Throttling effect model for multiphase flow system with high CO₂ content

In order to ensure the safe operation of gathering pipeline in the process of CO₂ flooding, wellhead throttling characteristics shall be predicted accurately to prevent the formation of ice blockage in the pipeline after the throttling.In this paper, the throttling effect model suitable for multiphase flow with high CO₂ content was developed based on BWRS equation of state, phase equilibrium principle and thermal equilibrium equation.The accuracy of this model is high under low pressure(lower than 5 MPa).The calculation error between Aspen HYSYS and this model is±1%.It is indicated that in the applicable scope of this model, the temperature of CO₂-H₂O multiphase flow system after the throttling is increased by CH₄, N₂ and H₂ contained in the CO₂ multiphase flow system and the contribution of H₂ to the temperature rise after the throttling is the greatest.In addition, the temperature drop after the throttling increases with the increase of gas/liquid ratio, and the effect of gas/liquid ratio on the temperature after the throttling is more obvious when it is lower than 10.The research results can be used as the reference for the throttling safety control and pipeline ice blockage control of the liquid produced from the oil wells of CO₂ flooding.