Effect of ocean load on axial force of coiled tubing with different helical post-buckling degrees

Coiled tubing (CT) is prone to helical post-buckling with variable pitch when being operated in deep water. The influence of ocean load on the axial force of a variable pitch pipe is complex and lacks relevant research. In this study, a pipe-in-pipe system test-bed was established for simulation experiments. Based on the experimental results, a mechanical analysis of the CT's buckling model is carried out. The effects of different ocean loads and helical post-buckling configurations on the axial force are studied. The results show that the greater the amplitude of ocean load and the degree of helical post-buckling, the greater is the axial force fluctuation of the CT. Because the buckling configuration is of variable pitch, the decrease in the axial force is different when ocean loads with the same size and opposite direction are applied. Besides, with the increase in the helical postbuckling, the pitch gradually changes from variable pitch to equal pitch, and the pitch number increases. The research results are helpful to the supplement of CT's buckling system.

Automated summary

This study investigates the influence of ocean load and helical post-buckling configuration on the axial force of coiled tubing through experimental and mechanical analysis. The results show that greater ocean load and helical post-buckling lead to increased axial force fluctuation. Additionally, the pitch transitions from variable pitch to equal pitch with increasing helical post-buckling.