Abstract: The existing calculation methods for the minimum volumetric flow rate of air are only suitable for carrying drilling cuttings without considering any impacts on drilling cuttings during air-nitrogen drilling.The actual volumetric flow rate needed in drilling is often bigger than the value calculated by these methods.The error might come from ignorance of the energy consumption in the repeated fragmentation of drilling cuttings caused by multiple impacts.The conception of repeated fragmentation of cuttings was introduced.The energy consumption in repeated fragmentation of cuttings would be determined according to the difference of particle size between well head and bottom hole.By modifying the Angel model,a new method for calculating the minimum volumetric flow rate of air was deduced.The flow situation and pressure loss of air and solid would be described more exactly using the modified Angel model.Consequently,it is a better way for choosing the surface equipments and saving the drilling cost.

Key words: air-nitrogen drilling, volumetric flow rate of air, calculation method, air-solid flow situation, cuttings, repeated fragmentation, pressure loss

摘要： 目前对空气-氮气钻井最小气体体积流量的计算方法仅适用于岩屑不受碰撞作用力的理想情况下的携岩要求,而实际所需的体积流量往往高于该方法的计算结果,主要原因可能是未考虑岩屑多次碰撞、重复破碎造成的能量损耗.引入了岩屑重复破碎概念,根据井底和井口岩屑粒径的变化,确定了岩屑重复破碎能耗.并据此对Angel模型进行了修正,得到一种更加准确地确定气体钻井最小气体体积流量的新方法.利用该方法可以更加清晰、准确地描述气体钻井过程中气-固流动状态及沿程压力损失,从而更好地选择设备及节约钻井成本.

关键词: 空气-氮气钻井, 气体体积流量, 计算方法, 气-固流动状态, 岩屑, 重复破碎, 压力损失