In-Line Quench-and-Temper Technology Applied to CT Improves Safety and Reliability
Authors: Carpenter Chris 
Published: May 2019

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 194255, “In-Line Quench-and-Temper Technology Applied to Coiled Tubing Improves Safety and Reliability in Extended-Reach US Shale Operations,” by Eric Gagen, SPE, and Gaston Piller, SPE, Coil Tubing Partners, and Irma Irais Galvan and Garry McClelland, Global Tubing, prepared for the 2019 SPE/ICoTA Well Intervention Conference and Exhibition, The Woodlands, Texas, USA, 26–27 March. The paper has not been peer reviewed.
In unconventional resource plays across the United States, lateral well sections are being extended beyond 10,000 ft. The increased application of larger coiled tubing (CT) of 2.375-in. and 2.625-in. diameter for operations in high-pressure wells has pushed the reliability envelope for conventional CT strings. This paper discusses the advantages of the in-line quench-and-temper (Q&T) process, which enhances overall CT life and reliability by producing tubing with more-uniform microstructure throughout its entire length, increased material strength, and improved bend-fatigue performance.
Technology Background
Applying Q&T technology to CT has transformed well intervention in unconventional shale plays, particularly for multistage fracturing applications in 10,000-ft laterals or longer that are commonly completed with more than 80 intervals per wellbore. With some laterals 14,000 to 16,000 ft long, with 130 or more entry points, manufacturers and service companies have strived to deliver safe, cost-effective solutions for operational challenges. The implementation of technological innovations in surface equipment, downhole tools, and Q&T custom-engineered CT strings, along with refined operational practices and logistics, allows the performance of low-risk completions with over 10,000-ft laterals on a larger scale. At the time of writing, predictions suggested that more than 90% of the US CT market would switch to Q&T products by the end of 2018.
Extended-Reach CT Design With Rapid-Taper-Strip Technology
Rapid-taper-strip technology, which features a quick increase or decrease of wall thicknesses within the CT string, is an engineered solution for CT applications in difficult well conditions and geometries. This technology provides rapid wall-thickness strip transitions of 300-ft to 700-ft long to place specific thicknesses purposefully along the length of the string.
Rapid-taper strips combined with Q&T grades enable engineers to design unique string configurations that can achieve unprecedented well lateral reach and service life. The technology helps minimize tubing weight in the horizontal section and increase stiffness in the vertical section to avoid the onset of CT buckling inside the wells.
After its successful application in North America, the flexibility and operational benefits of this strip technology became well known. It has expanded into other applications, particularly in unconventional-resource developments where CT is subjected to extremely challenging environments.
With weight restrictions being the pre-dominant challenge in extended-reach CT-string designs, the flexibility of rapid-taper strips allows for custom-engineered hourglass CT strings that maximize reach, overpull, and fatigue life while meeting CT surface-equipment-design constraints. An hourglass string configuration features a reduced wall thickness in the upper end of the CT string. This reduced wall provides safe overpull capacity during operations. Hourglass CT-string configuration advantages include weight optimization, reduction of frictional pressure losses, and added rigidity where needed while minimizing wall thickness elsewhere in the string to re-duce overall tubing costs.