Coiled tubing (CT) becomes oval during normal use due to plastic bending on the reel. This ovality significantly decreases the collapse resistance of the CT, and, in extreme cases, can restrict the passage of the CT through the surface equipment. During pumping operations, the internal pressure can cause the CT to balloon as it plastically deforms on the reel and guide arch. The increase in the CT diameter causes a corresponding decrease in the wall thickness. Both effects substantially weaken the CT's collapse resistance and decrease its working life. Some CT software can estimate the ballooning and its effects on collapse and working life. However, no models exist for predicting the ever-changing ovality of CT.
A newly-developed tool can automatically measure the diameter and ovality of the tubing during actual CT operations. This real-time information is available to the CT operator for monitoring the status of the tubing and determining its suitability for continued use. Communications ports in the electronics module can feed the diameter data to a computer or data acquisition system for permanent storage or input to other monitoring software.
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