Problem
A North Sea platform had identified external corrosion wear in the 13 3/8" 54.5# casing at 151 ft which was also the sea level depth from RKB. The plan prior to identifying this corrosion was to drill an 11" sidetrack below the 13 3/8" shoe.
Solution and Achievement
To pinpoint the leak in the 13 3/8” casing, a Coretrax CXRTP (Retrievable Test Packer) was set and pressure tested over five separate depths between 100ft and 164ft. With the leak depth now identified, the two onboard Coretrax expandable casing and liner engineers ran a 148ft Coretrax CORE HYD 10 ¾” OD patch system which was set from 251ft up to 103ft with a five stack HNBR seal assembly above and below the leak point to completely isolate this issue.
The HYD system uses hydraulic pressure to push the expansion cone up through the expandable casing usually until it exits, however, due to the shallow depths and the fact that the top of the expanded casing was dry, casing jacks were used on the rig floor to safely expand the final 9ft to avoid a final sudden shallow release of pressure as the expansion cone exits the top of the system. This was done with great success.
With the patch set and tested, a large post expansion ID of 11.798” allowed the sidetrack operations to be carried out.
The operator was happy with the efficiency and being able to continue drilling operations.
