Experimental study on effective stress sensitivity of coal permeability based on dynamic drainage process
The dynamic changes in reservoir permeability during coalbed methane well drainage largely depend on variations in effective stress and pore structure. It is very important to analyze the stress sensitivity of coal reservoir to understand the dynamic change effect of reservoir drainage and productio...
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| Format: | Article |
| Language: | Chinese |
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Editorial Department of Coal Science and Technology
2025-07-01
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| Series: | Meitan kexue jishu |
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| Online Access: | http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2024-0639 |
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| author | Kang LI Xiaoyang ZHANG Binbin HU Weijiang KONG Yunfei DOU Junjian ZHANG Dongdong WANG |
| author_facet | Kang LI Xiaoyang ZHANG Binbin HU Weijiang KONG Yunfei DOU Junjian ZHANG Dongdong WANG |
| author_sort | Kang LI |
| collection | DOAJ |
| description | The dynamic changes in reservoir permeability during coalbed methane well drainage largely depend on variations in effective stress and pore structure. It is very important to analyze the stress sensitivity of coal reservoir to understand the dynamic change effect of reservoir drainage and production. Based on this, coal samples from the No. 3 coal seam in the Sihe Mine on the southeastern edge of the Qinshui Basin were collected. The pore and fracture distribution characteristics of coal were analyzed using CT scanning and nuclear magnetic resonance (NMR) techniques. Helium permeability tests of coal samples with different water saturation under variable pore pressure were carried out. The effective stress coefficient (ESCK) of coal permeability was obtained by the response surface method. Based on the improved S&D model, the dynamic change law of permeability was analyzed according to the actual drainage process. The results show that the NMR T2 spectra of coal samples in dry and saturated water state are approximately unimodal distribution, and the pore structure is dominated by micropores. SK1 sample has a penetrating main fracture and good continuity of diffusion pore and seepage pore, which can provide seepage channel, resulting in better permeability than SK3 sample. For the same water saturation, permeability decreases with increasing net stress, showing a good power-law fitting relationship between them. As water saturation increases, the permeability of coal samples decreases with increasing net stress under the same pore pressure, following a power-law fitting relationship. The relationship between conversion permeability (k') and confining pressure and pore pressure is binary linear. The ESCK values of coal samples with different water saturations are constant and significantly less than 1.0, ranging from 0.244 5 to 0.475 3. The effective stress of coal reservoir is greater than the net stress, and the permeability stress is sensitive, which has greater influence on the permeability. The drainage system should be formulated reasonably to avoid excessive drainage and pressure reduction rate. |
| format | Article |
| id | doaj-art-7db4f9b0d70f40e29c6e68cfeb45fec2 |
| institution | Matheson Library |
| issn | 0253-2336 |
| language | zho |
| publishDate | 2025-07-01 |
| publisher | Editorial Department of Coal Science and Technology |
| record_format | Article |
| series | Meitan kexue jishu |
| spelling | doaj-art-7db4f9b0d70f40e29c6e68cfeb45fec22025-08-04T02:53:35ZzhoEditorial Department of Coal Science and TechnologyMeitan kexue jishu0253-23362025-07-0153719720610.12438/cst.2024-06392024-0639Experimental study on effective stress sensitivity of coal permeability based on dynamic drainage processKang LI0Xiaoyang ZHANG1Binbin HU2Weijiang KONG3Yunfei DOU4Junjian ZHANG5Dongdong WANG6College of Earth Sciences & Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Sciences & Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Sciences & Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Sciences & Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Sciences & Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Sciences & Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaCollege of Earth Sciences & Engineering, Shandong University of Science and Technology, Qingdao 266590, ChinaThe dynamic changes in reservoir permeability during coalbed methane well drainage largely depend on variations in effective stress and pore structure. It is very important to analyze the stress sensitivity of coal reservoir to understand the dynamic change effect of reservoir drainage and production. Based on this, coal samples from the No. 3 coal seam in the Sihe Mine on the southeastern edge of the Qinshui Basin were collected. The pore and fracture distribution characteristics of coal were analyzed using CT scanning and nuclear magnetic resonance (NMR) techniques. Helium permeability tests of coal samples with different water saturation under variable pore pressure were carried out. The effective stress coefficient (ESCK) of coal permeability was obtained by the response surface method. Based on the improved S&D model, the dynamic change law of permeability was analyzed according to the actual drainage process. The results show that the NMR T2 spectra of coal samples in dry and saturated water state are approximately unimodal distribution, and the pore structure is dominated by micropores. SK1 sample has a penetrating main fracture and good continuity of diffusion pore and seepage pore, which can provide seepage channel, resulting in better permeability than SK3 sample. For the same water saturation, permeability decreases with increasing net stress, showing a good power-law fitting relationship between them. As water saturation increases, the permeability of coal samples decreases with increasing net stress under the same pore pressure, following a power-law fitting relationship. The relationship between conversion permeability (k') and confining pressure and pore pressure is binary linear. The ESCK values of coal samples with different water saturations are constant and significantly less than 1.0, ranging from 0.244 5 to 0.475 3. The effective stress of coal reservoir is greater than the net stress, and the permeability stress is sensitive, which has greater influence on the permeability. The drainage system should be formulated reasonably to avoid excessive drainage and pressure reduction rate.http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2024-0639coalbed methane drainagepore and fracture of coalpermeability variationvarying pore pressureeffective stress |
| spellingShingle | Kang LI Xiaoyang ZHANG Binbin HU Weijiang KONG Yunfei DOU Junjian ZHANG Dongdong WANG Experimental study on effective stress sensitivity of coal permeability based on dynamic drainage process Meitan kexue jishu coalbed methane drainage pore and fracture of coal permeability variation varying pore pressure effective stress |
| title | Experimental study on effective stress sensitivity of coal permeability based on dynamic drainage process |
| title_full | Experimental study on effective stress sensitivity of coal permeability based on dynamic drainage process |
| title_fullStr | Experimental study on effective stress sensitivity of coal permeability based on dynamic drainage process |
| title_full_unstemmed | Experimental study on effective stress sensitivity of coal permeability based on dynamic drainage process |
| title_short | Experimental study on effective stress sensitivity of coal permeability based on dynamic drainage process |
| title_sort | experimental study on effective stress sensitivity of coal permeability based on dynamic drainage process |
| topic | coalbed methane drainage pore and fracture of coal permeability variation varying pore pressure effective stress |
| url | http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2024-0639 |
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