H级抽油杆许用应力计算及疲劳寿命预测方法

摘要

In order to effectively use the H-class sucker rod,the method of allowable stress calculation and fatigue life prediction was studied.Using the indoor tensile strength test as a starting point,the ratio of tensile strength to yield strength was calculated,by which the calculation parameter for the maximum API allowable stress of H-class sucker rod was adjusted from 0.562 5 to 0.716 3.In addition,stress-fatigue plots of H-class sucker rod by fitting method were developed,so as to determine the ultimate fatigue stress of the sucker rod at the stress ratio of 0.1.By testing the fatigue performances of H-class sucker rods in different media and different stroke frequencies,the relationship among water cut,stroke frequencies and service life of the sucker rod were obtained.The innovative techniques for the calculation of allowable stress and prediction of fatigue life of the sucker rod were applied in 10 wells in the Xingnan Area of the Changqing Oilfield,and the results showed that the stress conditions of the H-class sucker rod could be improved through the optimal design,and tap the potential of the sucker rod,so as to meet the demands of field application for stresses and service life.%为了有效使用H级抽油杆,对其许用应力计算方法和疲劳寿命预测方法进行了研究.在对H级抽油杆进行室内拉伸试验的基础上,计算了其抗拉强度与屈服强度的比值,根据该比值将H级抽油杆API最大许用应力计算系数由0.562 5修改为0.716 3;拟合建立了H级抽油杆的应力-疲劳曲线,折算了H级抽油杆在应力比为0.1条件下的极限疲劳应力;通过H级抽油杆在不同介质中和不同冲次下的疲劳测试,获得了含水率和冲次与抽油杆寿命的关系.研究的H级抽油杆许用应力计算及疲劳寿命预测方法,在长庆油田杏南作业区10口井进行了应用,结果表明,利用该方法对H级抽油杆进行优化设计可以改善其受力条件,充分发挥H级抽油杆的性能,使其满足现场生产对杆柱应力、寿命的需求.