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Ace Ratchet Collar delivers cost-effective solution in offshore wells

North Sea operator chooses Ace Ratchet Collar (ARC) and centralizer over costly centralizer subs as the solution for their offshore wells in Norway

Premium stop collars
offshore wells in Norway


  • ARC stop collars used with 1-piece centralizers provides high axial load capabilities and meet wellhead drift requirements

  • Forty (40) ARCs and the centralizers installed off-line by two trained installers in a few hours

  • Proven to saves $300,000 each run

The challenge

An operator working in the North Sea needed to install a 17” liner in an 18-1/2” open hole across a 3,295ft interval. This required passing the liner through the tight wellhead restriction, while ensuring the position of centralizers, to maintain the planned stand-off across the interval.

Reliability was a primary concern for the operator, who also required a high holding force, low insertion force through the restriction and a low running force inside the wellbore. Execution in a more timely manner and at a lower cost than other field-proven technologies, such as typically used centralizer subs, was also required.

The solution

For this specific well, the client needed to install the 17" liner through a 17-3/4” wellhead restriction.  With a maximum OD of 17.58” and a thin wall (0.161”), the patented slim ARC is specifically designed for use in close-tolerance applications to pass tight restrictions and to manage surge and swab for faster running speeds in formations with narrow mud margins. In addition, the ARC delivers over 90,000lbf axial load delivering the high holding force required.

As a result, Ace Well Technology recommended the slim ARC stop collars be used with 1-piece centralizers secured to the liner without subs.  The partnering centralizer is Centek’s ultra-premium UROS-CT bow spring centralizer. This 1-piece nonwelded design compresses virtually flat when run, allowing it to travel through tight restrictions, yet still capable of expanding to the designed open-hole size for optimal stand-off and cement placement.


This fit-for-purpose solution would then provide high axial load capabilities and meet wellhead drift requirements.  In addition, each unit is easily installed off-line in just a few minutes and does not require pipe preparation or transportation off-site for installation. Overall, the solution would deliver substantial cost savings versus integral centralizer subs.


The result

Forty (40) ARCs and the centralizers were installed off-line by two trained installers at the client’s pipe yard within a few hours. The liner was shipped to the rig then run in the hole, past the wellhead restriction and brought to total depth. The liner annulus was then circulated clean and liner cemented.


The running and cementing of the liner was executed flawlessly using the combination of the ARCs and centralizers.

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