TR-SCSSV Failure During Master Valve Replacement & WR-SCSSV Bypass Strategy 

In 2015, at an onshore high-pressure oil producing well operated by OXY LLC Oman, the wellhead maintenance team planned to replace a 4" 1/16" 10K Master Valve on the X-Mas Tree as part of routine maintenance. As per standard well integrity procedure, they attempted to shut in the well by closing the TRSCSSV (Tubing Retrievable Surface Controlled Subsurface Safety Valve) to establish a downhole barrier. However, the operation could not be completed because the TRSCSSV failed mechanically in the open position, preventing isolation of the wellbore. This unexpected failure created a critical barrier deficiency, forcing the team to reassess the intervention plan. 

To avoid a costly workover involving tubing retrieval, a common industry practice was considered: deploying a WRSCSSV (Wireline Retrievable SCSSV) inside the existing tubing. In such situations, the WRSCSSV can be run and set within the completion profile to effectively bypass the non-functional TRSCSSV and restore subsurface safety. This approach allows re-establishment of a downhole barrier without pulling the tubing, as certain WRSCSSVs are specifically designed for this purpose. However, this method requires strict verification of valve integrity and proper setting to ensure effective pressure isolation before proceeding with wellhead maintenance activities.