Abstract:
Nonmetallic composite coiled tubing with cable-laying will be subjected to tensile load due to its self-weight in the process of frequent lifting and lowering of wells for oil extraction, and clarifying the mechanical behavior of the pipe under this load can provide guidance for the safe service of the pipe. The study analyzes the mechanical behavior of composite coiled tubing with cable-laying under tensile load and the mechanical response of each structural layer and explores the influence of cable-laying process parameters, such as cable winding angle and distribution, on the mechanical properties of the pipe, by using finite element software to construct a 3D numerical model of the pipe. The results indicate that, under tensile load, the stresses in all structural layers of the pipe exhibit a spiral distribution because of cable winding. When the pipe is stretched to failure, it undergoes three stages: elastic deformation, transition stage, and yield deformation. Meanwhile, the cables are in a state of small plastic uniform deformation. Reducing the cable winding angle can enhance the elastic modulus and axial load-bearing capacity of the pipe. However, it may cause the pipe to enter into the transition stage prematurely, and then to yield in advance. The cable distribution angle has a minimal impact on the mechanical properties of the pipe. Thus, when manufacturing this type of tubing, special emphasis should be placed on the winding angle of the cables, as this process parameter is highly correlated with the mechanical properties of the tubing under tensile loads.