Abstract: The erosion of pipe string resulted from gas-solid two-phase flow in the gas drilling was analyzed quantitatively.The maximum point of erosion locates in the bottom hole,which benefits for drilling,and the secondary point of erosion locates in the top of the pipe string,which is unfavorable for drilling.A method for controlling erosion of pipe string by loading backpressure on the annular of wellhead was proposed.The rules for loading proper value of backpressure were put forward.The rules demand that annular velocity is between the minimum carrying solid velocity and critical erosion velocity.

Key words: gas drilling, erosion, critical velocity, quantitative analysis, annular flow velocity

摘要： 定量分析了气体钻井中气-固两相流对井筒的冲蚀作用。结果表明,冲蚀作用最大的点在井底,这有助于破岩;井口段套管和钻杆的冲蚀作用次之,这是有害的。提出了在环空井口加载回压来控制气体钻井过程中气固两相流对井筒冲蚀的方法,确定了加载合理回压值的准则,即:确保环空内流速介于最小携岩速度和冲蚀临界速度之间。

关键词: 气体钻井, 冲蚀作用, 临界速度, 定量分析, 环空流体流速