南海西部海域某井在采用半潜式钻井平台进行钻井作业时，φ244.4 mm套管下至井深2546.00 m时遇阻，距离设计井深还有35.00 m。通过多种技术手段处理后未能成功解卡，选择切割φ244.5 mm套管，使用套管外回接技术回接套管并实现套管挂坐挂及密封。在泥线以下40～60 m位置（单根套管中间位置）切割回收套管及套管挂；下入套管壁内外修整铣鞋磨铣修整套管割口0.2～0.5m；下入套管外回接补贴工具，使原套管进入外回接补贴工具并进入延伸筒，直至套管挂坐挂到位，使套管外回接补贴工具与原套管连为一体；加压对套管外回接补贴工具密封进行测试；该井在井深203.02 m处成功切割回收了9根φ244.5 mm套管及套管挂，对套管割口磨铣0.24 m后，套管外回接补贴工具下至井深205.40 m进行回接，试压20.69 M Pa合格，实现套管对接及密封。现场应用表明，套管外回接工艺不缩小现有管串内径，保障套管通径，密封寿命满足油田开发要求，能够解决半潜式平台套管未下到位的问题。%Pipe-sticking occurred in a well drilled on semi-submersible platform in Western South Chi-na Sea during running the φ244.5 mm casing at 2 546 m ,35 m away from the designed depth 2 581 m .Mul-tiple measures were tried but failed ,then the casing had to be cut and casing external tieback technique was used to tieback casing so that the casing hanger could land on the subsea wellhead and besealed .The tie-back process included :cut and retrieved casing and casing hanger at 40 60 m below the mud line ,dropped mill shoe to mill 0.2 0.6 m on casing scarfing ,dropped the tool of external casing tieback patch and made the initial casing into casing external tieback patch until the casing hanger land on the subsea wellhead so that the outer casing tieback patch could connect with original casing ;applied pressure in the casing exter-nal tieback patch tool and tested the seal ;cut at 203.02 m and retrieve nine φ244.5 mm casing joints and casing hanger ,milling 0.24 m on casing scarfing ,running casing external tieback patch to 205.40 m ,pres-sure test at 20.69 MPa ,butted and sealed casing smoothly .Field application showed that casing external tieback would not reduce the inner diameter of the existing pipe string so ensured casing drift ,the sealing life could meet the requirements of oilfield development .It was able to solve the semi-submersible platform casing problem w hen casing could not reach the designed position .
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