Characterization of natural fractures and in-situ stress in high-steep coal-bearing strata in the Midong area in Xinjiang and influence on engineering
The Midong area in Xinjiang is located in the foreland thrust belt of Bogda Mountain on the southern margin of Junggar Basin, with high and steep strata and complex structures. At present, the characteristics of natural fractures and the current in-situ stress and their influence on engineering are...
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| Format: | Article |
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Editorial Department of Coal Science and Technology
2025-03-01
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| Series: | Meitan kexue jishu |
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| Online Access: | http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2024-1796 |
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| author | Jiawei WU Jian ZHANG Yumin LYU Yanhe ZHU Cunwu WANG Yue ZHANG Silu CHEN Jingyu ZI |
| author_facet | Jiawei WU Jian ZHANG Yumin LYU Yanhe ZHU Cunwu WANG Yue ZHANG Silu CHEN Jingyu ZI |
| author_sort | Jiawei WU |
| collection | DOAJ |
| description | The Midong area in Xinjiang is located in the foreland thrust belt of Bogda Mountain on the southern margin of Junggar Basin, with high and steep strata and complex structures. At present, the characteristics of natural fractures and the current in-situ stress and their influence on engineering are unclear, which restricts the efficient development of coalbed methane. To clarify the characteristics of natural fractures and the current in-situ stress in high-steep coal-bearing strata and their influence on engineering, fracture characteristics and types were first observed in cores from four wells. Fracture occurrences are further counted from imaging logging of well M2 by Stereonet software. Analyzing the fold axis and counting strikes of induced fractures in well M2 from image logging, we describe the current maximum horizontal principal stress direction of the north monocline and the Badaowan syncline, respectively. Parameters measured from injection/falloff tests of four wells are used to calculate magnitudes of the current in-situ stress. Through micro-seismic monitoring and vector scanning for microseismic, the extension direction of coal seam fractures in M8 and M9 wells located in the Badaowan syncline and M10 and M11 wells located in the northern monocline is reflected. The results show that bedding fractures/weak planes, cleats in coal, and shear fractures are the three main types of natural fractures in high-steep coal-bearing strata. Among them, bedding fractures/weak planes are easily activated during strata uplifts under NNW compression. Imaging logging reveals that bedding fractures/weak planes are widely developed in the syncline core of the Badaowan Formation, and their occurrences are consistent with those of strata. Current in-situ stress fields of the Badaowan syncline-Qidaowan anticline and the north monocline are obviously different. Near the north monocline, vertical directions to the Qidaowan anticline axis indicate that the current maximum horizontal principal stress direction of the north monocline is nearly along the NNW direction. NEE-trending induced fractures suggest that the direction of the maximum horizontal principal stress in the core of the Badaowan syncline is along the NEE direction, reflecting that the syncline is locally controlled by the tensile stress field below the neutral surface. In the northern monocline, from shallow to deep (492–1135 m), horizontal principal stresses are always greater than vertical principal stresses, showing a strike faulting stress state dominated by compression. In the Badaowan syncline-Qidaowan anticline, from shallow to deep (524–784 m), the strike faulting stress state transits into the normal faulting stress state. Microseismic monitoring and vector scanning for microseismic reveal that the hydraulic fractures of M8, M9, M10, and M11 wells extend along the NEE-trending coal seam. Under the background of the current stress field, steep bedding fractures/weak planes tend to induce casing deformation during hydraulic fracturing, and they affect wellbore stability. In particular, bedding fractures/weak planes have a significant induction effect on the extension of hydraulic fractures in coal seams. Consequently, the main extension direction of hydraulic fractures is consistent with the occurrence of coal seams, which means limited stimulation of coal seams. Considering the influence of fracturing fluid viscosity and displacement on stress transfer, it is worth further practice to improve different viscosities and displacements of fracturing fluids and compare the fracturing effect and production. |
| format | Article |
| id | doaj-art-d9738bcef0a744288d76b903bac6896b |
| institution | OA Journals |
| issn | 0253-2336 |
| language | zho |
| publishDate | 2025-03-01 |
| publisher | Editorial Department of Coal Science and Technology |
| record_format | Article |
| series | Meitan kexue jishu |
| spelling | doaj-art-d9738bcef0a744288d76b903bac6896b2025-08-20T02:10:41ZzhoEditorial Department of Coal Science and TechnologyMeitan kexue jishu0253-23362025-03-0153322623710.12438/cst.2024-17962024-1796Characterization of natural fractures and in-situ stress in high-steep coal-bearing strata in the Midong area in Xinjiang and influence on engineeringJiawei WU0Jian ZHANG1Yumin LYU2Yanhe ZHU3Cunwu WANG4Yue ZHANG5Silu CHEN6Jingyu ZI7CNOOC Research Institute Ltd., Beijing 100028, ChinaCNOOC Research Institute Ltd., Beijing 100028, ChinaCNOOC Research Institute Ltd., Beijing 100028, ChinaCNOOC Research Institute Ltd., Beijing 100028, ChinaCNOOC Research Institute Ltd., Beijing 100028, ChinaCNOOC Research Institute Ltd., Beijing 100028, ChinaCNOOC Research Institute Ltd., Beijing 100028, ChinaCNOOC Research Institute Ltd., Beijing 100028, ChinaThe Midong area in Xinjiang is located in the foreland thrust belt of Bogda Mountain on the southern margin of Junggar Basin, with high and steep strata and complex structures. At present, the characteristics of natural fractures and the current in-situ stress and their influence on engineering are unclear, which restricts the efficient development of coalbed methane. To clarify the characteristics of natural fractures and the current in-situ stress in high-steep coal-bearing strata and their influence on engineering, fracture characteristics and types were first observed in cores from four wells. Fracture occurrences are further counted from imaging logging of well M2 by Stereonet software. Analyzing the fold axis and counting strikes of induced fractures in well M2 from image logging, we describe the current maximum horizontal principal stress direction of the north monocline and the Badaowan syncline, respectively. Parameters measured from injection/falloff tests of four wells are used to calculate magnitudes of the current in-situ stress. Through micro-seismic monitoring and vector scanning for microseismic, the extension direction of coal seam fractures in M8 and M9 wells located in the Badaowan syncline and M10 and M11 wells located in the northern monocline is reflected. The results show that bedding fractures/weak planes, cleats in coal, and shear fractures are the three main types of natural fractures in high-steep coal-bearing strata. Among them, bedding fractures/weak planes are easily activated during strata uplifts under NNW compression. Imaging logging reveals that bedding fractures/weak planes are widely developed in the syncline core of the Badaowan Formation, and their occurrences are consistent with those of strata. Current in-situ stress fields of the Badaowan syncline-Qidaowan anticline and the north monocline are obviously different. Near the north monocline, vertical directions to the Qidaowan anticline axis indicate that the current maximum horizontal principal stress direction of the north monocline is nearly along the NNW direction. NEE-trending induced fractures suggest that the direction of the maximum horizontal principal stress in the core of the Badaowan syncline is along the NEE direction, reflecting that the syncline is locally controlled by the tensile stress field below the neutral surface. In the northern monocline, from shallow to deep (492–1135 m), horizontal principal stresses are always greater than vertical principal stresses, showing a strike faulting stress state dominated by compression. In the Badaowan syncline-Qidaowan anticline, from shallow to deep (524–784 m), the strike faulting stress state transits into the normal faulting stress state. Microseismic monitoring and vector scanning for microseismic reveal that the hydraulic fractures of M8, M9, M10, and M11 wells extend along the NEE-trending coal seam. Under the background of the current stress field, steep bedding fractures/weak planes tend to induce casing deformation during hydraulic fracturing, and they affect wellbore stability. In particular, bedding fractures/weak planes have a significant induction effect on the extension of hydraulic fractures in coal seams. Consequently, the main extension direction of hydraulic fractures is consistent with the occurrence of coal seams, which means limited stimulation of coal seams. Considering the influence of fracturing fluid viscosity and displacement on stress transfer, it is worth further practice to improve different viscosities and displacements of fracturing fluids and compare the fracturing effect and production.http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2024-1796midong area in xinjianghigh-steep coal-bearing stratanatural fracturecurrent in-situ stressgeology-engineering integration |
| spellingShingle | Jiawei WU Jian ZHANG Yumin LYU Yanhe ZHU Cunwu WANG Yue ZHANG Silu CHEN Jingyu ZI Characterization of natural fractures and in-situ stress in high-steep coal-bearing strata in the Midong area in Xinjiang and influence on engineering Meitan kexue jishu midong area in xinjiang high-steep coal-bearing strata natural fracture current in-situ stress geology-engineering integration |
| title | Characterization of natural fractures and in-situ stress in high-steep coal-bearing strata in the Midong area in Xinjiang and influence on engineering |
| title_full | Characterization of natural fractures and in-situ stress in high-steep coal-bearing strata in the Midong area in Xinjiang and influence on engineering |
| title_fullStr | Characterization of natural fractures and in-situ stress in high-steep coal-bearing strata in the Midong area in Xinjiang and influence on engineering |
| title_full_unstemmed | Characterization of natural fractures and in-situ stress in high-steep coal-bearing strata in the Midong area in Xinjiang and influence on engineering |
| title_short | Characterization of natural fractures and in-situ stress in high-steep coal-bearing strata in the Midong area in Xinjiang and influence on engineering |
| title_sort | characterization of natural fractures and in situ stress in high steep coal bearing strata in the midong area in xinjiang and influence on engineering |
| topic | midong area in xinjiang high-steep coal-bearing strata natural fracture current in-situ stress geology-engineering integration |
| url | http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2024-1796 |
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