UK based centranlizer specialist Centek is launching its Inter Casing Centralizer Sub (ICCS) at this week's Offshore Technology Conference. The ICCS is designed to be run as part of a tight tolerance casing string in deepwater, ultra-narrow annulus applications.
Centek and Halliburton collaborated in developing the ICCS. The body of the centralizer sub is machined to Centek and Halliburton’s standards. Centek’s patented UROS (under reamed offset bow) centralizer technology is installed on the sub body by Halliburton. The sub body, manufactured to API 5CT requirements, meets or exceeds all burst, collapse and tensile ratings. The UROS centralizer gives optimum restoring performance with minimal starting and running forces when passing through the tightest restrictions.
The centralizer is designed and manufactured with minimal clearance to the casing, and with a precisely formed cross bow curvature so that there are no “knife edges” (common among standard bow spring centralizers) which reduces the risk of subsea well head damage. Crucially, during operation the centralizer can recess completely into the sub body and so pass through the tightest of 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, and this coupled with precise manufacturing enables the centralizer sub to rotate within the centralizer at minimal torque values. The 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,” said Cliff Berry, Vice-President, Global Business Development at Centek Group. “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 7.3/4in through to 18in or as required, and the sub body can be threaded to meet the customer’s requirements for the casing string.
UROS-CT
Centek will also be showing its established UROS-CT centralizer at OTC 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 deep water 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 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 (RIH) methods. The UROS-CT provides the highest levels of standoff, better well clean-out during well conditioning, and improved cement displacement to ensure good zonal isolation as well as minimizing corrosion later in the life of the well.
“The UROS-CT is being used at various water depths from 5,000 feet and beyond,” said Cliff Berry. “In deep water 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 successfully in the Gulf of Mexico by both US and Mexican operators, and off Norway, Brasil, Brunei, and Malaysia.
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