可伸缩扩孔钻头在深厚砂卵砾石层跟管钻进中的应用

针对雅鲁藏布江冷达水电站深厚砂卵砾石层钻进遇到孤石致使跟管受阻问题，采用一种可伸缩两翼扩孔钻头，将套管下方的孤石扩出口径略大于套管外径的环状空隙，使套管继续跟进到达计划深度。该方法既可避免传统孔内爆破炸碎孤石方法的危险性和繁琐性，也可克服采用套管钻头旋转跟进套管由于扭矩大导致的套管磨损大、易断裂、成本高等问题。该工艺操作易掌握，不受深度限制，在跟管扩孔钻进中，甚至于处理孔内事故时均可采用，值得推广。

Application of Scalable Reaming Bit in Deep Sand Gravel Stratum with Casing

According to drilling encountered boulder in deep sand gravel stratum in Yarlung Zangbo River Leng-da hydropower station, a scalable two-wing reaming bit was used to solve pipe blocking. By enlarging a hole in the boulder under the casing, the hole diameter is slightly larger than the outer diameter of the casing pipe to ensure the casing going down to the planned depth. This method can not only avoid the danger and complexity of hole blasting shattering boulder but also can overcome casing wear, broken and high cost caused by high torque of casing bit drilling for casing following. This process is easy to master with no limitation of hole depth and can be popularized in pipe-following ream drilling, even in hole accidents treatment.