Experimental investigation of the functional mechanism of methane displacement by water in the coal

Huang, Bingxiang; Lu, Weiyong; Chen, Shuliang; Zhao, Xinglong

doi:10.1177/0263617420948700

“…V CH 4 at all detection points increased at the initial stage (less than 5%) and then decreased sharply. The phenomenon also appears in the experimental studies of other scholars [11]. A reasonable explanation is: under water injection, affected by high injection pressure, pressure gradient forces the methane carried by water and the methane V 1 displaced by water to passively flow to the outside, plus the external coalbed methane V 2 that has not been affected by hydraulic permeability.…”

Section: Numerical Modelmentioning

confidence: 59%

“…There-fore, the problem of low methane recovery rate in coal seam cannot be fundamentally solved. Water displacement is considered an effective method to recover methane from small coal pores [11].…”

Section: Introductionmentioning

confidence: 99%

Effects of Injection Pressure and Duration on Alternate High-Pressure Water-Gas Sequestration of Coalbed Methane

Li

¹

,

Zhu

²

,

Liu

³

et al. 2022

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To solve the problems of high ground stress, low permeability and low coalbed methane recovery, this paper proposes an optimization technique for improving coal seam permeability, i.e., water-gas alternating displacement enhances coalbed methane recovery (WGA-ECBM). The seepage field of gas-water two-phase flow is derived and a multiphase fluid-solid coupling model between physical parameters is established. This paper studies the effects of three displacement methods (water injection, air injection and water-air alternating injection) on methane recovery. The influence of injection pressure and injection duration on the WGA-ECBM technique is also studied. The V C H 4 (methane volume fraction) of the three methods decrease by 17.84%, 12.72% and 44.62% in the borehole, respectively. The influence ranges (diameter) are 24.68 m, 149.73 m and 135.21 m, respectively. Pore pressures and displacement area also increase as injection pressure increases in a 5 MPa gradient. And V C H 4 in the borehole decrease by 35.57%, 43.82%, 46.78% and 51.72% from 10 MPa to 25 MPa, respectively. With the increase of injection duration, the influence range expands significantly but the pore pressure distribution changes little. And V C H 4 decreases slightly in the displaced area and the displacement velocity gradually slows down. This technique promotes multiphase flow migration in coal seam, and increases the displacement range and methane recovery efficiency.

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“…However, according to the saturated competitive adsorption simulation results shown in Figure , the pre-adsorbed gas molecules will preferentially occupy the primary adsorption sites and reduce the surface free energy of the coal to make the system more stable. , When the water molecules are adsorbed later, gas and water will compete to be adsorbed due to the limited adsorption sites. Therefore, the water molecules need more energy to get inside the coal body, making the contact angle increase.…”

Section: Discussionmentioning

confidence: 99%

Study on Coal Wettability under Different Gas Environments Based on the Adsorption Energy

Ding

¹

,

Si

²

,

Wei

³

et al. 2023

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Coal seam water injection is a kind of comprehensive prevention and control measure to avoid gas outburst and coal dust disasters. However, the gas adsorbed in the coal seriously influence the coal-water wetting effect. With the deepening of coal seam mining, the gas pressure also gradually increases, but there is still a lack of in-depth understanding of the coal-water wetting characteristics under the high-pressure adsorbed gas environment. Therefore, the mechanism of coal-water contact angle under different gas environments was experimentally investigated. The coal-water adsorption mechanism in pre-absorbed gas environment was analyzed by molecular dynamics simulation combined with FTIR, XRD, and 13C NMR. The results showed that the contact angle in the CO2 environment increased most significantly, with the contact angle increasing by 17.62° from 63.29° to 80.91°, followed by the contact angle increasing by 10.21° in the N2 environment. The increase of coal-water contact angle in the He environment is the smallest, which is 8.89°. At the same time, the adsorption capacity of water molecules decreases gradually with increasing gas pressure, and the total system energy decreases after the coal adsorbs gas molecules, leading to a decrease in the coal surface free energy. Therefore, the coal surface structure tends to be stable with rising gas pressure. With the increase in environmental pressure, the interaction between coal and gas molecules enhances. In addition, the adsorptive gas will be adsorbed in the pores of coal in advance, occupying the primary adsorption sites and thus competing with the subsequent water molecules, resulting in a decline of coal wettability. Moreover, the stronger the adsorption capacity of gas, the more obvious the competitive adsorption of gas and liquid, which further weakens the wetting capacity of coal. The research results can provide a theoretical support for improving the wetting effect in coal seam water injection.

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“…Coalbed methane (CBM) is a valuable energy source [16] and its use can reduce the impact of coal mining on the climate and the environment [17]. At the same time, methane is Energies 2022, 15, 1047 2 of 12 a limiting factor in high-productivity production, being one of the most dangerous factors in mining [18]. Safe and efficient coal mining is achieved through coal bed degassing (ECBM), which is carried out in underground mine workings [19], from the surface [20], or complexly [21].…”

Section: Introductionmentioning

confidence: 99%

Improvement of Intensive In-Seam Gas Drainage Technology at Kirova Mine in Kuznetsk Coal Basin

Slastunov

¹

,

Kolikov

²

,

Batugin

³

et al. 2022

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One of the ways to resolve the “green energy-economic development” dilemma, in which the coal industry is situated, is by the improvement of technologies and the integrated use of extracted resources, including methane gas as a clean energy source. Using the example of the Kirova mine, located in Kuznetsk coal basin—one of the ecologically unfavorable coal mining regions of Russia—this article discusses an integrated technology for the extraction of coalbed methane (ECBM), which makes it possible to reduce greenhouse gas (methane) emissions and improve the safety and intensity of coal mining. The Kirova mine, with its 3 Mt production in 2019, is one of the coal mining leaders in Russia. The available mining equipment has the potential to significantly increase the output; however, gas is a limiting factor to this. The customary approaches to coal seam degassing have already been petered out. The miners and mine science are facing a challenge to validate and test an alternative technology to ensure effective in-seam gas drainage prior to vigorous mining. This article gives an account of the improvement track record of the in-seam gas drainage technology used to pre-treat coal seams for intensive and safe extraction. This technology suggests, at the first stage, hydraulic loosening of the target coal seam through wells drilled from the surface (SSHL), then hydraulic fracturing (HF) of the coal seam through the boreholes drilled from underground development headings, followed by methane extraction from the high-permeability coal-gas reservoir created through standard in-seam gas drainage underground wells. Results are presented in this paper of field testing of the improved SSHL technique. Findings are presented on the effective parameters of the HF technology. Methodological recommendations are offered for selecting viable in-seam gas drainage technology.

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Experimental investigation of the functional mechanism of methane displacement by water in the coal

Cited by 9 publications

References 26 publications

Effects of Injection Pressure and Duration on Alternate High-Pressure Water-Gas Sequestration of Coalbed Methane

Effects of Injection Pressure and Duration on Alternate High-Pressure Water-Gas Sequestration of Coalbed Methane

Study on Coal Wettability under Different Gas Environments Based on the Adsorption Energy

Improvement of Intensive In-Seam Gas Drainage Technology at Kirova Mine in Kuznetsk Coal Basin

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