90年代以来 ,欠平衡钻井受到人们高度重视 ,欠平衡钻井技术迅速发展 ,钻井数逐年增加 ,从而也促进了连续油管在欠平衡钻井中的应用。欠平衡连续油管钻井 ,可减少钻井过程中对地层和产层的损害 ,可提高机械钻速 ,安全高效率钻井 ,降低钻井成本。文中介绍了国外欠平衡连续油管钻井概况 ,着重介绍了欠平衡压力条件下采用连续油管钻井的特点、钻井所需的地面设备及底部钻具组合 ,并介绍欠平衡连续油管钻井成功的实例 Since the 1990s, underbalanced drilling has received great attention. Underbalanced drilling technology has been rapidly developed and the number of drilling wells has been increasing year by year, thus promoting the application of coiled tubing in underbalanced drilling. Underbalanced coiled tubing drilling can reduce the damage to strata and formation during drilling, improve ROP, safe and efficient drilling, and reduce drilling cost. In this paper, the author introduces the general situation of overseas underbalanced coiled tubing drilling, emphasizes the characteristics of coiled tubing under under-balanced pressure, the ground equipment and bottom hole assembly required for drilling, and introduces the successful drilling of underbalanced coiled tubing