In all downhole applications, the secure placement of tools and accessories on the outside of the casing or completion string is a critical factor. On average, it is estimated that 50 centralizer tools typically need to be attached to a drillstring in a given project. Traditionally, stop collars or centralisers have been used. However, both of these approaches come with myriad of issues or limitations and can cost as high as USD 350,000 per project.
The Ace Ratchet Collar (ARC) is a unique ratchet locking mechanism designed with simplicity, reliability, and ease of installation in mind. The goal behind its development was to overcome the limitations of traditional methods and create a new cost-efficient solution. One that delivers an extremely high holding force under all operating conditions, with no impact on drift. Simple and innovative in design, the ARC removes the risk of slippage on the pipe and can be used with any third-party centralizer or casing accessory.
On average, the Ace Ratchet Collar saves clients 80% when compared with the use of stop collars or centralisers. On a recent application in Senegal for a major operator, the system saved in the region of USD 80-150,000 in a close tolerance application.
The traditional approach
The traditional approach by the industry was to use stop collars. While inexpensive, stop collars pose a higher risk because of the limited holding force on the pipe they can guarantee. This makes them more susceptible to failure. Slippage on the pipe of any kind risks damage, increases the chance of junk downhole and undermines the structural integrity of the well. In addition, further complications can arise with stop collars as they are not suitable for all conditions, e.g. on critical wells or in drilling programs that use semi-flush or flush-joint connections.
The solution of centraliser subs was developed latterly to increase the holding force downhole. Centraliser subs, however, are more expensive and impose limitations on string design. To prevent them from sliding along the string as they are run into the wellbore, they feature machined profiles, which ensure the subs interface with the centralizers. The application-specific design of each sub is based on a number of factors. This means that subs are custom built and are limited to specific string designs – making them an expensive solution.
An 11 3/4″ liner was required by a major operator to be run and set inside a 13 3/8″ casing, above a 12-1/4″ x 14-3/4″ under reamed hole. The 11-3/4″ string utilised flush joint connections. A tool with sufficient holding capability under all operating conditions was necessary to prevent casing accessories from coming loose, possibly sticking the liner or causing junk in the hole.
The operator had the choice of running two centralisers on each joint to achieve standoff. However, this would have resulted in high costs.
The Ace approach
The ARC locks together to deliver a holding force equivalent to over 90,000 pounds. Tested to withstand axial loads up to 180,000 lbs, while meeting passthrough requirements, its slim design has been specifically intended for close-tolerance applications. The slim design also allows for faster running speeds, even in formations with narrow mud margins. The ARC makes minimal impression on the pipe and has the ability to rotate independently of the casing or liner string.
Simple and innovative in design, the ARC is built around Ace Oil Tool’s proprietary “ratcheting” mechanism. The ratcheting mechanism works by pressing the female and male parts of the collar together, creating a self-locking device. The carefully designed teeth are machined on the male part, which generates the holding force by gripping onto the pipe. With the ability to be installed under all operating conditions without affecting drift, it can be used with any third-party centralizer or casing accessory. Each unit can be easily installed offline, requiring no pipe preparation or transportation offsite for installation. The process usually takes less than a minute per unit.
In partnership with a major service company, Ace Oil Tools provided the ARC as the fit-for-purpose solution to prevent centralizer movement while running in hole. With the ARCs rated to minimum 90,000 lbs to resist high axial load while meeting passthrough requirements of the 13 3/8″ casing string, the ARC presented a substantial cost saving for the major operator versus alternative centralizer subs.
Forty ARCs and twenty centralizers were installed offline at the pipe yard, on ten joints. The pipe was sent to the rig, then run down to a total depth of 2,776 metres. The casing annulus was circulated clean and cement was pumped. The liner was successfully run to total depth. Ace Oil Tools successfully prevented centralizer movement while the ARC was running in hole. The cost savings of using ARC was between USD 80,000 and 150,000.
The Ace Oil Tools product portfolio
Since its development, the Ace Ratchet Collar (ARC) has been installed on projects across 27 countries and five continents. Due to its holding force, the ARC acts as the foundation for other solutions. To date, it has enabled the development and delivery of six other products by performing as a stop collar to hold both solid body and bow-spring centralizers or other accessories on the liner. The wider Ace portfolio also includes the Ace Drilling Centralizer (ADC), Ace Fixed Centralizer (AFC), Ace Tracer Carrier (ATC), Ace Screen Clamp and Ace Splice Clamp.
Espen Sørbø, Ace Oil Tools CEO, has more than 20 years of oil service experience, including Managing Director at WellDynamics and Operations Manager at Halliburton HCT. He has also headed the TETRA office in Norway and founded Oil Tools of Norway. Prior to joining ACE Oil Tools, Sørbø served as VP Completions with global focus on Sales and Operations activity at Norwegian company TCO.