In order to prevent collapse and block of drilling hole in short time when conducting gas extraction in soft coal seam, and improve the gas drainage efficiency of drilling, the equipments and methods of inserting casing in drill pipe for soft coal seam were analyzed and studied.By comparing and analyzing the experimental results in soft coal seam with conventional technology of casing running, original technology of inserting casing in drill pipe and improved technology of inserting casing in drill pipe, it showed that:the length of inserting casing by the improved technology is much greater than that by conventional technology, and the design of drill bit and drilling rob on e-quipment of inserting casing in drill pipe have a greater influence on the drilling and length of inserting casing.In the design, the diameter of drilling bit should be moderate and the smooth joint connection should be adopted on drilling rob.The gas drainage capacity of drilling per hundred meters by this technology is much greater than that by ordinary technology.%为了防止软煤层钻孔在瓦斯抽采过程中短时间内塌孔堵死，提高钻孔瓦斯抽放效率，对软煤层钻孔钻杆内下套管设备和工艺方法进行了分析和研究。通过对比分析常规下套管方式、原有钻杆内下套管方式和改进后钻杆内下套管方式的在软煤层试验，得出以下结论：采用钻杆内下套管设备下套管的长度远大于采用常规钻进方式下套管的长度；钻杆内下套管设备的钻头和钻杆设计对钻进和下套管长度影响较大，设计时钻头直径大小应适中，钻杆应尽量采取内平丝扣连接；采用钻杆内下套管方式的百米钻孔瓦斯抽放量要远大于普通钻进下套管钻孔的百米钻孔瓦斯抽放量。
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