Method of warning of pipe sticking during drilling operations

摘要

A method of warning of the onset of pipe sticking in a rotary drilling operation using a drill string comprising: (a) monitoring the pressure of a drilling fluid being pumped through the drill string during drilling over predetermined periods of time to obtain series of pressure measurements; (b) monitoring the torque required to rotate the drill string during said periods to obtain series of torque measurements; (c) obtaining the skew (third moment) of each series of pressure measurements according to the relationship ##EQU1## wherein N is the number of pressure measurements xi in the series, xmean is the average value of the measurements in the series, and is the standard deviation of the measurements in the series; (d) obtaining the normalized standard deviation n of the torque measurements in each corresponding series of torque measurements according to the relationship n=(. sigma. /ymean) wherein is the standard deviation of the measurements in the series and ymean is the average value of the measurements in the series; and (e) comparing skew and n for the series so as to identify corresponding changes in both and raising an alarm when the magnitude of said changes pass predetermined alarm values.