Downhole Cable: The Cost vs. Quality Conundrum

When it comes to Downhole Tubing Encapsulated Cable (TEC) do you really get what you pay for?

The cost vs. quality conundrum is ever-present, does paying more really equate to better quality and increased performance?

Tubing Encapsulated Cables (TEC) form an integral and critical part of any downhole monitoring solution. TEC failure most certainly delivers a catastrophic outcome. Therefore, a focus on quality is an absolute consideration. In this post, we seek to outline the main points of differentiation between GEO PSI and our competitors TEC and why quality should take precedent over cost.

TEC History

Until 1985, permanent downhole monitoring solutions used braided wireline logging cables to connect downhole gauges back to the surface.

The wireline logging service company’s utilized braided wireline cables for short-term wireline logging deployments. The first use of a braided wireline logging cable in a permanent downhole gauge application was in Gabon in 1972. During the ’80s, Shell developed the first ¼” Tubing Encapsulated Cable (TEC) to operate an electric downhole safety valve.

Over the coming years, TEC-based real-time permanent downhole gauge systems found greater integration into operator completions. This ¼” TEC design did not change for decades. That is until we here at GEO PSI developed the world’s first 4mm TEC in 2008.

In a previous blog post titled “Downhole Cable History“, we provide a detailed introduction of 4mm (0.160”) Single Conductor TEC and look at our first 12 years of innovation, achievement, and excellence in TEC manufacturing.

Paraphrasing for those interested in a quicker read, the philosophy behind reimagining ¼” TEC was to create a far superior product in a more cost-effective manner, leading to increased installation success with broader adoption.

Is All TEC Created Equally?

The global distribution and installation of more than 5,000,000 meters of 4mm TEC shows that the recipe for success is known.

The problem that comes with success is imitation. The question addressed in this blog post? Are all TEC’s created equally, and does cost really affect the installation risk?

The following comparative analysis will highlight the importance of TEC design, quality raw materials, state-of-the-art manufacturing and robust QA/QC process.

This post will posit that where substandard quality exists, catastrophic failure risk is high.

TEC Anatomy

Understanding the anatomy of a TEC is an excellent place to start.

As we look at TEC quality we will focus on Conductor and Armour components, illustrating the difference between a high-quality TEC and a substandard one. The aim is to highlight why quality matters and to point to some critical differentiators.

The illustration below showcases a Tubing Encapsulated Table in our 4mm (0.160”) format.


Figure 1: GEO PSI 4mm TEC Engineering Drawing

TEC Armour

The primary function of the TEC Armour is to mechanically protect the conductor and insulation while creating a waterproof barrier against wellbore fluids.

High-quality raw materials and state-of-the-art manufacturing processes are vitally important, as poor quality inputs will lead to catastrophic failure. The following pictures highlight the our 4mm (0.160”) TEC and a Competitors 4mm (0.160″) TEC.


Some points to note the significant quality differences:

  • Our TEC showcases superior weld quality, exhibiting high quality and immaculate non-polished weld lines. The Competitor TEC exhibits inferior weld quality, unmistakable weld porosity, and a post-weld polished finish
  • Our TEC exhibits “normal” and flexible handling traits, while the Competitor TEC is “work hardened” and extremely difficult to handle

Utilizing state-of-the-art manufacturing processes to execute a clean and robust weld line is a critical aspect of producing a high-performance TEC.

A high-quality weld line is crucial because the armour provides a physical barrier against the wellbore fluids. If the weld line fails, then a catastrophic failure will occur.

TEC flexibility and increased mechanical performance are high on the list of favourable TEC characteristics as well. TEC that has been work hardened during the manufacturing process can cause significant installation challenges when working in tight spaces at the tubing hanger, wellhead, and especially when terminating wellhead outlets.

TEC Conductor

The primary function of the TEC conductor is to provide a power and communication pathway between the downhole gauge and the surface electronics. The conductor design and quality of the raw materials significantly impact the survivability of TEC.

The following picture highlights our 4mm (0.160”) TEC and a Competitor 4mm (0.160″) TEC.


Some points to note the significant quality differences:

  • Our 4mm (0.160″) TEC utilizes a high-quality AWG 18 conductor (Stranded 19 x AWG30 Tinned Cu Wire) while the Competitor TEC uses a much lower quality AWG 18 conductor (Stranded 7 x AWG26 Non-Tinned).

The design of the conductor contributes to its handling performance. Our TEC conductor utilizes a higher number of smaller gauge AWG 30 wire to make up the total Conductor size. This design increases TEC flexibility significantly.

TEC designs that use a smaller number of thicker stands lead to much stiffer TEC formats. These stiffer conductors increase the stress on the insulation and armour weld line leading to an increased potential for failure. 

An increased number of smaller diameter wire stands that make up the TEC conductors improve the ductile performance. Increased flexibility is more favorable in completions with high levels of vibration and tubing string movement. Increased ductility performance allows the TEC to stretch or pinch, while keeping mechanical and electrical integrity.

The following performance tests will highlight this importance.  

TEC Crush Perfomance Test

Under most well installations or dynamic production scenarios, TEC is damaged via crush events, tubing movement, or vibration wear.

Encapsulation provides an additional layer of protection for higher vibration environments. The previous pictures comparing our 4mm (0.160″) TEC to the competition clearly illustrate a significant difference in quality.

Another way to showcase this quality variation is to conduct TEC crush tests. Here at GEO PSI we follow the UL 2225 UL standard, utilizing the crush test procedure defined in UL 1569.

This standard requires the TEC to withstand a crushing force of up to 1500 Lb-F (Pound-Force). For this report, each test continued past the 1,500 lbs to catastrophic failure. The diagram below illustrates the test apparatus used to conduct crush tests.


Figure 2: TEC Crush Test Illustration

These crush test results illustrate that our 4mm (0.160″) TEC outperformed the Competitor TEC by more than three times. The reason for this significant difference is design geometry, higher quality raw materials, state-of-the-art manufacturing processes, and best-in-class QA/QC.

The graph below illustrates these test results.


Figure 3: 4mm (0.160″) TEC Crush Test Results Graph (GEO PSI vs. Competitor E)

Interestingly, as both TEC’s were taken to catastrophic failure during crush tests one performed significantly better than the other.

The positive observation was that our TEC kept its integrity with no fissures or breakage while the competitor’s TEC split along the weld line. These results further highlight the significant quality difference between TEC’s.   



The conclusion of this post is simple – not all TEC’s are created equally!

There is a justified cost associated with quality, and catastrophic failures associated with sub-par products are a real risk for consideration.

To learn more about the benefits of our downhole cable products we encourage you to contact us!

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This Post Has One Comment

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    Qty 15: 14,000’ PDC, 0.25” 0.035 thickness I-825 ETFE PP NYLON permanent downhole cable.

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