Long Term Storage of Coiled Tubing: Industry Best Practices and Conclusions Based on Evaluation of Stock Strings

摘要

An unprecedented industry downturn has created surplus stock: new coiled tubing strings that have been stored at manufacturing facilities and at coiled tubing bases all over the world. This paper will address best practices for coiled tubing storage as well as recommendations based on the testing program for stock strings that have been destroyed. Methods, Procedures, Process: An unprecedented industry downturn has led to a surplus of inventory of strings that have been stored for at least one year. This program will evaluate stored inventory by gathering samples at multiple locations of stored strings including bias welds and parent tubing from both ends and the center. Additional samples will be located on the bottom of the wrapping (to verify if residual fluids affect coiled tubing storage). These samples will be tested in low cycle fatigue and evaluated for the presence of corrosion pitting. Results, Observations, Conclusions: The low cycle fatigue testing program evaluates multiple stored strings, including different grades and outer diameters. The samples are compared against existing commercially available models and can also be visually examined (after the removal of any surface rust) for the presence of corrosion pits. The results of the testing program will allow for the comparison of performance against storage conditions and time. Additionally, it will provide an opportunity to confirm that all workstring grades experience similar storage issues (regardless of grade) as all grades have a similar alloy chemistry (high strength low alloy steel). The test results will then be evaluated against commercially available modeling software to determine if storage corrosion led to defects, and if so provide some coiled tubing storage best practices that can be applied for coiled tubing manufacturers. These best practices can then be carried over to service companies storing the strings at their yards around the world. Novel or Additive Information: This testing program is the first-ever destructive evaluation of coiled tubing strings after long-term storage to determine the effects of storage. The paper is expected to set guidelines for long-term storage of coiled tubing.