In order to solve the contradiction between borehole diameter and the depth of borehole of high pressure jet drilling in laterally radial horizontal wells, a new type of jet bit design was proposed which integrated both advantages of round jet and swirling jet. The design method was given,and the jet flow structure and its rock breaking characteristics were analyzed in terms of high speed photograph and rock drilling experiments. The results show that the jet formed by the new designed jet bit has both features of round straight jet and swirling jet, with larger hole diameter than a conical round jet bit and deeper depth than a swirling jet bit. Furthermore, many structural parameters of the jet bit affect the rock breaking results. By optimizing jet bit structure configure, hole drilling characteristics could be adjusted. The study can provide a reference for jet bit design in radial horizontal drilling. It is further needed to perform flow field, and rock breaking mechanism analysis to improve the jet utilization efficiency.%为解决高压水射流径向水平钻孔时孔径和孔深相互矛盾的问题,设计了一种兼具直射流和旋转射流特点的直旋混合射流钻头.给出了射流钻头设计方法,通过破岩实验,分析了直旋混合射流钻头结构对其破岩特性的影响.结果表明,直旋混合射流结合了直射流和旋转射流优点,比锥形喷嘴圆直射流扩孔能力强,比纯旋转射流钻孔深度大.影响直旋混合射流钻头破岩效果的结构参数较多,存在最优破岩效果结构参数,可通过不同参数组合调节破岩钻孔特征.需要进一步开展流场结构与破岩机理分析,为径向水平钻孔中射流钻头的设计提供更好的指导.
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