Slim stop collar intended for close-tolerance applications

May 1, 2020
The secure placement of tools and accessories along both well construction and completion strings is an essential component of all successful downhole applications.

Espen Sørbø, Ace Oil Tools

The secure placement of tools and accessories along both well construction and completion strings is an essential component of all successful downhole applications. Traditional stop collars, while inexpensive, are susceptible to failure due to limited holding force on the pipe. Slippage on the pipe of any kind risks damage, increases the chance of junk downhole, and undermines the structural integrity of the well. While centralizer subs offer an alternative solution to stop collars, they are more expensive and impose limitations on string design.

Ace Oil Tools wanted to create a new cost-efficient solution that worked under all conditions. Removing the risk of slippage on the pipe, while also increasing the holding force for operators looking to centralize the pipe, the Ace Ratchet Collar (ARC) brings unrivalled holding force to the market. 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.

The ARC was built around the company’s proprietary ‘ratcheting’ mechanism. Simple and innovative in design, 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.

Reliably anchoring accessories to the casing without a complex installation process, each unit can be easily installed offline. Therefore, it requires no pipe preparation or transportation offsite for installation. A bespoke installation tool is used to securely fix the ratchet collar to the outside of the pipe. With minimal HSE impact to workers and environment, the full process usually takes less than a minute per unit.

Since it was developed in 2012, the ARC has been installed on projects across 27 countries and five continents. Smart and cost-effective, the ARC technology adds reliability and efficiency when attaching tools to the pipe. It typically results in cost savings of up to 80%, while also protecting equipment downhole.

The ARC locks together to deliver a holding force equivalent to more than 90,000 lbs. 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. This is important especially in cases where it needs to pass tight restrictions and effectively manage surge and swab. The slim design also allows for faster running speeds, even in formations with narrow mud margins. The collar makes minimal impression on the pipe and can rotate independently of the casing or liner string.

It is available in standard, slim, and ultra-slim models. ARC works as a stop collar to hold both solid body and bow-spring centralizers or other accessories on the liner. The Ace Drilling Centralizer (ADC) is a rotating, solid-body centralizer for use in casing and liner drilling. The Ace Tracer Carrier (ATC) houses and protects tracer elements conveyed into the wellbore on the production string.

For a major operator in Senegal, a stop collar with a slim design was required to be installed on a 11¾-in. casing, pass through a drift restriction of 12¼ in., and to provide a holding force under all operating conditions. Forty ARCs and 20 centralizers were installed offline at the pipe yard on 10 joints. The pipe was sent to the rig, then run down to a total depth of 2,776 m (9,108 ft). The casing annulus was circulated clean and cement was pumped. The company prevented centralizer movement while the ARC was running in hole. The cost savings of using the collar was in the range of $80-$150,000. •