气体钻井中气体携岩对钻杆的冲蚀机理研究

Study on drill pipe erosion of gas carrying cuttings in gas drilling

气体钻井中气体携岩冲蚀钻杆是引起钻杆快速失效的主要原因之一。基于此,文中采用计算流体动力学（CFD）方法建立了圆形规则井眼、钻杆居中情况下的高速气体携岩冲蚀钻杆的两相流模型。通过对环空气体流场、钻杆表面冲蚀速度和岩屑颗粒对钻杆的冲蚀过程及其运动轨迹的分析后发现,与钻杆接头斜坡碰撞的岩屑颗粒对钻杆有冲蚀作用,最大冲蚀速度发生在钻杆接头斜坡面上,其次在公接头以上0.2～1.8m长度范围内的钻杆本体表面上。这些区域可能形成严重的冲蚀坑,也可能出现微裂纹,在受到钻井过程中的弯、扭、拉等动载荷联合作用下可能发生裂纹扩展、失效现象。

Erosion of gas carrying cuttings in gas drilling is one of the causes of rapid drill pipe failure.Based on this,two phase flow model for drill pipe erosion of high-speed gas carrying cuttings is established by use of the computational fluid dynamics（CFD） method.Through the analysis of the annular gas flow field,the erosion rate of drill pipe surface,the erosion process and motion tracks of cuttings particles,some conclusions are drawn that some cuttings particles collided with drill pipe joints slope is contributed for erosion and the maximum erosion rate lies on the slope,the second worst erosion zone is the drill pipe surface up to the joint from 0.2 m to 1.8m in length.These areas may lead to serious erosion pits and micro-cracks.Ultimately,the crack propagation and failure phenomenon may also appear in the drilling process under combined action of tension,bend and torsion dynamic load.