Technology Update: System Adds Reliability, Efficiency to Attaching Well Construction and Completion Tools
- Mike Moffitt (Ace Oil Tools)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- July 2017
- Document Type
- Journal Paper
- 18 - 19
- 2017. Copyright is retained by the author. This document is distributed by SPE with the permission of the author. Contact the author for permission to use material from this document.
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The secure placement of tools and accessories along well construction and completion strings is essential to executing downhole applications.
In wellbore cementing, for example, job success depends on efficient mud removal and cement displacement around the tubular. Both of these objectives may be compromised if channeling occurs, where the cement does not spread evenly in all directions. Prevention of channeling depends on designing the right cementing program, which includes achieving the optimal standoff between the string being cemented and the open hole.
Selecting the right centralizers and planning their location along the string are critical to achieving standoff. And securing the centralizers to keep them from sliding along the pipe is also essential to prevent damage to the string and the risk of leaving junk in the hole if the string must be removed from the wellbore.
A new attachment system designed for simplicity, reliability, and ease of installation has been developed by Ace Oil Tools to overcome the limitations of traditional methods used to secure tools and accessories to drilling and completion strings.
The patented design includes slim-profile male and female collars that are slid onto API casing joints and pressed together with a lightweight machine. As they are pressed together, corresponding ramps work to engage slip wickers to the joint to produce a very high holding force while maintaining a slim profile. The collars also feature a ratchet mechanism to prevent them from coming apart, forming a permanent lock to the joint.
Current Industry Practices
Historically, the most common method for holding casing equipment in place has been to use stop collars that are secured to the liner with set screws. These simple, inexpensive tools are used when only a low holding force is needed and their relatively high profile does not prevent the string from passing through restrictions.
This type of stop collar is not typically suitable for critical wells or in drilling programs that use semi-flush or flush-joint connections. If the collar fails, there are no couplings within the string to push accessories past restrictions, possibly preventing the string from reaching total depth. Collar failure can also result in suboptimal standoff, pipe damage, and junk left in the hole.
As the offshore drilling industry evolved, centralizer subs were developed as a more reliable solution. These short tubulars are threaded into the string between joints. Subs contain machined profiles to interface with the centralizers to prevent them from sliding along the string as they are run into the wellbore. Because the profiles are integral to the sub, they will not fail under high loads.Some of the issues with centralizer subs are their high expense and the limitations they impose on string design. Only one centralizer per joint can be run, and it can only be placed in a suboptimal location between the joints.
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