SC-CO₂射流钻完井技术能保证煤层气井稳定性、提高钻井速度和破岩效率，具有广泛的应用前景。但较高的破煤能耗和复杂的系统限制了其工程推广，自激振荡脉冲SC-CO₂射流冲击频率和煤岩体的固有频率相同或满足相位关系，能充分发挥谐振效应，达到更好的破煤效果。喷嘴结构是影响射流冲击频率的关键，现有的自振脉冲水射流频率调制方法并不适用于SC-CO₂射流。为实现对SC-CO₂射流冲击频率的调制，采用大涡模拟研究不同喷嘴结构对自激振荡脉冲SC-CO₂射流冲击频率的影响规律，通过权重分析得到不同喷嘴结构参数对射流冲击频率的影响程度。采用射流冲击频率测定实验及破煤实验验证喷嘴结构对射流冲击频率的影响规律以及射流冲击频率调制方法的可靠性。结果表明：振荡腔直径、振荡腔长度、碰撞壁角度是影响射流冲击频率的关键因素，可通过调节振荡腔结构实现对射流冲击频率的大幅调制，从而达到谐振效应。调节振荡腔结构使射流冲击频率与煤的固有频率形成谐振时破煤效果显著提升，且谐振倍数越小，射流破煤效果越好，能够有效提高破煤效率。当煤的固有频率是25 Hz时，设置上游和下游喷嘴出口直径为2.5、3 mm，调节振荡腔直径、长度、角度分别为10 mm、3 mm、120°，射流冲击频率达到25 051.83 Hz，是煤体固有频率的1 002.0倍，与煤的固有频率形成谐振效应，有效提高了破煤效率。

The SC-CO₂ jet drilling and completion technology can ensure the stability of coalbed methane wells, improve drilling speed and rock breaking efficiency, and has a wide application prospect. However, the high energy consumption and complex system of coal breaking limit its engineering application. The impact frequency of self-excited oscillation pulse SC-CO₂ jet is the same as the natural frequency of coal and rock mass or satisfies the phase relationship, which can give full play to the resonance effect and achieve a better coal breaking effect. The nozzle structure is the key to affect the jet impact frequency. The existing frequency modulation method of self-resonating pulsed water jet is not suitable for the SC-CO₂ jet. In order to realize the modulation of the impact frequency of the SC-CO₂ jet, a large eddy simulation was used to study the influence law of different nozzle structures on the impact frequency of self-excited oscillation pulse SC-CO₂ jet, and the influence degree of different nozzle structure parameters on jet impact frequency was obtained by weight analysis. The influence rule of nozzle structure on the jet impact frequency and the reliability of jet impact frequency modulation method are verified by jet impact frequency measurement experiment and coal breaking experiment. The results show that the diameter and length of the oscillating cavity, and the angle of the collision wall are the key factors affecting the jet impact frequency. The jet impact frequency can be substantially modulated by adjusting the structure of the oscillating cavity, so as to achieve the resonance effect. By adjusting the oscillating cavity structure, the jet impact frequency forms resonance with the inherent frequency of coal, then the coal breaking effect is significantly improved, and the smaller the resonance multiplier, the better the coal breaking effect of the jet, which can effectively improve the coal breaking efficiency. When the natural frequency of coal is 25 Hz, the outlet diameter of the upstream and downstream nozzle is set as 2.5 mm and 3 mm, and the diameter, length and angle of the oscillating chamber are adjusted to 10 mm, 3 mm and 120° respectively. The jet impact frequency reaches 25051.83 Hz, which is 1002.0 times of the natural frequency of coal and forms a resonance effect with the natural frequency of coal, effectively improves the coal breaking efficiency.