High Value Learning - Gas release from newly completed well

When a newly completed well was restarted after a 7-day shut down the O-ring in the tree cap failed, resulting in a gas release and a full platform shut down. The well’s tree cap had been successfully tested on installation and the well had produced for a few weeks prior to incident. The investigation found that the incorrect assembly of the tree cap resulted in damage to the O ring and led to its failing to seal as intended. Up to the point of the gas release the incorrect assembly had not been correctly recognised due to the successful pressure test.

When the tree cap is correctly assembled the cap’s plug is fully engaged, the collar is screwed on with only 1-2 threads left exposed, and the O-ring is correctly placed in the tree cap’s seal-bore.