Coiled tubing drilling (CTD) uses wireline inside coiled tubing (CT) for real-time downhole measurements and controlled actuation of the bottomhole assembly (BHA). In the CTD case under study, after several hundred thousand running feet, the wireline disconnected from its BHA anchor, resulting in lost communication and nonproductive time. By using the input of a CT integrity monitoring system based on magnetic flux leakage (MFL), it was shown that the CT experienced linear plastic elongation, resulting in the wireline being disconnected from the BHA anchor. CT pipe is fabricated from metal skelps joined together with bias welds. The pipe integrity monitoring system based on MFL was used from the first run of a CT string until its last run, before retiring the pipe. The system was originally designed to detect defects along CT string, but it can also analyze bias weld profile, which cannot be seen outside the tubing. Lengths of each metal strip were noted by comparing the distance between two bias weld points in the same run. CT elongation was then determined by comparing the length of each strip from initial and subsequent runs. This paper comprehensively studies CT elongation growth over each run and elaborates on the consequence of this elongation for CT operations using wireline or fiber optic cable (e.g., jeopardizing operations). The outcome from this paper helps to prevent recurrence by recognizing the root cause and modifying the slack management practices especially for this operation, which is sensitive to accurate slack calculation.

Despite many successful applications of coiled tubing drilling (CTD) technology, CTD still faces challenges in the field. For CTD technology to be reliable and economical, the coiled tubing (CT) pipe must be properly managed so that its useful life can be maximized while string reliability is improved. Through several case studies, this paper provides best practices for the use of nondestructive evaluation (NDE) technology to safeguard pipe integrity during CTD operations. The CT defect detection method relies on a portable measurement technology for CT pipe. The technology is primarily based on magnetic flux leakage (MFL) measurements. The characterization procedure includes extracting defect signals from hundreds of field inspection jobs and building a comprehensive and high-fidelity defect library. The inspector is then able to identify the type of defect, to track its evolution from job to job, and to evaluate its impact on CT fatigue life. A variety of case studies demonstrate the applicability and benefit of being able to identify the defect type, to track its initiation and progression during field operations, and to quantitatively evaluate its impact on CT fatigue life. This type of engineered pipe management technology offers a new way to reduce costly pipe failures during CTD operations as well as to maximize CT useful life.