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  • Steel for coiled tubing

  • This article also featured in the December 2016 edition of Update
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Custom-made alloy maximises oil and gas reserve recovery

Based in Houston (USA), Quality Tubing produces coiled, high strength steel tubes used in oil- and gas-well interventions and shale hydrocarbon extraction. The company’s latest product is QT-1400, a high strength coiled tube for oil and gas applications. Developed in close partnership with ArcelorMittal Europe – Flat Products, QT-1400 is the most advanced, and strongest solution on the market today.

Quality Tubing, a part of NOV’s Intervention and Stimulation Equipment business unit, introduced its first coiled tubes for oil-well applications more than 40 years ago. Known as QT-700, the first product had a strength of 700,000 pounds per square inch (psi). With the introduction of QT-1400 in 2016, the strength of these tubes has effectively doubled.

By increasing the strength of the steel alloy used to manufacture the coiled tube, Quality Tubing’s customers can significantly reduce tube weight, or increase tube diameter. “Many older offshore wells rely on coiled tubing to maximise production levels,” explains Kevin Elliott, senior metallurgist for Quality Tubing. “However, the lifting capacity of their cranes is often limited. Lighter coiled tubing means these cranes can lift longer strings onto the well. In the past they had to lift shorter strings and weld them together which can affect the performance of the tube.”

The economics of increasing tube diameter are also interesting to operators notes Kevin: “With wider diameter tubes, you can pump more into the well. Or you can have a smaller diameter and higher strength so products such as acids can be pumped in under very high pressure. Either way, service time is reduced and the well gets back to full production quicker.”


QT-1400 can reduce string weight, making it ideal for offshore installations where the lifting capacity of rig cranes is limited

Alloy ready to go from day one

The new product was developed with ArcelorMittal Fos-sur-Mer (France) as Kevin Elliott explains: “We showed the Fos team what we needed from the steel. Our only specification was that they should use a high strength, low alloy (HSLA) grade. Fos came back with an alloy design and samples which we tested in our processes. The alloy they supplied was ready to go from day one.”

“The key challenge with QT-1400 has been to address BIAS-weld softening concerns,” says Denis Lebre, new product senior engineer at ArcelorMittal Fos-sur-Mer. “Thanks to ArcelorMittal’s experience with automotive steel grades, we have been able to design an alloy which reacts positively to our customer’s processes and which minimises detrimental effects in the heat affected area.”

The development of the QT-1400 alloy was completed in less than a year by the team at ArcelorMittal Fos-sur-Mer (France). But it was not the first time the two businesses had worked together. As well as the development of ultra high strength grades for coiled tubing applications, both companies have recently cooperated to explore variable thickness concepts. “We have been cooperating with Quality Tubing for over 30 years,” notes Henri Olivier, account manager for ArcelorMittal International. “Together we have been exploring the use of ultra high strength grades for coiled tubing applications. This has been proven to be the best approach to sustain our coiled tubing business in Houston.”

Quality Tubing has also made use of OCAS, a leading steel research centre established by the government of Belgium’s Flemish region and ArcelorMittal. “We involved OCAS welding specialists to characterise the joins of our QT-900 product,” notes Kevin Elliott. “This is the weakest part of the coiled tube and OCAS has the research-level equipment we needed to prove the solution worked. The OCAS welding experts were extremely helpful and their testing gave us confidence in the strength of the QT alloys.”

“After several years of limited development of coiled tubing steel grades, we began to work with Quality Tubing in 2010 to design more complex grades. This led to the development of QT-1300 and then QT-1400,” explains Pierre Fize, global account manager for ArcelorMittal.

Demand to grow with market recovery

Quality Tubing recently completed testing of QT-1400, the final step before industrialisation explains Kevin Elliott: “We’ve tested QT-1400 with hydrogen sulphide at 100-bar. With a pH of 2.8, it’s the nastiest environment this coiled tubing will be exposed to and proves the inherent qualities of the product.”

Although the oil and gas market is subdued, Kevin Elliott expects QT-1400 will become one of Quality Tubing’s leading products: “QT-1400 has received a warm reception from customers. We expect demand for it to grow quickly once oil prices start to recover.”

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This article featured in our client newsletter Update of December 2016, click on the image below to read it


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