Microscopical and macroscopic structural damage evolution of low-rank coal by supercritical CO2 pulsation treatment
In order to clarify the effect and mechanism of supercritical CO2 pulsation on low-rank coal, deep low-rank coal from the Aiwiergou Mine in Xinjiang was collected as the experimental object. Experimental research was carried out through an independently built supercritical CO2 pulsation fracturing e...
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| Format: | Article |
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Editorial Department of Coal Science and Technology
2025-02-01
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| Series: | Meitan kexue jishu |
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| Online Access: | http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2024-0758 |
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| author | Jiajia LIU Yuanlong LI Jianliang GAO Dan WANG Yunlong ZHANG |
| author_facet | Jiajia LIU Yuanlong LI Jianliang GAO Dan WANG Yunlong ZHANG |
| author_sort | Jiajia LIU |
| collection | DOAJ |
| description | In order to clarify the effect and mechanism of supercritical CO2 pulsation on low-rank coal, deep low-rank coal from the Aiwiergou Mine in Xinjiang was collected as the experimental object. Experimental research was carried out through an independently built supercritical CO2 pulsation fracturing experimental system. Before and after the pulsation, the coal samples were respectively measured by XRD, FTIR, low-temperature liquid nitrogen adsorption test, low-field nuclear magnetic resonance, and uniaxial compression test. The changes in the microscopic structure, pore structure, and mechanical properties of the coal before and after the supercritical CO2 pulsation were quantitatively analyzed. The results show that after the supercritical CO2 pulsation, the mass fractions of calcite and clay minerals in the coal increase. The change in the mass fraction of clay minerals is mainly affected by the increase of ammoniated illite. The peak values of various organic functional groups in the coal show different degrees of decrease, indicating that the extraction effect of supercritical CO2 on organic matter is obvious. After the pulsation, the microcrystalline structure of the coal is damaged, the crystal lamellar spacing increases by 0.002 9 nm, and the coal structure tends to be loose. Compared with before the supercritical CO2 pulsation, the effective porosities of coal samples XJ-A and XJ-B increase by 66.7% and 128.6% respectively after the pulsation. The connectivity of pores inside the coal is enhanced, and the pulsation has a more obvious effect on the modification of micropores and mesopores. After the supercritical CO2 pulsation, the mechanical properties of the coal deteriorate significantly. The uniaxial compressive strength and elastic modulus decrease by 54.73% and 59.82% respectively. The acoustic emission ring-down count and cumulative energy are both greatly reduced. The peak value of the ring-down count drops to 51% of that before the pulsation, the cohesion of internal particles in the coal sample decreases, and the cumulative energy decreases by 62%. In conclusion, the supercritical CO2 pulsation can significantly damage the micro-macro structure of low-rank coal, which is of great significance for the fracturing and permeability enhancement of deep low-rank coal reservoirs and the extraction of coalbed methane. |
| format | Article |
| id | doaj-art-a48374ce688c4e4e8d6f7c4edb096b64 |
| institution | OA Journals |
| issn | 0253-2336 |
| language | zho |
| publishDate | 2025-02-01 |
| publisher | Editorial Department of Coal Science and Technology |
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| series | Meitan kexue jishu |
| spelling | doaj-art-a48374ce688c4e4e8d6f7c4edb096b642025-08-20T02:08:32ZzhoEditorial Department of Coal Science and TechnologyMeitan kexue jishu0253-23362025-02-0153219019910.12438/cst.2024-07582024-0758Microscopical and macroscopic structural damage evolution of low-rank coal by supercritical CO2 pulsation treatmentJiajia LIU0Yuanlong LI1Jianliang GAO2Dan WANG3Yunlong ZHANG4School of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, ChinaSchool of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, ChinaSchool of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, ChinaSchool of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, ChinaSchool of Safety Science and Engineering, Henan Polytechnic University, Jiaozuo 454003, ChinaIn order to clarify the effect and mechanism of supercritical CO2 pulsation on low-rank coal, deep low-rank coal from the Aiwiergou Mine in Xinjiang was collected as the experimental object. Experimental research was carried out through an independently built supercritical CO2 pulsation fracturing experimental system. Before and after the pulsation, the coal samples were respectively measured by XRD, FTIR, low-temperature liquid nitrogen adsorption test, low-field nuclear magnetic resonance, and uniaxial compression test. The changes in the microscopic structure, pore structure, and mechanical properties of the coal before and after the supercritical CO2 pulsation were quantitatively analyzed. The results show that after the supercritical CO2 pulsation, the mass fractions of calcite and clay minerals in the coal increase. The change in the mass fraction of clay minerals is mainly affected by the increase of ammoniated illite. The peak values of various organic functional groups in the coal show different degrees of decrease, indicating that the extraction effect of supercritical CO2 on organic matter is obvious. After the pulsation, the microcrystalline structure of the coal is damaged, the crystal lamellar spacing increases by 0.002 9 nm, and the coal structure tends to be loose. Compared with before the supercritical CO2 pulsation, the effective porosities of coal samples XJ-A and XJ-B increase by 66.7% and 128.6% respectively after the pulsation. The connectivity of pores inside the coal is enhanced, and the pulsation has a more obvious effect on the modification of micropores and mesopores. After the supercritical CO2 pulsation, the mechanical properties of the coal deteriorate significantly. The uniaxial compressive strength and elastic modulus decrease by 54.73% and 59.82% respectively. The acoustic emission ring-down count and cumulative energy are both greatly reduced. The peak value of the ring-down count drops to 51% of that before the pulsation, the cohesion of internal particles in the coal sample decreases, and the cumulative energy decreases by 62%. In conclusion, the supercritical CO2 pulsation can significantly damage the micro-macro structure of low-rank coal, which is of great significance for the fracturing and permeability enhancement of deep low-rank coal reservoirs and the extraction of coalbed methane.http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2024-0758supercritical co2pulsation crackingcoal microstructureporemechanical properties |
| spellingShingle | Jiajia LIU Yuanlong LI Jianliang GAO Dan WANG Yunlong ZHANG Microscopical and macroscopic structural damage evolution of low-rank coal by supercritical CO2 pulsation treatment Meitan kexue jishu supercritical co2 pulsation cracking coal microstructure pore mechanical properties |
| title | Microscopical and macroscopic structural damage evolution of low-rank coal by supercritical CO2 pulsation treatment |
| title_full | Microscopical and macroscopic structural damage evolution of low-rank coal by supercritical CO2 pulsation treatment |
| title_fullStr | Microscopical and macroscopic structural damage evolution of low-rank coal by supercritical CO2 pulsation treatment |
| title_full_unstemmed | Microscopical and macroscopic structural damage evolution of low-rank coal by supercritical CO2 pulsation treatment |
| title_short | Microscopical and macroscopic structural damage evolution of low-rank coal by supercritical CO2 pulsation treatment |
| title_sort | microscopical and macroscopic structural damage evolution of low rank coal by supercritical co2 pulsation treatment |
| topic | supercritical co2 pulsation cracking coal microstructure pore mechanical properties |
| url | http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2024-0758 |
| work_keys_str_mv | AT jiajialiu microscopicalandmacroscopicstructuraldamageevolutionoflowrankcoalbysupercriticalco2pulsationtreatment AT yuanlongli microscopicalandmacroscopicstructuraldamageevolutionoflowrankcoalbysupercriticalco2pulsationtreatment AT jianlianggao microscopicalandmacroscopicstructuraldamageevolutionoflowrankcoalbysupercriticalco2pulsationtreatment AT danwang microscopicalandmacroscopicstructuraldamageevolutionoflowrankcoalbysupercriticalco2pulsationtreatment AT yunlongzhang microscopicalandmacroscopicstructuraldamageevolutionoflowrankcoalbysupercriticalco2pulsationtreatment |