大口径瓦斯抽放井施工工艺

瓦斯抽放孔要求井斜小，孔径大，下入的井管重量大。以实例介绍了使用GZ-2000型钻机在某煤矿瓦斯抽放站成功施工深400m，直径φ690mm瓦斯抽放井的施工工艺。在施工过程中采用φ216mm牙轮钻头＋满眼钻具和钟摆钻具施工先导井眼，再采用φ410mm、φ690mm组合牙轮钻头＋塔式钻具分级扩眼，使用电子多点测斜仪及时监测井斜变化，用钟摆钻具组合进行纠斜，在φ426mm管体上设置三组镶焊合金的肋骨条做成圆井器来进行圆井，在管体底部设置浮力阀，合理掏空以减少井管重量，确保了工程质量。

Construction Technology of Large Diameter Gas Drainage Wells

Small well deviation, large diameter and heavy well type lowering are required by the gas drainage wells. Examples introduced gas drainage well construction technology by the use of GZ-2000 drill rig drilled a 400m depth, φ690mm for a coalmine gas drainage station. During construction, a pilot well drilled by φ216mm roller bit, packed hole assembly and pendulum assembly, then φ410mm, φ690mm assembled roller bits and tapered drill string reaming in tandem. Well deviation is monitored by multipoint electronic inclinometer; hole straightening by pendulum assembly; well rounded out by a rounder made of φ426mm pipe set on three sets of carbide ribs; a buoyant valve has set on the bottom of the pipe and reasonable hollow out to reduce pipe weight thus ensure to construction quality.