摘要：Gas kick detection is an essential part of safe well control process in deep water drilling. The conventional gas kick detection methods are based on the drilling mud flow velocity measured near the well mouth which often results in a high probability of delay. For deep water drilling, the gas kick detection method based on non-intrusive detection at mud line is one of the most commonly used methods with low cost and strong timeliness. In this article, the reflection model of continuous Doppler ultrasonic wave in multiphase fluid was analyzed and an improved gas kick detection method at mud line was proposed. The proposed method gives a comprehensive judgment on gas kick state based on continuous Doppler shift frequency (multiphase flow velocity), amplitude, and spectral shape. Experimental results on water and 1 . 1 g/cm3 oil-based drilling mud demonstrated that the proposed method can detect early gas kick with over 3% void fraction effectively and measure multiphase flow velocity accurately under the steady flow state, showing a relative error smaller than 10%.
关键词：Ultrasound; drilling; multiphase flow; velocity; frequency
