Air drilling,as a member of under balance pressure drilling family,is different from conventional drilling methods. The drilling fluid along double wall drilling tool annular gap reach the hole bottom. There is a positioning device which is also called correcting block between the inner tube and the outer tube of the double wall,and because of the correcting block,the flow field is more complex. The pressure parameter of correcting block between the inner tube and the outer tube of the double wall is researched. Based on the fluid dynamics,pressure model is built through mathematical derivation. Combined with practical engineering examples,programming calculations,the model is solved. The total pressure loss value as a result of correcting blocks is obtained. It provides a strong basis to further explore the entire circulatory system pressure model.%气体反循环钻井技术是欠平衡钻井技术的重要分支,以压缩气体为主的钻井循环流体沿双壁钻具环状间隙到达井底.在双壁钻具的内外管之间有同轴定位装置导正块,导正块的存在使该处流场更加复杂.针对双壁钻具内外管间导正块处压力参数开展研究,基于流体力学通过数学推导,建立导正块处压力模型.结合实际工程算例,编程计算,对模型进行求解,得出由于导正块存在而导致的总压力损失值,为进一步探索整个循环系统压力模型提供了有力依据.
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