Well Control Near Miss: The Missing Barrier Story. CASE STUDY

This case study highlights a barrier verification failure during X-mas tree replacement in a high-pressure onshore(Onshore Swamp Wellhead) high pressure gas well (THP 8,300 psi). Although the SCSSV was closed and BPV installed, the operation proceeded without a tubing blanking plug, which is a critical primary mechanical barrier. As a result, pressure migrated into the wellhead cavity after tree removal, exposing a serious well control risk. The key lesson is that SCSSV and BPV alone do not constitute two verified barriers, and proper barrier philosophy requires a pressure-tested tubing plug as the primary barrier, supported by secondary surface barriers, in line with IWCF standards. 

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

In 2015, at an onshore high-pressure oil producing well operated by Occidental 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 and consider alternative methods to restore subsurface safety before proceeding with the valve replacement.