大北X井盐膏层尾管精细控压固井技术

大北X井是塔里木盆地库车坳陷克拉苏构造带克深区带的一口预探井，该井五开φ177.8+182 mm尾管固井存在纯盐层易发生蠕变、高低压互存，裸眼段长、环空间隙小、套管下入深、钻井液安全密度窗口只有0.03 g/cm3，极易出现上喷下漏、上漏下喷、漏涌交替发生等复杂，为了解决该井固井施工存在的技术难题，尝试实践了精细控压固井技术，通过精确控制井口压力，防止溢流、井漏的发生，采取正注精细控压固井+反挤平推水泥浆的方案，配套防窜压稳和防漏等固井技术措施，安全顺利完成了大北X井固井施工，经CBL/VDL测井，重叠段和裸眼段封固质量合格，管鞋以上200 m封固质量优质，六开降钻井液密度后钻进正常。该技术为窄密度窗口井段安全固井施工积累了经验，并对该区块类似复杂井固井施工提供了借鉴意义。 

Cementing Liner String through Salt Formation in Well Dabei-X by Precise Pressure Control

Well Dabei-X is an exploratory well drilled in the Keshen block, an area located in the Kelasu structure, Kuche depression, Tarim Basin. The fifth interval of the well, which was to be cased with φ177.8 mm+φ182 mm liner strings, penetrated creeping pure rock salt and had coexistence of high- and low-pressure zones. Long open hole, narrow annulus, deep running of liner strings and narrow safe drilling window (only 0.03 g/cm3) were very likely to result in downhole troubles such as coexistence of blowout and mud losses in different depths or alternate occurrence of mud losses and well kicks. To avoid and solve these potential downhole problems, precise control of wellhead pressure was tried during cementing job. By precisely controlling pressure at the wellhead, the occurrence of well kick and well leaking can be avoided. During cementing, the wellhead pressure was precisely controlled in normal injection of cement slurry, and the cement slurry was further reversely squeezed into the annular space. Measures related to the safety of well cementing, such as anti-channeling, prevention of well kick and well leaking, were all put in practice to ensure the success of the cementing job. CBL/VDL logs proved that the bonding in the overlapping section and the open hole section was qualified. Quality of the cementing of the 200 m above the upper casing shoe was excellent. Low density drilling fluid can be safely used in the next interval because of the successful cementing job of the fifth interval. Techniques used in the cementing operation have provided experiences for cementing wells with narrow drilling windows and wells in the Keshen block with similar downhole problems.