School of Energy Science and Engineering, Henan Polytechnic University

为解决抽采钻孔喷孔瓦斯超限的技术难题，提出将钻孔瓦斯喷涌压力在孔内进行削弱的思路，构建了孔底组合阻尼钻具结构模型，通过建立气流阻力力学方程、孔底组合钻具阻尼效果数值模拟，分析孔底组合钻具瓦斯喷涌阻尼机制，研制了孔底组合阻尼钻具，包括揭露钻头、熔涂阻尼钻杆、扩孔钻头，并在屯兰矿8号煤层18407轨道巷开展了现场钻进工业性试验。研究结果表明：① 降低钻孔孔底揭露面积和增加喷孔源高压气体流动的阻力是削弱瓦斯喷涌压力技术的关键，采用小直径钻头钻进、大直径钻头扩孔分层、分段逐渐增大钻孔，通过合理设计阻尼钻具“降压间隙”β，改变钻具相对粗糙度，提高沿程阻力系数，增加风阻，能够将喷出的瓦斯压力降低到初始的25%以下。② 数值计算表明：孔底组合钻具能够大幅削弱喷孔的气流压力，降低了高压气流在孔口高速喷出的风险；揭露钻头与阻尼钻杆形成的“降压间隙”对阻尼效果起决定作用。③ 现场使用孔底组合阻尼钻具施工，钻具供水阀门开度全开，钻进速度略有降低，同时在钻孔孔口处检测到2次明显瓦斯波动现象，钻孔揭露到高压瓦斯富集区，未出现喷孔瓦斯超限，表明孔底组合阻尼钻具对钻孔瓦斯涌出压力具有显著的削弱作用，降低了孔口防喷装置的防喷压力。

In order to solve the technical problem of gas blowhole over-limit in gas drainage holes, a method of weakening the gas gushing in the borehole was proposed. The structural model of a hole-bottom combined damping drilling tool was constructed. By establishing airflow resistance mechanics equation and numerical simulation of damping effect of the hole-bottom combined damping drilling tool, the analysis of gas gushing mechanism of the hole-bottom combined damping drilling tool and the industrial test of on-site hole drilling were carried out. The hole-bottom combined damping drilling tool was developed, including exposing drill bit, melting coating damping drill pipe and reaming drill bit. The research results show that ① the drilling tool reduces the exposed area at the bottom of the hole and increases the resistance of the high-pressure gas flow at the spray hole source, which are the keys to the weakened gas gushing pressure technology. By rationally designing the “depressurization gap” β, changing the relative roughness of the drilling tool, increasing the resistance coefficient along the path, and increasing the wind resistance, the pressure of the ejected gas can be reduced to less than 25% of the initial value. ② The numerical calculations show that the hole-bottom combined damping drilling tool can greatly weaken the airflow pressure of the nozzle orifice, and reduce the risk of high-pressure air current jetting out at high speed at the orifice. The study reveals that the “depressurization gap” formed by the drill bit and the damping drill pipe plays a decisive role in the damping effect. ③ The hole-bottom combined damping drilling tool was used for construction on site. The opening of the drilling tool water supply valve was fully opened, and the drilling speed was slightly reduced. At the same time, two obvious gas fluctuations were detected at the hole of the drilling hole, and gas was detected at the orifice. In the area, there was no gas over-limit in the nozzle hole, indicating that the combined damping drilling tool at the bottom of the hole has a significant weakening effect on the gas gushing pressure in the hole. The blowout pressure of the orifice blowout preventer is reduced.

国家自然科学基金资助项目(41872188)

王永龙，裴宇翔，孙玉宁，等. 孔底组合钻具瓦斯喷涌阻尼机制及工程应用[J]. 煤炭学报，2023，48(9)：3420−3427.

WANG Yonglong，PEI Yuxiang，SUN Yuning，et al. Gas gushing damping mechanism and its engineering application of bottom hole combined drilling tool[J]. Journal of China Coal Society，2023，48(9)：3420−3427.