| 摘要 |
An apparatus for measuring the internal diameter of a wellbore for a wireline formation sample taking instrument, including an hydraulically actuated probe and back up shoe for selective engagement with the wall of a wellbore, an hydraulic pump and selectively controllable valves for selectively controlling extension and retraction of the probe and back up shoe, and an hydraulic fluid reservoir to supply hydraulic fluid to the pump for extending and retracting the probe and back up shoe. The reservoir includes a pressure compensator for balancing the pressure in the reservoir to an hydrostatic pressure in the wellbore. A position sensor is coupled to the compensator to determine its position. The position of the compensator corresponding to the fluid volume in the reservoir, the extension distance of the probe and back up shoe, and the internal diameter of the wellbore at the location of the probe and back up shoe.
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