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

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