Abstract: The self-excited pulse jet can produce large instantaneous impact energy, which can further improve the operation efficiency of rock-breaking, plugging removal and reservoir stimulation, as well as the single well production of oil and gas wells. A new self-excited pulsed jet device is developed using the wall attachment effect of fluid based on the theory of forced steering for feedback channel. The structural parameters of the device are simulated using the finite element numerical simulation method, so as to analyze the response characteristics of different structural parameters to the device performance. The physical model experiment of impact performance evaluation is performed to test the impact load of pulsed jet produced by the device under different discharge rates; by conducting the physical model experiment of large-size granite surface erosion, the characteristics of rock-breaking by pulsed jet can be obtained according to the internal and surface failure patterns of granite samples. The device is used to carry out the reservoir stimulation in Shixi block of Xinjiang oilfield, and a comparison is performed on the stimulation effect through field test. The results show that the inlet-outlet ratio is the most sensitive to the pressure amplitude of the inner cavity of spray gun, and the cross-sectional area ratio of the feedback channel is the most sensitive to the frequency of the device. With the increase of the displacement, the extreme value and amplitude of the impact load of pulsed jet at the outlet of the device takes on an approximately linear growth, and the impact load shows obvious pulse fluctuation effect, which fully demonstrates that the wall-attached oscillating cavity has good fluctuation performance and can produce regular pulsed jet. The pressure in the spray gun cavity of the wall-attached self-excited pulsed jet device will increase with an increase in the displacement and has good pulse fluctuation characteristics; the pressure fluctuation amplitude in the spray gun cavity takes on approximately linear growth. The vibration of granite sample caused by the self-excited pulsed jet is more intense than that caused by the continuous jet, and the acceleration variation amplitude of the self-excited pulsed jet is 3.4 times of that of the conventional jet. The pulsed jet produced by the new device has stronger rock surface crushing ability and rock internal radial damage ability. Compared with fracturing without using the device, the effect of reservoir stimulation has been significantly improved. The research results can provide not only new ideas for the research and development of new self-excited pulsed jet device, but also technical support for the stimulation of fractured reservoirs.

Key words: wall-attachment effect, self-excited pulsed jet, jet impingement, erosion test, reservoir stimulation

摘要： 自激脉冲射流能够产生较大的瞬时冲击能量，可进一步提升破岩、解堵和储层改造等作业的效率，提高油气井单井产量。利用流体附壁效应，结合反馈通道强制转向理论，研制了一种新型自激脉冲射流装置。采用有限元数值模拟方法对装置的结构参数进行模拟，分析了不同结构参数对装置性能的响应特性。开展了冲击性能物理模拟评价实验，对装置在不同排量下产生的脉冲射流冲击载荷进行了测试，并进行了大尺寸花岗岩表面冲蚀物理模拟实验，根据花岗岩试样内部和表面的破坏形态得出了脉冲射流破岩特性。使用该装置在新疆油田石西区块实施储层改造，通过现场试验对比增产效果。研究结果表明：进出口比对喷枪内腔压力幅值敏感性最强，反馈通道截面积比对装置频率敏感性最强；随着排量的增加，装置出口脉冲射流冲击载荷极值、幅值均近线性增长，且冲击载荷有明显的脉冲波动效应，充分说明了附壁摆动腔有着良好的波动性能，可产生规律的脉冲射流；随着排量增加，自激附壁脉冲射流装置的喷枪内腔压力呈相应增长趋势，且具有良好的脉冲波动特性，喷枪内腔压力波动幅值随排量增加呈近线性增长；自激脉冲射流引发的花岗岩试样振动较连续射流更为强烈，加速度变化幅值为常规射流的3.4倍；新装置产生的脉冲射流具有更强的岩石表面破碎能力和岩石内部径向破坏能力；与不使用该装置的压裂施工相比，储层增产改造效果显著提高。研究结果不仅可为新型自激脉冲射流装置的研发提供新思路，同时可为压裂储层增产改造提供技术支持。

关键词: 附壁效应, 自激脉冲射流, 射流冲击, 冲蚀试验, 储层改造