Effects of initial curvature on coiled tubing buckling behavior and axial load transfer in a horizontal well

This paper builds an analytical model to describe the comprehensive buckling behavior of coiled tubing (CT) with initial curvature in a horizontal well. The new buckling equation and contact force considering the effect of initial curvature is built on the basis of beam-column theory. With the new contact force expression, the work done by lateral friction can be obtained, thus the total potential energy of CT with initial curvature can be calculated. By use of the principle of virtual work and energy conservation, the critical sinusoidal and helical buckling load can be obtained. Moreover, the effect of initial curvature on axial load transfer is also calculated by a new axial load equation. The calculation results indicate that initial curvature has a strong influence on buckling loads and a CT with initial curvature is less efficient for axial load transfer compared to a straight CT. To verify the proposed model, the results of this paper are compared to experimental results, which support the proposed solutions.