空气钻井钻柱疲劳寿命预测研究

On Fatigue Life Prediction of Air Drill String

空气钻井采用具有极大压缩性的空气作为循环介质,可大幅提高机械钻速、有效发现及保护油气层、高效治理恶性井漏,因而获得快速发展。然而空气钻井经常发生钻具失效断裂事故,增加了钻井周期和成本,给后续钻井作业带来了困难。针对这一问题对钻柱进行了三向应力分析,改进了钻柱疲劳寿命计算模型。该模型反映了运动状态对寿命的影响,可用于无裂纹和有裂纹钻柱的疲劳寿命预测,计算结果和现场实际情况基本相符,对空气钻井的现场运用具有一定的指导意义。

Taking the compressed air as circulated fluid, air drilling has many different characteristics from mud drilling. Air drilling has some advantages： high rate of penetration, effectively protection the hydrocarbon reservoir and the malignant mud loss disposal, etc. However, drill string failure usually takes place during air drilling. It increases the period and cost of the air drilling, brings difficulty to follow-up drilling operation. Aiming at this problem a triaxial stress analysis is carried on and the model for the calculation of fatigue life of drill-string is improved, which can be used for the prediction of fatigue life of non -crackled or crackled drill string. Computational results show that the improved model is basically reasonable and coincident with the field data, which is better of guiding significance to utilizing reasonably the gas drilling and preventing the drill string from failure.