Coiled tubing failure analysis and ultimate bearing capacity under multi-group load

Influence study on ultimate bearing capacity of coiled tubing (CT) under the multi-group load can effectively avoid early failure and improve the service life. Based on the classical mechanics model, the mathematical model of CT under the multi-group load is established. The feasibility of the finite element (FE) model and the mathematical model are verified by the experimental result. Under tensile load, bending moment load, internal pressure and collapse load, the ultimate bearing capacity of 238″ CT is comparatively researched. The computed result shows the result of axial stress is correlated to the tensile load and bending moment load, the results of hoop stress and radial stress are linked to internal pressure and collapse load, respectively. According to the calculation results, the theory result is less than the FE result, and the error is acceptable in engineering. And by comparison, the maximum influence on ultimate bearing capacity of CT is internal pressure and collapse load.