Full
Outline
In order to explore the feasibility of efficient rock breaking and cavitation by abrasive jets with conical nozzles，abrasive jet cavitation tests were carried out.A visualization experimental method based on digital image correlation （DIC） was adopted to study the distribution characteristics of the strain field in horizontal well cavity completion.Combined with the finite-discrete element method （FDEM），the morphological characteristics of cavitation‑induced fractures and the evolution process of stress in cavity completion were characterized.The effects of cavity diameter and in‑situ stress on the stress evolution and fracture extension of the cavity in coalbed methane （CBM） horizontal wells were investigated.The research results show that under the condition of submerged jet，the abrasive jet with a conical nozzle can penetrate a coal body with a length of 62 cm within 30 s under a pressure of 25 MPa and produce a volume‑breaking effect.With the increase of vertical stress and cavity diameter，the strain localization zones increase significantly，and the strain localization zones distributed vertically gradually appear.Natural fractures are the main factor affecting the damage degree of coal rock plates.Stress concentration occurs first around the cavity，and then cracks initiate at the intersection of the bedding/cleat weak planes and the cavity.When the vertical stress is greater than the horizontal stress，a fracture network is more likely to be formed，thus inducing stress release.The research findings provide a theoretical basis for the stress release mechanism of cavity completion in CBM horizontal wells.
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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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