Centek launched its inter casing centralizer sub (ICCS) at the 2015 OTC. Developed in collaboration with Halliburton, the ICCS is designed to be run as part of a tight tolerance casing string in deepwater, ultra-narrow annulus applications. It features Centek’s patented UROS (under reamed offset bow) centralizer technology, which is installed on the sub body by Halliburton. The sub body is manufactured to API 5CT requirements.
According to Centek, the centralizer is designed and manufactured with minimal clearance to the casing and with a precisely formed crossbow curvature so that there are no “knife edges.” This helps to reduce the risk of subsea wellhead damage. Further, during operation, the centralizer can recess completely into the sub body to pass through tight restrictions while protecting the bows from damage.
The centralizer’s single piece construction eliminates the risk of failure associated with welded bow to end-band type designs. Coupled with precise manufacturing, this enables the centralizer sub to rotate within the centralizer at minimal torque values. The unique interlocked band design means that the strength of the centralizer end-bands does not depend on quality or installer skill but is as strong as the single piece of steel used in Centek’s centralizers.
In addition, the weld pocket recesses are designed to ensure there is no need for a pronounced weld bead with the risk of friction grinding the bead down and weakening the weld.
“Centek appreciates the need for a close tolerance centralizer for use in very tight annulus applications, where the margins between pore pressure and the fracture gradient are narrow,” Cliff Berry, Vice President, Global Business Development at Centek Group, said. “Not only can the UROS centralizer fully compress within the sub body, but the Centek sub has the ability to rotate when fully compressed in the tightest of restrictions with no loss of eccentricity at the end-bands.”
The size range is expected to be 7.3/4 in. through to 18 in. or as required, and the sub body can be threaded to meet customer requirements for the casing string.
Centek also continues work on its UROS-CT centralizer, designed for use in tight tolerance casings. The UROS-CT is engineered to precise ring-gauge tolerances, partly because casing drift downhole is a major concern when running deepwater wells but also because the centralizer must compress as closely as possible to the casing as every millimeter saved allows for greater expansion in the open hole.
This centralizer significantly reduces insertion forces and drag, and the unit does not need to be pulled into the well as the design allows for normal run-in-hole methods.
“The UROS-CT is being used at various water depths from 5,000 ft and beyond,” Mr Berry said. “In deepwater wells, you may have up to nine strings running through each other, so the tolerances are tight, and a tool to optimize the cement job is of vital importance.”
The UROS-CT is being run in the Gulf of Mexico by both US and Mexican operators, as well as offshore Norway, Brazil, Brunei and Malaysia.