US Patent 9109433 Early kick detection in an oil and gas well

An apparatus, method and computer-readable medium for detecting a gas influx event in a borehole fluid during a drilling operation is disclosed. A measurement of an acoustic velocity of the borehole fluid is obtained at an acoustic sensor disposed in a borehole. A measurement of temperature of the borehole fluid is obtained at a temperature sensor disposed in the borehole. A process compares the measurement of the acoustic velocity of the borehole fluid to the measurement of the temperature of the borehole fluid to detect the gas influx event.