Methods and apparatus for determining the stuck point of a conduit in a borehole

摘要

In the representative embodiment of the new and improved apparatus disclosed herein, a so-called "stuck-point indicator" or "freepoint-indicator" tool includes a deformation-responsive sensor tandemly supported between upper and lower hydraulically-operated tool anchors cooperatively arranged to be sequentially engaged with longitudinally-spaced wall portions of a string of well pipe believed to be stuck in a well bore. In the preferred embodiment of the tool, each tool anchor respectively includes a piston actuator which, upon application of a predetermined pressure as developed by a hydraulic-control system on the tool, operates to retract a set of movable anchoring elements and, upon a reduction in that hydraulic pressure, is biased by a spring to extend the anchoring elements. To assure sequential operation of the upper and lower anchors, the hydraulic-control system of the tool further includes a flow restrictor for cooperatively delaying the reduction of the hydraulic pressure acting to retain the lower anchoring elements in their retracted positions until such time that the upper elements are moved into anchoring engagement with the pipe wall.