连续管空气钻井排屑能力分析

The Analysis of Cuttings Removal Ability in Air Drilling with Coiled Tubings

使用连续管进行空气钻井，关键是要将破碎的岩石颗粒循环出井筒。岩石在井底破碎后，形成大小不一的岩石颗粒，根据岩石破碎的分形理论，岩石破碎后的形状是自相似的，粒径符合Weibull分布规律。应用BWRS方程计算空气密度，Lemmon方法计算空气黏度，Weibull分布规律拟合粒径分布，用Bagheri非球形颗粒拖曳力关系式计算岩屑空气阻力和井筒中的空气速度、压力分布，以及连续管钻井的井口压力。计算的携岩最小流量与文献值相符，证明了连续管空气钻井的可行性。

In air drilling with coiled tubings,the key was to recycle broken rock particles out of the wellbore.According to the fractal theory of rock fragmentation,the shape of rock was self-similar,and the particle size conformed to the law of Weibull Distribution Law.The BWRS equation was used to calculate the air density and Lemmon method was used to calculate air viscosity and Weibull Distribution Law to fit the particle size distribution.The drag force relation of Bagheri non-spherical particles was used to calculate the air resistance of cuttings and the air velocity and pressure distribution in the wellbore,and the wellhead pressure of coiled tubing drilling.The minimum flow rate calculated with the algorithm presented in this paper is in good agreement with the flow rate in the literature.The feasibility of air drilling with coiled tubing is also proved.