Early monitoring of gas influx of drilling fluid in risers during deepwater drilling using Lamb waves

Abstract

Early warning of gas in deepwater drilling risers is critical to the timely detection of seepage and consequently blowout reduction. We numerically simulate the acoustic field in water-based drilling fluids from a sound source outside the riser by using a 3D cylindrical coordinates finite-difference method. By changing the gas content of the drilling fluid, the relation between the amplitude and attenuation of the A0- and the S0-mode Lamb waves in the riser, the fluid properties in the pipe, and the position of the top and bottom interfaces of the slug flow were assessed. The simulation results suggests that the amplitude and attenuation of the Lamb waves reflect the gas content in the riser and are sensitive to low gas content. Moreover, the Lamb waves amplitude and attenuation reflect the position of the top and bottom interface of the slug flow.