The presented acoustic methods and devices are intended for early detection and determining parameters of the gaseous packet (gas kick) rising in the annulus of the well during a gas blowout. The action of the tool is based on the comparison of pressure pulses generated in the mud by the mud pump using dynamic pressure sensors located in the annulus above the blowout preventer and in the high-pressure line. When the output signal decreases to the pre-specified level corresponding to the danger of blowout, the drilling is stopped and a pressure pulse is generated in the annulus; the location, velocity, size and arrival time of the gaseous packet is determined using the arrival time of the reflected signals. The information obtained this way is used for making a decision whether to resume drilling or to take measures to suppress gas entry into the borehole. The tool also makes it possible to detect free-phase highly dissolved gas entering the annulus at the saturation pressure; such gas is especially dangerous when formations saturated with hydrogen sulfide and carbon dioxide are penetrated. The tool is recommended to be incorporated in well-logging units, MWD systems and also as a stand-alone tool among the other instruments used at the well site. The tool makes it possible not only to ensure safety during drilling, but also to facilitate the introduction of the state-of-the-art drilling technologies based on reduction of the bottom-hole differential pressure.
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