NEWS The Unsung Hero of Centralization: Why Stop Collars Matter More Than You Might Think

03 June 2025

In the complex world of well construction, centralizers often take center stage. But one small, often overlooked component plays a crucial role in ensuring their effectiveness: the stop collar.

Stop collars are essential to centralization performance. Their job is simple yet critical: to hold the centralizer in its designed position on the casing string, maintaining optimal standoff throughout casing deployment and cementing. When stop collars are incorrectly specified, poorly installed, or fail under load, the effectiveness of centralization—and the success of the entire well—can be compromised.

What Stop Collars Do—and Why Fit Matters

Stop collars are mechanical restraints designed to prevent axial movement of centralizers. They keep centralizers fixed at engineered intervals where optimal standoff is required to promote even mud removal and reliable cement placement.

If a stop collar doesn’t fit securely or rides over the centralizer, it can lead to:

• Centralizer displacement during run-in-hole
• Poor standoff and suboptimal centralization
• Inadequate cement coverage and channeling
• Increased risk of differential sticking
• Higher likelihood of remedial operations and added rig time

Even small displacements can have a major impact. Under API 10D2 testing, centralizers are allowed to move up to 4 inches along the casing during the test procedure. While this is technically within the standard, in real-world operations that much movement can result in reduced performance, especially in high-angle or washed-out sections where placement is critical. Operators should understand the implications of this tolerance and look beyond compliance to actual performance under downhole conditions.

Installation Matters: Set Screws, Torque, and Real-World Failures

Incorrect installation is one of the most common causes of stop collar failure. Many stop collars rely on set screws to grip the casing and maintain position. While quick and convenient to install, these collars depend heavily on correct torque during installation.

If set screws are under-torqued, the collar may slip under the forces of casing movement. If over-torqued, the screws can strip or damage the collar body or casing surface. Competitor testing has shown that some suppliers either don’t provide torque specifications—or their products fail to hold even when installed to their own published instructions.

These inconsistencies pose a real risk to operations, particularly in challenging well environments. In contrast, Centek provides full torque guidance with every product and validates our performance under extreme conditions to deliver proven holding force.

Stop Collar Types: More Than Just Fitment

There are several types of stop collars available to suit different operational needs:

• Set screw collars: Common and easy to install, but torque must be applied precisely to ensure holding strength.

• Quick-latch or snap-on collars: Fast to fit on site but may lack the holding force required in demanding wells.

• Hinged collars with set screws: Useful where collars need to be fitted over large casing couplings.

• Close tolerance stop collars: Ideal for tight and ultra-tight applications but tend to require specialized installation.

At Centek, every stop collar is engineered for specific operational demands, tested to exceed holding force expectations, and backed by installation and torque guidelines to eliminate ambiguity on the rig floor.

When a Small Component Makes a Big Impact

Stop collar failure isn’t a minor issue—it’s a major operational risk. A centralizer that moves just a few inches from its intended location can undermine the performance of the entire string, resulting in poor zonal isolation, reduced cement bond, and increased risk of failure in production or abandonment phases.

That’s why Centek designs stop collars to work as an integral part of a complete centralization system. From engineering through manufacturing and testing, we ensure every collar delivers the strength and reliability needed in the world’s toughest wells.

In Summary

Stop collars may be small, but their performance has big consequences. With API standards allowing several inches of movement during testing, and some suppliers falling short of their own claims, choosing the right product and installing it correctly is vital.

At Centek, we deliver stop collars that meet and exceed expectations—ensuring centralizers stay where they’re needed most. Because when well integrity is on the line, performance isn’t optional.

Learn more with our competitor testing:

Over-Torque Stop Collar Test

This film highlights potentially dangerous inaccuracies in competitors’ grub screw torque recommendations and the potential for competitor stop collars to slip on the casing, leading to delays and jeopardizing the performance of the centralizers.

Stop Collar Burst Test

Our stop collar burst test is used to assess the strength and the toughness of the stop collars. In particular, we are looking for weaknesses such as cracks propagating from the screw threads and also any weakness across the joints of the stop collars. This film demonstrates the superior performance of Centek stop collars compared to DHP, Sledgehammer and Weatherford stop collars.

 

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