套管钻井多轴疲劳试验与可靠性研究

根据套管钻井中套管柱承受的载荷状况,借助现有的技术水平和手段,首先进行了套管试件的拉-拉单轴高周疲劳试验,通过相关的试验数据获得了套管试件在不同应力水平下的疲劳寿命及其统计分布,为进一步获得试件的基于概率的等效P-S-N曲线奠定基础。然后通过拉压-扭转双轴循环复合疲劳试验,验证了等效P-S-N曲线的正确性。最后根据P-S-N曲线,采用有限元疲劳分析软件,进行典型工况下套管的疲劳可靠性分析,计算得到套管体中的最大等效循环应力,并据此计算出要求可靠度(或存活率)下套管的疲劳寿命,再由钻井周期得到套管疲劳的剩余寿命。

A study of the multiaxial fatigue test of casing drilling and its reliability

According to the loading of the string in casing drilling and by means of existing technology and devices,a pull-pull uniaxial high-cycle fatigue experiment of the casing test-piece was first conducted. The fatigue life-span and its statistical distribution of the casing test-piece at different stress levels were obtained through relevant experimental data,laying a foundation for obtaining the probability-based equivalent P-S-N curve of the test-piece. Then,the correctness of the curve was proved by a pull-twist biaxial compound fatigue experiment. Finally,referring to the curve,using the software of the finite element fatigue analysis and analyzing the fatigue reliability of the casing in typical working conditions,the maximum equivalent cyclic stress was obtained by calculation and based on this,the fatigue life-span of the casing under the required reliability (or survival rate) was calculated and then the remaining fatigue life-span of the casing was obtained through the drilling cycle.