In order to explore the influence of deep sea T⁃tube flow difference and pipe diameter abrupt change on the flow characteristic parameters of the vertical pipe, a certain oil and gas field in the South China Sea was taken as the research object, and the numerical simulation method was used. The results show that the influence of flow rate difference is related to the sum of the total flow rate instead of the each flow; the effect of changing diameters of riser pipe on relevant parameters can be divided into three stages: DC=0.03 m, DC=0.06~0.12 m and DC=0.24 m. And when the vertical riser has a sudden change, the flow parameters are mainly related to its minimal pipe diameter.

In order to explore the flow characteristics of vertical pipe in the deep⁃sea horizontal pipe⁃catenary system, in this paper, aiming at an oil and gas field in the south China sea, the influence of diameters, total flow rate, water cut and outlet pressure were simulated. The results show that the position of the flow state in the pipe is the boundary, and the influence of each influencing factor on the flow state parameters in the pipe shows different changes, but the temperature distribution along the pipe is not affected by the relevant factors; From the perspective of the research scope of the above four parameters, the influence process of each parameter is divided into different stages. The influence of pipe diameter is divided into two stages: D=0.06~0.12 m and D=0.12~0.50 m, the total flow of Q=0.001~0.030 m3/s and Q=0.100~0.300 m3/s, the water content of w=10%~25% and w=25%~30%, and the outlet pressure is divided into three stages, including 0~5.0, 5.0~7.0, 7.0~10.0 MPa.