PRODUCTION • PROCESSING • HANDLING
Advances in tubing technology
New grade for control line tubing designed to deliver greater mechanical strength and higher corrosion resistance. By Mark Ayers
A
decade ago, there was much debate around the question of peak oil. Had we reached the maximum point of pumping? Were we effectively reaching the end of the world’s oil reserves? Over the past 10 years, the
force of that debate declined as major new discoveries were made and a growing number of oil companies announced that they were sitting on large new fields. Today, however, with the declining rate of economic growth in China, a background of oil market over-supply, and what many now are regarding as a ‘new normal’ with oil prices as low as US$40 per barrel, companies in the supply base that support the oil and gas industry are facing a serious fall off in demand for their services. Yet despite this, if those companies want to remain competitive, they need to keep investing in R&D to satisfy the industry’s now overriding demand for greater cost efficiency and a lower cost of ownership.
A TIME TO REFOCUS For UK-based Fine Tubes, now a unit of Ametek, with its US-based sister company, Superior Tube, the approach has been to refocus its R&D activities to remain responsive to the needs of a changing market. A current example of this approach is the development of a modified chemistry Alloy 825 in collaboration with one of Fine Tubes’ key raw material suppliers.
Already widely used for downhole completion lines in the oil industry, Alloy 825 (UNS N08825) is an austenitic nickel-iron-chromium alloy with additions of molybdenum, copper and titanium. Developed to provide corrosion resistance in both oxidizing and reducing environments, it is resistant to chloride stress-corrosion cracking and pitting. Te addition of titanium stabilises the alloy against sensitisation in the as-welded condition, making it resistant to intergranular attack after exposure to the operating temperatures typically found in downhole environments. Te new grade of Alloy 825 has a higher molybdenum content that offers the prospect of higher corrosion resistance as well as greater mechanical strength. As a result, the potential exists to make tubing products with thinner walls having the same pressure rating, thereby delivering savings to the industry either by reducing the total weight of product, or, in some cases, by eliminating the need to move to more highly alloyed and expensive grades. Laboratory and production trials have already established that this modified Alloy 825 performs as expected – many of the corrosion-resistance and mechanical properties already have been validated – and that it can be successfully used for the manufacture of tubing products. Next steps will be the presentation of results in anticipation of NACE approval on the grade, expected in early 2016.
From left to right: ¼ in tube encased conductor (TEC), tube encased fibre (TEF) and heater cables
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