第33卷第4期 2016年7月
钻井液与完井液
DRILLINGFLUID&COMPLETIONFLUID
doi: 10.3696/j.issn.1001-5620.2016.04.015
Vol.33 No.4 July2016
循环应力作用下水泥环密封性实验研究刘仍光1.2，张林海，陶谦"，周仕明'，丁士东（1.中国石化石油工程技术研究院，北京100101；2.中国石油大学（北京），北京102249）
刘仍光等.循环应力作用下水泥环密封性实验研究[].钻井液与完并液，2016，33（4)：74-78.
摘要利用自主研发的水泥环密封性实验装置研究了套管内加卸压循环作用下水泥环的密封性，根据实验结果得出了循环应力作用下水泥环害封性失效的机理。实验结果显示，
在较低套管内压循环作用下，水泥环保持密封性所能承受的应
力循环次数较多；在较高循环应力作用下受的应力较低，应力水平处于弹性状态，水泥环内部固有的微裂纹和缺陷逐渐扩
变形也不断地累积。循环压力卸载时，
泥
诺环
次费较少
表明在套管内较低压力作用下，水泥环所
「随之弹性变形和弹性恢复；在较高应力作用下，
性变形；随着应力循环次数的增加，塑性
，2者在界面处的变形不协调而引起
套管弹性回缩而水泥环型性受形不可完全恢复，
拉应力。当拉应力趣过界面处的胶结强度时出现微环隙，
导致水泥环密封性失效，水泥环发生循环应力作用的低周期密封
性疲劳破坏。套管内压力越大，水泥环中产生的应力水平越高，产生的塑性变形越大，每次卸载时产生的残余应变和界面处拉应力也越大，因此引起密封性失效的应力循环次数越少。
关键词水泥环；密封性装置；循环应力；微环隙；疲劳破坏
中图分类号：TE256.9
文献标识码：A
文章编号：1001-5620（2016）04-0074-05
Experimental StudyonAirtightnessofCementSheathUnderAlternatingStress
LIU Rengguang'-2, ZHANG Linhai', TAO Qian', ZHOU Shiming', DING Shidong
(1. Sinopec Research Institute of Petroleum Engineering, Bejing 100101;2. China University of Petroleum, Beijing 102249) Abstract The airtightness of cement sheath under altermating loading and unloading was studied using self-developed experiment facilities, and the mechanism of airtightness failure of cement sheath under altemating loading and unloading was understood based on the experimental results. Under the action of lower altermating pressure inside the casing, the time for the cement sheath to fail can be long; the action of high altermating pressure, on the other hand, will soon break down the airtightness of the cement sheath. This indicates that low pressure inside the casing string imposes low force on cement sheath which still retains its elasticity, and elastic deformation takes place in the cement sheath under altermating loading and unloading. Under the action of high stresses, on the other hand, the intrinsic micro fractures and deficiencies inside the cement sheath begin to connect with each other, and both elastic deformation and plastic deformation take place inside the cement sheath. As the altermating goes on, the plastic deformation becomes accumulated, to the extent that the plastic deformation does not vanish after unloading. Differences in the deformations of casing string and cement sheath at the interface result in a tensile stress, which, when exceeding the cementation strength at the interface, will cause the airtightness of the cement sheath to fail. This is the so-called low cycle fatigue failure of the airtightness of cement sheath under the action of alternating loading and unloading. Higher internal pressure in the casing string results in higher induced stress inside the cement sheath, larger plastic deformation, higher residual strain and tensile stress at the interface after unloading, and, the less of the number of cycles required to cause the airtightness of the cement sheath to fail.
Key words Cement sheath; Airtightness tester; Altemating stress; Micro annular space; Fatigue failure
目前由于水泥环密封性失效而引起的环空带压
等现象时常发生，影响了油气井的生产和安全等问
基金项目：国家自然科学基金面上项目（51374218）；中国博士后科学基金资助项目（2015M571228)。
第一作者简介：刘仍光，博士，现在主要从事油井水泥浆性能与水泥环密封性等研究。电话18911027279；E-mail： jiangonglrg@163.com。
通讯作者：丁士东，教授级高级工程师。E-mail：dingsd.sripesinopec.com。万方数据