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Goal Convey TVD uncertainty with reference to measured depth

Description Bit depth is calculated by the integration of the vertical motion of the bit and drillstring. The vertical motion of the bit is a function of top drive vertical motion, block height vertical motion, change in surface hookload, and change in downhole WOB. The measured vertical motion of the top drive is affected by rig heave; the measured vertical motion of the block is affected by calibration and measurement accuracy and the top drive may be slightly bent, leading to uncertainty in block height. The integration is reset (“truthed”) on “pipe-down” using the pipe tally, which leads to jumps in measured bit depth. The integration is started with recognition of “bit on-bottom” which is remotely evaluated on surface, and is uncertain.