THE CHALLENGE
A major operator drilling an exploratory well in record water depth off the coast of Uruguay required placement of a 13-5/8" casing string below a 17-7/8" liner. Being an exploration well, there was uncertainty whether downhole challenges would require a 16" contingency liner to be set between the 17-7/8" and 13-5/8" strings. Running the 13-5/8" directly through the 17-7/8" string would allow for a cost-effective centralization solution using conventional centralizers and stop rings, where the presence of the 16" liner would require centralizer subs in the 13-5/8" string.
Prior to the introduction of the UROS-CT (Close Tolerance) centralizers and the Ace Ratchet Collar (ARC) the operator would have had only 2 solutions — purchase centralizer subs and run them regardless of the presence of the 16" liner, or purchase both the centralizer subs and traditional centralizers and stop rings, then run either based upon presence of the liner. Neither option is cost-effective, in terms of high initial investment and long-term inventory management.
THE SOLUTION
To prevent these issues, the operator selected the ground breaking UROS-CT and the as the best solution to reduce overall spend on centralization. This combination delivers a flexible, cost-saving alternative because it can be run regardless of the presence of the 16" contingency liner.
The slim OD of both the UROS-CT and the ARC means they have the capability of passing through the 16" liner. The ARCs do so while delivering the high holding force required to ensure the centralizers remain in place on the casing string.
The UROS-CT can pass through a 16" liner and retain maximum restoring force and low run in force whilst still delivering sufficient fluid flow to prevent surge effect. 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 patented slim ARC from Ace has a 14.11" OD and is rated to over 90,000Ibf axial load. It is designed to maintain sufficient bypass to help prevent formation breakdown during run-in. Each ARC is easily installed off-line in just a few minutes and doesn't require pipe preparation or transportation off-site for installation.
THE RESULT
Over 20 UROS-CT and over 40 13-5/8" ARCs were installed off-line at the pipe yard by 2 trained installers in less than a day. The pipe was shipped to the rig, run in the hole and successfully cemented at total depth without issue. A 9-7/8" string was also outfitted with the ARCs and centralizers to realize further savings.
This was the first run of the UROS-CT and ARC for this major operator, having saved over $250,000 in costs on both 13-5/8" and 9-7/8" strings.
