自进式岩屑磨料直旋混合射流钻头流场数值模拟

Numerical Simulation of Flow Field for Straight & Swirling Jet Bit of Self-supplying Cutting Abrasive

为了解决超短半径径向水平井水力钻头破岩效率低的问题,将膛线引入水力学中,利用膛线的螺旋切割产生直旋混合射流,同时根据磨料射流高效破碎靶件的特点,利用岩屑产生磨料射流的优势,设计了A、B 2种结构的自进式岩屑磨料直旋混合射流钻头,并利用数值模拟方法分析了钻头的流场分布规律。分析结果表明,钻头的螺旋切槽能够形成旋转射流,磨料漏斗均能吸入岩屑形成磨料射流;钻头的扩展段和井底两侧均能产生涡漩,该涡漩可以促进岩屑翻滚,进而提高清岩效果,轴向速度分布规律与常规喷嘴圆形射流规律相似;自进式岩屑磨料直旋混合射流钻头设计时应优选A型。

To solve the low ROP of hydraulic bit in radial horizontal well with ultra-short radius, rifling has been introduced into hydraulics. By using spiral cutting of tiffing, straight ＆ swirling jet flow can be genera- ted. With consideration to high efficiency crushing of targets by jet flow of abrasives, straight ＆ swirling jet bit of self-supplying abrasives generated by cuttings has been designed with two optional structures： A and B. In addition, distribution of flow field of the jet bit has been determined through numerical simulation. Analyses results show that spiral groove of the bit may generate spiral jet flow, whereas abrasive funnel may absorb cuttings to generate jet flow of abrasives; swirling flows can be generated in the expansion interval and on both sides of the bottom hole. These swirling flows can facilitate rolling of cuttings to enhance sweeping efficiency. Distribution of axial veloc- ities is similar with the pattern of circular jet flows generated by conventional nozzle. Test results show that Structure A shall be used preferably during design of straight ＆ swirling jet bit of self-supplying cutting abrasive.