Freeze and Hot Tap Case History #20

Objective: Hot tap 2 7/8” gate valve to gain access to tubing in order to freeze and remove damaged gate valve.

Well Information: 32 Mpa water injections well

Procedure: Confirm damaged valve is holding, remove all wellhead equipment above faulty valve, use appropriate crossover over flange and rig in hot tap drill. Pressure test equipment to 35 Mpa as restricted by wellhead rating. Bleed off drill to 30 Mpa drill ¾ inch hole completely through gate making sure to go through both halves-pressure equalizes at 32 Mpa when completed. Retract drill close working valve, bleed off drill assembly and rig out drill. Build cribbing, inject gel into surface casing and production casing to transfer freeze. Rig in gel injection equipment to tubing and inject gel into tubing, fill cribbing with dry ice and maintain through the night. Maintain and monitor freeze operation overnight. After sufficient freeze time, pressure test freeze plug, tested OK, bleed off pressure and replace damaged valve. Apply equal pressure above freeze plug and hand over well for thawing.

Time on location: 28 hours