The Returned Cuttings Monitoring Method for Gas Drilling Based on Audio Signals

To find the best way to monitor the process of well drilling (e.g.wellbore collapse and bottom hole rock burst),the method of returned cuttings monitoring in gas drilling based on audio signals was studied.In this method,an audio acquisition system is used to collect the audio signals generated from the migration of the returned cuttings in the clearance pipe.The starting and ending points of sound segments are determined and correlatedto the short-time energy by which their characteristic parameters can be calculated.After a sound characteristic parameter database is created,interference sound is eliminated through a neural network algorithm.Then,the acoustic characteristics of cuttings with different size in the clearance pipe are analyzed.The cuttings sizes can be differentiated by using the dynamic time warping after which the flow rate of cuttings then is calculated.Accordingly,the carrying status of the cuttings and downhole working condition of gas drilling can be primarily determined.This method was tested on site in Well Shuangtan 7 and results demonstrated that the classification success rate of interference sounds reached 96.8% and the identification rate of cuttings size reached 85%.Results also indicate that this method of monitoring the amount of returned cuttings in gas drilling based on the audio signal can also be used to monitor the variation trend of cuttings flow rate and effectively determine downhole working conditions and thus reduce risk in drilling gas wells.