Technology Focus: Coiled Tubing Applications (June 2016)
Authors: Crabtree Alex 
Published: January 2017

Technology Focus
Another tough year has passed since the last coiled-tubing feature in JPT. In spite of the difficult economic climate, the SPE/ ICoTA Coiled Tubing and Well Intervention Conference and Exhibition moved to a new venue this year, the George R. Brown Convention Center in Houston, because of the continued growth of the exhibition in prior years. Attendance was down by only a small percentage, which, I hope, is an encouraging sign.
As mentioned in last year’s feature, the coiled-tubing industry is adapting to the changing environment. Several papers at this year’s conference discussed various aspects of subsea work performed with coiled tubing. Two papers presented different methods to use coiled tubing to enter or drill wellbores by using either an injector or a snubbing jack at the seabed and a secondary coiled-tubing injector at the surface. In both methods, the coiled tubing runs freely through the water— that is, the coiled tubing is not contained within a secondary riser pipe—and, hence, many in the industry are referring to this new technique as riserless coiled tubing. Other subsea operations mentioned included the use of coiled tubing as a downline for pumping fluids from a vessel to a subsea tree or pipeline. While this is not new to the coiled-tubing industry, tooling and vessel-based-equipment improvements have been developed to make operations safer and more versatile. Also in this arena, new thermoplastic composite materials are being introduced to the market and may bring further enhancements. These types of developments require considerable investment on behalf of the companies involved and tend to signal confidence in the longer-term return.
Meanwhile, investment in furthering the understanding of the performance of steel materials for coiled-tubing well-intervention operations continues to grow. This performance envelope is being examined in terms of both the mechanical (e.g., abrasion and fatigue) and the environmental (e.g., sour-well environments). For example, renewed studies are being conducted on the combination of high-cycle elastic and low-cycle plastic fatigue, which currently has relevance to subsea work. Formerly, such studies were limited to the use of coiled tubing as a pump string. Additionally, established knowledge of solids transport in high-angle wells, from both field experience and laboratory work, is being applied more widely to reduce costs through increased efficiency. This has been a long implementation curve for the coiled-tubing industry.
The next 12 months could bring upturns and downturns and greater or lesser volatility. Whatever may happen, the coiled-tubing industry’s record last year indicates that it will still be moving forward.
Recommended additional reading at OnePetro: www.onepetro.org.
SPE 179096 Localized Extreme Coiled-Tubing Wall Loss—Causes and Remediation Practices by Steven Craig, Baker Hughes, et al.
SPE 179083 Novel Abrasive Perforating With Acid-Soluble Material and Subsequent Hydrajet-Assisted Stimulation Provide Outstanding Results in Carbonate Gas Well by Alejandro Chacon, Halliburton, et al.
SPE 168294 Coiled-Tubing-Material Selection for Velocity Strings in Sour Brine Service by I. Ward, Shell Canada, et al.