experiment

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Changes in the Microstructure and Wettability of Water-Containing Coal after Hot Flue Gas (CO₂–N₂) Injection