Objective  The composite coiled tubing cable occurred cracking about one month after the first test in the B48 steam huff and puff well of N Oilfield in the Bohai Sea. It is necessary to determine the causes of the cable cracking and to optimize the most suitable cable material for offshore steam huff and puff well conditions.

Method  A corrosion failure analysis was conducted on the cracked CT90 material cable, and hydrogen-induced cracking (HIC) and sulfide stress cracking (SSC) tests were conducted on both the base material and welds of a 2205 material cable in accordance with relevant standards.

Result The failure of the CT90 material was attributed to the absence of normalizing treatment on the cable welds. The untreated welds exhibited coarse grains, with numerous ferrite needles forming brittle planes within the grains, resulting in reduced ductility, leading to SSC in the H₂S environment. The base material and welds of the 2205 material cable exhibited no cracking after undergoing HIC and SSC tests. Field testing also revealed no cracking in the 2205 material composite coiled tubing cable following its use in an offshore steam huff and puff well.

Conclusion The 2205 material exhibits superior adaptability to steam injection environments compared to the CT90 material, thereby meeting the production requirements of offshore steam huff and puff wells.