超临界CO2直旋混合射流破岩特性的实验研究

超临界二氧化碳(CO₂)射流破岩既能降低岩石门限压力又能有效保护储层，直旋混合射流兼具直射流和旋转射流特点可提高破岩效率，基于此提出了超临界CO₂直旋混合射流的破岩方法。为了揭示超临界CO₂直旋混合射流破岩特性，设计加工出叶轮式直旋混合射流喷嘴，通过岩石定点冲击破碎实验对比了该射流与常规水射流的破岩效果，并研究了叶轮长度、叶轮中心孔直径、混合腔长度、喷射距离、射流压力等重要参数对超临界CO₂直旋混合射流破岩效果的影响。结果表明:相同实验条件下，该射流方法的平均破岩能力比常规水射流提高了42.9%；超临界CO₂直旋混合射流破岩易出现较大体积岩屑崩落现象；随着叶轮长度、混合腔长度、喷射距离的增大破岩效果均先增强后减弱，实验条件下上述参数存在最优范围值；叶轮中心孔直径的增大会导致岩石破碎孔深度增加、直径减小；随着射流压力的升高，超临界CO₂直旋混合射流破岩效果有着较为明显的提升。研究结果可为超临界CO₂直旋混合射流破岩方法的进一步研究提供实验依据。

Experimental study on rock-erosion features with combined swirling and round jet of supercritical carbon dioxide

Integrating supercritical carbon dioxide jet, known for its capability of reducing the threshold pressure of the rock and protecting the reservoir, with the combined swirling and round jet, known for its capability of enhancing the efficiency of rock erosion owing to its features, we would have a new highly efficient jet technology that may be called as combined swirling and round jet with supercritical carbon dioxide. In order to investigate the law governing its rock erosion, we carried out an experiment aiming at comparing the rock erosion capacity of this method with that of the conventional water jet and studying the effects produced by the of five important factors (the impeller length, the central hole diameter of the impeller, the length of the mixing chamber, the standoff, and the jet pressure) on rock erosion by using the nozzle which has been designed and fabricated especially for this purpose. The result shows that the rock erosion efficiency of this jet method is 42.9% higher than that of the conventional water round jet; the swirling and round jet with supercritical carbon dioxide may lead to the occurrence of rock mass breakaway; with the increase of the impeller length, the length of the mixing chamber and the standoff, the erosion performance tends to slacken after an initial good efficiency; the increase of the central hore diameter of the impeller can result in both a greater erosion depth and a reduced erosion diameter; and erosion efficiency can be enhanced by increasing the jet pressure. The results from the present study can be serve as an experimental basis for further research.