Analysis of the running capacity of coiled tubing in three-dimensional curved borehole

Abstract When coiled tubing enters three-dimensional borehole, elastic deformation is very easy to occur, leading to the decrease of running depth. In order to study the running capacity of coiled tubing, the running friction of coiled tubing under sinusoidal buckling and helical buckling in three-dimensional borehole was analyzed according to the structure of coiled tubing and the characteristics of borehole trajectory, considering the different contact points between the coiled tubing load and the borehole wall. According to the friction analysis results of each section of the running coiled tubing, the torque balance differential equation of the running coiled tubing micro-element was established and solved, and the friction torque of the running coiled tubing was obtained. The running capacity of Φ38.1mm×2.6mm QT-900 coiled tubing in three-dimensional borehole is analyzed. A theoretical algorithm for analyzing the running capacity of coiled tubing is established through the analysis of an example. This research can provide important theoretical research value and practical significance for the analysis of the running capacity of coiled tubing.