The phase states of carbon dioxide are gaseous, liquid, solid and supercritical. Generally, it is in gaseous state. However, due to the high formation pressure, carbon dioxide is usually in supercritical state when it is produced from a carbon dioxide well. Therefore, in order to make full use of formation energy and save additional energy, carbon dioxide is generally kept in supercritical state when transported by pipeline. In addition, due to the relatively large occupied space and low transportation efficiency when transporting gaseous carbon dioxide by pipeline, the pressure of carbon dioxide will be increased in the actual operation process to make it reach liquid or supercritical state, while the density of carbon dioxide in supercritical state is slightly lower than that in liquid state, but its viscosity is much lower than that in liquid state, which is equivalent to that in gaseous state. Therefore, the friction along the pipeline will be greatly reduced, so transporting carbon dioxide in supercritical state has its own advantages.