Rapid and Reliable Gas Influx Detection

Abstract

Abstract A new and reliable method for early gas influx detection is described. It is based on the increase in sonic propagation time which is observed when gas is present in the annulus. Unlike detection methods based on differential flow or pit gains, the instrumentation required for this technique is simple, reliable and cost effective. Pressure transducers which are mounted on the standpipe and on the annulus a few feet below the flowline monitor the sonic pressure waves generated by the mud pumps. The output from the pressure transducers is used to measure the rate of change of sonic propagation time around the circulating system. This quantity is strongly influenced by the presence of gas. In addition to the theory behind the technique, the paper describes controlled tests and field examples from around the world.