针对热采井口装置用螺栓在现场工况下的应力松弛现象展开实验研究,分别进行了常、高温拉伸试验,蠕变实验和应力松弛试验.通过对比研究发现螺栓材料在高温下强度降低,塑性增加;在初始应力下蠕变变形明显,从原理上解释了螺栓松弛出现应力松弛的原因;通过应力松弛试验可以发现螺栓在现场工况下会产生明显的应力松弛,根据应力松弛实验数据拟合出现场工况下的应力松弛回归方程;利用有限元软件计算KR21-370型热采井口装置各法兰达到密封所需的最小螺栓预紧载荷,结合应力松弛回归方程计算出法兰由于螺栓的应力松弛而出现密封失效所需的时间,并针对易出现失效的螺栓提出解决措施.

针对热采井口装置在蒸汽驱和蒸汽吞吐两种工况下的热蠕变失效情况,进行了其材料30CrMo在390℃,四个不同应力下的蠕变试验,对试验结果进行了拟合,获得了复合时间强化模型参数.用短期的试验进行了验证,复合时间强化模型的计算值与试验值之间的误差小于15％.运用Ansys Workbench模拟了热采井口装置主要承压件在恒温恒载工况和断续加载工况下的蠕变失效过程,得到主要承压件在两种工况下的失效时间,对热采井口装置的使用寿命评估具有重要的意义.

In view of the evaluation of the service life of the thermal recovery wellhead in the oil field, the tensile and creep property of 30CrMo are studied. The tensile properties at room temperature and 390 °C are obtained by tensile test;The creep tests of the material at 390 °C and five different stresses are carried out. The Norton Bailey equation is used to fit the test data, and the creep constitutive equations of low stress zone and high stress zone are obtained;Scanning electron microscope and transmission electron microscope are used to observe the original samples and five samples after creep. It is found that when the material is kept at 390 °C for a long time, the diffusion of carbon element in the crystal result in the increase of carbide quantity and particle size on the matrix , resulting in the decrease of the strength of the material. The mechanism of creep microstructure change of 30CrMo in low stress zone and high stress zone is different. The creep mechanism in low stress zone is dominated by dislocation thermal climbing, and the mechanism in high stress zone is dominated by Orowan winding.