Abstract: A lock open mechanism for downhole safety valve of the type having a valve head movable downwardly from a closed to an open position relative to the bore of a well conduit. The housing of the safety valve is provided with a first downwardly facing locking shoulder above the valve head. The upper portion of the safety valve housing is provided with a no-go shoulder and above that a second downwardly facing latching shoulder. A mandrel has a tubular locking body shearably secured to its lower end which locking body is abutable with the valve head. The valve head is displaced downwardly by incremental jar produced downward movements of the mandrel until a locking collet carried on the locking body engages the first downwardly facing locking shoulder.

Abstract: A mechanism for accurately positioning a well tool in axially concentric relationship to a well conduit comprises a housing having a plurality of stabilizer linkages mounted thereon with one end of each linkage being pivotally secured to the housing and the other end free to move in an axial direction. A compression spring engages a force transmitting connection to the other ends of the stabilizer linkages to bias same to a radially expanded position engaging the conduit wall. The connection between the compression spring and the stabilizer linkage includes two telescopically related sleeve elements which are secured together by a shear screw. In the event that the stabilizer linkage becomes stuck in the well, upward jarring movements of the housing will shear the shear screw and permit the stabilizer linkages to collapse radially inwardly and thus permit removal from the well.