Freeze and Hot Tap Case History #32
Objective: Inject freeze gel and freeze the three well head valves enabling the safe removal of all equipment above the well head valves and install a 4 1/16th 10K bop dressed with slip rams and pipe rams to fit the 1 ½” weight bar which is across the well head. Then add sufficient riser spool and another gate valve on top to regain proper well control and give the ability to be able to rig in proper equipment to fish out the stuck tool string.
Well Information: 45MPA gas well. Wire line tools stuck across wellhead valves with 2 sets of wire line bops on top of well head with 80’ of lubricator on top and 2 X 2 1/16th gate valves on top of lubricator closed maintaining well control.
Procedure: Upon arrival to the well site a pre job inspection occurred. The ice cribbing was assembled. The equipment above where the freeze plug was to be was wrapped with steam and heat trace as well as insulation to prevent the equipment to be removed from freezing. Utilizing 10K 3 1/16” 10’sections of lubricator filled with freeze gel and a wiper plug we used a 10K pump truck to push the wiper plug in turn pushing the freeze gel into the well bore. Once sufficient freeze gel was injected Dry Ice was added to the ice cribbing and a pressure gauge installed above where the freeze was actually going occur. The gel was then allowed to freeze for approximately 36hrs while monitoring pressure above the plug and maintaining a solid ice pack. After allowing sufficient time for the freeze to occur, a positive pressure test to 65mPa was held for 1 hour. Once the positive pressure test was confirmed a success a negative pressure test was performed at 0 mPa and held for 1 hour and was completed successfully. Another safety meeting was held involving all parties on site and ensured that all required equipment was available. Ensure good line of communication between the well control crew and the 2 picker operators involved. One picker to remove the lubricator from the well head and the other with the new set of 4 1/16th bops ready to position on to the well head. The lubricator was then unbolted from the top of the well head and swung clear of the area. The tool string was then disassembled to the lowest point above the well head, and a new fish neck installed, for future fishing operations. The 4 1/16th bop was then positioned onto the well head and tightened down and closed, and a 4’ section of 4 1/16th riser spool and two 4 1/16th gate valves was then installed on top of the bop. The BOP’s were then pressure tested and once all connections were tested, there was 50 MPA left above the freeze plug and the cribbing and ice removed allowing the thawing process to begin.
Time on location: 5 days