完井作业油管柱失效的力学机理--以塔里木盆地某高温高压井为例  

Mechanical mechanisms of tubing string failures in well completion operation: A case study from one HTHP well in the Tarim Basin

作　　者：杨向同[1] 沈新普 王克林[1] 沈国阳 耿海龙[1] 邓鹏[1] Yang Xiangtong;Shen Xinpu;Wang Kelin;Shen Guoyang;Geng Hailong;Deng Peng(PetroChina Tarim Oil Company,Korla,Xinjiang 841000,China;Tianjin Chenxing Engineering and Technology LLC,Tianjin 301500,China;Guoyang Technology and Services LLC,Houston,TX 77064,USA)

机构地区：[1]中国石油塔里木油田公司,841000 [2]天津辰兴工程技术有限公司 [3]Guoyang Technology and Services LLC

出　　处：《天然气工业》2018年第7期86-92,共7页Natural Gas Industry

基　　金：国家科技重大专项课题“超深超高压高温气井优快建井与采气技术”(编号：2016ZX05051003); 国家自然科学基金面上项目“非常规天然气开采中关键力学问题理论与试验研究”(编号：11272216)

摘　　要：塔里木盆地某高温高压井井深约7 000 m、地层温度180℃、地层压力120 MPa,该井在完井作业中发生两处油管工厂端丝扣根部断裂的工程问题。如何从管柱变形与应力变化进行解释并提出应对措施,进而保证管柱完整性和保障安全生产是一个值得讨论的问题。为此,采用有限单元法进行管柱的三维力学数值分析,建立起三维有限元管柱力学模型,模拟完井作业中下封隔器坐封、压裂、测试3个工况下的管柱结构变形,分析管柱系统的位移和应力的变化规律,进而基于疲劳强度计算的理论公式得出了疲劳安全系数的计算公式。研究结果表明:(1)依据该井完井管柱各处的轴向应力有限元数值计算结果,得到了各弯曲应力部位的疲劳安全系数值;(2)测试作业各油管段的疲劳安全系数都大于3,属于安全状态;(3)断裂的2段油管疲劳安全系数值分别为1.99和1.11,处于预警区,而其他管段的疲劳安全系数均大于1.99,属于安全区。结论认为,该方法为具有类似结构的超深高温高压井的管柱力学设计提供了有效的分析手段。There is one HTHP well（high temperature, high pressure） in the Tarim Basin about 7 000 m deep with formation temperature 180 ℃ and formation pressure of 120 MPa. In the process of its completion operation, the root of thread at the factory end was broken at two points. Therefore, it is necessary to discuss the reasons for the breaking from the aspects of string deformation and stress change and propose the corresponding measures so as to ensure string integrity and production safety. In this paper, 3 D mechanics of strings was analyzed using finite element method. Then, a 3 D finite element string mechanics model was established to simulate the string deformation in 3 working conditions（i.e., packer setting, fracturing and testing） in the process of well completion and analyze the displacement of string system and the change laws of stress. Finally, the calculation formula of fatigue safety factor was derived based on the theoretical calculation formula of fatigue strength. And the following research results were obtained. First, the fatigue safety factor of bending stress positions is obtained based on the finite-element numerical calculation results of axial stress at different positions of completion string in this well. Second, the fatigue safety factor of each tubing section during the testing is higher than 3, so it is in the state of safety. Third, the fatigue safety factor of two broken tubing sections is 1.99 and 1.11, respectively, so they are marked as red-warning zones. The fatigue safety factor of other sections is higher than 1.99, so they are classified as safety zones. In conclusion, this method provides an effective analysis means for the string mechanics design of similar ultra-deep HTHP wells.

关 键 词：高温高压井 管柱失效 水力压裂 三维有限元 屈曲 热膨胀 疲劳 安全系数 塔里木盆地 

分 类 号：TE925.3[石油与天然气工程—石油机械设备]