| Popis: |
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. |
