Abstract: An apparatus for accurately determining the relative positioning of a well logging sonde or downhole tool in a bore hole is disclosed. The apparatus comprises an anchor for engaging the wall of the bore hole in fixed position and adapted to be carried into the bore hole on the downhole tool suspended on a logging wireline to a selected level, and a release mechanism controllable from the surface for releasing the anchor from the tool so that the tool can move independently of the anchor element. A sensing cable interconnects the anchor and the tool and is payed out from a reel carried by the tool as the tool separates from the anchor. Means actuated by the sensing cable are provided for transmitting electrical pulses up the wireline to the surface to indicate the relative distance between the anchor and tool.

Abstract: An hydraulic drive apparatus for use in downhole tools is described. The apparatus provides rotational and translational movement to a cutting tool element disposed in a downhole tool or sonde automatically adjusting advancing motion of the cutting tool to the rate of rotational movement or cutting. The apparatus is controllable from the surface through a wireline and is capable of operating in various modes to facilitate unjamming.

Abstract: A side wall clamp is disclosed for use in conjunction with downhole tools, the clamp having a fail-safe mechanism which permits unclamping of the tool from the bore hole wall even if the clamp actuator means is inoperative, by exerting upward pull on the wire line or drill string to which the tool is attached.