Early gas-kick detection while drilling boreholes using ultrasonic LWD transducers

Detecting the presence of small amounts of gas in the drilling fluid is crucial for safe drilling operations of oil and gas boreholes. Current methods for evaluating the gas content rely on analysis of returned drilling fluid at the surface, causing significant information delay. This paper describes a method for detecting free gas in drilling fluids from the ultrasonic signal using conventional LWD tools. The use of higher order statistics to make the method noise robust is also described and demonstrated using simulations and experiments. Further a concept for applying ultrasonic methods for detecting dissolved gas in deep boreholes is also discussed.