Interaction mechanism of water movement and gas desorption during spontaneous imbibition in gas-bearing coal

Yue, Jiwei; Wang, Zhaofeng; Shi, Biming; Dong, Jiaxin; Shen, Xiaojing

doi:10.1016/j.fuel.2022.123669

Cited by 27 publications

(18 citation statements)

References 27 publications

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“…The experimental results show that the experimental error of restoring the in situ volume of the coal core by the contact water injection decreases with the increase in adsorption equilibrium pressure. The reason is that the density of adsorbed methane increases with the increase in pressure, when the injected water interacts with the adsorbed methane in pores of different sizes, and replacing the same volume of adsorbed methane under high pressure will produce more free methane than under low pressure. − The greater the gas pressure is, the more the free gas is . The proportion of the amount of free gas increased by water displacement to the amount of free gas at the initial adsorption equilibrium also decreases with the increase in adsorption equilibrium pressure, and the recovery value of gas pressure is relatively closer to the initial adsorption equilibrium pressure.…”

Section: Resultsmentioning

confidence: 99%

In Situ Volume Recovery Method for Non-Seal Gas Pressure Measurement Technology: A Comparative Study

Hua

Wang

et al. 2022

ACS Omega

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Coal seam gas pressure is one of the basic parameters for coalbed methane resource exploitation and coal mine gas disaster prevention. However, the present coal seam gas pressure measurement technology requires harsh field measurement conditions and a long testing period. In this study, a novel non-seal gas pressure measurement technology is proposed, and this technology is mainly aimed at three different changes before and after the collection of coal samples and realizes the real gas pressure measurement through the compensation of gas leakage, in situ volume recovery of the coal core, and reservoir temperature simulation. The technique not only can measure the original gas pressure of coal seam quickly and accurately but also does not need to seal the measuring hole. This paper focuses on the study of a key factor that affects the accuracy of non-seal gas pressure measurement: the restoration of in situ volume. Based on this, the influence of four different in situ volume recovery methods on the measurement accuracy is compared with the self-developed non-sealing gas pressure measuring system. Experimental results show that the in situ volume of the coal core cannot be completely restored by stress loading. Although the contact injection method can restore the original volume of the coal core, the pressure recovery error is large due to the replacement and displacement of the gas effect of water and the inclusion of the coal body effect of oil. Interestingly, the combination of stress loading and contact oil injection can not only restore the original volume of the coal core but also minimize the pressure recovery error, which is only less than 10%. Finally, based on the abovementioned experimental results, the in situ volume recovery method of non-seal gas pressure measurement technology is improved. Therefore, the research results of this paper provide a scientific basis for the field application of non-seal gas pressure measurement technology.

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Section: Resultsmentioning

confidence: 99%

In Situ Volume Recovery Method for Non-Seal Gas Pressure Measurement Technology: A Comparative Study

Hua

Wang

et al. 2022

ACS Omega

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“…Hydraulic measures are important means of coal seam gas mining. 4−6 When hydraulic measures, such as water injection, are taken to the coal seam, spontaneous imbibition occurs inside the coal body, 7−9 and water will soften and moisten the coal body, 10,11 induce fracture in coal body, promote gas desorption, 12 and eventually suppress dust and prevent gas outburst and rockburst. 13,14 The complex macro bedding and micropore structures of the coal body also affect water imbibition in the coal body.…”

Section: Introductionmentioning

confidence: 99%

“…Coalbed methane is a disaster gas threatening coal mine safety production, but it is also a natural, efficient, and clean energy. − The development and utilization of coalbed methane is significant in maximizing clean energy and improving coal mine safety production conditions. Hydraulic measures are important means of coal seam gas mining. − When hydraulic measures, such as water injection, are taken to the coal seam, spontaneous imbibition occurs inside the coal body, − and water will soften and moisten the coal body, , induce fracture in coal body, promote gas desorption, and eventually suppress dust and prevent gas outburst and rockburst. , The complex macro bedding and micropore structures of the coal body also affect water imbibition in the coal body. − Therefore, the microscopic pore structure characteristics of the coal body in a loaded environment and spatial distribution and evolution characteristics of water during the imbibition process should be investigated to study the mechanism of deep CBM water injection and extraction.…”

Section: Introductionmentioning

confidence: 99%

Nuclear Magnetic Resonance Experiment on the Influence of Confining Pressure on Spontaneous Imbibition of Water in Coal

Deng

Yue

et al. 2022

Energy Fuels

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Residual water after hydration measures can wet a coal sample to lead to spontaneous imbibition; it is a common phenomenon in the process of extracting coalbed methane using hydraulic measures. To study the characteristics of the microscopic pore structure of a coal body and spontaneous imbibition of water in the pore structure by simulating the actual deposition environment, the T 2 spectra and spatial distribution of water in the imbibition process of coal samples under different circumferential pressure conditions were obtained by online testing using the low-field NMR technique. Results show that during the process of coal sample imbibition, the T 2 spectra shows the characteristics of multi-peak distribution, and the number of adsorption and seepage pores is considerably higher than the fracture. Moreover, the influence of confining pressure on imbibition mainly appears in the seepage pore. The spontaneous imbibition behavior at different stages is accurately described by the Handy equation combined with the NMR signal; the higher the confining pressure, the worse the imbibition ability of the coal sample. The rate of water migration to the end of coal sample will be higher than the rate of migration to the surrounding. Finally, the three-dimensional signal distribution indicates that the imbibition is not a piston advance but a wave advance, and the rate of water migration in the longitudinal direction is higher than the rate of diffusion in the lateral direction.

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“…By studying the gas desorption characteristics of coal under the coupling conditions of water, pressure, and temperature, it can be concluded that steam can effectively enhance the gas desorption capacity . Yue et al, through the coupling experiment of air pressure and water, proved that the lower the air pressure is, the better the wetting effect of micropores and some mesopores is going to be, and the much more easily the replacement of adsorbed gas by water will take place, thus increasing the amount of desorption gas …”

Section: Introductionmentioning

confidence: 99%

“…29 Yue et al, through the coupling experiment of air pressure and water, proved that the lower the air pressure is, the better the wetting effect of micropores and some mesopores is going to be, and the much more easily the replacement of adsorbed gas by water will take place, thus increasing the amount of desorption gas. 30 Research on gas desorption law under a positive pressure environment is relatively less compared with normal pressure. Zhang and others conducted experimental research on the desorption process of gas-bearing coal under pressure and normal pressure and believed that the determination of whether the gas is minable and the gas extraction time should be based on the desorption law under pressure.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Gas Loss Derived from Positive Pressure

Wang

Yuan

et al. 2022

ACS Omega

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Positive pressure sampling enables the fixed-point and rapid acquisition of coal samples, but the derivation of loss volume during sampling is usually based on the law of gas desorption from granular coal at atmospheric pressure, which seriously affects the reasonableness of loss amounts under positive pressure and thus leads to errors in gas content determination. The gas loss under positive pressure is the key to the accurate determination of the gas content of coal seams. To obtain reliable loss data, under different positive pressures, we tested the gas desorption process of anthracite coal samples with different adsorption equilibrium pressures, analyzed the effect of positive pressure on gas desorption, studied the changes in the gas desorption rate caused by positive pressure, recorded the fluctuation of the amount of gas loss, and compared the values of loss under different conditions. The results show that the positive pressure is the main factor affecting gas desorption compared to the adsorption equilibrium pressure. The positive pressure has an inhibitory influence on gas desorption. Under the same positive pressure, the gas desorption rate shows a decreasing trend over time, and at the same time, the gas desorption rate gradually decreases accompanied by the increasing positive pressure. The gas loss error rate increases with increasing adsorption pressure under the same positive pressure. However, under the same adsorption pressure, the error rate of loss quantity presents a significant increase with positive pressure. The relative error of gas loss under different positive pressures can reach 63–180%, and the positive pressure has an obvious influence on gas loss. This study has experimentally confirmed that positive pressure has a greater effect on gas desorption than adsorption pressure, which will theoretically improve the method of deriving the amount of gas loss and will provide a basis for the accurate determination of gas content under positive pressure in engineering terms.

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Interaction mechanism of water movement and gas desorption during spontaneous imbibition in gas-bearing coal

Cited by 27 publications

References 27 publications

In Situ Volume Recovery Method for Non-Seal Gas Pressure Measurement Technology: A Comparative Study

In Situ Volume Recovery Method for Non-Seal Gas Pressure Measurement Technology: A Comparative Study

Nuclear Magnetic Resonance Experiment on the Influence of Confining Pressure on Spontaneous Imbibition of Water in Coal

Experimental Study on Gas Loss Derived from Positive Pressure

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