Usually, carbon dioxide gas comes f

Usually, carbon dioxide gas comes from power plants or natural gas treatment plants, and some of it comes from carbon dioxide gas wells. Before treatment, these carbon dioxide all contain certain water, impurity gas and solid particles, and the existence of impurities will affect or even destroy the whole carbon dioxide treatment process and equipment. Therefore, it is necessary to establish a complete set of carbon dioxide ground engineering to ensure that the whole process from capture-pressurization-drying to injection is carried out safely and efficiently.The gas source of carbon dioxide is generally far away from the injection point, so an economical transportation mode is needed to make it reach the injection point. Ship transportation is not suitable for inland, and truck tanker transportation mode is only suitable for small-scale and short-distance conditions, because this pipeline transportation mode has become the first choice for large-scale and long-distance transportation of carbon dioxide.When transporting carbon dioxide by pipeline, there are three forms: gaseous state, liquid state and supercritical state. In order to determine the most favorable transportation state, the changes of its density, viscosity, heat capacity and thermal conductivity with temperature and pressure are analyzed from the perspective of carbon dioxide physical properties, and it is concluded that the most favorable state is supercritical state when transporting carbon dioxide by pipeline. Furthermore, the transport distance limit of each state is explored, and it is concluded that the effective transport distance is only 37.5km when transporting gaseous state, and 204.4km when transporting carbon dioxide in supercritical state because of the influence of supercritical state. If the requirement for supercritical state is not high, the transport distance can be further increased to achieve.Nitrogen and methane are the main impurities in carbon dioxide gas, which will have a certain impact on its performance when transporting mixed gas in pipeline. Through analysis, it is known that the influence of a small amount of nitrogen and methane on the pressure drop and temperature drop of gas and supercritical pipeline can be ignored, but the temperature drop and pressure drop of liquid pipeline are larger, and the influence of nitrogen is greater than that of methane, so it should be avoided as far as possible.At last, the paper analyzes the carbon dioxide transportation and injection mode in Daqingzijing Oilfield, and puts forward two optimization modes. By comparing the energy consumption and cost of the sequential mode and the improved mode, it is determined that it is the most economical to carry out low-pressure supercritical pressurization of carbon dioxide at the gas gathering station, and the transportation mode is low-pressure supercritical transportation and high-pressure supercritical injection at the injection station.