Numerical modelling of two-phase CO2 flow in pipes

The energy industry has decades of experience with modelling the multiphase flow of gas, oil, and water through wells and pipelines. This has led to state-of-the art design tools like OLGA and LedaFlow. Currently, the industry is working on upgrading the multiphase flow tools, to make them reliable for the design of CO2 transport. A particular challenge is modeling CO2 transport under two-phase flow conditions, which occurs during transient operations and even during steady-state operation for the case of injection into depleted gas reservoirs. This paper presents an accurate numerical method to solve the Homogeneous Equilibrium Model for single component CO2 transport under single-phase and two-phase flow conditions. The model performance is demonstrated through several test cases featuring fast transients. The same test cases are also simulated with OLGA, and a few of them also with LedaFlow and WANDA. The model and the test cases can be used as a basis for further developing, testing, and optimizing the numerical methods used to model CO2 transport. Our study shows that state-of-the art simulation models can provide numerically reliable solutions for fast transients with two-phase CO2 flow in pipes.