Retrievable packers or plugs typically have a multi-element sealing system between upper and lower slips. When set mechanically with a known setting tool relative movement is created when the outer assembly of slips and the sealing system are pushed on while the setting tool pulls on the mandrel at the same time. Generally, the result is that the upper slips set and then the seal is axially compressed followed by the extension of the lower slips. The outer assembly features a lock ring that can hold the outer assembly is the compressed and set position. The release occurs when the lock ring that fixates the outer assembly with respect to the mandrel is defeated. Defeating the locking mechanism can occur with a mandrel pull that shears a retainer or with cutting the mandrel to allow the outer assembly to relax or by running a tool into the mandrel to forcibly defeat a shear device that holds the set of the outer assembly.
One potential problem with releasing the outer assembly components at the same time is the potential for binding the slips with the released rubber pressure in the sealing element assembly causing one of the slip assemblies to bind. One way to alleviate this problem is to provide a mechanism that is designed to relieve rubber pressure on the seal assembly before releasing the slips. While that is the intention of the device shown in U.S. Pat. No. 8,291,989 FIG. 2B using engaged threads 75 and 76 and selectively raising a mandrel slot 78 into alignment with threads 75 to let fingers 73 flex toward the mandrel with the hope that a separation will occur, the reality is that the force holding threads 75 and 76 in the set position can be so strong such that aligning the slot 78 will still not result in a release of the pressure in the seal assembly 42. What is needed and provided by the present invention is a rubber pressure release system where mandrel movement takes with it initially a part of the outer assembly that underpins a lock for the set of the sealing system and provides a large space outside the mandrel for the force of the retained rubber pressure to forcibly push the locking member to retract in a radial direction by including a radial component of the release force toward the mandrel topromote lock retraction. The lock has a wedge pulled out from under it to allow it to flex toward the mandrel outer surface and to be pushed by the force of the relaxing seal assembly. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while understanding that the full scope of the invention is to be determined from the appended claims.
USPTO Backgrounds
USPTO Backgrounds