THE CHALLENGE
A major operator drilling an exploratory well in record water depth offshore Uruguay needed to run a 13-5/8 in. casing string below a 17-7/8 in. liner.
Because it was an exploration well, there was uncertainty over whether downhole conditions would require a 16 in. contingency liner to be installed between the two strings. If the contingency liner was required, the 13-5/8 in. centralizers would need to pass through its restricted internal diameter.
The conventional option was to purchase centralizer subs in advance, regardless of whether the contingency liner was ultimately installed. This would have increased upfront costs and created additional inventory-management requirements.
THE SOLUTION
The operator selected Centek UROS-CT close-tolerance centralizers as a flexible solution that could be run with or without the 16 in. contingency liner.
The UROS-CT’s slim profile allows it to pass through tight restrictions while retaining the restoring force required to provide effective casing standoff. Its low running force and open bow design also provide sufficient flow-by to help manage surge and equivalent circulating density in narrow annular clearances.
The centralizer end bands are manufactured to precise tolerances, with an internal diameter only 0.030 in. greater than the maximum casing OD. Their roundness enables them to fit closely around the casing and supports reliable passage through restricted sections.
THE RESULT
More than 20 UROS-CT centralizers were installed offline at the pipe yard before the casing was transported to the rig.
The casing string was successfully run to total depth and cemented without issue. The installation demonstrated that the UROS-CT could provide a practical alternative to centralizer subs while giving the operator the flexibility required for an exploration well with an uncertain casing program.
