Subsurface barrier valves such as a formation isolation valves (FIVs) isolate the formation from the production bore after the first perforation and the lower completion has been installed. This enables installation of the upper completion and in some cases multiple perforation runs before the well starts producing. During this time, they protect the formation from fluid loss and pressures by acting as a bidirectional fluid barrier. In addition to reduced rig time, a key advantage of FIVs is reduced intervention costs. FIVs can be openend and closed multiple times as required, mechanically with an intervention tool such as a primary shifting tool (PST) (Fig. 1). The conveyance method for PSTs can be on coiled tubing, work string, perforating string, or wireline (using a tractor and stroker) to open and close FIVs. PSTs then must reliably engage and release from shifting profiles in the FIVs to operate the valve and release from the profile after successful valve actuation.
Hence design of the PST is critical for relaible FIV operation. In the event of an emergency where the shifting profile in the tool is unable to release from the engaging profile in the FIV, it is critical to have an emergency release feature inherent in the PST that can enable release of the tool yet not damage the FIV. A novel methodology was developed to design PSTs to enable emergency release if required, through controlled plastic deformation at loads below work string shear limitation. This methodology also avoids fracturing of PST components as free-hanging pieces could be caught in the wellbore while pulling out the tool from the well after emergency release.
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