Drilling rig operators may trip pipe by pulling the drill string out of the well bore and then running it back in due to the wearing of drill-bits, fishing for items dropped in the well bore, replacing a damaged drill pipe or well logging. The two most common of these instances are replacing a worn out drill bit or replacing a damaged drill pipe.
Like most standard drill bits that sustain heavy usage, oil drill bits tend to wear out and may be unable to drill at an acceptable rate or make a full-gauge hole. Crew members need trip the pipe and replace the drill bit or other piece of the drill string. In a similar event, if the drilling pipe itself is damaged, crew members should trip pipe to replace or repair the damaged pipe.
If a crew member drops a tool or any other piece of equipment in the well bore, the pipe also needs to be tripped to retrieve the lost equipment that could potentially damage the drill. Crew members may also trip pipe to log the hole at various depths while drilling. The drill string is removed from the well bore to allow the logging crew to survey the well and note the geologic formations penetrated by a borehole.