Carbon steel Coiled Tubing strings have been used in sour wellbore environments for many years. The use of Coiled Tubing in sour service has increased by job number, job complexity, pipe size and the stresses to which the pipe is subjected. A number of papers have been written on the steel chemistry and low cycle fatigue behaviour. These have been based on both theoretical and laboratory work. Great progress has been made in understanding the chemical and physical interaction of Coiled Tubing and hydrogen sulfide but little information is available from "real world" situations where the pipe has been worked in a variety of job types (acidising, gas lifting, drilling, etc) and where a large number of other factors may come into play (injector damage, well stimulation chemicals, sour inhibitor application techniques, erosion of inhibitors, CO2, high chloride water production, etc).

This paper will discuss the application of a Coiled Tubing technical specification (based on theoretical and laboratory work) in the operational world. Comparisons will be made between theoretical expectation and practical observation for 70 and 80 grade Coiled Tubing with regard to low cycle fatigue, pipe life and damage in sour environments.

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