A survey of coiled tubing failures in various field applications was conducted. The survey included the collection of information on failure type, number of strain cycles to failure, service environment, well depth, failure location on the coiled tubing string, and coiled tubing grade employed. The most prevalent causes of failures and the impact of localized corrosion on the performance of coiled tubing were assessed fi-om over thirty case studies herein reported. Pitting and tensile overload were the primary causes for failure in fifty percent of the cases reported from the field. Fatigue and weld area failures were the next most common types of ftilure. Most failures occurred within the range of 10 to 50 strain cycles. H2S and brine/water containing environments were the most prevalent service conditions. Most failures occurred at well depths between 5,001 to 10,000 feet (1524.3 to 3048 meters). Also, most ftilures
occurred in the coiled tubing string near the surface (less than 1,000 feet (304.8 meters)). Failures in roughly similar numbers were reported in 70, 80 and 100 coiled tubing grades. The understanding of the principal modes of failure herein reported should help in the development of improved handling and running procedures to minimize coiled tubing ftilures. Keywords: coiled tubing, field experience, failures, fatigue, serviceability, sulfide stress cracking, general corrosion, and localized corrosion