| 摘要 |
A top sub for connection to a production well tubing string is movable between an engaged position and a disengaged position relative to a mandrel. The engaged position allows an anchor to be set in a well casing by rotating the tubing string. Tension can be applied to the tubing string to move the top sub to the disengaged position, allowing the tubing string to be rotated without rotating the mandrel. The anchor can be moved to a different position, without pulling the tubing string to the surface, by removing tension from the tubing string to move the top sub from the disengaged position to the engaged position, rotating the tubing string in an opposite direction to release the anchor, and resetting the anchor by again rotating the tubing string. Embodiments in which a sealed internal volume of the swivel remains constant are also disclosed.
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