气体连续循环钻井技术在博孜区块砾石层的应用

博孜区块上部地层发育着近5 000 m厚的砾石层，砾石层硬度大、可钻性差，导致了上部大尺寸井眼常规钻井机械钻速低、钻井周期长，近年来尝试了多种提速工具、工艺技术，效果都不理想。为此，进行了气体连续循环钻井技术研究，设计了气体连续循环钻井技术方案，制定了井斜控制、沉砂清理等工艺技术措施，形成了适合巨厚砾石层地质特征的气体连续循环钻井工艺技术，并开展了6口井、9井次现场应用，显著提高了机械钻速，缩短了钻井周期，较大节省了钻井成本。气体连续循环钻井技术克服了沉砂30 m以上无法接立柱的困难，有效延长了微出水地层气体钻井进尺，将最大井斜控制在5°的安全范围内，未影响后期技术套管下入及完井改造工艺实施。气体连续循环钻井技术正在成为博孜区块巨厚砾石层钻井提速提效的一项关键技术，它为博孜-大北区块万亿方产能建设目标提供了有力的技术支撑。

Application of Gas Continuous Circulation Drilling Technology in Gravel Layer in Bozi Block

There are over 5 000 m of gravel layers in the upper strata of deep and ultra deep wells in Bozi Block. It has high hardness and poor drillability, which leads to low ROP and long drilling cycle of conventional drilling at the upper large-size borehole when conventional drilling is used. In recent years, a variety of speed-up tools and technologies have been tested, but the effect is unsatisfactory. Aiming at the difficulties of low ROP and long drilling cycle of conventional drilling for the huge-thick gravel layer in Bozi Block, using underbalanced drilling method, the scheme of gas continuous circulation drilling technology is designed, and technical measures such as well deviation control, grits cleaning and mud conversion have been formulated, and a gas continuous circulation drilling process technology suitable for the geological characteristics of huge-thick gravel layer is formed. This technology has been applied to 6 wells for 9 times in total, which has significantly improved the ROP, shortening the drilling cycle, and greatly saving the drilling costs. The gas continuous circulation drilling technology overcomes the difficulty that the stands cannot be connected when the sand setting is more than 30 m. It effectively prolongs the drilling footage of gas drilling in micro water-producing formation, and controls the maximum well deviation within the safe range of 5ånd does not affect the implementation of casing running and completion modification technology in the later stage. The gas continuous circulation drilling technology is becoming a key technology for speeding up and improving the efficiency drilling of the huge-thick gravel layer in the Bozi Block, which provides strong technical support for the trillion cubic meter capacity construction target in the Bozi-Dabei Block.