Axial force transfer characteristics of a coiled tubing conducting offshore rotary operation

The coiled tubing (CT) rotary operation is a new technology being explored in the industry, where relevant research on the top torque's influence on the CT during rotary operation is missing. An indoor CT offshore rotary operation physical simulation system was built. Through theory and experiment, the influence of torque on the CT's axial force transmission characteristics in the offshore 'pipe in pipe' system is studied. The results show that the small constant torque applied at the CT top will not directly lead to string instability. However, the small constant torque applied at the CT top will reduce the limit loads of sinusoidal and helical buckling, leading to string instability at an earlier stage. Additionally, it is shown that torque would accelate string instability whereas the small top torque has little effect on the CT's axial force transfer efficiency. The research results will help to establish the theoretical guidance system of the CT offshore rotary operation.