CASE STUDY Operators selects UROS-CT as an alternative to centralizer sub for deep water in Norway
A 13-3/8” liner needed to be run and set inside 16” casing above a 14-1/2” x 17-1/2” under-reamed hole. The 13-3/8” string utilized flush joint connections and was run through the subsea wellhead in 8,000ft of water. The operator had to select a stop collar they were confident had extreme holding capability under all operating conditions and a centralizer which could stand up to downhole conditions to prevent casing accessories from coming loose, possibly sticking the liner or causing junk in the hole.
A centralizer and stop collar with a slim design was needed to pass through the 14-3/4” drift of the 16” casing and to provide sufficient holding force under all operating conditions. This is especially critical when passing through the wellhead restriction at the mudline where centralizer insertion force creates the highest load on the centralizer.
The innovative UROS-CT and patented slim Ace Ratchet Collar (ARC) are specifically designed for close-tolerance applications to both pass tight restrictions and effectively manage surge and swab, allowing faster running speeds even in formations with narrow mud margins. Both units are easily installed off-line and don't require pipe preparation or transportation off-site for installation.
Through a major service company, UROS-CT and ARC were provided as the fit-for-purpose solution. Centek UROS-CT close tolerance centralizers have end-bands which are manufactured to very tight tolerances where the ID of the centralizer is only 0.030 in. over the maximum casing OD.
The ARCs are rated to over 90,000lbs to resist high axial load while meeting pass-through requirements of the 16” casing string at a substantial cost savings versus alternative solutions.
15 Centek UROS-CT and 30 ARCs were installed off-line by trained personnel at the pipe yard. The pipe was sent to the rig then run down hole through the subsea wellhead located in over 8000ft of water to total depth of over 12,500’ at 70° inclination. The casing annulus was circulated clean and cement pumped as per plan.
This run is another example of a successful installation and that considerable changes in temperature do not affect the restoring force of the UROS-CT nor the holding capabilities of the Ace Ratchet Collar.