It is desirable to pursue the coiled tubing (CT) as an alternative to snubbing in performing through tubing work over operations. With the advances in high pressure CT, it is feasible to contain high pressures. High yield strength (100,000 psi) coiled tubing material has allowed for coiled tubing intervention in the Mobile Bay Norphlet completions. These wells are approximately 22,000 feet vertical depth, high pressure, Hydrogen Sulfide (H2S) gas wells.
The operations performed include:
A scale clean out to approx. 22,000 feet.
A HCl acid job has been performed at 415F.
Clearing a safety valve from build up.
The first operation performed was a scale clean out to 22,000 feet utilizing a spiral wash tool. The well was killed with a 10 ppg NaBr and the same brine was used for clean out fluid. Cost savings of 60% were realized.
The second operation was a HCl matrix acid job performed at 415F.
The third job was a scale clean out across the down hole safety valves. The safety valve was blocked by scale build up and was rendered inoperative. Remedial work was needed. If the through tubing work over did not work, a rig work over was needed. The safety valve was cleared of debris in one operational day. It is estimated that the CT operation cost less than 5–10% of a rig work over.