Analysis of axial force transmission characteristics and contact mechanism of coiled tubing in the spoolable compliant guide during injection

The spoolable compliant guide (SCG) maintains S-shaped dynamic stability in the marine environment. At present, limited studies have been reported on the mechanical laws of coiled tubing (CT) injection by employing SCG. In this study, an experimental platform was developed to simulate the CT injection process in SCG. The axial force transmission characteristics, buckling laws, and contact mechanism of the CT were investigated. The results showed that an increase in the diameter of the inner pipe delayed the occurrence of sinusoidal and helical buckling and improved the transmission efficiency by 13.0%. An increase in the outer pipe diameter showed no significant effect on the efficiency, however, it increased the injection length of the inner pipe by 30.4%. The friction force increased significantly after the helical buckling of the inner pipe. Based on the results, the pre-sented research is beneficial in establishing CT's theoretical framework and enhancing operational effectiveness.