Reliability – The Fundamentals of MWD
By Paul Deere
September 1, 2015
Tolteq’s new TruCourseTM MWD/LWD System is full of impressive features such as fast pulsing, continuous inclination, asynchronous warnings, advance drilling dynamic measurements and the addition of pressure and resistivity measurements, but we know all of these bells and whistles are useless unless the basic fundamental feature of MWD is established – Reliability. Let’s face it, it really doesn’t matter how many bells and whistles your MWD tools have if you aren’t receiving good data at the surface.
Reliability of a system doesn’t just happen; it is designed in from the very beginning. We approach design for reliability with two basic questions, 1) Does the system work in the required environment indefinitely? 2) Does the system continue to work in the required environment consistently after normal maintenance?
Take the iTPM (iSeries Tolteq Pulser Module). This pulser has been accepted by the industry as very reliable and successful. Our approach to the design was that an easily maintainable pulser is a more reliable pulser. To make a pulser easy to maintain we eliminated as may parts as possible and greatly simplified the maintenance process.
This approach continues to guide our development even now. The picture below compares the design of a typical Tensor-based gamma module (on the bottom) and a TruCourse gamma module (on the top). Notice the simplicity of the TruCourse design. TruCourse has eliminated 18 screws, 10 O-rings, 4 connectors, 2 pigtails, and 12 additional machine parts. This means no more screws and no more Loctite® to deal with during maintenance. No more pigtails or exposed wiring to inspect for nicks or shorts. No more loose screws allowing parts to rattle inside the barrel. No more complicated assembly or disassembly procedures. No more ensuring that you or your employees are breaking down tools in such a way as to avoid twisting and breaking pigtails.
Comparison of TruCourse Gamma Module vs Tensor-Based Gamma Module
I don’t think anyone would question that the downhole environment is much more demanding of tools than it was 10 years ago. As a tool designer and manufacturer, we cannot demand that the end users “be nice” to the tools. No. We must develop tools for today’s MWD demands.
In TruCourse, we’ve done just that. We took the years of experience in MWD and how the downhole environment affects tools and made our tools more rugged. For instance, we learned that shock and vibration can do some pretty interesting damage to a tool. As a result, we designed an improved vibration snubber for both the top and bottom end of our chassis. These ruggedized snubbers are designed so that if a failure should occur, the chassis cannot rotate. This was accomplished by keying every part in the snubber. (NOTE: The ruggedized snubbers are available in iSeries tools as well.)
Another weakness we identified was in the pigtails; we’ve completely eliminated the need for pigtails in TruCourse. In TruCourse, all connectors are spring-loaded and in compression when the tools string is made up. What does that mean? It means no more loose pigtails flopping around inside barrels.
Wiring is also susceptible to damage due to vibration. All wiring throughout TruCourse is secure and cannot move or be removed. TruCourse uses a simple J-Latch (patent pending) to remove the chassis from the centralizer. Around the J-Latch is a split shell held in place by O-rings. This split shell provides mechanical support to the chassis plus ensures the chassis cannot break from the centralizer due to the fact that the split shell keeps the chassis from moving down, unable to disengage from the J-Latch.
We admit the design is quite simple, but it addresses many potential failure modes. In our experience, a simple design leads to a more reliable tool. A simple design is also quick and easy to maintain correctly, which is a critical part of tool reliability.
If you would like to learn more about TruCourse or are interested in a shop or field demo let your account manager know. If you do not know your account manager please call us at 512-331-4241 or if you prefer, email us.
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