Study on typical temperature effect mechanism of multi-component coal during low-temperature thermal expansion

Cong, Yuzhou; Zhai, Cheng; Xu, Yu; Xu, Jizhao; Sun, Yong; Tang, Wei; Zheng, Yangfeng; Wu, Jieying

doi:10.1016/j.csite.2023.102744

Cited by 5 publications

(2 citation statements)

References 32 publications

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“…Like any material, coal exhibits thermal expansion and contraction and is sensitive to temperature changes. Variations in the thermal expansion and contraction coefficients of coal are due to differences in coal rank, petrological composition, molecular structure, and rock mass structure [14][15][16]. Heating experiments on coal indicate that, as the temperature increases, the deformation of coal gradually increases, and its permeability decreases [17,18].…”

Section: Introductionmentioning

confidence: 99%

Study on the Thermal Expansion Characteristics of Coal during CO2 Adsorption

Song,

Sun,

Liu

2024

Processes

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The adsorption of CO2 fracturing fluid into coal reservoirs causes the expansion of the coal matrix volume, resulting in changes in the fracture opening, which alters the permeability of the coal reservoir. However, it is not yet clear whether thermal expansion during CO2 adsorption on coal is the main cause of coal adsorption expansion. Therefore, by testing the thermal properties, expansion coefficient, and adsorption heat of the three coal samples, the adsorption thermal expansion characteristics of coal and their impact on the permeability of coal reservoirs are clarified. The results reveal the following: (1) Under the same conditions, the adsorption heat increases with increasing pressure, while it decreases with increasing temperature. The relationship between adsorption heat and pressure conforms to the Langmuir equation before 40 °C, and it follows a second-order equation beyond 40 °C. At 100 °C, the adsorption heat of coal samples to CO2 is primarily determined by temperature. (2) The maximum temperature variation in coal samples from Xinjiang, Liulin, and Zhaozhuang during CO2 adsorption is 95.767 °C, 87.463 °C, and 97.8 °C, respectively. The maximum thermal expansion rates are 12.66%, 5.74%, and 14.37%, and the maximum permeability loss rates are 16.16%, 7.51%, and 18.24%, respectively, indicating that thermal expansion is the main reason for coal adsorption expansion. (3) This research can elucidate the impact of CO2 fracturing fluid on coal reservoirs and its potential application value, thus providing theoretical support for coalbed methane development and CO2 geological storage.

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Section: Introductionmentioning

confidence: 99%

Study on the Thermal Expansion Characteristics of Coal during CO2 Adsorption

Song,

Sun,

Liu

2024

Processes

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“…However, this technology consumes large amounts of water and brings a series of environmental problems. , Waterless stimulation methods have become an important trend in constructing EGS. Liquid nitrogen is an ultralow temperature fluid (boiling point of −196 °C at normal pressure) and can be used as a new thermal stimulation fluid. − Some scholars have proposed the fracturing and permeability enhancement method of cyclic liquid nitrogen cold shock on high-temperature granite. − Therefore, clarifying the damage and destruction characteristics of liquid nitrogen on high-temperature granite is crucial for improving geothermal energy exploitation.…”

Section: Introductionmentioning

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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