The feasibility of gas kick early detection outside the riser was analyzed based on gas-liquid multiphase flow theory. Then an experimental platform for gas kick early detection based on Doppler ultrasonic wave was established and the propagation experiments in two-phase flow of gas-water (sucrose solutions) were conducted. The time and frequency domains of the Doppler ultrasonic wave signals during the experiments were analyzed. The results show that: (1) No matter the pump was on or off, the detected average Doppler ultrasonic signal voltage increased first and then decreased with the increase of the gas void fraction, and had a quadratic function relation with gas void fraction, so the average voltage change of the monitored signals can be used to deduce the approximate gas void fraction. The Doppler ultrasonic wave signal voltage was significantly reduced in magnitude and variation in the solution with higher viscosity, and the viscosity has stronger impact on the magnitude of signal than density. (2) When the pump was stopped, the Doppler shift increased with the increase of gas void fraction, and the two showed a nearly linear relation, so the detected amount of Doppler shift can reflect the variation of gas void fraction quantitatively. When the pump was on, the sound energy produced by frequency converter had a more significant impact on amplitude spectrum than gas void fraction, so it is impossible to determine whether gas kick occurs by frequency domain signal analysis. (3) This method is a non-contact measurement, with no contact with the drilling fluid and no disruption to the drilling operation. It can quantitatively characterize the gas void fraction according to the change of Doppler ultrasonic signal, enabling earlier detection of gas kick.

基于气液多相流理论，分析了立管外气体突跳早期检测的可行性。然后建立了一个基于多普勒超声的气体涌动早期检测实验平台，并进行了气水（蔗糖溶液）两相流传播实验。分析了实验过程中多普勒超声信号的时域和频域。结果表明：（1）无论泵开启还是关闭，检测到的平均多普勒超声信号电压均随气体空隙率的增加先上升后减小，并且与气体空隙率呈二次函数关系，因此监视信号的平均电压变化可用于推导近似的气体空隙率。具有较高粘度的溶液中多普勒超声波信号电压的幅度和变化明显降低，并且粘度对信号幅度的影响大于密度。（2）当泵停止工作时，多普勒频移随气体空隙率的增加而增加，二者呈近似线性关系，因此检测到的多普勒频移量可以定量地反映出气体空隙率的变化。当泵启动时，变频器产生的声能对振幅谱的影响要比气体空隙分数更大，因此无法通过频域信号分析来确定是否发生气体反冲。（3）此方法为非接触式测量，不与钻井液接触，也不会干扰钻井作业。