A Novel Testing Facility for Coiled Tubing Fatigue Evaluation Under Deep Drilling Conditions

Abstract

Over the last 30 years, Coiled Tubing (CT) has become one of the most important tool for wellbore interventions, completions and even drilling. The success of this technology lies in its high degree of flexibility which is based on the conscious destruction of its own working material – the Coiled Tubing itself – caused by low cycle fatigue. The current standards and best practices for the fatigue simulation are based on testing frames that are as old as the coiled tubing itself. In a working environment such as the oil and gas industry, where safety of operation is a key parameter, a reliable fatigue model that allows to track the fatigue damage and to stop using a pipe before it breaks becomes critical. Therefore, this paper provides a discussion of the existing fatigue testing setups and an inside of the prediction models. The second part of the paper will focus on discussing the true loads of a coiled tubing used for drilling applications. Finally a newly built for purpose testing facility is presented, showing the latest developments in accurate testing of coiled tubing used for deep drilling applications. The experimental tests have shown a good compatibility with existing testing setups, but the new added capabilities exceed the actual performance, and allow the development of a new coiled tubing fatigue prediction model.