| 摘要 |
A method for determining a depth of a wellbore is disclosed. The method includes determining change in a suspended weight of a drill string from a first time to a second time. A change in axial position of the upper portion of the drill string between the first time and the second time is determined. An expected amount of drill string compression related to the change in suspended weight is corrected for movement of a lower portion of the drill string between the first time and the second time. A position of the lower portion of the drill string is calculated from the change in axial position and the corrected amount of drill string compression. In one embodiment, the correcting includes estimating drill bit movement by determining an axial motion of the drill string at the earth's surface between two times having a same suspended weight of the drill string.
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