Influence of natural weak surface on extension of multiple fractures during fracturing of gas extraction horizontal wells
In view of the difficult problem of strip gas extraction in coal roadways of broken soft and low permeability coal seam, this paper puts forward the technology of segment fracturing and high efficient pre-gas extraction in horizontal wells of strip roof of coal roadways of coal roadways.For balanced...
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| Main Authors: | , , , , |
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| Format: | Article |
| Language: | Chinese |
| Published: |
Editorial Department of Coal Science and Technology
2025-06-01
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| Series: | Meitan kexue jishu |
| Subjects: | |
| Online Access: | http://www.mtkxjs.com.cn/article/doi/10.12438/cst.2023-2000 |
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| Summary: | In view of the difficult problem of strip gas extraction in coal roadways of broken soft and low permeability coal seam, this paper puts forward the technology of segment fracturing and high efficient pre-gas extraction in horizontal wells of strip roof of coal roadways of coal roadways.For balanced gas extraction without blank zone, fracture network construction based on segmented multi-cluster fracturing is the key to technical success.In order to study the propagation patterns of multi-fractures in coal measures strata, the development characteristics of natural weak surface in coal measures strata are analyzed, and the discriminant formula of natural weak surface to multi-fractures propagation patterns is established, the influence of single natural weak surface and multi-natural weak surface on multi-fracture propagation is analyzed by finite element method.The results show that there are a lot of natural weak planes such as fissures, bedding and interfaces in coal seam and roof and floor strata, which affect the propagation of hydraulic fracture.The interaction between fracture and natural weak surface is affected by in-situ stress, induced stress of fracture and stress field of fracture tip.The natural weak surface can induce the initiation and rapid propagation of fractures when the distance between the natural weak surface and the preset fracture is small, while the natural weak surface with small angle can induce the rapid propagation of nearby fractures when the distance is large, when the angle is 90° , the interference between slits is not affected.Under the condition of multi-natural weak surface, the fracture net is easy to form when the stress difference is low, and easy to form a simple single fracture when the stress difference is large, and easy to form the fracture net when the density of natural weak surface is high and the shape is complex, the in-situ stress has little effect on the form of fracture net.The engineering application shows that the hydraulic fracturing in the test well has formed a seam net covering the coal roadways to be driven, and the daily gas production is in the rising stage, and has reached 1708 m3, which has a good prospect of extraction. |
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| ISSN: | 0253-2336 |