Since there is not a single reference or measurement system for calculating the depth in sub-surface environments, two engineers talking about a single drilling might give different answers when asked to give a measurement of depth.
Weakened or damaged ends of a pipe section will be reworked, resulting in reduced length.
This is usually referred to as a wash-out, or words to that effect, and can occur in any part of the drill string or bottom hole assembly.
[2] Tracking and recording of drill pipe at the rig site starts when individual joints are picked up.
Typically three sections of pipe are joined into a stand (of about 27–29 m in length) and stacked in rows of 10, with their base resting on the drill floor.
Pipe stretch and compression will occur from time to time but are not corrected for during normal operations, even though they can introduce fairly significant cumulative errors on driller's depth, particularly in deep wells or in areas of hard rock.
Wireline depth correction for temperature and tension has been around since before the days of computer data acquisition, and is generally seen as reliable.
There are a few in the industry who know how to correct for this real time and some service companies have developed conceptual or prototype tools/processes to account for this elongation effect.
The impact of errors in depth is most critical when integrating data from more than one well, e.g. to build a reservoir model.
This impact, however, is usually apparent only long after the depth measurement process has occurred and is not seen as being an issue during the well construction.