煤矿大口径瓦斯抽排孔施工技术

结合金能二号大口径瓦斯抽排孔的施工实践，总结出大口径瓦斯抽放孔的施工技术：按照先施工小径导向孔，然后分级扩孔的成孔工序，采用轻压吊打防斜，单点测斜，螺杆钻具定向纠斜，确保钻孔偏斜率控制在规定范围以内；上部第四系、新近系黄土及不含大块砾石的松软地层选择刮刀钻头，基岩段及沙砾石地层采用组合式钻头，以提高钻进效率；按每组滚刀15～30kN，每个牙轮10～20kN控制钻压，钻速控制在0．4～0．6m／h；换用小直径牙轮，以减轻钻具振动，采用高粘度、低固相、不分散泥浆体系以保持孔壁稳定；在下管时采用在套管端部割孔穿杠钢丝绳提吊，套管底部加浮箍浮鞋的综合下管法。

Coalmine Large Diameter Gas Drainage Well Construction Technology

Based on the Jinneng No.2 large diameter gas drainage well construction practice, summed up large diameter gas drainage well construction technology. According to the working procedure of small pilot hole first, then graded reaming to the well completion. To control the borehole inclination rate within prescribed limit, light pressure hanging drilling, single point inclination surveying and positive displacement drill directional deviation correction were used. For upper part Quaternary and Neogene systems loess and crumbly strata with no large pebbles, drag bits can be used, while in bedrock and sandy gravels to use combined drill to improve drilling efficiency. According to 15-30kN on every bobbing set, 10-20kN on every roller cone to control bit pressure and drilling rate within 0.4-0.6m/h. Small diameter miler cone is used to reduce drilling string vibration, and high viscosity, low solid and non - dispersed mud to keep borehole wall stable. During casing lowering, tie the wire rope up to a bar perforated through holes on casing end to hang the casing and add floating hoop and shoe on the casing bottom to keep the lowering stable.