Why A Downhole WOB Sensor Is So Important When Drilling With Coiled Tubing
A direct measurement of downhole WOB is vital for accurate control of the drilling process during Coiled Tubing Drilling (CTD). Without it, motor stalls will be more frequent and directional control will be more difficult.
In a vertical well with conventional jointed pipe drilling it is a reasonable assumption that the weight applied to the drill bit is directly related to the hook load at surface. This assumption starts to become less valid as soon as the well becomes deviated or horizontal because of the friction between the pipe and the wellbore. But even then, it is possible to compare upward and downward loads to estimate the friction and therefore determine WOB.