松软煤层护孔抗压多通道集输花管研究与应用

Research and application of multi-channel gathering and conveying flower pipe with pressure resistance and hole protection in soft coal seam

  • 摘要: 针对松软煤层预抽钻孔封孔后出现失稳坍塌引起预留花管堵塞或破损阻断瓦斯运移通道、严重影响瓦斯治理效果的问题,研究一种用于松软煤层钻孔瓦斯抽采的集输花管,其结构由瓦斯抽采管、小花管、抽采管−花管连接器、端头连接器和护孔防堵器构成。通过理论分析、数值模拟结合现场试验的研究方法,对钻孔失稳坍塌造成花管失效原因进行分析,基于COMSOL与Fluent仿真软件对原始花管和集输花管的抗挤压强度及流体流动状态进行模拟分析。结果表明:采用1 m的集输花管单孔瓦斯流量比原花管提高42.5%,过流面积提升152%,增加花管与钻孔负压接触面积的同时提高了单孔瓦斯流量;在花管外部施加不同围压时,集输花管的变形量始终小于原花管,且大部分压力被外部花管承担,对内部花管起到了很好的保护作用;原花管中流体流动较为紊乱,而集输花管中流体流动稳定,集输花管有效避免了抽采管中涡流现象的产生,减少了流体在管道流动中的能量损失,提升了花管内部的瓦斯流量。现场工业性对比试验结果表明:抽采初期,采用2种类型花管的钻孔瓦斯抽采浓度和流量相近;抽采60 d后,采用集输花管的试验组钻孔平均瓦斯体积分数比采用原始花管的对比组提高50.7%,平均瓦斯流量提升57.1%,随着抽采时间的延长,试验组钻孔瓦斯浓度和流量衰减更慢,采用集输花管的钻孔抽采效果优于采用原花管的钻孔。集输花管提高了钻孔瓦斯抽采流量和浓度,缩短了煤层瓦斯的治理周期。

     

    Abstract: In response to the problem of instability collapse caused by pre-drainage borehole sealing after gas extraction in soft coal seams, leading to blockage or damage of reserved flower tubes and obstructing gas migration channels, severely affecting the gas treatment effect, a gathering flower tube for gas extraction in soft coal seams is studied. The structure comprises a gas extraction pipe, small flower tube, an extraction pipe-perforated pipe connector, an end connector, and a hole protection anti-blockage device. Through theoretical analysis, numerical simulation, and field experiments, the study analyzes the causes of flower tubes failure due to borehole instability and collapse. Using COMSOL and Fluent simulation software, the crushing resistance and fluid flow state of the original flower tube and the gathering flower tube are simulated and analyzed. The study shows: The use of a 1 meter length gathering flower tube increases the gas flow rate by 42.5% compared to the original flower tube, and increases the flow area by 152%, increasing the gas flow rate of a single hole while increasing the negative pressure contact area between the flower tube and the borehole; When different confining pressures are applied externally to the flower tube, the deformation of the gathering flower tube is always less than that of the original flower tube, and most of the pressure is borne by the external flower tube, providing good protection for the internal flower tube; The fluid flow in the original flower tube is relatively chaotic, whereas the fluid flow in the gathering flower tube is stable, effectively preventing the generation of vortices in the extraction pipe, reducing energy loss in fluid flow within the pipe, and enhancing gas extraction flow rate within the perforated pipe. Field industrial comparative test results show: at the beginning of extraction, the gas concentration and flow rate of gas extraction boreholes using two types of flower tubes are similar; after 60 days of extraction, the average gas concentration of the experimental group using the gathering flower tube is 50.7% higher than that of the comparison group using the original flower tube, and the average gas flow rate is increased by 57.1%. As the extraction time extends, the decline in gas concentration and flow rate in the test group boreholes is slower, indicating that the extraction effect of boreholes using the gathering flower tube is better than that of boreholes using the original flower tube. Gathering flower tube increases gas extraction flow rate and concentration, shortening the gas control cycle of coal seams.

     

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