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To address wellbore instability caused by differences in the physical-mechanical properties of coal-rock and gangue seams, this study established a numerical model for borehole collapse in deep horizontal wells with composite coal-rock layers. The model leveraged triaxial compression test data on coal-rock and gangue mechanics, integrating composite material failure criteria with poroelastic coupling equations. This model was used to simulate how coal-gangue configurations affect peripheral collapse pressure in horizontal wells and analyze the influence of interface positioning and dip angles on collapse pressure distribution. The results show that significant differences in mineral composition ratios between coal and gangue create compromised cementation strength at interfaces, where coal samples fracture more readily due to lower strength. Disparities in physical-mechanical properties and weak interfacial bonding cause pronounced pressure discontinuity at contacts when drilling traverses varied composites. While interface position dictates coal-gangue collapse pressure differentials, dip angle variations not only modulate peak collapse pressure magnitudes but also trigger migration of extreme-value locations along the borehole wall.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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