Development and Initial Trials of Thermally Processed 95-Ksi Coiled Tubing

With a significant number of exploration and production programs pushing intervention boundaries, 95-ksi grade quenched and tempered (Q&T) coiled tubing (CT) has begun to be utilized in high-profile sour environments. This paper details the development of the newest 95-ksi grade of (Q&T) CT, specifically designed for increased fatigue life of existing products with performance in sour environments. The authorship team is comprised of a multidisciplinary group within the CT business, including manufacturers, service companies, and the operator. Each stakeholder has different expectations regarding this development, but the main outputs of the program need to be (1) a repeatably manufacturable grade with (2) improved fatigue life and (3) resistance to catastrophic failure due to exposure to sour environments. This study describes the design control process that accounts for the concerns of all stakeholders. The present review covers the initial development activity of identifying an alloy to make 95-ksi grade tubing. The process examined improvements to low cycle fatigue life and sour performance over 90-grade non-Q&T CT. Laboratory test results of 95-grade Q&T tubing are presented in this work. The low cycle fatigue testing comprises tests both with and without sour exposure. The testing without sour exposure is useful for providing comparative information to show how this grade can have an increased service life compared to 90-grade conventionally produced CT. The testing with sour exposure can be compared to the testing without exposure to show that low cycle fatigue life can be successfully modeled despite even in sour environments. The testing presents an examination of bias welds testing in low cycle fatigue as bias welds are considered a sensitive location for CT failure. In the present decade, CT intervention requirements combining deeper extended reach horizontal sections and high-pressure cycling in sour environments are becoming more frequent, driving operators, service companies, and manufacturers to jointly pursue technologies and engineered solutions for safe and effective CT work. The study presented here paves the road for implementation of a value Q&T offering for such challenging environment.