Study on Sizes Limit of Coiled Tubing under Internal Pressure and Bending Cyclic Complex Loads

摘要

The size of the pipe body of coiled tubing would change applied by internal pressure, cyclic bending complex loads. CT fatigue was accompanied by the sizes of the pipe body, namely diameter, circumference, ellipse degree increasing. When the sizes got to some degree, the CT's mechanism would decreased, when it passed the guide arch, injection and other equipments, it could lead to incompatibilities with deployment equipment which could cause severe mechanical damage and the several sticking accidents. Therefore, grasping the change law and an accurate prediction for CT sizes limits growth was necessary for both safety and reliability in CT operations. In this study, the full-scale fatigue and sizes testing on the CT fatigue machine were investigated under 25MPa internal pressure and bending cyclic complex loads. The data from the testing experiment of size of the pipe body was analysed and the relationship between sizes limits, namely, diameter, circumference, ellipse degree and the cycle (Residual Life) was found. And according to the curve fitting equation, the increasing laws of sizes for CT was established under the internal pressure of 25 MPa. The sizes of CT were accurately and timely predicted and the sizes limits were controlled and monitored which could provide reliable method for the safety service for CT.