Drilling technique for large-diameter injection-production wells of the Shuang-6 Underground Gas Storage

To deal with the incompetence of the current injection-production well pattern of the Shuang 6 Underground Gas Storage (UGS), the first three large-diameter injection-production wells were deployed. Given the intensive alternating load during injection and production, insufficient cutting-carrying of drilling fluids and low cement slurry displacement efficiency in large wells, optimize the design of the wellbore structure of the cover layer, seal the top of the cover layer with technical casing, seal the middle of the cover layer with production casing, and seal the bottom of the cover layer with a half way cementing of the Ø177.8 mm oil layer tail pipe, improving wellbore integrity; the continuous cutting weighting was performed to monitor cutting return in real time and reduce risks of downhole accidents; the cementing tools and parameters were optimized and the casing centering was enhanced for better cementing quality. These efforts resulted in excellent effects in practice. The cement bond logging showed the cementing qualification rates of the Ø339.7 mm intermediate casing and Ø244.5 mm production casing of the drilled well Shuang 6-H431 reach 93.1% and 99.9%, respectively, and the high-quality cemented section along the caprock is 221 m long. These indicators are far higher than those specified in the industrial standard of underground gas storage. This research provides practical experience for drilling engineering of large-diameter wells in the Liaohe UGS as well as other UGS in China.