Effects of Buckled Tubing on Coiled Tubing Passibility

Abstract Many coiled tubing(CT) operations involve passage through the production tubing. However, due to the adverse wellbore trajectory or tubing geometries, especially in helically buckled tubing, the CT operations are still encountering various bottlenecks when it is pulled or lowered through the tubing. In this paper, a new concept "local model", which provides a sophisticated description of CT deflection in buckled tubing from local perspective, is proposed to help supplement the integral torque-drag model. Firstly, the CT can pass through the buckled tubing freely without any deformations. According to the constrained geometric relationship between the tubing and CT, the maximum CT length and maximum outside diameter can be calculated. Secondly, when the CT dimension parameters are beyond the scope of the above rigid dimension, the CT can pass through the tubing flexibly with deformations. So a beam-column model is established to analyze the CT deflection and bending behavior in snaky and helically buckled tubing. The results show that the buckled tubing configurations have significant effects on the CT passage dimension. Once the CT dimension parameters are out of the range of rigid dimension, it would contact the tubing at some points with large buckled tubing amplitude. Moreover, the contact forces and bending moments are influenced by the axial force and buckled tubing amplitude. This "local model" analysis results can be implemented in the torque-drag modeling to optimize the CT extended reach and axial force transfer.