THE CHALLENGE
A 9 7/8" casing string needed to be run in to 10 5/8" x 12-1/4" open hole through both 13-3/8" casing and an 11-7/8" liner. The 9 7/8" string utilized flush joint connections. This left only a 3/4" restriction for a centralizer and stop collar to travel through. A close tolerance centralizer was required with a slim stop collar to prevent slippage of the centralizers during run-in and while cementing. Considering flush joint casing connections, it is especially critical for the stop collars to prevent the centralizers from slipping and collecting above the 11 7/8" liner during run-in and to hold the centralizers in place while cementing to deliver the calculated stand-off.
THE SOLUTION
Through a major service company, a UROS-CT centralizer and the Ace Ratchet Collar (ARC) from Ace were provided as the fit-for-purpose solution. The endbands (or rings) on Centek UROS-CT close tolerance centralizers are manufactured to very tight tolerances where the ID of the centralizer is only 0.030 in. over the maximum casing OD. They are also manufactured with superior roundness which allows for closer hugging of the casing.The ARCs resist high axial loads, while meeting drift requirements of the 11-7/8" liner at a substantial cost saving. The patented slim ARC is rated to over 90,000Ibs axial load. Both the UROS-CT and ARC are specifically designed for close-tolerance applications to pass tight restrictions and effectively manage surge and swab, allowing faster running speeds 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.
THE RESULT
15 UROS-CT centralizers and 30 ARCs were installed off-line by trained installers at the service company location within a few hours. The liner was shipped to the rig then run in the hole through both the parent casing and 11-7/8" liner to total depth of over 4,300m and 20° inclination. The casing annulus was circulated clean and cement pumped as per plan. This was the first installation for this client and in this region. The same solution has now been used on two strings for the next well.
