大直径钻孔联合孔内下套护孔增透技术研究

Study on permeability improvement technology of the large-diameter drilling combined with hole protection

为了解决西南地区矿井因地质条件复杂,煤质松软,煤层透气性低导致预抽钻孔存在堵塞、塌孔等问题,研究了大直径钻孔增透原理及其工艺,并在石壕煤矿南四区回风巷进行了现场对比试验。结果表明:相比于常规钻孔、单大直径钻孔,大直径钻孔联合孔内下套护孔增透技术瓦斯抽采体积分数分别提高20%、47%,抽采浓度衰减缓慢; 90 d内累计抽采量分别提高1.45、3.80倍;大直径钻孔联合套管护孔技术平均抽采纯量约为0.18 m^3/min,分别提高1.42、3.87倍。现场试验表明大直径钻孔联合孔内下套护孔增透技术能有效扩大煤体的卸压区域,提高煤体中瓦斯的渗流,明显增加煤层的透气性,减少预抽钻孔堵塞、塌孔情况,提高瓦斯抽采浓度和抽采效果。

Due to the geological condition complicated,coal soft,low seam permeability,which caused pre-gas drainage borehole jammed and collapsed and other problems,a study was conducted on the permeability improved principle and technology of the large diameter borehole.Also a site comparison test was conducted in the air returned gateway of South No.4 Block in Shihao Mine.The results showed that comparison with the conventional borehole and single large borehole,the gas drainage volume fraction of the large diameter borehole combined with the casing protection borehole technology could be improved by 20%and 47%,the attenuation was slow and the gas drainage concentration was slowly attenuated.Within 90 days,the accumulated gas drainage volume was increased by 1.45 and 3.8 times.The average gas drainage pure volume of the large diameter borehole with the casing protection technology was 0.18 m 3/min and was increased by 1.42 and 3.87 times individually.The site test showed that the large diameter borehole combined with the casing protection technology could effectively expand the pressure released area of the seam,could improve the gas seepage in the seam,could obviously improve the seam permeability,could reduce the pre-drainage borehole jammed and collapsed and could improve the gas drainage concentration and gas drainage effect.