Freeze and Hot Tap Case History #19
Well Information:Sweet Gas Well Drilled in 1993. CSG is full of inhibited fluid with packer set 2334 meters from surface. Estimated SITP = 4000 KPA
Procedure:Perform JHA and Safety meeting with all personnel. Take measurements and ensure hot tap equipment is suitable for task. (Enough stroke to get through valve and can still retract back enough to get behind safety valve. Confirm valve is holding pressure. Remove all wellhead equipment above faulty valve. Install x/o flange onto valve, 2 9/16 x 2”, c/w 2 9/16”x 2” threaded nipple. Install 2” x 5K ball valve. Fill valve up with fluid. Install hot tap drill. Rig in pressure pump and pressure test all connections and drill to 21 MPA. Estimated SITP is 4 MPA. Bleed pressure back, maintaining 10 MPA. Start drilling through valve monitoring pressure above valve at all times. Pressure dropped to approximately 4.3MPA.Continue drilling until ¾” hole has been reamed clean, and the bit can pass through un hindered without rotating. Retract bit into drill housing and close 2” ball valve. Bleed off drill and remove. Hook up flow back line and flow tubing to ensure good access. Remove flow back line. Build Ice cribbing around surface casing and inject freeze gel into surface and production casings as well as tubing. Add dry ice and wait allotted time for gel to freeze. Pressure test freeze plug on the tubing side and when verified plug is holding, remove faulty master valve and install new valve and the rest of the well head components. Pressure test well head against freeze plug. Remove ice from well and let thaw.
Time on location: 24 hours